Protective immunization with plasmid DNA containing the outer surface lipoprotein A gene of Borrelia burgdorferi is independent of an eukaryotic promoter

Abstract

Plasmid DNA encoding the outer surface lipoprotein A (OspA) of Borrelia burgdorferi under the control of either strong eukaryotic/viral or its own bacterial promoter was injected intramuscularly (m. tibialis anterior) or intradermally into BALB/c and AKR/N mice. OspA-specific antibodies and OspA-reactive T helper 1 cells (Th1) were induced only with those plasmids containing the ospA structural gene including its own regulatory control region immediately upstream. In the absence of the ospA promoter, no or only marginal immune responses to OspA were obtained, even when strong eukaryotic promoter/enhancer elements were present. Together with the finding that the ospA promoter is active in a mouse B-lymphoma line, the data suggest that spirochetes are able to express at least part of their genes in the mammalian environment. Mice previously vaccinated with the relevant ospA plasmid DNA were protected against subsequent experimental challenge with a virulent strain of B. burgdorferi, as measured by the appearance of antibodies to a prominent protective epitope (LA-2) and the failure to re-isolate spirochetes from ear biopsies. In addition, C.B-17 severe-combined immunodeficient mice could be protected against infection by passive transfer of immune sera from ospA plasmid DNA-inoculated normal mice. Protective LA-2-related antibody titers obtained after repeated immunization persisted for 200 days and longer. This simple procedure of immunization using plasmid DNA consisting of a prokaryotic gene under the control of its own promoter holds great promise for the development of alternative subunit vaccines against bacterial infections, including Lyme disease. In addition, the availability of this novel prokaryotic promoter element now allows the study of the basis for the differential expression of bacterial genes in prokaryotic and eukaryotic environments.

Eukaryotic expression plasmid transfer from the intracellular bacteriumListeria monocytogenesto host cells

“…Antibiotics treatment of plasmid-harbouring bacterial strains during infection could lead to transfer of bacterial DNA to the host cell nucleus under natural conditions. This could lead to expression of bacterial genes, as bacterial promoters have been shown to be functional in eukaryotic cells (Simon et al, 1996). Indeed, the exchange of genetic information between bacteria and somatic cells is a hitherto poorly studied area that clearly deserves further attention.…”

Borrelia burgdorferi-Induced Inflammation Facilitates Spirochete Adaptation and Variable Major Protein-Like Sequence Locus Recombination

“…Outer surface protein A, which is predominantly expressed in the unfed tick, facilitates B. burgdorferi-vector adherence (54), and decorin-binding protein A and BBK32, which are prominently expressed during mammalian infection, bind to host decorin and fibronectin, respectively (55)(56)(57)(58). During infection on the mammalian host, B. burgdorferi are exposed to a humoral and cellular immune response, particularly Ab production, that is important in immunity (33,59,60), and both preferential gene expression and vls recombination are likely to be mechanisms by which B. burgdorferi attempt to evade host defenses. Herein we show that B. burgdorferi use the host cytokine response to promote vls recombination, and that in the absence of these signals, B. burgdorferi survival is impaired.…”

A fusion product of the complete Borrelia burgdorferi outer surface protein A (OspA) and the hepatitis B virus capsid protein is highly immunogenic and induces protective immunity similar to that seen with an effective lipidated OspA vaccine formula

“…The IgG isotypes of OspA-specific Ab were measured in a solidphase ELISA as described [47], with the modification that plates were pre-coated with rLipOspA (1 mg/ml) instead of spirochete lysate. Ab with the same specificity as the mAb LA-2, which recognizes the main protective epitope of OspA [1], were measured by a competitive ELISA, as described [48]. Western blot analysis using whole-cell lysate of B. burgdorferi strain ZS7 (2.5Â10 6 cell equivalents/lane) or recombinant proteins (250 ng/lane) as antigen preparation was done as described [48].…”