Specificity of Phlebotomus papatasi and Phlebotomus tobbi recombinant salivary proteins developed as serological surveillance tool

Background Sand flies are vectors of various pathogens, primarily Leishmania and phleboviruses. The effectiveness of disease control strategies can be assessed using serological tests that measures antibodies against sand fly saliva as a marker of host exposure and a proxy biomarker of sand fly-borne pathogens transmission. Recently, we proposed novel recombinant salivary proteins to evaluate exposure of dogs to Phlebotomus tobbi and P. papatasi . The aim of this study was to test vector and host specificity of these recombinant proteins. Methods Recombinant salivary proteins of P. papatasi (PAP-rSP32, PAP-rSP36, and PAP-rSP42) and P. tobbi (TOB-rSP10, TOB-rSP38, TOB-rSP56, TOB-rSP60) were tested in an enzyme-linked immunosorbent assay (ELISA) using sera from dogs and mice experimentally bitten by a single sand fly species as well as from naturally exposed dogs. Results Among the three P. papatasi recombinant proteins tested, rSP36 apyrase exhibited the highest vector species-specificity. It did not cross-react with antibodies from dogs or mice experimentally bitten by P. perniciosus , P. tobbi , P. sergenti , Sergentomyia schwetzi , Lutzomyia longipalpis , or two mosquito species ( Culex pipiens molestus and C. quinquefasciatus ), closely followed by rSP42 yellow-related protein. In contrast, PAP-rSP32 showed host-related species specificity, cross-reacting with murine anti- P. perniciosus antibodies, but not with canine ones. Among the four P. tobbi recombinants, rSP38 yellow-related protein was the only vector subgenus-specific antigen across all the murine sera tested, followed by rSP10 apyrase and rSP60 D7-related protein, which cross-reacted with anti- P. papatasi IgG. The other D7-related protein, rSP56, lacked sand fly-specificity as it cross-reacted with antibodies against Culex saliva. Conclusions ELISA assays based on PAP-rSP36, PAP-rSP42, and TOB-rSP38 are recommended for large-scale field studies as they exhibited the highest species-specificity. These assays can provide epidemiologically relevant data that complement other surveillance and leishmaniasis control tools.