Jacquet, Maxime

2017, Jacquet, Maxime, Margos, G., Fingerle, V., Voordouw, Maarten

2016-3, Jacquet, Maxime, Durand, Jonas, Rais, Olivier, Voordouw, Maarten

Vector-borne pathogens use a diversity of strategies to evade the vertebrate immune system. Co-feeding transmission is a potential immune evasion strategy because the vector-borne pathogen minimizes the time spent in the vertebrate host. We tested whether the Lyme disease pathogen, Borrelia afzelii, can use co-feeding transmission to escape the acquired immune response in the vertebrate host. We induced a strain-specific, protective antibody response by immunizing mice with one of two variants of OspC (A3 and A10), the highly variable outer surface protein C of Borrelia pathogens. Immunized mice were challenged via tick bite with B.afzelii strains A3 or A10 and infested with larval ticks at days 2 and 34 post-infection to measure co-feeding and systemic transmission respectively. Antibodies against a particular OspC variant significantly reduced co-feeding transmission of the targeted (homologous) strain but not the non-targeted (heterologous) strain. Cross-immunity between OspC antigens had no effect in co-feeding ticks but reduced the spirochaete load twofold in ticks infected via systemic transmission. In summary, OspC-specific antibodies reduced co-feeding transmission of a homologous but not a heterologous strain of B.afzelii. Co-feeding transmission allowed B.afzelii to evade the negative consequences of cross-immunity on the tick spirochaete load.

2015-12, Jacquet, Maxime, Durand, Jonas, Rais, Olivier, Voordouw, Maarten

Cross-reactive acquired immunity in the vertebrate host induces indirect competition between strains of a given pathogen species and is critical for understanding the ecology of mixed infections. In vector-borne diseases, cross-reactive antibodies can reduce pathogen transmission at the vector-to-host and the host-to-vector lifecycle transition. The highly polymorphic, immunodominant, outer surface protein C (OspC) of the tick-borne spirochete bacterium Borrelia afzelii induces a strong antibody response in the vertebrate host. To test how cross-immunity in the vertebrate host influences tick-to-host and host-to-tick transmission, mice were immunized with one of two strain-specific recombinant OspC proteins (A3, A10), challenged via tick bite with one of the two B. afzelii ospC strains (A3, A10), and infested with xenodiagnostic ticks. Immunization with a given rOspC antigen protected mice against homologous strains carrying the same major ospC group allele but provided little or no cross-protection against heterologous strains carrying a different major ospC group allele. There were cross-immunity effects on the tick spirochete load but not on the probability of host-to-tick transmission. The spirochete load in ticks that had fed on mice with cross-immune experience was reduced by a factor of two compared to ticks that had fed on naive control mice. In addition, strain-specific differences in mouse spirochete load, host-to-tick transmission, tick spirochete load, and the OspC-specific IgG response revealed the mechanisms that determine variation in transmission success between strains of B. afzelii. This study shows that cross-immunity in infected vertebrate hosts can reduce pathogen load in the arthropod vector with potential consequences for vector-to-host pathogen transmission. (C) 2015 Elsevier B.V. All rights reserved.