Pa. Kozlowski et al., CONTRASTING IGA AND IGG NEUTRALIZATION CAPACITIES AND RESPONSES TO HIV TYPE-1 GP120 V3 LOOP IN HIV-INFECTED INDIVIDUALS, AIDS research and human retroviruses, 10(7), 1994, pp. 813-822
Quantitative analysis for HIV-l-specific antibodies present in IgA and
IgG preparations purified from the serum of HIV-seropositive individu
als indicated that the proportion of HIV-specific antibodies present w
ithin the IgG isotype was seven times greater than the proportion of I
gA HIV antibodies present within the IgA isotype. Dilution of IgA HIV-
specific antibodies by nonspecific IgA was observed in patients with e
levated serum IgA concentrations, whereas proportions of IgG HIV antib
odies rose with increases in concentrations of serum IgG. Although pro
portions of IgA HIV antibodies were not observed to correlate with the
CD4 counts of the individuals from whom immunoglobulins were purified
, a significant association between the numbers of such cells and prop
ortion of HIV antibodies present in the IgG isotype was found. Equival
ent amounts of IgG were also more effective than IgA at inhibiting HIV
-1(IIIB) infection of a susceptible T cell line. This may be due to th
e presence of higher proportions of IgG antibodies directed toward non
-V3 determinants because reactivity against an HIV-1(IIIB) V3 peptide
was low and did not differ significantly between these isotopes. IgA a
ntibodies reacting against a V3 peptide containing the HIV consensus s
equence could be detected in the majority of IgA samples purified from
infected individuals. Proportions of IgG consensus V3-specific antibo
dies within the purified IgG samples were, however, much higher. The p
resence of accompanying increases in serum IgG concentration and propo
rtions of IgG HN antibodies, higher proportions of both HIV- and conse
nsus V3-specific antibodies within this isotype, and more effective ne
utralization by IgG suggests that an HIV-driven response is dominated
by B cells committed to production of this immunoglobulin isotype. The
observed low proportions of HIV antigen-specific IgA antibodies with
dilution in many individuals by elevations in non-HIV-specific IgA sug
gests that IgA B cells may be more susceptible to factors that mediate
the polyclonal activation believed to be responsible for many of the
B cell disorders characteristic of HIV infection.