Elevated serum levels of soluble tumour necrosis factor receptors (sTNF-R) in patients with HIV infection

Serum levels of the soluble form of tumour necrosis factor receptor type II (p75) (sTNF-R) were determined in HIV-infected individuals and risk groups and were then correlated with the course of infection and prognosis. sTNF-R levels were determined by an ELISA with MoAbs and polyclonal antibodies to urine-derived sTNF-R proteins. The mean ± s.e. levels of sTNF-R in the sera of 49 HIV⁺ male homosexuals, 34 HIV^- male homosexuals and 44 matched controls were 6.1 ± 0.3 ng/ml, 4.4 ± 0.3 ng/ml and 3.4 ± 0.2 ng/ml, respectively. All these values were significantly different between each of the groups (P < 0.001-0.05). Sequential studies of sTNF-R revealed higher levels following seroconversion in 5/8 individuals, remained persistently high during the asymptomatic phase of the infection and became even more elevated in some ARC and AIDS patients. At the same time TNF-α was undetectable in sera obtained from HIV⁺ male homosexuals and from healthy controls. This was independent of stage of HIV infection, serum sTNF-R level and type of ELISA kit used. These findings suggest that TNF-α/TNF-R system is turned on before and during HIV infection and raise the possibility that sTNF-R, the natural inhibitor of TNF, may be of importance in determining the course and probably prognosis of the disease.