Long-term follow-up of serum-interferon and its acid-stability in a group of homosexual men.

For a period of over two years 99 volunteer healthy homosexual men were examined periodically for the presence of interferon (IFN) in their serum. Thirty-nine subjects had either undetectable IFN levels in serum or IFN was detected only once in three to five samples tested. In another 45 subjects low IFN levels were detected throughout the study period. None of these subjects had or developed any disease symptoms. In the remaining 15 subjects high serum IFN levels were detected at their enrollment or during the study period. All these subjects started to manifest clinical symptoms compatible with AIDS. In six subjects the mean time elapsed between the first detection of serum IFN and disease symptoms was 6.5 months. In all subjects but one, the IFN was of type alpha. The acid-stability of serum IFN alpha decreased with time, and when its decrease was abrupt it was associated with a more rapid evolution of AIDS. Sera containing acid-labile IFN alpha can induce IFN alpha synthesis in normal lymphocyte cultures (LC), but do not influence IFN gamma synthesis in LC stimulated with phytohemagglutinin. LC stimulated with viral antigens in the presence of serum with acid-labile IFN alpha synthesized IFN with an increased sensitivity for acid treatment. The results confirm the prognostic value of serum IFN alpha in the development of AIDS, and suggest that the transition to acid-lability may be a gradual process.