Genetic association of the antiviral restriction factor TRIM5alpha with human immunodeficiency virus type 1 infection

The innate antiviral factor TRIM5alpha restricts the replication of some retroviruses through its interaction with the viral capsid protein, leading to abortive infection. While overexpression of human TRIM5alpha results in modest restriction of human immunodeficiency virus type 1 (HIV-1), this inhibition is insufficient to block productive infection of human cells. We hypothesized that polymorphisms within TRIM5 may result in increased restriction of HIV-1 infection. We sequenced the TRIM5 gene (excluding exon 5) and the 4.8-kb 5' putative regulatory region in genomic DNA from 110 HIV-1-infected subjects and 96 exposed seronegative persons, along with targeted gene sequencing in a further 30 HIV-1-infected individuals. Forty-eight single nucleotide polymorphisms (SNPs), including 20 with allele frequencies of >1.0%, were identified. Among these were two synonymous and eight nonsynonymous coding polymorphisms. We observed no association between TRIM5 polymorphism in HIV-1-infected subjects and their set-point viral load after acute infection, although one TRIM5 haplotype was weakly associated with more rapid CD4(+) T-cell loss. Importantly, a TRIM5 haplotype containing the nonsynonymous SNP R136Q showed increased frequency among HIV-1-infected subjects relative to exposed seronegative persons, with an odds ratio of 5.49 (95% confidence interval = 1.83 to 16.45; P = 0.002). Nonetheless, we observed no effect of individual TRIM5alpha nonsynonymous mutations on the in vitro HIV-1 susceptibility of CD4(+) T cells. Therefore, any effect of TRIM5alpha polymorphism on HIV-1 infection in primary lymphocytes may depend on combinations of SNPs or on DNA sequences in linkage disequilibrium with the TRIM5alpha coding sequence.     

Orthostatic panic as a key Vietnamese reaction to traumatic events: the case of September 11, 2001

This article discusses a culturally specific response to traumatic events: orthostatic panic attacks among Vietnamese refugees. We compared the rate and severity of orthostatic panic as well as the rates and severity of associated flashbacks a month before and a month after September 11, 2001. After that date, the rate and severity of orthostatic panic greatly increased, as did the rate and severity of associated flashbacks. The central role of orthostatic panic as a response to traumatic events is illustrated through a patient's vignette. An explanation of why September 11 so profoundly influenced this population is adduced, including an explanation of why it resulted in considerable worsening of orthostatic panic.     

Maximal heart rate prediction in adults that are overweight or obese

An accurate predictor of maximal heart rate (MHR) is necessary to prescribe safe and effective exercise in those considered overweight and obese when actual measurement of MHR is unavailable or contraindicated. To date, accuracy of MHR prediction equations in individuals that are overweight or obese has not been well established. The purpose of this study was to examine the accuracy of 3 equations for predicting MHR in adults that are overweight or obese. One hundred seventy-three sedentary adults that were overweight or obese enrolled in weight-loss study and performed a VO?peak treadmill test before the start of the weight loss treatment. A total of 132 of the 173 participants met conditions for achieving maximal exercise testing criteria and were included in this study. Maximal heart rate values determined from VO?peak treadmill tests were compared across gender, age, and weight status with the following prediction equations: (a) 220 - age, (b) 208 - 0.7 × age, and (c) 200 - 0.48 × age. Among 20- to 40-year-old participants, actual MHR averaged 180 ± 9 b·min?1 and was overestimated (p < 0.001) at 186 ± 5 b·min?1 with the 220 - age equation. Weight status did not affect predictive accuracy of any of the 3 equations. For all participants, the equation, 200-0.48 × age estimated MHR to be 178 ± 4 b·min?1, which was greater than the actual value (175 ± 12, p = 0.005). Prediction equations showed close agreement to actual MHR, with 208 - 0.7 × age being the most accurate.     

Notch receptor-ligand binding and activation: insights from molecular studies

The Notch receptor is part of a core signalling pathway which is highly conserved in all metazoan species. It is required for various cell fate decisions at multiple stages of development and in the adult organism, with dysregulation of the pathway associated with genetic and acquired diseases including cancer. Although cellular and in vivo studies have provided considerable insight into the downstream consequences of Notch signalling, relatively little is known about the molecular basis of the receptor/ligand interaction and initial stages of activation. Recent advances in structure determination of the extracellular regions of human Notch-1 and one of its ligands Jagged-1 have given new insights into docking events occurring at the cell surface which may facilitate the development of new highly specific therapies. We review the structural data available for receptor and ligands and identify the challenges ahead.     

MyD88 plays a critical T cell-intrinsic role in supporting CD8 T cell expansion during acute lymphocytic choriomeningitis virus infection

During acute lymphocytic choriomeningitis virus (LCMV) infection, CD8 T cells rapidly expand and differentiate into effectors that are required for viral clearance. The accumulation of activated T cells is greatly reduced in mice lacking the adaptor molecule MyD88. Although MyD88 has generally been considered to indirectly regulate adaptive immune responses by controlling inflammatory cytokine production and Ag presentation in innate immune cells, in this study, we identify an unappreciated cell-intrinsic role for MyD88 in LCMV-specific CD8 T cells. Using reciprocal adoptive transfer models and bone marrow chimeras, we show that Myd88(-/-) CD8 T cells are defective in their clonal expansion in response to LCMV infection, independent of their environment. Furthermore, we show that while MyD88 is dispensable for initial activation and division of LCMV-specific CD8 T cells during the early stages of viral infection, MyD88-dependent signals are critical for supporting their survival and sustained accumulation.     

The use of fluorescent fatty acid analogs as labels in trematode experimental infections

We examined the utility of fluorescent fatty acid analog dyes for labeling larval trematodes to use in experimental infections. Our goals were to identify two dyes that label larval trematodes belonging to the species Maritrema novaezealandensis and Coitocaecum parvum, determine if the dyes influence survival and infectivity of larval trematodes and/or host mortality, and if larval trematodes labeled with alternative dyes could be distinguished post-infection. The two dyes tested, BODIPY FL C₁₂ and BODIPY 558/568 C₁₂, successfully labeled all treated larval trematodes, did not influence cercariae survival or infectivity, and did not influence host mortality in either host-parasite system. All larval parasites were fluorescent and distinguishable after 5 days in amphipod intermediate hosts. In addition, larval Acanthoparyphium sp. were strongly fluorescent with both dyes after 5 weeks within cockle hosts. This method should be extremely useful for experimental studies using trematode-host systems as models for addressing a range of ecological and evolutionary questions.     

PMR5, an acetylation protein at the intersection of pectin biosynthesis and defense against fungal pathogens

Powdery mildew (Golovinomyces cichoracearum), one of the most prolific obligate biotrophic fungal pathogens worldwide, infects its host by penetrating the plant cell wall without activating the plant's innate immune system. The Arabidopsis mutant powdery mildew resistant 5 (pmr5) carries a mutation in a putative pectin acetyltransferase gene that confers enhanced resistance to powdery mildew. Here, we show that heterologously expressed PMR5 protein transfers acetyl groups from [¹⁴C]‐acetyl‐CoA to oligogalacturonides. Through site‐directed mutagenesis, we show that three amino acids within a highly conserved esterase domain in putative PMR5 orthologs are necessary for PMR5 function. A suppressor screen of mutagenized pmr5 seed selecting for increased powdery mildew susceptibility identified two previously characterized genes affecting the acetylation of plant cell wall polysaccharides, RWA2 and TBR. The rwa2 and tbr mutants also suppress powdery mildew disease resistance in pmr6, a mutant defective in a putative pectate lyase gene. Cell wall analysis of pmr5 and pmr6, and their rwa2 and tbr suppressor mutants, demonstrates minor shifts in cellulose and pectin composition. In direct contrast to their increased powdery mildew resistance, both pmr5 and pmr6 plants are highly susceptibile to multiple strains of the generalist necrotroph Botrytis cinerea, and have decreased camalexin production upon infection with B. cinerea. These results illustrate that cell wall composition is intimately connected to fungal disease resistance and outline a potential route for engineering powdery mildew resistance into susceptible crop species.     

HIV-mediated phosphatidylinositol 3-kinase/serine-threonine kinase activation in APCs leads to programmed death-1 ligand upregulation and suppression of HIV-specific CD8 T cells

Recent evidence demonstrates that HIV-1 infection leads to the attenuation of cellular immune responses, which has been correlated with the increased expression of programmed death (PD)-1 on virus-specific CD8(+) T cells. PD-1 is induced upon T cell activation, and its prolonged expression facilitates CD8(+) T cell inhibitory signals when bound to its B7 family ligands, PD-ligand (L)1/2, which are expressed on APCs. Importantly, early reports demonstrated that blockade of the PD-1/PD-L interaction by Abs may help to counter the development of immune exhaustion driven by HIV viral persistence. To better understand the regulation of the PD-1 pathway during HIV infection, we examined the ability of the virus to induce PD-L expression on macrophages and dendritic cells. We found a direct relationship between the infection of APCs and the expression of PD-L1 in which virus-mediated upregulation induced a state of nonresponsiveness in uninfected HIV-specific T cells. Furthermore, this exhaustion phenotype was revitalized by the blockade of PD-L1, after which T cells regained their capacity for proliferation and the secretion of proinflammatory cytokines IFN-γ, IL-2, and IL-12 upon restimulation. In addition, we identify a critical role for the PI3K/serine-threonine kinase signaling pathway in PD-L1 upregulation of APCs by HIV, because inhibition of these intracellular signal transducer enzymes significantly reduced PD-L1 induction by infection. These data identify a novel mechanism by which HIV exploits the immunosuppressive PD-1 pathway and suggest a new role for virus-infected cells in the local corruption of immune responses required for viral suppression.