HIV1-viral protein R (Vpr) mutations: associated phenotypes and relevance for clinical pathologies

Viral protein R (Vpr)-induced neuroinflammation and its potential contribution to neuronal dysfunction: a scoping review

HIV-associated neurocognitive disorders (HAND) are the result of the activity of HIV-1 within the central nervous system (CNS). While the introduction of antiretroviral therapy (ART) has significantly reduced the occurrence of severe cases of HAND, milder cases still persist. The persistence of HAND in the modern ART era has been linked to a chronic dysregulated inflammatory profile. There is increasing evidence suggesting a potential role of Viral protein R (Vpr) in dysregulating the neuroinflammatory processes in people living with HIV (PLHIV), which may contribute to the development of HAND. Since the role of Vpr in neuroinflammatory mechanisms has not been clearly defined, we conducted a scoping review of fundamental research studies on this topic. The review aimed to assess the size and scope of available research literature on this topic and provide commentary on whether Vpr contributes to neuroinflammation, as highlighted in fundamental studies. Based on the specified selection criteria, 10 studies (6 of which were cell culture-based and 4 that included both animal and cell culture experiments) were eligible for inclusion. The main findings were that (1) Vpr can increase neuroinflammatory markers, with studies consistently reporting higher levels of TNF-α and IL-8, (2) Vpr induces (neuro)inflammation via specific pathways, including the PI3K/AKT, p38-MAPk, JNK-SAPK and Sur1-Trpm4 channels in astrocytes and the p38 and JNK-SAPK in myeloid cells, and (3) Vpr-specific protein amino acid signatures (73R, 77R and 80A) may play an important role in exacerbating neuroinflammation and the neuropathophysiology of HAND. Therefore, Vpr should be investigated for its potential contribution to neuroinflammation in the development of HAND.

HIV-1 Subtype C Vpr Amino Acid Residue 45Y and Specific Conserved Fragments Are Associated with Neurocognitive Impairment and Markers of Viral Load

There is increasing evidence that HIV-1 viral protein R (Vpr) plays an important role in the pathogenesis of cognitive impairment. We investigated the relationship between HIV-1 subtype C Vpr sequence variation and HIV-associated neurocognitive impairment as measured by global deficit score (GDS) in treatment-naive individuals. We used different bioinformatic tools and statistical models to correlate vpr variation and cognitive function. We identified a tyrosine at position 45 (45Y) as a signature for neurocognitive impairment and histidine (45H) as a signature in the non-impaired individuals. The presence of signature 45Y was associated by 3.66 times higher GDS, 525 times higher plasma viral load, 15.84 times higher proviral load, and 60% lower absolute CD4-T cell count compared with those without the signature. Additionally, we identified four conserved Vpr fragment sequences, PEDQGPQREPYNEWTLE (5-21), LGQYIY (42-47), TYGDTW (49-54), and PEDQGPQREPYNEW (5-18), that were associated with higher plasma viral load and proviral load. The implication of these findings is that variation of Vpr leads to neurocognitive impairment in HIV infection and worsens the progression of disease in general by promoting the production of provirus, promoting HIV replication and depletion of CD4+ T cells in the periphery.

The influence of viral protein R amino acid substitutions on clinical outcomes in people living with HIV: A systematic review

BACKGROUND

The HIV viral protein R (Vpr) is a multifunction protein involved in the pathophysiology of HIV-1. Recent evidence has suggested that Vpr amino acid substitutions influence the pathophysiology of HIV-1 and clinical outcomes in people living with HIV (PLWH). Several studies have linked Vpr amino acid substitutions to clinical outcomes in PLWH; however, there is no clear consensus as to which amino acids or amino acid substitutions are most important in the pathophysiology and clinical outcomes in PLWH. We, therefore, conducted a systematic review of studies investigating Vpr amino acid substitutions and clinical outcomes in PLWH.

METHODS

PubMed, Scopus and Web of Science databases were searched according to PRISMA guidelines using a search protocol designed specifically for this study.

RESULTS

A total of 22 studies were included for data extraction, comprising 14 cross-sectional and 8 longitudinal studies. Results indicated that Vpr amino acid substitutions were associated with specific clinical outcomes, including disease progressions, neurological outcomes and treatment status. Studies consistently showed that the Vpr substitution 63T was associated with slower disease progression, whereas 77H and 85P were associated with no significant contribution to disease progression.

CONCLUSIONS

Vpr-specific amino acid substitutions may be contributors to clinical outcomes in PLWH, and future studies should consider investigating the Vpr amino acid substitutions highlighted in this review.

Differential CXCR4 expression on hematopoietic progenitor cells versus stem cells directs homing and engraftment

Gene therapy involves a substantial loss of hematopoietic stem and progenitor cells (HSPC) during processing and homing. Intra-BM (i.b.m.) transplantation can reduce homing losses, but prior studies have not yielded promising results. We studied the mechanisms involved in homing and engraftment of i.b.m. transplanted and i.v. transplanted genetically modified (GM) human HSPC. We found that i.b.m. HSPC transplantation improved engraftment of hematopoietic progenitor cells (HPC) but not of long-term repopulating hematopoietic stem cells (HSC). Mechanistically, HPC expressed higher functional levels of CXCR4 than HSC, conferring them a retention and homing advantage when transplanted i.b.m. Removing HPC and transplanting an HSC-enriched population i.b.m. significantly increased long-term engraftment over i.v. transplantation. Transient upregulation of CXCR4 on GM HSC-enriched cells, using a noncytotoxic portion of viral protein R (VPR) fused to CXCR4 delivered as a protein in lentiviral particles, resulted in higher homing and long-term engraftment of GM HSC transplanted either i.v. or i.b.m. compared with standard i.v. transplants. Overall, we show a mechanism for why i.b.m. transplants do not significantly improve long-term engraftment over i.v. transplants. I.b.m. transplantation becomes relevant when an HSC-enriched population is delivered. Alternatively, CXCR4 expression on HSC, when transiently increased using a protein delivery method, improves homing and engraftment specifically of GM HSC.

Evolution of a concept: From accessory protein to key virulence factor, the case of HIV-1 Vpr

Back in 1989 some studies have shown that the viral protein Vpr was dispensable for HIV-1 replication in vitro. From then the concept of accessory or auxiliary protein for Vpr has emerged and it is still used to date. However, Vpr soon appeared to be very important for in vivo virus spread and pathogenesis. Vpr has been involved in many biological functions including regulation of reverse transcriptase activity, the nuclear import of the pre-integration complex (PIC), HIV-1 transcription, gene splicing, apoptosis and in cell cycle arrest. Thus, we might rather consider Vpr as a true virulence factor instead of just an accessory factor. At present, Vpr can be regarded as a potential and promising target in different strategies aiming to fight infected cells including latently infected cells.

Dual role of the chromatin-binding factor PHF13 in the pre- and post-integration phases of HIV-1 replication

Viruses interact with multiple host cell factors. Some of these are required to promote viral propagation, others have roles in inhibiting infection. Here, we delineate the function of the cellular factor PHF13 (or SPOC1), a putative HIV-1 restriction factor. Early in the HIV-1 replication cycle PHF13 increased the number of integrated proviral copies and the number of infected cells. However, after HIV-1 integration, high levels of PHF13 suppressed viral gene expression. The antiviral activity of PHF13 is counteracted by the viral accessory protein Vpr, which mediates PHF13 degradation. Altogether, the transcriptional master regulator and chromatin binding protein PHF13 does not have purely repressive effects on HIV-1 replication, but also promotes viral integration. By the functional characterization of the dual role of PHF13 during the HIV-1 replication cycle, we reveal a surprising and intricate mechanism through which HIV-1 might regulate the switch from integration to viral gene expression. Furthermore, we identify PHF13 as a cellular target specifically degraded by HIV-1 Vpr.