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Persistent viruses cause chronic disease, and threaten the lives of immunosuppressed individuals. Here, we elucidate a mechanism supporting the persistence of human adenovirus (AdV), a virus that can kill immunosuppressed patients. Cell biological analyses, genetics and chemical interference demonstrate that one of five AdV membrane proteins, the E3-19K glycoprotein specifically triggers the unfolded protein response (UPR) sensor IRE1α in the endoplasmic reticulum (ER), but not other UPR sensors, such as protein kinase R-like ER kinase (PERK) and activating transcription factor 6 (ATF6). The E3-19K lumenal domain activates the IRE1α nuclease, which initiates mRNA splicing of X-box binding protein-1 (XBP1). XBP1s binds to the viral E1A-enhancer/promoter sequence, and boosts E1A transcription, E3-19K levels and lytic infection. Inhibition of IRE1α nuclease interrupts the five components feedforward loop, E1A, E3-19K, IRE1α, XBP1s, E1A enhancer/promoter. This loop sustains persistent infection in the presence of the immune activator interferon, and lytic infection in the absence of interferon.

Dysregulated endogenous retroelements (EREs) are increasingly implicated in the initiation, progression, and immune surveillance of human cancer. However, incomplete knowledge of ERE activity limits mechanistic studies. By using pan-cancer de novo transcript assembly, we uncover the extent and complexity of ERE transcription. The current assembly doubled the number of previously annotated transcripts overlapping with long-terminal repeat (LTR) elements, several thousand of which were expressed specifically in one or a few related cancer types. Exemplified in melanoma, LTR-overlapping transcripts were highly predictable, disease prognostic, and closely linked with molecularly defined subtypes. They further showed the potential to affect disease-relevant genes, as well as produce novel cancer-specific antigenic peptides. This extended view of LTR elements provides the framework for functional validation of affected genes and targets for cancer immunotherapy., (© 2019 Attig et al.; Published by Cold Spring Harbor Laboratory Press.)

Cytomegalovirus (CMV) infection elicits a strong T-cell immune response, which increases further during aging in a process termed "memory inflation." CMV downregulates the expression of HLA-A and HLA-B on the surface of infected cells to limit presentation of viral peptides to T-cells although HLA-C is relatively spared as it also engages with inhibitory killer immunoglobulin receptor receptors and therefore reduces lysis by natural killer cells. We investigated the magnitude and functional properties of CMV-specific CD8 + T-cells specific for 10 peptides restricted by HLA-C in a cohort of 53 donors between the age of 23 and 91 years. This was achieved via peptide stimulation of PBMCs followed by multicolor flow cytometry. Three peptides, derived from proteins generated in the immediate-early period of viral replication and restricted by HLA-Cw*0702, elicited strong immune responses, which increased substantially with age such that the average aggregate response represented 37% of the CD8 + T-cell pool within donors above 70 years of age. Remarkably, a single response represented 70% of the total CD8 + T-cell pool within a 91-year-old donor. HLA-Cw*0702-restricted CD8 + T-cell responses were immunodominant over HLA-A and HLA-B-restricted CMV-specific responses and did not show features of exhaustion such as PD-1 or CD39 expression. Indeed, such CTL exhibit a polyfunctional cytokine profile with co-expression of IFN-γ and TNF-α and a strong cytotoxic phenotype with intracellular expression of perforin and granzymeB. Functionally, HLA-Cw*0702-restricted CTL show exceptionally high avidity for cognate peptide-HLA and demonstrate very early and efficient recognition of virally infected cells. These observations indicate that CD8 + T-cells restricted by HLA-C play an important role in the control of persistent CMV infection and could represent a novel opportunity for CD8 + T-cell therapy of viral infection within immunosuppressed patients. In addition, the findings provide further evidence for the importance of HLA-C-restricted T-cells in the control of chronic viral infection.

Neither kcat. nor kcat./Km for five aryl alpha-D-glucopyranosides correlates with aglycone pKa, and isotope effects, described according to the convention used by Cleland [(1982) CRC Crit. Rev. Biochem. 13, 385-428], of 18(V) = 1.002 +/- 0.008, alpha D(V) = 1.01 +/- 0.04 and alpha D(V/K) = 0.969 +/- 0.035 are observed for p-nitrophenyl, and one of beta D(V) = 1.02 +/- 0.04 for phenyl alpha-D-glucopyranoside; kcat. but not kcat./Km, correlates with aglycone pKa for five alpha-D-glucopyranosyl pyridinium ions with a Brønsted coefficient of -0.61 +/- 0.06, and isotope effects of alpha D(V) = 1.22 +/- 0.02, beta D(V) = 1.13 +/- 0.01 and alpha D(V/K) = 1.018 +/- 0.046 for the 4-bromoisoquinolinium, and alpha D(V) = 1.15 +/- 0.02 and beta D(V) = 1.085 +/- 0.011 for the pyridinium salts are observed. These data require that a non-covalent event, fast in the case of the N-glycosides but slow in the case of the O-glycosides, precedes bond-breaking, and that bond-breaking involves substantial charge development on the glycone and near-perpendicularity of the C2-H bond to the planar oxocarbonium ion system. A model meeting these requirements is that the non-covalent event is a conjoint change of protein and substrate conformation which puts the pyranose ring in the 2,5B conformation of the bond-breaking transition state. This model also explains the contrast between the powerful inhibition of the enzyme by deoxynojirimycin (Ki = 23 +/- 3 microM) and feeble inhibition by castanospermine [Saul, Chambers, Molyneux & Elbein (1983) Arch. Biochem. Biophys. 221, 593-597], but is directly contrary to the predictions of Deslongchamps' 'Theory of Stereoelectronic Control' [Deslongchamps (1975) Tetrahedron 31, 2463-2490; (1983) Stereoelectronic Effects in Organic Chemistry, p. 39, Pergamon Press, Oxford].