Background: Curative strategies using stimulators such as histone deacetylase inhibitors, disulfiram and IL-7 to reactivate HIV have thus far demonstrated only modest activity. In contrast, transient increases in viremia after administration of standard vaccines have been observed even during antiretroviral therapy (ART). In this study we investigate whether routine influenza vaccination can reactivate HIV.
Methods: Eleven HIV-infected individuals on suppressive ART (<50 copies/ml) were selected from the intervention arm of a randomized trial that studied the effects of a vaccination schedule on viral rebound after structured treatment interruption (NCT00329251). Blood samples were obtained at baseline and 1 month after influenza vaccination. DNA and RNA were extracted from cryopreserved peripheral blood mononuclear cells using a Qiagen AllPrep DNA/RNA Mini Kit. Cell-assoiated HIV DNA and RNA transcripts were quantified by droplet digital PCR using primers for gag and 2-LTR (for HIV DNA), unspliced gag RNA (HIV usRNA), multispliced tat-rev RNA (HIV msRNA), polyA and RPP30 (cellular marker for normalization). Values were adjusted for percentage of CD4 T cells as measured by flow cytometry.
Results: Nine of 11 subjects showed an increase in HIV usRNA after influenza vaccination despite undetectable viral loads throughout. Median HIV usRNA levels pre- and post-vaccination were 28.7 [4.2-56.4] and 91.0 [43.2-173.1] copies/106 CD4 T cells, respectively (p=0.049). Mean increase in HIV usRNA after vaccination ranged from 0 to 49-fold (mean 10.6). No significant changes were observed in HIV msRNA (p=0.25), polyA (p=0.91), total HIV DNA (p=0.15), or 2-LTR circle copies (p=0.74).
Conclusions: This study demonstrated a clear increase in cell-associated HIV usRNA 1 month after influenza vaccination, consistent with antigenic stimulation of the HIV reservoir during suppressive ART. The mean 10.6-fold increase in HIV usRNA is comparable to or better than that seen with administration of Vorinostat. Total HIV DNA and 2-LTR circles did not change, suggesting reactivation of replication-incompetent virus and/or ART-mediated suppression of viral propagation. Although we do not propose that standard vaccinations will cure HIV, these findings suggest that a component of immune stimulation could be considered in the development of eradication strategies.