IgG Subclass Distribution in Serum and Various Mucosal Fluids of HIV Type 1-Infected Subjects

Abstract

We measured total IgG ₁, IgG₂, IgG₃, and IgG ₄ concentrations by ELISA in serum (S), total saliva (TS), cervicovaginal secretions (CVS), seminal secretions (SPE), and rectal secretions (RS) from either CDC II/III HIV1-infected subjects or healthy volunteers. Human serum albumin was measured in parallel to calculate the relative coefficient of excretion (RCE). Levels of IgG ₁ and IgG ₃ directed against gp120 MN also were measured by ELISA in all samples, and the specific activity (SA) calculated. HIV-1-specific IgG₂ and IgG ₄ were not compared, as total IgG ₂ and total IgG₄ levels in HIV-1-infected subjects were found to be lower than in the healthy controls. Despite substantial interindividual variability, total IgG ₁ and IgG₃ concentrations in all fluids were greater in the HIV-1-infected subjects than in the healthy controls. Calculations of RCE indicated predominantly a transudative origin for IgG subclasses in the different mucosal fluids, except for CVS, in which IgG₁, IgG₂, and IgG₄ was produced locally. The transduction behavior of IgG₃ in secretions appears to be different from that of other IgG subclasses. HIV-1-infected subjects were considered positive for IgG ₁ and IgG₃ antibodies against gp120 MN if their antibody levels exceeded the maximum titer measured in the control group. Positive levels of anti-gp120 MN IgG ₁ were detected for 100% of HIV-1-infected individuals in S, CVS, and SPE, 97% in TS, and 75% in RS. Fewer subjects had positive levels of IgG₃ to gp120 MN in their secretions (maximum 67% in CVS). Despite the low concentrations of total IgG ₃, mean SA values for IgG ₃ to gp120 M N were greater in secretions than in serum. No significant difference in the SA values for IgG ₁ to gp120 MN was observed between the different fluids. Only CVS had a local production of HIV-specific IgG₁ Our results highlight the importance of an HIV-specific IgG₁ and IgG₃ immune response in mucosal fluids from HIV-1-infected subjects.