Dominant influence of HLA-B in mediating the potential co-evolution of HIV and HLA.

The extreme polymorphism in the human leukocyte antigen (HLA) class I region of the human genome is suggested to provide an advantage in pathogen defence mediated by CD8+ T cells. HLA class I molecules present pathogen-derived peptides on the surface of infected cells for recognition by CD8+ T cells. However, the relative contributions of HLA-A and -B alleles have not been evaluated. We performed a comprehensive analysis of the class I restricted CD8+ T-cell responses against human immunodeficiency virus (HIV-1), immune control of which is dependent upon virus-specific CD8+ T-cell activity. In 375 HIV-1-infected study subjects from southern Africa, a significantly greater number of CD8+ T-cell responses are HLA-B-restricted, compared to HLA-A (2.5-fold; P = 0.0033). Here we show that variation in viral set-point, in absolute CD4 count and, by inference, in rate of disease progression in the cohort, is strongly associated with particular HLA-B but not HLA-A allele expression (P < 0.0001 and P = 0.91, respectively). Moreover, substantially greater selection pressure is imposed on HIV-1 by HLA-B alleles than by HLA-A (4.4-fold, P = 0.0003). These data indicate that the principal focus of HIV-specific activity is at the HLA-B locus. Furthermore, HLA-B gene frequencies in the population are those likely to be most influenced by HIV disease, consistent with the observation that B alleles evolve more rapidly than A alleles. The dominant involvement of HLA-B in influencing HIV disease outcome is of specific relevance to the direction of HIV research and to vaccine design.

Time in Therapeutic Range for Left Ventricular Assist Device Patients Anticoagulated With Warfarin: A Correlation to Clinical Outcomes.

Left ventricular assist devices (LVADs) require anticoagulation therapy with vitamin K antagonists to reduce the risk of thrombotic events. The quality of anticoagulation may be assessed by the time in therapeutic range (TTR). We analyzed a retrospective cohort of LVAD patients at a single institution from January 2012 to September 2014. Primary outcomes included TTR during the study time period and TTR 30 days preceding a bleeding or thrombotic event. Fifty-one patients (mean age 57.0 ± 14.6 years; 78% male) had an overall TTR of 52%. Median international normalized ratio (INR) preceding a bleeding and thrombotic event was 2.7 and 2.2, respectively (p = 0.049). In the 30 days before an event, patients with a bleeding event were more likely to be on low-dose aspirin (37% vs. 12%; p = 0.018) and spend a higher proportion of time above therapeutic range (41% vs. 17%; p = 0.007) compared with those with thrombotic events. The association between a greater percentage of time above therapeutic range in the 30 days before a bleeding event demonstrates the importance of avoiding a supratherapeutic INR in the LVAD patient population and the usefulness of TTR as a measure of the overall quality of anticoagulation and monitoring in an LVAD cohort.

Percutaneous Venoarterial Extracorporeal Membrane Oxygenation for Refractory Cardiogenic Shock Is Associated with Improved Short- and Long-Term Survival.

Mortality due to refractory cardiogenic shock (RCS) exceeds 50%. Venoarterial extracorporeal membrane oxygenation (VA-ECMO) has become an accepted therapy for RCS. The aim of our study was to evaluate outcomes of patients with RCS treated with percutaneous VA-ECMO (pVA-ECMO). Retrospective review of patients supported with VA-ECMO at our institution in 2012-2013. Clinical characteristics, bleeding, vascular complications, and outcomes including survival were assessed. A total of 37 patients were supported with VA-ECMO for RCS. The majority of VA-ECMO (76%) was placed in the catheterization laboratory. Nearly half (49%) of the patients presented with acute myocardial infarction. Seven patients (19%) underwent insertion of pVA-ECMO in the setting of cardiopulmonary resuscitation with mechanical chest compression device. Median duration of support was 5 days. Index hospitalization, 30-day, and 1-year survival were 65%, 65%, and 57%, respectively. Survival rate for discharged patients was 87.5% with a median follow-up of 450 days. Refractory cardiogenic shock supported with pVA-ECMO is associated with an improved survival in patients with a traditionally poor prognosis.

Precise identification of a human immunodeficiency virus type 1 antigen processing mutant.

Human immunodeficiency virus type 1 (HIV-1) evokes a strong immune response, but the virus persists. Polymorphisms within known antigenic sites result in loss of immune recognition and can be positively selected. Amino acid variation outside known HLA class I restricted epitopes can also enable immune escape by interfering with the processing of the optimal peptide antigen. However, the lack of precise rules dictating epitope generation and the enormous genetic diversity of HIV make prediction of processing mutants very difficult. Polymorphism E169D in HIV-1 reverse transcriptase (RT) is significantly associated with HLA-B*0702 in HIV-1-infected individuals. This polymorphism does not map within a known HLA-B*0702 epitope; instead, it is located five residues downstream of a HLA-B*0702-restricted epitope SPAIFQSSM (SM9). Here we investigate the association between E169D and HLA-B*0702 for immune escape via the SM9 epitope. We show that this single amino acid variation prevents the immune recognition of the flanked SM9 epitope by cytotoxic T cells through lack of generation of the epitope, which is a result of aberrant proteasomal cleavage. The E169D polymorphism also maps within and abrogates the recognition of an HLA-A*03-restricted RT epitope MR9. This study highlights the potential for using known statistical associations as indicators for viral escape but also the complexity involved in interpreting the immunological consequences of amino acid changes in HIV sequences.

CD8+ T cell epitope-flanking mutations disrupt proteasomal processing of HIV-1 Nef.

CTL play a critical role in the control of HIV and SIV. However, intrinsic genetic instability enables these immunodeficiency viruses to evade detection by CTL through mutation of targeted antigenic sites. These mutations can impair binding of viral epitopes to the presenting MHC class I molecule or disrupt TCR-mediated recognition. In certain regions of the virus, functional constraints are likely to limit the capacity for variation within epitopes. Mutations elsewhere in the protein, however, might still enable immune escape through effects on Ag processing. In this study, we describe the coincident emergence of three mutations in a highly conserved region of Nef during primary HIV-1 infection. These mutations (R69K, A81G, and H87R) flank the HLA B*35-restricted VY8 epitope and persisted to fixation as the early CTL response to this Ag waned. The variant form of Nef showed a reduced capacity to activate VY8-specific CTL, although protein stability and expression levels were unchanged. This effect was associated with altered processing by the proteasome that caused partial destruction of the VY8 epitope. Our data demonstrate that a variant HIV genotype can significantly impair proteasomal epitope processing and substantiate the concept of immune evasion through diminished Ag generation. These observations also indicate that the scale of viral escape may be significantly underestimated if only intraepitope variation is evaluated.