Decorin-binding protein A (DbpA) of Borrelia burgdorferi is not protective when immunized mice are challenged via tick infestation and correlates with the lack of DbpA expression by B. burgdorferi in ticks - PubMed (original) (raw)

Decorin-binding protein A (DbpA) of Borrelia burgdorferi is not protective when immunized mice are challenged via tick infestation and correlates with the lack of DbpA expression by B. burgdorferi in ticks

K E Hagman et al. Infect Immun. 2000 Aug.

Abstract

Previous studies showed that decorin-binding protein A (DbpA) of Borrelia burgdorferi was a protective immunogen in the murine model of Lyme borreliosis when mice were challenged (needle inoculated) intradermally with in vitro-cultivated spirochetes. In the present study, DbpA-immunized C3H/HeJ mice were not protected from infection when infested with Ixodes scapularis nymphs harboring virulent B. burgdorferi 297. This lack of protection correlated with the failure to detect DbpA on B. burgdorferi in ticks, suggesting that DbpA is not available as a target for bactericidal antibodies in serum when B. burgdorferi-infected ticks take their blood meal from an immunized host. The failure of DbpA immunization to protect tick-challenged mice contradicts the results of earlier needle inoculation vaccination experiments and suggests that DbpA may not be suitable as a Lyme disease vaccine.

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Figures

FIG. 1

SDS-PAGE and immunoblot analysis of DbpA expression in B. burgdorferi 297 cultivated at either 23°C (2 × 107 spirochetes) or 34°C (107 spirochetes). Polyclonal rat anti-DbpA antiserum and monoclonal antibody 8H3-33, directed against FlaB, were used as the respective antibody probes. Numbers at the left denote protein apparent molecular weights (in thousands).

FIG. 2

(A to F) IFAs of borreliae harvested from the midguts of either flat or 4-day-fed I. scapularis nymphs harboring B. burgdorferi 297. Nymph midgut contents were expressed onto microscope slides, dried, fixed with acetone, and then probed with rat antiserum directed against either whole-cell lysates of B. burgdorferi 297 (A and B), OspC (C and D), or DbpA (E to G). (G) Smear of B. burgdorferi 297 cultivated in vitro at 34°C and probed with anti-DbpA antiserum. The secondary antibody probe was fluorescein isothiocyanate-conjugated goat anti-rat immunoglobulin G. Spirochetes were observed under a 40× objective; data were recorded via a charge-coupled device camera mounted on an Olympus dark-field and fluorescence microscope. Panels shown are representative of at least 30 microscope fields examined in each of two separate experiments.

FIG. 3

IFAs of borreliae harvested from the salivary glands of _B. burgdorferi_-infected I. scapularis nymphs. Nymphs were allowed to feed on normal C3H/HeJ mice for 48 to 72 h, at which time the ticks were removed. Tick salivary glands were then dissected out (with caution to exclude midgut contents) and homogenized (by repeated gentle pipeting) in 10-μl aliquots of phosphate-buffered saline. The samples were then divided into two equal portions on microscope slides, dried, fixed with acetone, and probed with rat antiserum directed against either a whole-cell lysate of B. burgdorferi 297 (A) or DbpA (B). All other procedures were as described for Fig. 2. The panels shown are representative of at least 30 microscope fields examined in each of five separate salivary gland smears probed with each antiserum.

FIG. 4

Appearance of antibodies against DbpA during the course of tick-transmitted B. burgdorferi infection of C3H/HeJ mice. Groups of 10 mice were infested with I. scapularis nymphs harboring B. burgdorferi 297 (27); at various intervals postinfestation (denoted in weeks [wk] at the tops of the immunoblot strips), blood from mice within each group was collected and sera were then obtained and pooled. Recombinant DbpA was subjected to SDS-PAGE as previously described (14). Nitrocellulose strips were immunoblotted with 1:500 dilutions of the respective pooled sera. The lane at the right is a strip probed with rat antiserum against DbpA (α-DbpA). Numbers at the left denote protein apparent molecular weights (in thousands).

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Decorin-binding protein A (DbpA) of Borrelia burgdorferi is not protective when immunized mice are challenged via tick infestation and correlates with the lack of DbpA expression by B. burgdorferi in ticks - PubMed (original) (raw)