HIV-Leishmania co-infections in Italy: serological data as an indication of the sequence of acquisition of the two infections

Twenty-two sera from visceral leishmaniasis (VL) patients with human immunodeficiency virus (HIV) infection (50% with the acquired immune deficiency syndrome) were examined for anti-Leishmania immunoglobulin G (IgG) antibodies and compared with 35 sera from VL patients without HIV (controls). Significant titres of specific IgG were found in 81.8% of co-infections. However, while control sera showed a restricted range of anti-Leishmania IgG titres, sera from co-infection cases displayed a considerable degree of variability, both quantitative and qualitative. They were clearly divided into 2 groups: one (18 sera) showing a continuous grading from nil to mid-concentrations of specific antibodies, the other (3 sera) showing titres 30-fold higher than this range. Taking into account the major immunological abnormalities involving humoral response described in HIV patient, the 2 groups may reflect a different sequence of acquisition of the 2 infective agents; the former representing VL acquired after HIV infection, and the latter representing the contrary situation.