C1q Autoantibodies in HIV Infection: Correlation to Elevated Levels of Autoantibodies against 60-kDa Heat-Shock Proteins

Antibodies to solid phase C1q (C1qAb) were determined in 295 serum samples from 132 HIV-infected subjects and in sera from 140 HIV-seronegative healthy individuals as control. An ELISA method applied for the determination of C1qAb in other diseases was used. In part of these sera, other autoantibodies (antibodies reacting with 60-kDa human heat shock protein (hsp60) or mycobacterial hsp65; IgA and IgG class antibodies against the Fab and F(ab′)2 moieties of IgG) as well as complement-mediated antibody-dependent enhancement/neutralization (C′-ADE) were also determined. Increased amount of C1qAb was found in HIV-infected subjects as compared with HIV-seronegative controls (P= 0.0138). In 17 of 132 (13.0%) seropositive individuals but only in 7/140 (5.0%) samples from the controls, the amount of C1qAb exceeded the upper limit (95th percentile) of the normal values (P= 0.031). The amount of C1qAb significantly decreased during a follow-up period of 65 months. C1qAb levels were found to strongly correlate to hsp60/65 autoantibodies but did not correlate or only weakly correlated to the amount of anti-Fab or anti-F(ab′)2autoantibodies measured in the same serum samples. Anti-C1q antibodies recognized the solid phase hsp60/65. Three predicted epitope regions ofM. paratuberculosishsp65 were able to bind efficiently C1q antibodies. An inverse correlation was found between C1qAb and C′-ADE, neutralization was more frequent in the sera with detectable C1qAb, whereas sera without C1qAb more likely enhanced HIV infectionin vitro.