Infection with multiple strains of the Lyme disease bacterium in female mice can affect the strain-specific maternal antibody response in their offspring

BACKGROUND: The tick-borne spirochete Borrelia burgdorferi causes Lyme borreliosis in North America. In nature, rodent reservoir hosts are often infected with multiple strains of B. burgdorferi, which induce strain-specific antibody responses that are mediated by outer surface protein C (OspC). During pregnancy and lactation, female rodents infected with B. burgdorferi will transfer a finite amount of strain-specific maternal antibodies to their offspring. The purpose of our study was to investigate whether infection with multiple strains of B. burgdorferi in female mice reduces the per strain level of maternal anti-OspC IgG antibodies in their offspring. METHODS: The study used two B. burgdorferi strains, A and I, which carried ospC types A and I, respectively. Female C3H/HeJ mice were assigned to four different maternal infection treatments: (1) infected with strain A alone, (2) infected with strain I alone, (3) co-infected with both strains, and (4) uninfected. Female mice (dams) from all treatment groups were mated with uninfected males and allowed to produce offspring. The maternal anti-OspC IgG response was determined in the dams at 4 weeks post-infection and in the offspring at ≤2, 4, and 9 weeks of age. RESULTS: Infected dams transferred maternal anti-B. burgdorferi IgG antibodies to their offspring. The maternal anti-OspC IgG antibody titers waned over time and were specific for the OspC antigen of the infecting strain with limited cross-reactivity between strains. The absorbance of the maternal anti-OspC IgG antibodies in the offspring aged ≤2, 4, and 9 weeks were 83.6%, 46.9%, and 16.2% of the absorbance in the dams at 4 weeks post-infection, respectively. Compared to dams infected with single strains, co-infection in dams reduced the maternal anti-OspC IgG response in the offspring by 22.2% for strain A (p = 0.001) and 4.5% for strain I (p = 0.538). Our study suggests that co-infection with multiple strains can reduce the quantity and/or quality of maternal anti-OspC IgG antibodies per B. burgdorferi strain that are transferred from dams to their offspring. A future study will investigate whether co-infection in the dams reduces the protective efficacy of the maternal antibody response in the offspring against an infectious tick bite challenge.