The influence of HIV-1 viral protein R sequence variation on immune activation, inflammation, and metabolism: implications for neurocognitive impairment

Abstract

Background Human immunodeficiency virus (HIV) affects millions of people around the world and was shown to affect the central nervous system (CNS), resulting in HIV-associated neurocognitive disorder (HAND). Despite the use of antiretroviral therapy (ART), mild forms of HAND persist. HAND is associated with systemic inflammation and dysregulated metabolism. Although viral proteins have a role in HIV-1 pathogenesis and the development of HAND, the exact role of less common viral proteins such as viral protein R (Vpr), are not known. Little is known about the influence that Vpr amino acid sequence variants have on immune activation, inflammation, and metabolism in people living with HIV. Here, we investigated the relationship between Vpr amino acid sequence variants, inflammation, and metabolism in a cohort of South African people living with HIV. Methods A systematic review was conducted to determine the association of Vpr amino acid variants with clinical outcomes in people living with HIV by creating a search criterion and selecting articles based on this selection criterion. Plasma samples from n = 48 South African, subtype C people living with HIV were used to investigate the association between Vpr amino acid sequence variation and immune activation, inflammation, and metabolism in an antiretroviral (ART)-naïve cohort. Viral protein sequence analysis was done to determine the presence of amino acid variants at positions 22, 41, 45, and 55 which are associated with neurological outcomes in people living with HIV. Enzyme-Linked Immunosorbent Assay (ELISA) analysis was performed to measure sCD163, neutrophil gelatinase-associated lipocalin (NGAL), high-sensitivity C-reactive protein (hsCRP), soluble urokinase plasminogen activator receptor (suPAR), and interleukin-6 (IL-6) concentrations in people living with HIV. For liquid chromatography–tandem mass spectrometry (LC-MS/MS), plasma samples from n = 32 people living with HIV were used to investigate the levels of tryptophan, kynurenine, kynurenic acid, quinolinic acid (QUIN), and the tryptophan/kynurenine ratio. Various statistical analyses were conducted to determine the association between Vpr amino acid sequence variation and the levels of immune markers and metabolites of the tryptophan-kynurenine pathway.

Results A systematic review of the existing literature suggested that Vpr amino acid variants are associated with clinical outcomes such as disease progression, neurological outcomes, and treatment status in people living with HIV. In this regard, 77H and 85P Vpr amino acid variants were considered noteworthy. Furthermore, Vpr amino acid variants associated with negative neurological outcomes were identified. Among the many neuropathogenic Vpr amino acid variants and immune markers examined, the ELISA analysis revealed that after applying Bonferroni corrections (p = .05/3) and adjusting for sex and locality, suPAR levels were nearing significance for higher levels in participants with the 41G amino acid variant compared to those with the 41S variant (p = .035). Further, amino acid variations at position 41 (between 41G and 41S) exhibited a significant association with suPAR (adj R2 = .089, β = .386; 95% CI .125 to 3.251; p = .035). The metabolomics data found that, out of all the Vpr amino acid substitutions and metabolites that were investigated, only the Vpr 41G and 55A groups was nearing significance for higher levels of QUIN compared to the Vpr 41S and 55T groups, respectively (all p = .023) after applying Bonferroni corrections (p = .05/3) and adjusting for covariates (age and sex). Multiple regression results revealed that Vpr amino acid variations at position 41 (adj R2= .049, β = .505; p = .023), and 55 (adj R2= .126, β = .444; p = .023) displayed significant associations with QUIN after adjusting for age and sex. Lastly, the higher QUIN levels observed in the Vpr 41G group were found to be correlated with suPAR (r = .588, p = .005). Conclusions These findings suggest that Vpr amino acid sequence variations might contribute to dysregulated inflammation in people living with HIV, which could explain the observed association between specific Vpr variants and HAND found in prior research. Furthermore, the Vpr amino acid sequence variations could have an influence on metabolism and inflammation, potentially contributing to HIV-1 pathogenesis and the development of HAND. Thus, these Vpr variants merit further investigation to fully understand their roles in HIV-1 pathogenesis and neuropathogenesis.