Plasmid DNA and protein vaccination of mice to the outer surface protein A of Borrelia burgdorferi leads to induction of T helper cells with specificity for a major epitope and augmentation of protective IgG antibodies in vivo

Abstract

Plasmid DNA-based vaccination is an efficient way to evoke various forms of protective immunity in laboratory animals. Our previous experiments have shown that mice immunized with either plasmid DNA encoding the outer surface lipoprotein A (pOspA) of Borrelia burgdorferi or the respective lipoprotein (Lip-OspA) produce protective antibodies against subsequent challenge with virulent spirochetes. In the present study, we compared the specificity and function of T cells generated in AKR/N mice previously immunized to either pOspA or Lip-OspA. T cell populations derived by either of the two protocols consistently responded by proliferation in vitro to one (residues 186-203; B4) out of a panel of 27 overlapping 20-mer peptides spanning the entire OspA molecule of strain ZS7. B4 was shown to express allele-specific ligand motifs for I-Ek. Most of the other peptides produced variable and much less pronounced or marginal proliferative T cell responses. T cells reactive to B4 as well as to some minor epitopes were CD4+CD8- T cells which produced IFN-gamma but no detectable IL-4 upon antigen stimulation in vitro. Priming of AKR/N mice with B4 but not with inactive peptides of OspA led to an enhanced production of IgG antibodies, mainly of the IgG1 isotype, including those to a prominent protective epitope (LA-2) upon subsequent challenge with Lip-OspA or intact spirochetes. The data demonstrate that both plasmid DNA and protein immunization with OspA results in T cell responses with specificity for a dominant OspA epitope and suggest that priming of mice with immunodominant peptides accelerates the appearance of protective antibodies in vivo. The identification of T helper cell epitopes relevant for the induction of protective antibodies will also facilitate the design of more potent vaccines against Lyme disease.

DNA immunization confers systemic, but not mucosal, protection against enteroinvasive bacteria

“…Direct gene transfer into mouse muscle or skin leads to expression of an immunogenic protein encoded by the injected plasmid and has created a novel technology of immunization designated as nucleic acid or DNA vaccination [1,2]. In experimental animal models injection of a plasmid coding for a single antigenic protein confers protection against viral, protozoal, and more recently, intracellular bacterial infections including influenza virus [3], Plasmodium yoelii [4], Mycobacterium tuberculosis [5,6] and Borrelia burgdorferi [7,8]. Whether DNA vaccination protects against enteropathogenic extracellular bacteria, however, has not yet been investigated.…”

DNA Vaccines Expressing a Fusion Product of Outer Surface Proteins A and C fromBorrelia burgdorferiInduce Protective Antibodies Suitable for Prophylaxis but Not for Resolution of Lyme Disease

“…In this line, we and others have shown that vaccination with ospA-containing plasmids elicited Ab responses able to prevent subsequent infection (12,20,35). Similarly, immunization of mice with OspC-encoding DNA vaccines resulted in the production of specific Ab in mice, however, with unknown protective potential (28).…”

Cellular and molecular aspects of Lyme arthritis

“…Hence, T cells seem to be responsible for development of destructive arthritis as opposed to conferring protection from disease [31]. Attempts to map dominant T-helper-cell epitopes of OspA in humans with a variety of HLA.DR alleles [28], as well as in H-2 k mice [32,33], have been reported. Although several T cell epitopes of OspA have been identified [28], the number of patients tested to date is too small to draw conclusions regarding dominant epitopes for particular class II MHC alleles.…”

“…Although several T cell epitopes of OspA have been identified [28], the number of patients tested to date is too small to draw conclusions regarding dominant epitopes for particular class II MHC alleles. In the H-2 k mouse, a single, C-terminal peptide is able to prime the animal for a protective anti-OspA antibody response [32,33]. Despite intensive investigations by many research groups, we still do not understand the cellular and molecular mechanisms which lead to antibiotic treatment-resistant Lyme arthritis in certain individuals.…”