Dogs vaccinated with gentamicin‐attenuated Leishmania infantum or infected with wild‐type parasite can be distinguished by Western blotting

Abstract

An attenuated line of Leishmania infantum (the H-line), developed through exposure to gentamicin, has been shown to protect dogs against canine visceral leishmaniasis. A specific diagnostic test to differentiate dogs vaccinated with the attenuated line from dogs infected with L.infantum wild-type (L.infantum WT) could be a valuable tool in evaluating the effectiveness of canine vaccination. In this study, 28 healthy dogs were allocated into four groups. In Group I and Group II (eight dogs per group), dogs were immunized subcutaneously (s.c.) with L.infantum H-line, and the dogs of Group II challenged s.c. with L.infantum WT, at 2months post-immunization. In Group III, eight animals were challenged s.c. with L.infantum WT, and four dogs of Group IV were injected s.c. with PBS. We found that sera from vaccinated dogs recognize a 21kDa antigen of promastigotes of L.infantum H-line but not of L.infantum WT, whereas sera from unvaccinated dogs challenged with L.infantum WT, recognized a 21kDa antigen of promastigotes of L.infantum WT but not of L.infantum H-line. Sera from dogs challenged with L.infantum WT with prior vaccination with L.infantum H-line, recognized a 21kDa antigen of both L.infantum WT and L.infantum H-line. These results suggest that the Western blot analysis of antibodies against 21kDa antigens of L.infantum H-line and WT may be a useful technique for distinguishing between dogs vaccinated with L.infantum H-line and dogs naturally infected with L.infantum WT.