Maternal antibodies provide strain-specific protection against infection with the Lyme disease pathogen in a wild rodent

The vertebrate immune system can produce antibodies that protect the host against pathogens. Females can transmit antibodies to their offspring, which provide short-term protection against infection. The tick-borne bacterium Borrelia afzelii causes Lyme disease in Europe and consists of multiple strains that cycle between the tick vector ( Ixodes ricinus ) and vertebrate hosts such as the bank vole ( Myodes glareolus ). We used a controlled experiment to show that infected female bank voles transmit protective antibodies to their offspring that are specific for the strain of B. afzelii . To test the specificity of protection, the offspring were challenged with either the same strain to which the mothers had been exposed or a different strain. The maternal antibodies protected the offspring against the same strain, but not against the different strain. The offspring from the uninfected control mothers were equally susceptible to both strains. Our study shows that maternal antibodies provide strong but highly strain-specific protection against B. afzelii in an important rodent reservoir host. The transmission of maternal antibodies may have important consequences for the epidemiology of multiple-strain pathogens in nature. Author Summary Many pathogens that cause infectious disease consist of multiple strains. In vertebrate hosts, the immune system can generate antibodies that are highly specific for different pathogen strains. Mothers can transmit these antibodies to their offspring and thereby protect them from infectious disease. To date, few studies have investigated whether this transgenerational transfer of protective antibodies is important for pathogens that cycle in wild animal populations. The tick-borne spirochete bacterium Borrelia afzelii causes Lyme disease in Europe and cycles between Ixodes ticks and wild rodent hosts, such as the bank vole ( Myodes glareolus ). The purpose of our study was to test whether female bank voles infected with B. afzelii transmit antibodies to their offspring that protect them from an infected tick bite. Our study found that infected mothers do transmit antibodies, but the offspring were only protected against the strain of B. afzelii to which their mothers had been exposed and not to a different strain (i.e. protection was highly strain-specific). The broader implications of our study is that the transfer of protective antibodies between generations in the vertebrate host population could be important for organizing the community of pathogen strains that circulate in nature.