The immune response and PBMC subsets in canine visceral leishmaniasis before, and after, chemotherapy

Peripheral blood mononuclear cell subsets, in vitro lymphoproliferative res ponse to leishmanial antigen, and Leishmania-specific serum antibody levels were examined in 11 dogs, naturally infected with L. infantum, and 9 healt hy control dogs. A decrease in the percentage of CD4+ T-cells and an increa se in the proportion of gamma delta T-cells and sIgG+ B-cells were observed during canine visceral leishmaniasis (CVL). These changes may be responsib le for the marked humoral response and the absence of in vitro lymphoprolif eration to mitogen and specific parasite antigens. This possibility was sup ported by the analysis of these subsets after treatment with amphotericin B , One month after therapy, a significant increase in the percentage of CD4 T-cells and a decrease of gamma delta T-cells and sIgG+ B-cells were obser ved. At the same time, the lymphocyte blastogenesis assay with leishmanial antigen was positive and the levels of specific antibodies to Leishmania we re significantly lower than before the treatment, Five months after therapy , lymphocyte proliferative response to LSA disappeared, antibody and lympho cyte subsets levels returned to those observed during CVL, Therapeutic fail ure in CVL is associated with the inability of antileishmanial drugs to com pletely revert the profound immunodepression induced by the infection and p revent relapse. (C) 1999 Elsevier Science B.V. All rights reserved.