In the current retrospective study, Leishmania infantum-specific
IgG,
IgA and
IgM levels were determined by ELISA in 106 untreated dogs with clinically-patent
leishmaniasis (Sx) and in 171 clinically healthy dogs (Asx) from Spain to investigate the relationship between these
Ig isotypes and clinical status. In addition, we studied if different Leishmania-specific humoral pattern exists between Asx dogs with and without cellular mediated immunity (CMI). Fifty-six dogs were assessed by means of lymphoproliferation assay (LPA),
interferon production (IFN) and
leishmanin skin test (LST), 71 dogs by means of both LPA and IFN and 44 only by LST. Both Sx and Asx dogs produced Leishmania-specific
IgG,
IgA and
IgM antibodies, however the levels and proportion of positive dogs for each
Ig isotype were significantly higher in Sx than in Asx ones (P<0.001). Analysis of immunological profiles determined for each cellular technique (positive and negative cellular response for each technique combined with positive or negative specific humoral response) showed that Asx dogs constituted a high heterogeneous group. No correlations were observed between CMI tests and specific
IgG or
IgM levels. However, a significant inverse correlation was demonstrated between specific
IgA levels and LPA response (Spearman's r=-0.220; P=0.035). In general, the low correlation detected between CMI tests and isotype levels might indicate that the immune response is not strongly polarized in the majority of Asx dogs. Additionally, this study suggests that dogs developing T-cell response are probably able to avoid the dissemination of the parasite at least to mucosal surfaces and, as a consequence, to produce low or background specific
IgA levels. Further studies are needed to investigate the relationship between specific
IgA and parasite load, especially at mucosal site.