High levels of anti-Leishmania IgG3 and low CD4(+) T cells count were associated with relapses in visceral leishmaniasis

BACKGROUND: Visceral leishmaniasis (VL) is severe and potentially fatal. Brazil is one of the countries with the greatest endemicity for the disease in the world. The reduction of CD4(+) T lymphocytes, B cells activation and high levels of inflammatory cytokines (IL-6/IL-8/TNF/IL-1β), plasma LPS, soluble CD14, anti-Leishmania IgG3 and low leptin levels are involved in the immunopathogenesis of VL, most associated with severe VL. Despite relapses occurring in about 4–5% of patients with VL not associated with HIV infection, the factors underlying relapses are little known. Our aim was to identify clinical, laboratory and immunological parameters that may be associated with recurrences in VL. METHODS: Fifteen VL patients recruited from Hospital Eduardo de Menezes (BH-MG) were grouped into relapsing (R-VL, n = 5) and non-relapsing (NR-VL, n = 10) and evaluated during active disease, immediately after treatment (post-treatment) and 6 months post-treatment (6mpt). Clinical and laboratory data obtained from medical records were correlated with CD4(+) and CD8(+) T cell counts and anti-Leishmania Igs and IL-6 plasma levels and compared to those parameters of ten healthy controls. RESULTS: During the active phase of VL, despite similarity in the clinical symptoms, the rates of thrombocytopenia, elevated transaminases (AST and ALT) and hyperbilirubinemia were higher in the NR-VL group compared to R-VL (p < 0.05), a profile reversed during the post-treatment phase. All patients had low CD4(+) T counts in active phase, however, NR-VL patients had a higher gain of this cell type than R-VL in the post-treatment (p < 0.05). There was a significant reduction in IgG3 levels during the follow-up in the NR-VL group compared to the R-VL, especially at 6mpt (p < 0.05). In addition, IgG3 levels were negatively correlated with CD4(+) T counts in the R-VL group (r = − 0.52). Elevated levels of IL-6 were observed in active VL and correlated with clinical markers of severity. CONCLUSIONS: During active phase of VL, the NR-VL patients presented more severe laboratorial abnormalities compared to R-VL, probably because the latter had already received previous treatment. On the other hand, R-VL exhibited greater impairment of immune reconstitution and a high degree of B lymphocyte activation, which must be a factor that favored relapses. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12879-021-06051-5.