Lyme disease vaccine

Antigenic polypeptides comprising linear immunodominant epitopes of Borrelia outer surface protein A (OspA) or Borrelia outer surface protein C (OspC) are useful as vaccines against Lyme disease, and as diagnostics for detecting Borrelia infections. The OspA and OspC antigenic polypeptides typically comprise a plurality of peptides representing epitope containing regions from multiple distinct phyletic groups. The antigenic polypeptides may also include epitopes from both Borrelia OspA and Borrelia OspC.

1. A recombinant or synthetic fusion protein comprising

at least one linear epitope from Borrelia outer surface protein A (OspA), said at least one linear epitope having an amino acid sequence STLTITVNSKKTKDLVFTKE (SEQ ID NO: 1), and

one or more linear Borrelia OspA epitopes having an amino acid sequence selected from the group consisting of

2. The recombinant or synthetic fusion protein of claim 1, wherein said recombinant or synthetic fusion protein comprises linear Borrelia OspA epitopes having the amino acid sequences

This invention was made with government support under contract number R01 AI067746 awarded by the National Institutes of Health. The government has certain rights in the invention.

Field of the Invention

The invention generally relates to a vaccine and diagnostic for Lyme disease. In particular, the invention provides a Lyme disease vaccine and diagnostic that includes linear Borrelia outer surface protein A (OspA) epitopes and/or Borrelia outer surface protein C (OspC) epitopes, usually from multiple distinct phyletic groups.

Background of the Invention

Lyme disease is the most common arthropod-borne disease in North America and Europe, where in some areas up to 3% of the population is infected annually. Lyme disease is caused by the spirochetes Borrelia burgdorferi, B. garinii and B. afzelii. Transmission to mammals occurs through the bite of infected Ixodes ticks. Infection results in a multi-systemic inflammatory disease with early stage symptoms that may include erythema migrans, low-grade fever, arthralgia, myalgia, and headache. Late stage clinical manifestations can be severe and may include in part, arthritis and neurological complications. In addition, Lyme disease has significant socio-economic costs, manifested by reductions in outdoor recreational and social activities due to concerns about tick exposure.

The antigen used in first generation Lyme disease vaccines (e.g. LYMErix) was Outer surface protein A (OspA). OspA is only expressed by spirochetes in ticks, thus anti-OspA bactericidal activity occurs in the vector. However, a major drawback to the use of full-length OspA was the potential (whether real or perceived) for adverse events secondary to vaccination, such as the development of arthritis caused by immunological cross-reactivity with human proteins (e.g. LFA-1). This was a major factor in the withdrawal from the market of the original OspA-based LYMErix vaccine.

U.S. Pat. No. 6,248,562 (Jun. 19, 2001) to Dunn and Luft describes chimeric Borrelia proteins that can be used as immunodiagnostic reagents and vaccine immunogens against Borrelia infection.

U.S. Pat. Nos. 6,872,550 and 6,486,130 (Mar. 29, 2005, and Nov. 26, 2002, respectively) both to Livey, describe constructs for use a vaccines against Lyme disease.

U.S. Pat. No. 7,008,625 (Mar. 7, 2006) to Dattwyler et al. discloses chimeric Borrelia proteins that can be used as immunodiagnostic reagents and vaccine immunogens against Borrelia infection

The publication “Recombinant Chimeric Borrelia Proteins for Diagnosis of Lyme Disease” (Maria J. C. Gomes-Solecki et al. 2000. J. Clin. Microbiol., 38: 2530-2535) also describes recombinant chimeric proteins.

Despite the above-referenced technologies, to date the prior art has failed to provide an efficacious vaccine for use in the prevention and/or treatment of Lyme disease.

In order to address prior art problems with Lyme disease vaccines, the OspA protein from Borrelia burgdorferi has been epitope mapped by assessing the reactivity of sera generated during murine infection with recombinant OspA subfragments. The epitope map demonstrated several linear epitope-containing regions of OspA. While conformational epitopes of OspA have been mapped and described, linear epitopes have not previously been reported for use in a vaccine. The use of one or more of these small, defined epitope-containing sequences in a polypeptide vaccine formulation allows the avoidance of specific regions of OspA that have been implicated in vaccine-mediated adverse events when full-length OspA is used. The inclusion of linear epitopes from a plurality of phyletic groups of Borrelia results in a vaccine that provides broad protection against infection over large geographical areas.

In addition, in other embodiments of the invention, one or more defined epitope-containing sequences from the Borrelia OspC protein have been used in vaccine formulations. Typically, epitopes or epitope-containing sequences from multiple phyletic groups are utilized.

Finally, the invention provides vaccine compositions which contain epitopes or epitope regions from both OspA and OspC.

It is an object of the invention 1. An isolated recombinant or synthetic peptide or polypeptide comprising at least one linear epitope from Borrelia outer surface protein A (OspA), said at least one linear epitope having an amino acid sequence selected from the group consisting of: SEQ ID NO: 1; SEQ ID NO: 2; SEQ ID NO: 3; SEQ ID NO: 4; SEQ ID NO: 5; SEQ ID NO: 6; SEQ ID NO: 7; SEQ ID NO: 8; SEQ ID NO: 9; SEQ ID NO: 10; SEQ ID NO: 11; SEQ ID NO: 12; SEQ ID NO: 13; SEQ ID NO: 14; SEQ ID NO: 15; SEQ ID NO: 16; SEQ ID NO: 17; SEQ ID NO: 18; SEQ ID NO: 19; SEQ ID NO: 20; SEQ ID NO: 21; SEQ ID NO: 22; SEQ ID NO: 23; SEQ ID NO: 24; SEQ ID NO: 25; SEQ ID NO: 26); and SEQ ID NO: 27.

In one embodiment, the at least one linear epitope is selected from the group consisting of SEQ ID NO: 1; SEQ ID NO: 2; SEQ ID NO: 3; SEQ ID NO: 4; SEQ ID NO: 5; SEQ ID NO: 6; SEQ ID NO: 7; SEQ ID NO: 8; SEQ ID NO: 9; SEQ ID NO: 10; SEQ ID NO: 11; SEQ ID NO: 12; SEQ ID NO: 13; SEQ ID NO: 14; SEQ ID NO: 15; SEQ ID NO: 16; SEQ ID NO: 17; and SEQ ID NO: 18.

The isolated recombinant or synthetic peptide or polypeptide may further comprise one or more amino acid sequences that are epitopes of Borrelia outer surface protein C (OspC), for example, one or more amino acid sequences that are epitopes of Borrelia OspC from an OspC loop 5 region or an OspC alpha helix 5 region, or both. The epitopes of OspC may be OspC types selected from the group consisting of Smar, PLi, H13, PFiM, SL10, PMit, PKi, Pbes, HT22, Pko, PLj7, VS461, DK15, HT25, A,72a, F, E, M, D, U, I, L, H, Szid, PHez, PWa, B, K, N, and C. In some embodiments, the one or more amino acid sequences that are epitopes of Borrelia OspC are selected from the group of polypeptides having sequences as set forth in SEQ ID NOS: 65-73.

The invention also provides a method for eliciting an immune response against Borrelia in an individual in need thereof. The method comprises the step of administering to the individual an isolated recombinant or synthetic peptide or polypeptide comprising at least one linear epitope from Borrelia outer surface protein A (OspA). The at least one linear epitope having an amino acid sequence selected from the group consisting of: SEQ ID NO: 1; SEQ ID NO: 2; SEQ ID NO: 3; SEQ ID NO: 4; SEQ ID NO: 5; SEQ ID NO: 6; SEQ ID NO: 7; SEQ ID NO: 8; SEQ ID NO: 9; SEQ ID NO: 10; SEQ ID NO: 11; SEQ ID NO: 12; SEQ ID NO: 13; SEQ ID NO: 14; SEQ ID NO: 15; SEQ ID NO: 16; SEQ ID NO: 17; SEQ ID NO: 18; SEQ ID NO: 19; SEQ ID NO: 20; SEQ ID NO: 21; SEQ ID NO: 22; SEQ ID NO: 23; SEQ ID NO: 24; SEQ ID NO: 25; SEQ ID NO: 26); and SEQ ID NO: 27.

In some embodiments, the at least one linear epitope has an amino acid sequence selected from the group consisting of SEQ ID NO: 1; SEQ ID NO: 2; SEQ ID NO: 3; SEQ ID NO: 4; SEQ ID NO: 5; SEQ ID NO: 6; SEQ ID NO: 7; SEQ ID NO: 8; SEQ ID NO: 9; SEQ ID NO: 10; SEQ ID NO: 11; SEQ ID NO: 12; SEQ ID NO: 13; SEQ ID NO: 14; SEQ ID NO: 15; SEQ ID NO: 16; SEQ ID NO: 17; and SEQ ID NO: 18. According to some embodiments of the method, the isolated recombinant or synthetic peptide or polypeptide may further comprise one or more amino acid sequences that are epitopes of Borrelia outer surface protein C (OspC), for example, one or more amino acid sequences that are epitopes of Borrelia OspC from an OspC loop 5 region or an OspC alpha helix 5 region, or both. The epitopes of OspC may be OspC types selected from the group consisting of Smar, PLi, H13, PFiM, SL10, PMit, PKi, Pbes, HT22, Pko, PLj7, VS461, DK15, HT25, A,72a, F, E, M, D, U, I, L, H, Szid, PHez, PWa, B, K, N, and C. In some embodiments, the one or more amino acid sequences that are epitopes of Borrelia OspC are selected from the group of polypeptides having sequences as set forth in SEQ ID NOS: 65-73.

The invention further provides a method for ascertaining whether an individual has been exposed to or infected with Borrelia, or both. The method comprises the steps of 1) obtaining a biological sample from said individual; 2) exposing said biological sample to a recombinant or synthetic peptide or polypeptide comprising at least one linear epitope from Borrelia outer surface protein A (OspA), said at least one linear epitope having an amino acid sequence selected from the group consisting of: SEQ ID NO: 1; SEQ ID NO: 2; SEQ ID NO: 3; SEQ ID NO: 4; SEQ ID NO: 5; SEQ ID NO: 6; SEQ ID NO: 7; SEQ ID NO: 8; SEQ ID NO: 9; SEQ ID NO: 10; SEQ ID NO: 11; SEQ ID NO: 12; SEQ ID NO: 13; SEQ ID NO: 14; SEQ ID NO: 15; SEQ ID NO: 16; SEQ ID NO: 17; SEQ ID NO: 18; SEQ ID NO: 19; SEQ ID NO: 20; SEQ ID NO: 21; SEQ ID NO: 22; SEQ ID NO: 23; SEQ ID NO: 24; SEQ ID NO: 25; SEQ ID NO: 26); and SEQ ID NO: 27; and 3) determining whether antibodies in the biological sample bind to the recombinant or synthetic peptide or polypeptide, wherein detection of antibody binding is indicative of prior exposure to or infection with Borrelia. In some embodiments of this method, the recombinant or synthetic peptide or polypeptide further comprises one or more epitopes of Borrelia outer surface protein C (OspC), such as those having sequences as set forth in SEQ ID NOS: 65-73.

The invention further provides antibodies to a recombinant or synthetic peptide or polypeptide comprising at least one linear epitope from Borrelia outer surface protein A (OspA) or outer surface protein C (OspC). The at least one linear epitope having an amino acid sequence selected from the group consisting of: SEQ ID NOS: 1-27 (for OspA) and SEQ ID NOS: 65-73 (for OspC). In some embodiments, the antibody is bactericidal for Borrelia spirochetes.

The invention further provides an isolated recombinant or synthetic peptide or polypeptide comprising one or more epitopes from Borrelia outer surface protein A (OspA), said one or more epitopes being from an antigenic region selected from the group consisting of: antigenic region 221-240, antigenic region 17-67, antigenic region 94-144, and antigenic region 119-169. The isolated recombinant or synthetic peptide or polypeptide may further comprising one or more epitopes of Borrelia outer surface protein C (OspC).

The invention also provides an isolated recombinant or synthetic peptide or polypeptide comprising at least one linear epitope from Borrelia outer surface protein C (OspC). The at least one linear epitope may have an amino acid sequence selected from the group consisting of: SEQ ID NO: 65; SEQ ID NO: 66; SEQ ID NO: 67; SEQ ID NO: 68; SEQ ID NO: 69; SEQ ID NO: 70; SEQ ID NO: 71; SEQ ID NO: 72; and SEQ ID NO: 73. The isolated recombinant or synthetic peptide or polypeptide may, in some embodiments, further comprise one or more epitopes of Borrelia outer surface protein A (OspA).

The present invention is based on the identification and characterization of linear peptide epitopes from Borrelia OspA protein. Identification of these epitopes has made possible the design and construction of chimeric (fusion) polypeptides that can be used as vaccines against Lyme disease, or as diagnostic tools. The polypeptides, which are generally isolated and/or purified, comprise at least one copy of an epitope from one of four classes of Borrelia OspA epitopes or antigenic regions. The four classes are organized based on the amino acid sequences numbering of OspA Borrelia burgdorferi strain B31M1, as follows:

• Class I: Antigenic region 221-240;
• Class II: Antigenic region 17-67;
• Class III: Antigenic region 94-144; and
• Class IV: Antigenic region 119-169.

The prototype Class I sequence is from Borrelia burgdorferi strain B31M1:

• Class I: STLTITVNSKKTKDLVFTKE (SEQ ID NO: 1), which corresponds to residues 221-240 of OspA protein from B. burgdorferi. Additional corresponding or analogous type specific (i.e. phyletically related) exemplary Class I sequences that may be used in the practice of the invention include the following:

The prototype Class II sequence from Borrelia burgdorferi strain B31M1 is:

• Class II: CKQNVSSLDEKNSVSVDLPGEMKVLVSKEKNKDGKYDLIATVDKLELKGTS (SEQ ID NO: 19), which corresponds to residues 17-67 of OspA protein from B. burgdorferi.

The prototype Class III sequence from Borrelia burgdorferi strain B31M1 is:

• Class III: LGQTTLEVFKEDGKTLVSKKVTSKDKSSTEEKFNEKGEVSEKIITRADGTR (SEQ ID NO: 22), which corresponds to residues 94-144 of OspA protein from B. burgdorferi.

The prototype Class IV sequence from Borrelia burgdorferi strain B31M1 is:

• Class IV: KSSTEEKFNEKGEVSEKIITRADGTRLEYTGIKSDGSGKAKEVLKGYVLEG (SEQ ID NO: 25), which corresponds to residues 119-169 of OspA protein from B. burgdorferi. Additional exemplary Class II, II and IV type-specific sequences that may be used in the practice of the invention include those depicted in Table 2. The sequences in Table 2 (SEQ ID NOS: 19-27) are exemplary, in that a phylogenetic analysis of Borrelia OspA at the indicated regions would generate additional potential sequences for use in the practice of the invention (i.e. additional sequences from other Borrelia species, strains or types).

The use of one or more these linear epitopes in vaccine preparations advantageously avoids exposing the vaccine recipient to regions of OspA that have been implicated in putative adverse vaccine effects. The inclusion of a plurality of these linear sequences provides broad coverage against the development of Lyme disease for individuals over a broad geographical area. Or, when used as a diagnostic, the polypeptides of the invention enable detection of exposure to or infection with Borrelia of most important phyletic types over a broad geographical area. Further, the vaccine and/or diagnostic compositions can be “tuned” if desired, to represent one or more, but not all, geographical regions. For example, a vaccine or diagnostic developed for use in North America might contain only sequences derived from B. burgdorferi, as this is the only species associated with Lyme disease in that geographic area. In addition, in some embodiments of the invention, polypeptides containing one or more linear OspA epitopes or antigenic regions as described herein, may also include one or more OspC epitopes or antigenic regions, as described in detail below.

In order to facilitate the understanding of the present invention, the following definitions are provided:

• Antigen: term used historically to designate an entity that is bound by an antibody, and also to designate the entity that induces the production of the antibody. More current usage limits the meaning of antigen to that entity bound by an antibody, while the word “immunogen” is used for the entity that induces antibody production. Where an entity discussed herein is both immunogenic and antigenic, reference to it as either an immunogen or antigen will typically be made according to its intended utility. The terms “antigen”, “antigenic region” “immunogen” and “epitope” may be used interchangeably herein. As used herein, an antigen, immunogen or epitope is generally a portion of a protein (e.g. a peptide or polypeptide).
• Epitope or B-cell Epitope: a specific chemical domain on an antigen that is recognized by a B-cell receptor, and which can be bound by secreted antibody. The term as used herein is interchangeable with “antigenic determinant”.
• Immunodominant epitope: The epitope on a molecule that induces the dominant, or most intense, immune response. The immunodominant epitope would elicit the greatest antibody titer during infection or immunization, as measured by, for example, the fraction of reactivity attributable to a certain antigen or epitope in an enzyme-linked immunosorbant assay as compared with the total responsiveness to an antigen set or entire protein.
• Linear epitope: An epitope comprising a single, non-interrupted, contiguous chain of amino acids joined together by peptide bonds to form a peptide or polypeptide. Such an epitope can be described by its primary structure, i.e. the linear sequence of amino acids in the peptide chain. This is in contrast to conformational epitopes, which are comprised of at least some amino acids that are not part of an uninterrupted, linear sequence of amino acids, but which are brought into proximity to other residues in the epitope by secondary, tertiary and/or quaternary interactions of the protein. Residues in conformational epitopes may be located far from other resides in the epitope with respect to primary sequence, but may be spatially located near other residues in the conformational epitope due to protein folding.
• Protein: A linear sequence of about 100 or more amino acids covalently joined by peptide bonds.
• Polypeptide: A linear sequence of about 55 to about 100 amino acids covalently joined by peptide bonds.
• Peptide: A linear sequence of about 55 or fewer amino acids covalently joined by peptide bonds.
• Note: The terms “peptide”, “polypeptide” and “protein” may be used interchangeably herein.
• Chimeric: or fusion peptide or polypeptide: a recombinant or synthetic peptide or polypeptide whose primary sequence comprises two or more linear amino acid sequences which do not occur together in a single molecule in nature. The two or more sequences may be, for example, a peptide (e.g. an epitope or antigenic region) and a linker sequence, or two or more peptides (which may be the same or different) which are either contiguous or separated by a linker sequences, etc.
• Original or native or wild type sequence: The sequence of a peptide, polypeptide, protein or nucleic acid as found in nature.
• Recombinant peptide, polypeptide, protein or nucleic acid: peptide, polypeptide, protein or nucleic acid that has been produced and/or manipulated using molecular biology techniques such as cloning, polymerase chain reaction (PCR), etc.
• Synthetic peptide, polypeptide, protein or nucleic acid: peptide, polypeptide, protein or nucleic acid that has been produced using chemical synthesis procedures.
• Type-specific: associated primarily with a single phyletic group.
• Invasive infection: A protein is said to be “associated with invasive infection” if a Borrelia type bearing the protein has been isolated during human infection from locations other than the skin surrounding the initial inoculation by tick bite (e.g. from plasma, cerebrospinal fluid, etc.).

According to the invention, at least one amino acid sequence from Classes I-IV will be included in a peptide or polypeptide that is administered as a vaccine. In one embodiment of the invention, an antigenic chimeric (or fusion) polypeptide of the invention comprises one or more amino acid sequence from Class I, such as those set forth in, for example, SEQ ID NOS: 1 and 2. Usually, one or more copies of two or more Class I sequences will be included, and each distinct sequence may be present in the polypeptide one or more time, i.e. multiple copies of one or more of the sequences set forth in, for example, SEQ ID NOS: 1 and 2 are included. For example, from about 1 to about 10 of the Class I sequences may be included, and for each separate sequence that is included, that sequence may be present in from about 2 to about 12 (e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12) or more copies. Individual copies of the sequence may be separated by linker sequences (described below), although this need not always be the case, i.e. copies of the same or different antigenic regions may be contiguous in the polypeptide chain.

In other embodiments, one or more of the amino acid sequences set forth in or represented by the Class II or Class III or Class IV antigenic regions are included in the antigenic polypeptides of the invention. As is the case with the Class I epitopes, one or more of the peptides may be present in the antigenic polypeptide, and, for each distinct sequence that is present, multiple copies (e.g. from about 2 to about 12) may be included. Individual copies of the sequence may be separated by linker sequences, although this need not always be the case.

In yet other embodiments, mixtures of one or more copies of one or more Class I, Class II, Class III and/or Class IV antigenic regions are present in the antigenic polypeptides of the invention. In other words, the polypeptide includes a mixture antigenic regions from any of the four classes. Each of the sequences that is included may be present in one copy or, more frequently, as multiple copies. In this type of construct, the individual sequences may be present in any order. For example, one segment or section of the polypeptide may include multiple copies of e.g. SEQ ID NO: 1, while another section of the same polypeptide includes multiple copies of e.g. SEQ ID NO: 2, and so on. Alternatively, the sequences of e.g. SEQ ID NO: 1 and e.g. SEQ ID NO: 2 may alternate along the polypeptide chain so that the sequences are, in effect, interspersed amongst each other within the primary sequence of the polypeptide.

Other antigenic sequences of interest are those from other Borrelia proteins such as OspC. The invention thus provides chimeric polypeptides or proteins that comprise, one or more epitopes from OspC. Exemplary OspC epitopes include but are not limited to linear epitopes from the loop 5 and/or alpha helix 5 regions. The loop 5 region or domain of OspC is the region which includes residues that align with residues 131 to 159 of strain B31 (type A) OspC sequences (together with secondary structural elements such as a portion of alpha helix 3, loop 5, and alpha helix 4, as defined by Kumaran et al. The alpha helix 5 region/domain of OspC is the region which includes residues that align with amino acids 160 to 200 of the strain B31 (OspC type A) sequence and the C-terminal portion of the protein, amino acids 201-210 of the B31 sequence, as well as secondary structural elements including a portion of loop 6, alpha helix 5, and the unstructured C-terminal domain, as defined by Kumaran et al. (2001). According to the present invention, one or more peptides encompassing epitopes located within the primary linear sequence of OspC proteins from residues 131 to 200 (using the strain B31 type A OspC sequence as a reference for residue numbering) may be included in the immunogenic polypeptides of the invention, the polypeptides of the invention. Exemplary OspC regions from which epitopes may be selected are shown in FIG. 1, where the sequences corresponding to residues 131 to 200 of type A OspC from several Borrelia types are listed. One or more epitopes may be selected for inclusion, so that an entire 131-200 (or even 131-210 C-terminal) region encompassing several epitopes may be used. Alternatively, fragments of the 131-200 region may be employed, e.g. any contiguous sequence of from about 10 to about 50 amino acids. One or more of such contiguous sequences may be used in the practice of the invention, with preferable sequences being those corresponding to about amino acids 136 to 150 and about amino acids 168-203 of alpha helix 5.

In particular, the general epitope locations of suitable OspC-based sequences include Helix 3, Loop5, Loop6, Helix5 and a C-terminus sequence. Three exemplary constructs, denominated constructs A, B and C, are depicted schematically in FIGS. 2A-C (SEQ ID NOS: 62, 63 and 64). Constructs A, B and C differ in that the sequences contained therein are from different phyletic types. For example, as shown in FIG. 2A, Construct A contains sequences from Types A, B, K, I, H, N, C, M and D of B. burgdorferi. In addition, for each of Constructs A, B and C, various versions or variations have been developed. The versions differ, for example, by the inclusion or exclusion of an intervening Helix-4/Loop6 sequence, by the order of the individual epitopes, and by other exclusions and or additions, etc. Exemplary variations of Constructs A, B and C are shown in Table 3.

In some embodiments, at least two of the OspC epitopes included in the chimeric polypeptide are from different OspC types that are associated with invasive infection. For example, antigenic epitopes representing from about 2 to about 20, and preferably from about 6 to about 10, different OspC types are included in a chimeric protein. When used as a vaccine, such a multivalent (polyvalent) recombinant chimeric protein elicits broad protection against infection with Borrelia spirochetes expressing the OspC types that correspond to those in the chimeric protein, i.e. those Borrelia that are highly infective. While typically at least two of the epitopes are different from one another in primary sequence and originate from different OspC types, it is also possible to include multiple copies of a single type of OspC epitope in a chimera, or to include several sequences that are based on or derived from the original sequence of the same OspC type. While the total number of linear OspC epitopes in a chimera may vary somewhat, in general, the range will be from about 10 to about 20. In one embodiment of the invention, the immunodominant OspC epitopes are selected from OspC types Smar, PLi, H13, PFiM, SL10, PMit, PKi, Pbes, HT22, Pko, PLj7, VS461, DK15, HT25, A,72a, F, E, M, D, U, I, L, H, Szid, PHez, PWa, B, K, N, C. Those of skill in the art will recognize that epitopes from many combinations of OspC types may be used, so long as the resulting chimera produces a suitable immune response and/or is effective as a vaccine in preventing Lyme disease. Examples of suitable combinations of OspC epitopes (which may optionally be combined with OspA epitopes of Classes I-IV) include but are not limited to: 1) E, N, I, C, A, B, K, D; 2) A, B, K, D, E, N, C; 3) I, C, A, B, K, D; and 4) C, A, B, K, D.

In some embodiments, both the OspC loop 5 and OspC alpha helix 5 regions will be included. For example, an “E, N, I, C, A, B, K, D” construct may contain both the loop 5 and helix 5 regions of each of OspC types E, N, I, C, A, B, K, and D. However, this need not be the case. For example, the loop 5 region of type A and the alpha helix 5 regions of E, N, I, C, B, K, and D may be included; or only the loop 5 region for each OspC type may be included; or only the alpha helix 5 region; or other combinations may be included (e.g. loop 5 region of types E, N, I, and C and the alpha helix 5 region of types A, B, K, and D. Many such combinations will occur to those of skill in the art, and all such variations are intended to be encompassed herein.

In other embodiments of the invention, one or more of the sequences represented by OspA Classes I-IV are present in an antigenic polypeptide which also includes antigenic sequences of OspC as described above.

In addition, other peptide sequences may be included in the peptides and polypeptides of the invention. Such sequences include but are not limited to antigenic peptide sequences such as linker sequences which in and of themselves are antigenic.

Those of skill in the art will recognize that, while in some embodiments of the invention, the amino acid sequences that are chosen for inclusion in the peptides and polypeptides of the invention correspond exactly to the primary amino acid sequence of the original or native sequences of an OspA (or OspC) protein, this need not always be the case. The amino acid sequence of an epitope that is included in the peptides and polypeptides of the invention may be altered somewhat and still be suitable for use in the present invention. For example, certain conservative amino acid substitutions may be made without having a deleterious effect on the ability of the peptides and polypeptides to elicit an immune response. Those of skill in the art will recognize the nature of such conservative substitutions, for example, substitution of a positively charged amino acid for another positively charged amino acid (e.g. K for R or vice versa); substitution of a negatively charged amino acid for another negatively charged amino acid (e.g. D for E or vice versa); substitution of a hydrophobic amino acid for another hydrophobic amino acid (e.g. substitution of A, V, L, I, W, etc. for one another); etc. All such substitutions or alterations of the sequences of the peptides and polypeptides that are disclosed herein are intended to be encompassed by the present invention, so long as the resulting peptides and polypeptides still function to elicit a suitable immune response. In addition, the amino acid sequences that are included in the chimeric proteins of the invention need not encompass a full length native peptide or polypeptide. Those of skill in the art will recognize that truncated versions of amino acid sequences that are known to be or to contain antigenic peptides and/or polypeptides may, for a variety of reasons, be preferable for use in the practice of the invention, so long as the criteria set forth for an epitope is fulfilled by the sequence. Amino acid sequences that are so substituted or otherwise altered may be referred to herein as “based on” or “derived from” the original wild type or native sequence. In general, the OspA or OspC proteins from which the linear epitopes are “derived” or on which the linear epitopes are “based” are the OspA or OspC proteins as they occur in nature. These natural OspA/OspC proteins may alternatively be referred to as native or wildtype proteins.

Such changes to the primary sequence may be introduced for any of a variety of reasons, for example, to eliminate or introduce a protease cleavage site, to increase or decrease solubility, to promote or discourage intra- or inter-molecular interactions such as folding, ionic interactions, salt bridges, etc., which might otherwise interfere with the presentation and accessibility of the individual epitopes along the length of a peptide or polypeptide. All such changes are intended to be encompassed by the present invention, so long as the resulting amino acid sequence functions to elicit a protective antibody response in a host to whom it is administered. In general, such substituted sequences will be at least about 50% identical to the corresponding sequence in the native protein, preferably about 60 to 70, or even 70 to 80, or 80 to 90% identical to the wild type sequence, and preferably about 95, 96, 97, 98, 99, or even 100% identical to a native OspA (or OspC) sequence. The reference native OspA or OspC sequence may be from any suitable type of Borrelia, e.g. from any Borrelia which is known to infect mammals.

In some embodiments of the invention, the individual linear epitopes in the chimeric vaccinogen are separated from one another by intervening sequences that are more or less neutral in character, i.e. they do not in and of themselves elicit an immune response to Borrelia. Such sequences may or may not be present between the epitopes of a chimera. If present, they may, for example, serve to separate the epitopes and contribute to the steric isolation of the epitopes from each other. Alternatively, such sequences may be simply artifacts of recombinant processing procedures, e.g. cloning procedures. Such sequences are typically known as linker or spacer peptides, many examples of which are known to those of skill in the art. See, for example, Crasto, C. J. and J. A. Feng. 2000. LINKER: a program to generate linker sequences for fusion proteins. Protein Engineering 13(5): 309-312, which is a reference that describes unstructured linkers. Structured (e.g. helical) sequence linkers may also be designed using, for example, existing sequences that are known to have that secondary structure, or using basic known biochemical principles to design the linkers.

In addition, other elements may be present in the chimeric proteins, for example leader sequences or sequences that “tag” the protein to facilitate purification or detection of the protein, examples of which include but are not limited to histidine tags, detection tags (e.g. S-tag, or Flag-tag), other antigenic amino acid sequences such as known T-cell epitope containing sequences and protein stabilizing motifs, etc. In addition, the chimeric proteins may be chemically modified, e.g. by amidation, sulfonylation, lipidation, or other techniques that are known to those of skill in the art.

The invention further provides nucleic acid sequences that encode the chimeric proteins of the invention. Such nucleic acids include DNA, RNA, and hybrids thereof, and the like. Further, the invention comprehends vectors which contain or house such coding sequences. Examples of suitable vectors include but are not limited to plasmids, cosmids, viral based vectors, expression vectors, etc. In a preferred embodiment, the vector will be a plasmid expression vector.

The chimeric polypeptides of the invention may be produced by any suitable method, many of which are known to those of skill in the art. For example, they may be chemically synthesized, or produced using recombinant DNA technology (e.g. in bacterial cells, in cell culture (mammalian, yeast or insect cells), in plants or plant cells, or by cell-free prokaryotic or eukaryotic-based expression systems, by other in vitro systems, etc.). In some embodiments, the polypeptides are produced using chemical synthesis methods.

The present invention also provides compositions for use in eliciting an immune response. The compositions may be utilized as vaccines to prevent or treat Borrelia infection, particularly when manifested as Lyme disease (Lyme borreliosis). By eliciting an immune response, we mean that administration of the antigen causes the synthesis of specific antibodies (at a titer as described above) and/or cellular proliferation, as measured, e.g. by³H thymidine incorporation, or by other known techniques. By “vaccine” we mean a chimeric or fusion polypeptide that elicits an immune response which results in protection of an organicism against challenge with Borrelia. The protective response either wholly or partially prevents or arrests the development of symptoms related to Borrelia infection (i.e. the symptoms of Lyme disease), in comparison to a non-vaccinated (e.g. adjunct alone) control organisms, in which disease progression is not prevented. The compositions include one or more isolated and substantially purified chimeric peptides or polypeptides as described herein, and a pharmacologically suitable carrier. The chimeric polypeptides or proteins in the composition may be the same or different, i.e. the composition may be a “cocktail” of different chimeras, or a composition containing only a single type of chimera. The preparation of such compositions for use as vaccines is well known to those of skill in the art. Typically, such compositions are prepared either as liquid solutions or suspensions, however solid forms such as tablets, pills, powders and the like are also contemplated. Solid forms suitable for solution in, or suspension in, liquids prior to administration may also be prepared. The preparation may also be emulsified. The active ingredients may be mixed with excipients which are pharmaceutically acceptable and compatible with the active ingredients. Suitable excipients are, for example, water, saline, dextrose, glycerol, ethanol and the like, or combinations thereof. In addition, the composition may contain minor amounts of auxiliary substances such as wetting or emulsifying agents, pH buffering agents, and the like. The vaccine preparations of the present invention may further comprise an adjuvant, suitable examples of which include but are not limited to Seppic, Quil A, Alhydrogel, etc. If it is desired to administer an oral form of the composition, various thickeners, flavorings, diluents, emulsifiers, dispersing aids or binders and the like may be added. The composition of the present invention may contain any such additional ingredients so as to provide the composition in a form suitable for administration. The final amount of chimeric protein in the formulations may vary. However, in general, the amount in the formulations will be from about 0.01-99%, weight/volume.

The methods involve administering a composition comprising a chimeric recombinant protein in a pharmacologically acceptable carrier to a mammal. The mammal may be a human, but this need not always be the case, as veterinary applications of this technology are also contemplated. The vaccine preparations of the present invention may be administered by any of the many suitable means which are well known to those of skill in the art, including but not limited to by injection, inhalation, orally, intranasally, by ingestion of a food product containing the chimeric protein, etc. In preferred embodiments, the mode of administration is subcutaneous or intramuscular. In addition, the compositions may be administered in conjunction with other treatment modalities such as substances that boost the immune system, various anti-bacterial chemotherapeutic agents, antibiotics, and the like.

The present invention provides methods to elicit an immune response to Borrelia and to vaccinate against Borrelia infection in mammals. In one embodiment, the mammal is a human. However, those of skill in the art will recognize that other mammals exist for which such vaccinations would also be desirable, e.g. the preparations may also be used for veterinary purposes. Examples include but are not limited to companion “pets” such as dogs, cats, etc.; food source, work and recreational animals such as cattle, horses, oxen, sheep, pigs, goats, and the like; or even wild animals that serve as a reservoir of Borrelia (e.g. mice, deer, etc.).

The invention also provides a diagnostic and a method for using the diagnostic to identify individuals who have antibodies to the epitopes contained within the chimeric polypeptides of the invention. A biological sample from an individual (e.g. a human, a deer, or other mammals susceptible to infection by Borrelia spirochetes) suspected of having been exposed to Borrelia, or at risk for being exposed to Borrelia, is contacted with the chimeric proteins of the invention. Using known methodology, the presence or absence of a binding reaction between the chimeric protein and antibodies in the biological sample is detected. A positive result (i.e. binding occurs, thus antibodies are present) indicates that the individual has been exposed to and/or is infected with Borrelia. Further, the diagnostic aspects of the invention are not confined to clinical use or home use, but may also be valuable for use in the laboratory as a research tool, e.g. to identify Borrelia spirochetes isolated from ticks, to investigate the geographical distribution of Borrelia species and strains, etc.

The present invention also encompasses antibodies to the epitopes and/or to the chimeric polypeptides disclosed herein. Such antibodies may be polyclonal, monoclonal or chimeric, and may be generated in any manner known to those of skill in the art. In a preferred embodiment of the invention, the antibodies are bactericidal (borreliacidal), i.e. exposure of Borrelia spirochetes to the antibodies causes death of the spirochetes. Such antibodies may be used in a variety of ways, e.g. as detection reagents to diagnose prior exposure to Borrelia, as a reagent in a kit for the investigation of Borrelia, to treat Borrelia infections, etc.

Alternatively, appropriate antigen fragments or antigenic sequences or epitopes may be identified by their ability, when included in a chimeric protein, to elicit suitable antibody production to the epitope in a host to which the chimeric protein is administered. Those of skill in the art will recognize that definitions of antibody titer may vary. Herein, “titer” is taken to be the inverse dilution of antiserum that will bind one half of the available binding sites on an ELISA well coated with 100 ng of test protein. In general, suitable antibody production is characterized by an antibody titer in the range of from about 100 to about 100,000, and preferably in the range of from about 10,000 to about 10,000,000. Alternatively, and particularly in diagnostic assays, the “titer” should be about three times the background level of binding. For example, to be considered “positive”, reactivity in a test should be at least three times greater than reactivity detected in serum from uninfected individuals. Preferably, the antibody response is protective, i.e. prevents or lessens the development of symptoms of disease in a vaccinated host that is later exposed to Borrelia, compared to an unvaccinated host.

The following Examples are provided to illustrate various embodiments of the invention, but should not be considered as limiting in any way.

Materials and Methods

Recombinant Protein Production

Fragments of the outer surface protein A (OspA) gene were amplified by PCR using high fidelity DNA polymerase (Phusion HF, New England Biolabs), and the amplicons purified by agarose gel electrophoresis and gel extraction. Overhangs were generated by treatment with T4 polymerase to allow ligase-independent annealing to the pET-32 Ek/LIC vector. The annealed vector was transformed into Escherichia coli, and the transformants were selected for ampicillin resistance, and were screened for the presence of the OspA gene fragment by PCR. Plasmids were then extracted from the transformants and the sequence confirmed by DNA sequencing (MWG Biotech). The plasmids were then used to transform E. coli BL21 (DE3) cells for protein production.

To generate recombinant proteins, BL21(DE3) cells were grown at 37° C. to an OD₆₀₀of 0.5, then 1 mM IPTG was added to induce protein expression, and the cells were maintained at 37° C. for an additional 3 hours. The pET-32 Ek/LIC vector encodes a 17.1 kDa N-terminal protein tagging sequence which includes a hexahistidine motif that was used to purify the r-proteins by Ni-NTA nickel affinity chromatography, according to the manufacturer's protocol (Qiagen). The purified proteins were quantified by the bicinchoninic acid assay (Pierce).

Generation of Murine Infection Serum

Borrelia burgdorferi strains B31M1, LDP74, and B331 were grown to late log phase in BSK-H medium (Sigma). The cells were washed with fresh medium, quantified by microscopy, and diluted in BSK-H medium to 10⁴cells per 0.1 mL of medium. Strain C3H/HeJ mice were infected with 10⁴cells by subcutaneous injection between the scapulae, with 5 mice infected with each spirochete strain. The mice were bled at week 6 by tail nick, and infection was confirmed by culture of a 2 mm ear punch biopsy. Serum was prepared from the infected mouse blood samples, and will be referred to hereafter as infection serum.

Mapping of Linear B-Cell Epitopes on OspA

To map linear B-cell epitopes, overlapping recombinant subfragments of OspA were separated by 15% SDS-PAGE and blotted to PVDF. The membranes were blocked with 5% NFDM in PBS-T, and probed with mouse infection sera (1:500 dilution). To assess equality of protein loading, one blot was probed with a mouse monoclonal antibody specific to the hexahistidine motif in the expression tag sequence. The blots were then washed and probed with peroxidase-conjugated goat-anti-mouse IgG antiserum (1:20000; Pierce). The blots were washed, incubated with a chemiluminescent substrate (Supersignal West Pico; Pierce), and exposed to film. When reactive OspA fragments were determined, a series of smaller overlapping subfragments was made to further resolve the location of the linear epitope (FIG. 3).

OspA Sequence Analysis

The full length ospA gene from the Borrelia strains used to produce infection sera were PCR amplified and cloned into the pET-46 Ek/LIC vector as described above, and the DNA sequences were aligned and compared. In addition, the 204 full length OspA sequences from the Lyme spirochetes B. burgdorferi, B. garinii, and B. afzelii that are available in the NCBI databases were aligned and analyzed for polymorphisms in the epitope containing regions. This was done by multisequence alignment using ClustalX, and generation of neighbor joining phylogenetic trees. These analyses were done on the full length OspA gene, as well as on the epitope-containing subfragments. Once the alignments and trees were complete, representative sequences were extracted that demonstrate extant sequence variants, which may correspond to antigenic variants. Analytical tools included ClustalX, Bioedit, and TreeView.

Results:

Location of OspA Linear Epitopes

A western blot-based search for linear B-cell epitopes on OspA revealed several amino acid sequences that were reactive with antibodies generated during murine infection (FIG. 4). The reactive subfragments are located at the N-terminus (amino acids 17-67; noted in a single mouse), within a central single layer beta-sheet (amino acids 94-144, and 119-169; seen in multiple mice), and within a membrane-distal loop (amino acids 194-246 and 220-273; highly reactive in multiple mice). High resolution mapping of the beta-sheet epitope containing region failed to further localize the epitope. The most reactive linear epitope was found in the membrane distal loop, and subsequent high resolution mapping localized it to amino acids 221-240. The pattern of reactivity varied somewhat in intensity between mice, but was observed in sera from mice infected with each of the three test Borrelia strains.

OspA Sequence Analysis

Comparison of sequences among the three Borrelia strains used to infect mice revealed either one or two amino acid differences among them, at amino acid positions 39 (K/N) and 149 (G/E) (FIG. 5). An analysis of available OspA sequences demonstrated several major clades, which split primarily along species lines (B. burgdorferi, B. garinii, and B. afzelii). To better understand the impact of the clades on the development of an epitope-based vaccine, the 221-240 region was analyzed separately, aligned, and a neighbor joining tree created. This also demonstrated the presence of distinct clades of this epitope containing region, again separated primarily by species. There were 2 predominant epitope region sequences within B. burgdorferi, 5 within B. garinii, and 1 within B. afzelii derived OspA sequences. The 221-240 amino acid regions in each of these predominant groups is shown in Table 1. Representative alignments of the other three epitope-containing sequences are shown in Table 2. Using the methods described above, the potential variants of these epitopes can be easily analyzed.

Discussion:

The mapping of novel linear B-cell epitopes in OspA represents a significant advance in the development of second-generation Lyme disease vaccines. Previous research has primarily focused on known conformational epitopes, primarily the epitope recognized by the LA-2 monoclonal antibody. Linear OspA epitopes have been described, however, this study is novel in its use of serum derived from mice infected with clonal Borrelia populations. The similar epitope recognition pattern during infection with three distinct Borrelia burgdorferi strains further supports the relevance of these epitope containing regions during infection. While OspA is expressed during in vitro culture, it is normally downregulated upon exposure to the mammalian environment or during the tick blood meal during the normal enzootic cycle. Because of this regulation, it is likely that the OspA protein was expressed only for a short time during the infection, which may account for the variability in the intensity of responsiveness between mice. This apparent variability may be enhanced by the IgG-specific screening technique, requiring the B-cells of the infected mice to progress to a more mature immune response and undergo immunoglobulin heavy chain class switching.

The large degree of intraspecies conservation at the mapped epitope-containing regions is of particular advantage in development of a peptide or chimeric vaccine. For example, since B. burgdorferi is the only species associated with Lyme disease in North America, the occurrence of only a limited number of phylogenetic clades of OspA is particularly advantageous. At the epitope level, the number of major clades is also limited, with only two major antigenically distinct clades representing the large majority of the 221-240 epitope containing region. Borrelia afzelii, which occurs only in Europe and Asia, is limited to a single clade at this region, and B. garinii has approximately 6 clades, several of which are closely related, though it is not yet known if they are antigenically cross-reactive. It is clear that in order for broad protection to be achieved by a peptide vaccine approach, the use of a single OspA epitope sequence is not possible. For that reason, the development of a multi-epitope chimeric vaccine based on OspA epitope variants or on a combination of epitope variants of OspA and OspC is highly desirable. In addition, a significant advantage to the use of defined epitope containing sequences is the ability to avoid segments of the OspA molecule that have been reported to be associated with development of autoimmune responses. While there is disagreement in the literature as to the incidence of these responses caused by anti-OspA antibodies or anti-OspA immune responses, it is advantageous to avoid those portions of OspA that have been implicated (FIG. 6).

When administered to test mammals, this chimeric polypeptide construct comprising at least one 221-240 epitope containing region, and usually two or more 221-240 epitope containing regions from of different phyletic types, is found to elicit a robust immune response, and to provide protection from the development of Lyme disease.

While the invention has been described in terms of its preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. Accordingly, the present invention should not be limited to the embodiments as described above, but should further include all modifications and equivalents thereof within the spirit and scope of the description provided herein.