Elimination of Borrelia burgdorferi from vector ticks feeding on OspA-immunized mice.

Abstract

Although recombinant outer surface protein (6), as well as the immune-deficient scid (7,8). Indeed, we previously showed that mice actively immunized with a recombinant OspA were protected from infection and disease when challenged with an intradermal injection of three virulent B. burgdorferi isolates (6). The effectiveness of immunization against the natural mode of transmission of this tick-borne infection, however, was not reported. Tick-mediated transmission may differ from syringe transmission in several crucial ways. Antiinflammatory properties of the saliva of ticks may enhance pathogen transmission (9, 10) as occurs in the case of phlebotomine sandfly saliva and infection by Leishmania braziliensis (11). In addition, vector-borne pathogens may differ from those propagated in vitro in terms of immunogenicity as well as other transmission-related properties. A realistic challenge of a vector-borne agent of disease seems essential in evaluating a vaccine. We now demonstrate that active immunization with recombinant OspA protects mice against tick-borne spirochetal infection by destroying B. burgdorferi in ticks feeding on vaccinated mice. MATERIALS AND METHODSMice. Three-week-old, random sex, virus-antibody-free C3H/HeJ (C3H) mice were obtained from The Jackson Laboratory. They were shipped in filter-equipped crates and housed in micro-isolator cages. Food and water were provided ad libitum. Mice were killed with carbon dioxide gas. Outbred CD-1 mice were obtained from Charles River Breeding Laboratories.B. burgdorferi. Low in vitro passage isolates of B. burgdorferi N40, with previously proven infectivity and pathogenicity in C3H mice, were utilized (12). The spirochetes were grown to logarithmic phase in modified BarbourStoenner-Kelly (BSK II) medium and counted in a hemocytometer under darkfield microscopy.Recombinant OspA Fusion Protein. Recombinant OspA was expressed and purified as a fusion protein with glutathione transferase (GT) (6). In brief, the gene for OspA from N40 was ligated into plasmid pGEX-2T (Pharmacia) in frame with the GT gene. The recombinant plasmid was used to transform Escherichia coli strain DH5a. Production of the recombinant fusion protein was induced with isopropyl -Dthiogalactopyranoside, and the protein was purified from the cell extract by affinity chromatography on a glutathioneSepharose 4B column (Pharmacia) (6). Infection of Tiks with B. bwgdorfer. Ixodes dammini tickswere from a laboratory colony (maintained at the Harvard School of Public Health) derived from an Ipswich, Massachusetts, population, and had been determined to be free of inherited spirochetal infection. Outbred CD-1 mice were infected by means of intradermal inoculation of 103 lowpassage N40 spirochetes 3 weeks prior to serving as hosts. Ticks were infected with B. burgdorferi by allowing larvae to feed to repletion on these mice. Upon repletion, engorged larvae were collected, pooled in groups of 100-200, and permitted to molt to the nymphal stage at 21'C and 95% relative humidity. Prevalence of...

Mode of Inoculation of the Lyme Disease Agent Borrelia burgdorferi Influences Infection and Immune Responses in Inbred Strains of Mice

“…The finding that the transmission of B. burgdorferi organisms to ticks correlated inversely with the presence of antibodies to OspA and OspB in mice therefore suggests that these antibodies are responsible for the elimination of spirochetes and consequently for the reduction in the rate of transmission. This assumption is also supported by previous studies showing that OspA-and OspB-specific antibodies protect SCID [4,5] and C3H/HeJ mice [6,7] against infection and development of arthritis after experimental and tick-mediated infection with B. burgdorferi, when these antibodies are present at the time of inoculation [13,14].…”

An ecological approach to preventing human infection: Vaccinating wild mouse reservoirs intervenes in the Lyme disease cycle

“…We immunized mice with recombinant B. burgdorferi outer surface protein A (OspA) (11,12), which is the basis of a currently available vaccine for dogs (13). B. burgdorferi commonly expresses OspA in tick, but not mouse hosts, and consequently, OspAvaccinated mice, even infected ones, develop antibodies that kill B. burgdorferi in the tick while it feeds (12,14,15).…”

A Bactericidal Monoclonal Antibody Elicits a Change in Its Antigen, OspB of Borrelia burgdorferi, That Can Be Detected by Limited Proteolysis

“…The vaccinogen is a plasmid-encoded lipoprotein, outer surface protein A (OspA) 3 (3) that is expressed in cultured B. burgdorferi (6 -8) as well as in the unfed ticks (9 -12). Induced Abs to OspA in the vertebrate host can kill spirochetes in the midgut of ticks (11). OspB is another lipoprotein that is cotranscribed (by a two-gene operon in the 49-kb linear plasmid) with OspA and is also expressed in the tick and in culture.…”