Pa. Kozlowski et al., HIGH PREVALENCE OF SERUM IGA HIV-1 INFECTION-ENHANCING ANTIBODIES IN HIV-INFECTED PERSONS MASKING BY IGG, The Journal of immunology, 154(11), 1995, pp. 6163-6173
IgA and IgG purified from sera of 20 HIV-infected persons were separat
ely examined for ability to mediate Ab-dependent enhancement (ADE) of
HIV-1 infection of U937 cells. Both isotypes were capable of enhancing
infection of these cells. However, IgA from twice as many persons (14
/20) displayed infection enhancement when compared with IgG. This acti
vity was predominantly observed with IgA from asymptomatic HIV-seropos
itive subjects (9/9). Enhanced HIV infection by IgA was observed most
often at concentrations equivalent to serum dilutions in the range 10(
-3) to 10(-5) and could be inhibited by preincubation of U937 cells wi
th a mAb specific for the Fc alpha receptor. Concentrations of IgG med
iating ADE were generally present in sera at dilutions from 10(-4) to
10(-6). When Ige was adjusted to physiologic concentration and combine
d with an enhancing concentration of IgA, enhancement was not observed
unless IgG was also present at a concentration which exhibited this a
ctivity. These results suggest that, in comparison with Igc, HIV-infec
ted individuals more often produce IgA Abs reacting with enhancing det
erminants of HIV. IgA-mediated ADE of HIV infection may not play a sig
nificant role in facilitating systemic dissemination of HIV because of
the presence of higher concentrations of IgG. However, the production
of IgA HIV-enhancing Abs at mucosal sites, where fewer IgG plasma cel
ls are present, could contribute to the pathogenesis of HIV infection
and interfere with development of vaccines designed to induce HIV IgA
Abs at mucosal surfaces.