Background: Restriction factors are host proteins interfering at different steps of HIV replication cycle in an attempt to limit viral production and spreading. We conducted a longitudinal analysis of the expression profile of antiviral restriction factors and cofactors in a cohort of eleven HIV-1 infected, long-term treated patients who underwent analytical treatment interruption (ATI), the HIV-STAR study(NCT02641756). The expression of known HIV-1 restriction factors (APOBEC3G, SAMHD1, MX2, PAF1, SLFN11, TRIM5α and BST2/tetherin), cofactors (NLRX1 and PSIP1) and interferon stimulated genes (ISGs) IFIT1 and MX1 were evaluated at four well-defined time points: on cART (T1), after ATI (VL< 20copies/ml, T2), at rebound (VL>1000copies/ml, T3) and after treatment restart (VL< 20copies/ml, T4).
Methods: Peripheral blood mononuclear cells were isolated from all patients at the four time points. Quantitative real-time PCR was performed to determine the expression of these HIV-1 restriction factors, cofactors and ISGs. Statistical Friedman''s and post hoc Dunn''s analysis were performed and Spearman correlation was employed to identify associations between restriction factor/cofactor, ISG expression levels and patient clinical characteristics.
Results: For two restriction factors a significant increase in expression between T1 and T2 (APOBEC3G, SLFN11) was observed. Furthermore, upregulation of MX2 and both ISGs were observed between T1 and T3 (p< 0.05). Significant positive correlations between ISG and restriction factor/cofactor expression were identified at T1, T3 and T4. In addition, a correlation between high HIV DNA load and IFIT1 at T2 and high viral load zenith and SLFN11 at T4 was found, suggesting that these virological characteristics drive a more robust restriction factor response. Furthermore, a low CD4 nadir was correlated with a higher expression of the viral co-factor PSIP1 at T2. No associations were found between the expression of restriction- or co- factors and time to viral rebound.
Conclusions: A significant difference in restriction factor expression between at least two time points was identified for SLFN11, APOBEC3G and MX2 and a trend towards difference in expression levels for most of the other restriction factors studied. In contrast to the ISGs, our data indicate that restriction factors increase earlier after ATI before time of viral rebound, potentially implicating them as markers/predictors of rebound.