FIG 2.
Mice exhibit a strong differentiated immune response to vaccination with recombinant monomeric and dimeric OspC forms and subsequent Borrelia burgdorferi B31 challenge. (A) ELISA assessment of pan-IgG anti-OspC response to immunization with alum only (white bars), M-OspC31 (gray bars), and D-OspCB31 (black bars). Animals were injected with 1 μg of antigen on days 0, 14, 28, and 42 and were needle inoculated with 104 B. burgdorferi B31 bacteria on day 67; day 81 thus represents a 14-day postchallenge time point. Each group consisted of 6 animals. Sera were tested at a 1:4,000 dilution against dimeric OspC. Mean ± standard error (SE) absorbance is indicated. (B) Immunoblot analysis of murine sera. Sera from immunized and challenged mice were tested for reactivity to various Borrelia antigens using anti-Borrelia Euroline-WB. Immunization was with alum only (lanes 1 and 2), with D-OspCB31 and alum (lanes 3 and 4), and with M-OspCB31 and alum (lanes 5 and 6). Odd lanes (pre) were incubated with sera collected after immunization but prior to Borrelia challenge. Sera incubated in even lanes (post) were collected on day 14 postchallenge. Sera were tested in 1:500 dilutions. Immunization with both forms of OspC resulted in strong prechallenge reactivity with OspC (lanes 3 and 5); nonspecific reactivity to P41 (flagellin) was also observed. After B. burgdorferi challenge, animals immunized with the alum only (strip 2) and M-OspCB31 (strip 6) groups exhibited antibody reactivity to additional B. burgdorferi proteins (VlsE, p39, OspC, and p18) indicative of active infection.