Adaptive immune defense prevents Bartonella persistence upon trans-placental transmission

Abstract

Vertical transmission ofBartonellainfection has been reported for several mammalian species including mice and humans. Accordingly, it is commonly held that acquired immunological tolerance contributes critically to the high prevalence of Bartonellae in wild-ranging rodent populations. Here we studied an experimental model ofBartonellainfection in mice to assess the impact of maternal and newborn immune defense on vertical transmission and bacterial persistence in the offspring, respectively. Congenital infection was frequently observed in B cell-deficient mothers but not in immunocompetent dams, which correlated with a rapid onset of an antibacterial antibody response in infected WT animals. Intriguingly, B cell-deficient offspring with congenital infection exhibited long-term bacteremia whereas B cell-sufficient offspring cleared bacteremia within a few weeks after birth. Clearance of congenitalBartonellainfection resulted in immunity against bacterial rechallenge, with the animals mountingBartonella-neutralizing antibody responses of normal magnitude. These observations reveal a key role for humoral immune defense by the mother and offspring in preventing and eliminating vertical transmission. Moreover, congenitalBartonellainfection does not induce humoral immune tolerance but results in anti-bacterial immunity, questioning the contribution of neonatal tolerance toBartonellaprevalence in wild-ranging rodents.