A longitudinal study of the IgG antibody response to HIV-1 pl7gagprotein in HIV-1+ patients with haemophilia: titre and avidity

Abstract

SUMMARYThe IgG response to HIV-I pl7 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, pi 7 IgG titres were compared with p24 IgG titrcs. CD4 cell counts and p24antigenaemia. pi7 IgG avidity index was also examined. A strong similarity was found between the IgG titre to HlV-l pl7 and that to p24. In patients who developed AIDS the decline inpl7 IgG titres could precede by several years the drop in CD4 cells to under 200 cclls//il: whereas some long-term asymptomatic patients (CDCII) had increasing pl7 IgG titres and stable CD4 cell counts. Declining pl7 and p24 IgG titres were not always associated with an increase in p24 antigenaemia. IgG titres were found to be better predictors of di.sease progression than CD4 eell counts or p24 antigenaemia. Patients who developed AIDS during the study were also characterized by a lower pl7 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 onsetKeywords lUV-i gag antibody response p24 antigenaemia avidity prognostic markers INTRODUCTION

Differential maturation of avidity of IgG antibodies to gp41, p24 and p17 following infection with HIV-1

“…The variation in anti-p24 and anti-p17 antibody titres following recent infection with HIV also does not permit these perameters to confirm recent infection. However, whilst anti-gag avidity studies could not reliably differentiate between recent and earlier HIV infections, our anti-p24 avidity studies on sera from remote cases of HIV infection confirm the findings of Chargelegue and colleagues [20][21][22] that a decline in the avidity of anti-p24 or anti-p27 antibodies is a better predictor of the onset of AIDS than anti-p24 titre. Falls in anti-p24 titres before the onset of ARC/AIDS have been reported [30][31][32].…”

“…However, in view of the inability of some patients to mature their anti-p17/p24 responses over the same time span, anti-p17/p24 avidity studies are not suitable for confirmation of recent HIV seroconversion. Unless a 'trend' which indicates falling anti-p17/p24 avidity can be detected in sequential sera [20,21,29], the presence of low-avidity anti-p17/ p24 in a single serum is unlikely to be of value in the prediction of the onset of ARC/AIDS. A combination of anti-gp41 and anti-p17/p24 avidity results could be useful, however.…”

“…The method of Chargelegue and colleagues [20][21][22] was used. Prior tests showed that 8 M urea had no effect on the solid-phase antigen.…”

“…Analyses of sera from haemophiliacs have already shown the potential value of avidity tests in disease prognosis in HIV infection. Both the titre and avidity of anti-p17 and anti-p24 antibodies fell prior to the onset of AIDS, but the fall in avidity was a better predictor of disease progression than antibody titre [20][21][22].…”

Avidity of Antibodies to Cytomegalovirus in HIV-Seropositive Patients with and without CMV Retinitis

“…In the case of HIV-specific antigens, antibody avidity is not maintained in the late stages of AIDS. For antigens p24 and p17, antibody avidity and titers decline with disease progression and serve as prognostic indicators of the onset of AIDS (8,18). Antibody avidity to gp41 is, however, useful for identifying recent infections as avidity maturation to this antigen reflects the time elapsed since seroconversion and remains high even late in disease (18).…”