Serum IgG1 and IgG4 could contribute to partial control of viral rebound in chronically HIV-1-infected patients

OBJECTIVES: Few studies have investigated chronically infected individuals after antiretroviral therapy (ART) interruption (ATI, analytical therapy interruption); thus, we investigated the association between some HIV-specific antibodies and viral control. DESIGN: All enrolled patients were previously described in the APACHE study. Briefly, the study was conducted on HIV-1 chronically infected patients, with HIV-RNA less than 50 copies/ml for at least 10 years, CD4+ cell count greater than 500 cells/μl and HIV-DNA less than 100 copies/106 PBMC. The ART regimen in use at the time of ATI was resumed at confirmed viral rebound (CVR, defined as two consecutive HIV-RNA >50 copies/ml). METHODS: Collection of sera and analysis of both binding antibodies (BAbs) and neutralizing antibodies (NAbs) was performed at three different time points: ATI, CVR and time of viral re-suppression after ART resumption. RESULTS: IgG subclasses (IgG1, IgG2, IgG3 and IgG4) from the four patients with highest levels of neutralization were found to block viral infection. All patients had CVR after ATI at a median time of 21 days (14-56). After ART resumption, all the enrolled patients achieved HIV-RNA less than 50 copies/ml in 42 days (21-98). We observed a strong increase of either BAbs and NAbs titers from ATI to viral re-suppression in one patient, who showed the longest period of virus undetectability during ATI. In this patient, BAbs and NAbs specifically belonged to both IgG1 and IgG4 subclasses, directed to env antigen. CONCLUSION: env-specific NAbs and BAbs belonging to IgG1, IgG4 subclasses could be helpful to monitor long-term responses able to control virus replication and eradicate HIV infection.