IgM-antibody responses of chickens to salivary antigens of Triatoma infestans as early biomarkers for low-level infestation of triatomines

The recombinant form of a highly immunogenic 14.6 kDa protein in Triatoma infestans saliva (rTiSP14.6) is a potential epidemiological marker for the detection of triatomine bug populations using IgG responses in peridomestic chickens. However, the persistence of the IgG response prevents it being of value for several months in areas where triatomine control programmes have been implemented. In this investigation, IgM-antibody reactions to crude salivary antigens or rTiSP14.6 decayed rapidly after exposure of chickens and were measurable for only 18 days after a single challenge with T. infestans. In serial exposure experiments, chickens from low and high exposure groups showed no significant differences in anti-saliva and anti-rTiSP14.6 IgM-antibody titres. Highly immunogenic salivary antigens of 12 and 14 kDa were recognised by all chicken sera. Sera from peridomestic chickens from sites of known T. infestans infestation in Bolivia also recognised these two antigens and no differences in the IgM responses of sera from chickens from low and high infestation households were detected. IgM responses were specific to infested households and could not be detected in sera from non-infested households. Cross-reactivity studies showed that at least four other triatomine species share the 14.6 kDa salivary antigen. No IgM responses were detected against salivary proteins of mosquitoes and sandflies. Thus, we believe that rTiSP14.6 represents a promising epidemiological marker for the detection of low numbers of triatomines in peridomestic habitats, and the comparison of IgM and IgG responses can be used to detect re-infestation soon after insecticide-based control programmes.

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