Natural antibodies induced by host gut microbiota modulate tick microbiota, inhibiting Borrelia colonization.

The gut microbiome undergoes natural selection pressure, likely because it can affect infection resistance by stimulating natural antibody (NAb) production, notably against the glycan Galα1-3Galβ1-4GlcNAc-R (α-Gal). In our study, we explored whether particular glycans, such as α-Gal, from specific host microbiota components could trigger NAbs that, once ingested by Ixodes ricinus ticks during the blood meal, are capable of cross-reacting with bacterial strains in the tick microbiota that share these glycans. Such interactions might alter the tick microbiota and reduce Borrelia afzelii colonization in ticks. When mice were orally administered various Escherichia coli strains, it triggered the stimulation of NAbs and resulted in strain-specific alterations in the tick microbiota. These changes effectively decreased Borrelia colonization in the tick vector. Additionally, vaccination with the glycan α-Gal induced notable shifts in the tick microbiota and similarly reduced Borrelia colonization. Reduced Borrelia colonization was associated with shifts in bacterial diversity, abundance, and microbial network properties. The study provides evidence that natural mechanisms, such as the production of NAb in response to the host gut microbiome, can modulate the microbiota of disease vectors and reduce pathogen colonization within the vector. These findings offer new insights into potential strategies for reducing the transmission of vector-borne diseases through modulation of the host gut microbiome.