One-year follow-up of anti-Leishmania antibody concentrations in serum and saliva from experimentally infected dogs

Abstract

The quantification of anti-Leishmania antibodies in serum and saliva by a time-resolved immunofluorometric assay is useful for the diagnosis and treatment monitoring of dogs with clinical leishmaniasis. We compared the kinetics of anti-Leishmania IgG2 and IgA antibodies in serum and saliva from 11 Beagle dogs experimentally infected with Leishmania infantum. Most dogs showed detectable concentrations of anti-Leishmania IgG2 earlier in serum (between 3 and 4 months p.i.) than in saliva (between 4 and 6 months p.i.). Overall, a high correlation between concentrations of anti-Leishmania IgG2 in serum and saliva (r = 0.853; P < 0.0001) was observed. The quantification of anti-Leishmania IgA showed less diagnostic value than IgG2, since detectable amounts of IgA were not observed in the saliva of four dogs and in the serum of one dog. In addition, a very low correlation between anti-Leishmania IgA in serum and saliva (r = 0.289; P < 0.001) was observed. Our results indicate that the antibodies against L. infantum in saliva appear approximately 1 month later than in serum, and suggest that there is a threshold for the passing of immunoglobulins from serum to saliva in dogs. These facts should be taken into consideration for a proper interpretation of saliva assays for quantification of antibodies.