Detection of immunoglobulin M antibody in primary human immunodeficiency virus infection

Consecutive serum samples obtained from 20 homosexual men during symptomatic primary HIV infection were examined by a variety of IgG and IgM antibody assays. All sera obtained 2-5 weeks after onset of disease contained IgM anti-HIV as demonstrated by an IgM antibody capture assay. The IgM antibodies appeared during the 2 first weeks of illness, reached peak titres at 2-5 weeks and declined thereafter to undetectable levels at 2-3 months after the onset of disease. By contrast, IgG anti-HIV appeared later, during the second week after the onset of symptoms, and did not reach maximal levels until the IgM response had waned. The first IgM antibodies to appear were directed against gag proteins. IgM antibodies against env antigens were found less frequently and later in the course of the disease. These results suggest that IgM antibody determination may be helpful in the diagnosis of early HIV infection as a possible addition to the combined use of antigen detection and a second generation ELISA, which, in the present study, was found to be highly reliable for diagnostic purposes.