The APOBEC3 family comprises seven cytidine deaminases (APOBEC3A [A3A] to A3H), which are expressed to various degrees in HIV-1 susceptible cells. The HIV-1 Vif protein counteracts APOBEC3 restriction by mediating its degradation by the proteasome. We hypothesized that Vif proteins from various HIV-1 subtypes differ in their abilities to counteract different APOBEC3 proteins. Seventeen Vif alleles from seven HIV-1 subtypes were tested for their abilities to degrade and counteract A3G, A3F, and A3H haplotype II (hapII). We show that most Vif alleles neutralize A3G and A3F efficiently but display differences with respect to the inhibition of A3H hapII. The majority of non-subtype B Vif alleles tested presented some activity against A3H hapII, with two subtype F Vif variants being highly effective in counteracting A3H hapII. The residues required for activity were mapped to two residues in the amino-terminal region of Vif (positions 39F and 48H). Coimmunoprecipitations showed that these two amino acids were necessary for association of Vif with A3H hapII. These findings suggest that the A3H hapII binding site in Vif is distinct from the regions important for A3G and A3F recognition and that it requires specific amino acids at positions 39 and 48. The differential Vif activity spectra, especially against A3H hapII, suggest adaptation to APOBEC3 repertoires representative of different human ancestries. Phenotypic assessment of anti-APOBEC3 activity of Vif variants against several cytidine deaminases will help reveal the requirement for successful replication in vivo and ultimately point to interventions targeting the Vif-APOBEC3 interface.
HIV-1 requires the cellular transcription factor CBF to stabilize its accessory protein Vif and promote APOBEC3G degradation. Here, we demonstrate that both isoforms of CBF allow for increased steady-state levels of Vif, enhanced APOBEC3G degradation, and increased viral infectivity. This conserved functional interaction enhances the steady-state levels of Vif proteins from multiple HIV-1 subtypes and is required for the degradation of all human and rhesus Vif-sensitive APOBEC3 proteins by their respective lentiviral Vif proteins. Human immunodeficiency virus type 1 (HIV-1) and related lentiviruses require the viral accessory protein Vif to neutralize members of the APOBEC3 family of retrovirus restriction factors and render host cells permissive for productive viral replication. HIV-1 Vif neutralizes the APOBEC3 proteins by recruitment of an E3 ubiquitin ligase complex that polyubiquitinates APOBEC3 proteins and targets them for proteasomal degradation (13; reviewed in references 1, 9, and 12). Recently, the cellular transcription factor CBF was found to be associated with this complex and to allow for its reconstitution in vitro (6). Furthermore, CBF was found to be required for the stability of HIV-1 IIIB Vif in vivo, allowing for efficient degradation of APOBEC3G (A3G) and increased viral infectivity (6). The current model is that HIV-1 Vif hijacks cellular CBF to facilitate Vif folding and/or stability, as well as nucleation of the E3 ubiquitin ligase complex. While it has been shown that rhesus macaque simian immunodeficiency virus molecular clone 239 (SIV mac239 ) Vif also requires CBF to degrade rhesus A3G (6), the generality of the CBF/Vif/ APOBEC3 functional interplay remains to be determined. The goal of the current study was to determine which isoforms of CBF contribute to Vif stabilization, whether CBF is required to stabilize Vif proteins of multiple different HIV subtypes, and finally, if CBF is required by Vif to neutralize the entire repertoire of Vif-sensitive APOBEC3 proteins.Alternative splicing generates at least two isoforms of CBF in human cells (GenBank accession numbers NM_022845.2 and NM_001755.2). Though they differ in size and in amino acid sequence at their C-terminal end, these splice variants share 165 N-terminal residues, including the RUNX heterodimerization domain, and a clear functional difference has yet to be delineated. To determine if HIV-1 Vif distinguishes between these CBF isoforms, a stable CBF knockdown clone of HEK293T was created using a stably integrated small hairpin RNA (shRNA) that targets both isoforms (6). This line was transiently transfected with a Vif-proficient or Vif-deficient A200C HIV-1 IIIB molecular clone (3) in the presence or absence of human A3G and complemented with either the 187-amino-acid CBF isoform 1 (cloned from CEM cell cDNA by PCR and standard molecular biology techniques) or the shorter 182-amino-acid CBF isoform 2 (as used previously [6]). Forty-eight hours after transient transfection, cell lysates and viral particles were...
Direct-acting antivirals are an effective tool for the treatment of hepatitis C virus, enabling the elimination of the virus. However, some patients who have been successfully treated with direct-acting antivirals are at risk of reinfection. Our findings showed that the risk of reinfection was highest among people with recent injection drug use. Among people who inject drugs, daily use of opioid-agonist therapy was associated with a lower risk of reinfection.
Background: Population-level monitoring of hepatitis C virus (HCV) infected people across cascades of care identifies gaps in access and engagement in care and treatment. We characterized the population-level care cascade for HCV in British Columbia (BC), Canada before and after introduction of Direct Acting Antiviral (DAA) treatment. Methods: BC Hepatitis Testers Cohort (BC-HTC) includes 1.7 million individuals tested for HCV, HIV, reported cases of hepatitis B, and active tuberculosis in BC from 1990 to 2018 linked to medical visits, hospitalizations, cancers, prescription drugs and mortality data. We defined six HCV care cascade stages: (a) antibody diagnosed; (b) RNA tested; (c) RNA positive; (d) genotyped; (e) initiated treatment; and (f) achieved sustained virologic response (SVR). Results:We estimated 61 127 people were HCV antibody positive in BC in 2018 (undiagnosed: 7686, 13%; diagnosed: 53 441, 87%). Of those diagnosed, 83% (44 507) had HCV RNA testing, and of those RNA positive, 90% (28 716) were genotyped. Of those genotyped, 61% (17 441) received therapy, with 90% (15 672) reaching SVR.Individuals from older birth cohorts had lower progression to HCV RNA testing.While people who currently inject drugs had the highest proportional progression to RNA testing, this group had the lowest proportional treatment uptake. Conclusions: Although gaps in HCV RNA and genotype testing after antibody diagnosis exist, the largest gap in the care cascade is treatment initiation, despite introduction of DAA treatment and removal of treatment eligibility restrictions. Further interventions are required to ensure testing and treatment is equitably accessible in BC.
The hypothesis of potential transmission from fomites was supported by the experimental results. The anti-HCV activity of commercial antiseptics varied.
Chronic HCV is associated with a higher risk of mortality.SVR from DAAs was associated with a significant reduction in the risk of all-cause, liver-and drug-related mortality.Older age and cirrhosis were associated with higher risk of liverrelated mortality.Younger age, injection drug use, and problematic alcohol use were associated with higher risk of drug-related mortality.
, folded-back structure. Comparison of this structure with virion spikes suggests that a rearrangement, analogous to those of enveloped virus fusion proteins, may mediate membrane penetration by rotavirus during entry. To detect this inferred rearrangement of virion-associated authentic VP5*, we raised conformation-specific monoclonal antibodies against the recombinant VP5* fragment in its putative post-membrane penetration conformation. Using one of these antibodies, we demonstrate that rotavirus uncoating triggers a conformational change in the cleaved VP4 spike to yield rearranged VP5*.
This study provides evidence that patients experiencing virological failure frequently harbor Vif point mutants (i.e. K22H). Such Vif alleles lose their ability to counteract APOBEC3 proteins, leading to an increase of G-to-A viral mutations that can facilitate the emergence of some antiretroviral resistance mutations.
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