Major histocompatibility complex (MHC)-E is a highly conserved, ubiquitously expressed, non-classical MHC-Ib molecule with limited polymorphism primarily involved in NK cell regulation. We found that vaccination of rhesus macaques (RM) with ΔRh157.5/.4 Rhesus Cytomegalovirus (RhCMV) vectors results in MHC-E-restricted presentation of highly varied peptide epitopes to CD8α/β+ T cells, approximately 4 distinct epitopes per 100 amino acids in all tested antigens. Computational structural analysis revealed that MHC-E provides heterogeneous chemical environments for diverse side chain interactions within a stable, open binding groove. Since MHC-E is up-regulated on cells infected with HIV/SIV and other persistent viruses to evade NK cell activity, MHC-E-restricted CD8+ T cell responses have the potential to exploit pathogen immune evasion adaptations, a capability that might endow these unconventional responses with superior efficacy.

HIV infection induces phenotypic and functional changes to CD8+ T cells defined by the coordinated upregulation of a series of negative checkpoint receptors that eventually result in T cell exhaustion and failure to control viral replication. We report that effector CD8+ T cells during HIV infection in blood and SIV infection in lymphoid tissue exhibit higher levels of the negative checkpoint receptor TIGIT. Increased frequencies of TIGIT+ and TIGIT+ PD-1+ CD8+ T cells correlated with parameters of HIV and SIV disease progression. TIGIT remained elevated despite viral suppression in those with either pharmacological antiretroviral control or immunologically in elite controllers. HIV and SIV-specific CD8+ T cells were dysfunctional and expressed high levels of TIGIT and PD-1. Ex-vivo single or combinational antibody blockade of TIGIT and/or PD-L1 restored viral-specific CD8+ T cell effector responses. The frequency of TIGIT+ CD4+ T cells correlated with the CD4+ T cell total HIV DNA. These findings identify TIGIT as a novel marker of dysfunctional HIV-specific T cells and suggest TIGIT along with other checkpoint receptors may be novel curative HIV targets to reverse T cell exhaustion.

Polyploidy, the inheritance of more than two genome copies per cell, has played a major role in the evolution of higher plants. Little is known about the transition from diploidy to polyploidy but in some species, triploids are thought to function as intermediates in this transition. In contrast, in other species triploidy is viewed as a block. We investigated the responses of Arabidopsis thaliana to triploidy. The role of genetic variability was tested by comparing triploids generated from crosses between Col-0, a diploid, and either a natural autotetraploid (Wa-1) or an induced tetraploid of Col-0. In this study, we demonstrate that triploids of A. thaliana are fertile, producing a swarm of different aneuploids. Propagation of the progeny of a triploid for a few generations resulted in diploid and tetraploid cohorts. This demonstrated that, in A. thaliana, triploids can readily form tetraploids and function as bridges between euploid types. Genetic analysis of recombinant inbred lines produced from a triploid identified a locus on chromosome I exhibiting allelic bias in the tetraploid lines but not in the diploid lines. Thus, genetic variation was subject to selection contingent on the final ploidy and possibly acting during the protracted aneuploid phase. (McClintock 1929). resolved, independent assortment produces mostly anThese studies introduced the idea that triploids could euploid gametes. As a result, the immediate progeny of produce viable aneuploids, which were mostly trisomics. triploids can be composed of a complex swarm of varied Variation for aneuploid production exists. For example, karyotypes, which differ in the number of copies of each triploids of cherry tomato produce more aneuploids than chromosome.

Studies on mucosal-associated invariant T cells (MAITs) in nonhuman primates (NHP), a physiologically relevant model of human immunity, are handicapped due to a lack of macaque MAIT-specific reagents. Here we show that while MR1 ligand-contact residues are conserved between human and multiple NHP species, three T cell receptor (TCR) contact residue mutations in NHP MR1 diminish binding of human MR1 tetramers to macaque MAITs. Construction of naturally loaded macaque MR1 tetramers facilitated identification and characterization of macaque MR1-binding ligands and MAITs, both of which mirrored their human counterparts. Using the macaque MR1 tetramer we show that NHP MAITs activated in vivo in response to both BCG vaccination and M. tuberculosis infection. These results demonstrate that NHP and human MR1 and MAITs function analogously, and establish a preclinical animal model to test MAIT-targeted vaccines and therapeutics for human infectious and autoimmune disease.

Alterations in the RAS signaling cascade are almost uniformly present in melanoma. RAS itself is only infrequently mutated in melanoma although downstream of RAS lie BRAF on the mitogenactivated protein kinase pathway and PTEN on the protein kinase B/Akt pathway.These genes are often altered in melanomas; indeed, the most frequent target of mutation in melanomas is BRAF, which is mutated in f60% to 70% of superficial spreading melanomas. These mutations occur in a background that is not normal, with the CDKN2A locus also typically being mutated.We review herein the data that suggest that the distribution of the signaling mutations is important. In general, melanomas carry a mutated NRAS, a mutated BRAF, or concurrent BRAF and PTEN mutations. These data support the hypothesis that the biochemical functions of RAS are portioned by mutations in the pathways lying downstream. Moreover, these mutations have no apparent relationship to the patterns of alteration of CDKN2A and its downstream effectors.Thus, the data also suggest that successful exploitation of mutations in melanoma will be dependent on understanding not only mutations and their frequency but their genetic context as well.The development of rational treatments for melanoma will depend on our taking advantage of the molecular basis of its clinical features. The necessary understanding of the molecular genetics underlying melanoma is gradually emerging. It has become clear that alterations in two genes and their downstream effectors are almost uniformly present in melanoma. The first of these is the CDKN2A locus, and the second is the pathway that includes RAS. Understanding the role alterations in these pathways play in melanoma and understanding their interactions may provide key insights that will lead to therapeutic interventions that are rationally designed and implemented.The CDKN2A locus encodes two tumor suppressor genes, CDKN2A/p16 and p14ARF, which play central roles in the control of cell cycle progression and checkpoint control. The p16-CDK4-pRB pathway in melanoma is almost always abnormal. CDKN2A also encodes the p53-controlling p14 ARF , and disruption of CDKN2A therefore usually results in both loss of pRB and p53 control. However, altered tumor suppressor loci, with resultant loss of function of the encoded proteins, are problematic therapeutic targets. Efforts to develop small-molecule CDK inhibitors, essentially mimics of p16, are ongoing but progress thus far has been slow.More important at present in our thinking about targeted therapy for melanoma is the RAS pathway. The RAS gene itself is infrequently mutated in melanoma. However, the RAS protein does several important functions, and downstream of it lie BRAF on the mitogen-activated protein kinase (MAPK) pathway and phosphatase and tensin homologue (PTEN) on the protein kinase B/Akt pathway. These genes are frequently altered in melanomas and it seems that the RAS-PTEN/BRAF axis is almost always abnormal. Mutated targets on this pathway are appealing therapeutic targets.In...

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28Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of 29 coronavirus disease 2019 , is now pandemic with nearly three million cases 30 reported to date 1 . Although the majority of COVID-19 patients experience only mild or 31 moderate symptoms, a subset will progress to severe disease with pneumonia and acute 32 respiratory distress syndrome (ARDS) requiring mechanical ventilation 2 . Emerging results 33 indicate a dysregulated immune response characterized by runaway inflammation, 34including cytokine release syndrome (CRS), as the major driver of pathology in severe 35 -19 3,4 . With no treatments currently approved for COVID-19, therapeutics to 36 prevent or treat the excessive inflammation in severe disease caused by SARS-CoV-2 37 infection are urgently needed. Here, in 10 terminally-ill, critical COVID-19 patients we 38 report profound elevation of plasma IL-6 and CCL5 (RANTES), decreased CD8+ T cell 39 levels, and SARS-CoV-2 plasma viremia. Following compassionate care treatment with 40 the CCR5 blocking antibody leronlimab, we observed complete CCR5 receptor 41 occupancy on macrophage and T cells, rapid reduction of plasma IL-6, restoration of the 42 CD4/CD8 ratio, and a significant decrease in SARS-CoV-2 plasma viremia. Consistent 43 with reduction of plasma IL-6, single-cell RNA-sequencing revealed declines in 44 transcriptomic myeloid cell clusters expressing IL-6 and interferon-related genes. These 45 results demonstrate a novel approach to resolving unchecked inflammation, restoring 46 immunologic deficiencies, and reducing SARS-CoV-2 plasma viral load via disruption of 47 COVID MAIN TEXT 51 52Since the initial cases of COVID-19 were reported from Wuhan, China in December 53 2019 2 , SARS-CoV-2 has emerged as a global pandemic with an ever-increasing number 54 of severe cases requiring invasive external ventilation that threatens to overwhelm health 55

Hepatitis B virus (HBV) is a major global health concern, and the development of curative therapeutics is urgently needed. Such efforts are impeded by the lack of a physiologically relevant, pre-clinical animal model of HBV infection. Here, we report that expression of the HBV entry receptor, human sodium-taurocholate cotransporting polypeptide (hNTCP), on macaque primary hepatocytes facilitates HBV infection in vitro, where all replicative intermediates including covalently closed circular DNA (cccDNA) are present. Furthermore, viral vector-mediated expression of hNTCP on hepatocytes in vivo renders rhesus macaques permissive to HBV infection. These in vivo macaque HBV infections are characterized by longitudinal HBV DNA in serum, and detection of HBV DNA, RNA, and HBV core antigen (HBcAg) in hepatocytes. Together, these results show that expressing hNTCP on macaque hepatocytes renders them susceptible to HBV infection, thereby establishing a physiologically relevant model of HBV infection to study immune clearance and test therapeutic and curative approaches.