Reduction of serum melatonin levels in HIV-1-infected individuals' parallel disease progression: correlation with serum interleukin-12 levels.

Background: During the natural history of human immunodeficiency virus type I (HIV-1) infection, an impairment of interleukin-12 (IL-12) production precedes a switch from a T-helper 1 (Th1) to a T-helper 2 (Th2) stage of cellular immunity. Melatonin, the main hormone produced by the pineal gland, seems to promote a Th1 response by increasing the production of IL-12 in vitro. The aim of this study was to measure and correlate serum levels of melatonin and IL-12 in a cohort of HIV-1-infected individuals. Patients and Methods: 77 anti-HIV-1-positive subjects were enrolled: 20 were in CDC stage A, 25 in CDC stage B and 32 in CDC stage C. 30 healthy HIV-1-seronegative subjects were recruited as controls. IL-12 and melatonin concentrations were quantitated in serum samples. Results: Mean levels of serum melatonin were significantly lower in HIV-1-infected individuals in comparison with controls (p < 0.001). Within the HIV-1-seropositive group, mean melatonin and IL-12 concentrations were significantly lower in patients in CDC stage C, as compared with patients in CDC stages B and A (p < 0.01). Conclusion: During the natural history of HIV-1 disease, serum melatonin levels are progressively reduced. This reduction may be related to the impairment of Th1 immunoresponses.