A longitudinal study of the IgG antibody response to HIV-1 p17 gag protein in HIV-1+ patients with haemophilia: titre and avidity.

The IgG response to HIV-1 p17 gag protein was studied for up to 6 years in 12 HIV-1-infected patients with haemophilia, who had seroconverted between 1982 and 1985. To assess any prognostic value, p17 IgG titres were compared with p24 IgG titres, CD4 cell counts and p24 antigenaemia. p17 IgG avidity index was also examined. A strong similarity was found between the IgG titre to HIV-1 p17 and that to p24. In patients who developed AIDS the decline in p17 IgG titres could precede by several years the drop in CD4 cells to under 200 cells/microliters; whereas some long-term asymptomatic patients (CDCII) had increasing p17 IgG titres and stable CD4 cell counts. Declining p17 and p24 IgG titres were not always associated with an increase in p24 antigenaemia. IgG titres were found to be better predictors of disease progression than CD4 cell counts or p24 antigenaemia. Patients who developed AIDS during the study were also characterized by a lower p17 IgG avidity than patients who remained asymptomatic. This result suggests that IgG avidity could have prognostic relevance and be of importance for host resistance to AIDS onset.