RNA granules are cytoplasmic, microscopically visible, non-membrane ribo-nucleoprotein structures and are important posttranscriptional regulators in gene expression by controlling RNA translation and stability. TIA/G3BP/PABP-specific stress granules (SG) and GW182/DCP-specific RNA processing bodies (PB) are two major distinguishable RNA granules in somatic cells and contain various ribosomal subunits, translation factors, scaffold proteins, RNA-binding proteins, RNA decay enzymes and helicases to exclude mRNAs from the cellular active translational pool. Although SG formation is inducible due to cellular stress, PB exist physiologically in every cell. Both RNA granules are important components of the host antiviral defense. Virus infection imposes stress on host cells and thus induces SG formation. However, both RNA and DNA viruses must confront the hostile environment of host innate immunity and apply various strategies to block the formation of SG and PB for their effective infection and multiplication. This review summarizes the current research development in the field and the mechanisms of how individual viruses suppress the formation of host SG and PB for virus production.

Hepatitis C virus (HCV) entry into permissive cells is a complex process that involves interactions with at least four co-factors followed by endocytosis and low pH-dependent fusion with endosomes. The precise sequence of receptor engagement and their roles in promoting HCV E1E2 glycoprotein-mediated fusion are poorly characterized. Because cell-free HCV tolerates an acidic environment, we hypothesized that binding to one or more receptors on the cell surface renders E1E2 competent to undergo low pH-induced conformational changes and promote fusion with endosomes. To test this hypothesis, we examined the effects of low pH and of the second extracellular loop (ECL2) of CD81, one of the four entry factors, on HCV infectivity. Pretreatment with an acidic buffer or with ECL2 enhanced infection through changing the E1E2 conformation, as evidenced by the altered reactivity of these proteins with conformation-specific antibodies and stable association with liposomes. However, neither of the two treatments alone permitted direct fusion with the cell plasma membrane. Sequential HCV preincubation with ECL2 and acidic buffer in the absence of target cells resulted in a marked loss of infectivity, implying that the receptor-bound HCV is primed for low pH-dependent conformational changes. Indeed, soluble receptor-pretreated HCV fused with the cell plasma membrane at low pH under conditions blocking an endocytic entry pathway. These findings suggest that CD81 primes HCV for low pH-dependent fusion early in the entry process. The simple triggering paradigm and intermediate conformations of E1E2 identified in this study could help guide future vaccine and therapeutic efforts to block HCV infection. Hepatitis C virus (HCV)3 entry into permissive cells is initiated through its E1 and E2 glycoprotein interactions with at least four cellular co-factors as follows: CD81; scavenger receptor class B, type I (SR-BI); and two tight junction-resident proteins, claudin-1 and occludin (1-6). CD81 belongs to the tetraspanin family and thus contains two extracellular loops, of which the second larger loop (ECL2) specifically binds to the HCV E2 glycoprotein (7, 8). SR-BI, which is normally involved in the regulation of lipoprotein metabolism and cholesterol trafficking (9), plays a role in early steps of HCV entry (10 -12); however, its direct interaction with the virus has not been unambiguously demonstrated. Claudin-1 and occludin also consist of four transmembrane domains but are functionally distinct from tetraspanins. The HCV entry determinants of claudin-1 and occludin have been mapped to the first and the second extracellular loops of these proteins, respectively (4,13,14). Considering that all four HCV entry co-factors are expressed in non-liver tissues (1, 5), the narrow tropism of this virus is surprising. It is thus likely that the relative expression levels of entry co-factors, their spatial organization, and/or interactions with each other render a cell permissive to infection (15). An alternative possibility suggested in a rece...

We have previously reported that two receptor tyrosine kinase inhibitors (RTKIs), called AG879 and tyrphostin A9 (A9), can each block the replication of influenza A virus in cultured cells. In this study, we further characterized the in vitro antiviral efficacies and specificities of these agents. The 50% effective concentration (EC 50 ) of each against influenza A was found to be in the high nanomolar range, and the selectivity index (SI ‫؍‬ 50% cytotoxic concentration [CC 50 ]/EC 50 ) was determined to be >324 for AG879 and 50 for A9, indicating that therapeutically useful concentrations of each drug produce only low levels of cytotoxicity. Each compound showed efficacy against representative laboratory strains of both human influenza A (H1N1 or H3N2) and influenza B viruses. Importantly, no drug-resistant influenza virus strains emerged even after 25 viral passages in the presence of AG879, whereas viruses resistant to amantadine appeared after only 3 passages. AG879 and A9 each also exhibited potent inhibitory activity against a variety of other RNA and DNA viruses, including Sendai virus (Paramyxoviridae), herpes simplex virus (Herpesviridae), mouse hepatitis virus (Coronaviridae), and rhesus rotavirus (Reoviridae), but not against Pichinde virus (Arenaviridae). These results together suggest that RTKIs may be useful as therapeutics against viral pathogens, including but not limited to influenza, due to their high selectivity indices, low frequency of drug resistance, and broad-spectrum antiviral activities.

This study investigated the preparedness and views of patients with perinatally acquired HIV and their family caregivers about transitioning to adult medical care. Fifteen participants (ages 15-24 years) with perinatally acquired HIV and eight family caregivers participated in structured interviews. All interviews were recorded and analyzed for themes using qualitative research methodology. Three major themes emerged: (a) perceived lack of readiness for transition, (b) fear of change and anxiety about entering the adult health care system, and (c) burgeoning personal responsibility that comes with age. Participants also offered suggestions to improve the transition experience, including starting the process early with specific guidelines. All patients and family caregivers wanted early knowledge about transition; these individuals could be an important resource to find potential solutions to guide the transition process. Clinical outcomes must be assessed in patients undergoing transition to determine the effect on management of medical disease, and protocols must be developed.

TIA-1 positive stress granules (SG) represent the storage sites of stalled mRNAs and are often associated with the cellular antiviral response. In this report, we provide evidence that Kaposi’s sarcoma-associated herpesvirus (KSHV) overcomes the host antiviral response by inhibition of SG formation via a viral lytic protein ORF57. By immunofluorescence analysis, we found that B lymphocytes with KSHV lytic infection are refractory to SG induction. KSHV ORF57, an essential post-transcriptional regulator of viral gene expression and the production of new viral progeny, inhibits SG formation induced experimentally by arsenite and poly I:C, but not by heat stress. KSHV ORF37 (vSOX) bearing intrinsic endoribonuclease activity also inhibits arsenite-induced SG formation, but KSHV RTA, vIRF-2, ORF45, ORF59 and LANA exert no such function. ORF57 binds both PKR-activating protein (PACT) and protein kinase R (PKR) through their RNA-binding motifs and prevents PACT-PKR interaction in the PKR pathway which inhibits KSHV production. Consistently, knocking down PKR expression significantly promotes KSHV virion production. ORF57 interacts with PKR to inhibit PKR binding dsRNA and its autophosphorylation, leading to inhibition of eIF2α phosphorylation and SG formation. Homologous protein HSV-1 ICP27, but not EBV EB2, resembles KSHV ORF57 in the ability to block the PKR/eIF2α/SG pathway. In addition, KSHV ORF57 inhibits poly I:C-induced TLR3 phosphorylation. Altogether, our data provide the first evidence that KSHV ORF57 plays a role in modulating PKR/eIF2α/SG axis and enhances virus production during virus lytic infection.

The immunogenicity of the conjugate prepared from "processed" a-subunit of human chorionic gonadotropin (choriogonadotropin, HCG) and tetanus toxoid has been studied in animals and a human subject. The conjugate elicited the formation of high-affinity (Ka = 109-101' M-') anti-HCG and anti-tetanus antibodies. On primary immunization, the antibody response lasted for several months. Repeat injection of the conjugate in the declining phase of antibody titers produced a booster response without a lag period. The antibodies reacted with the ,8-subunit of HCG and the complete HCG molecule but were devoid of significant crossreactivity with human growth hormone, placental lactogen, follicle-stimulating hormone, thyroid-stimulating hormone, and luteinizing hormone at tonic and surge levels. The antibodies were competent for neutralizing the biological activity of HCG in the mouse uterine weight gain assay, the ventral prostate weight gain assay, and the radioligand assay for binding of 1251-labeled HCG to receptors on corpus luteum. HCG (5000 international units) administered to an immunized subject was completely bound by circulating antibodies. Administration of HCG (in contrast to conjugate) was without booster effect on anti-HCG titers.

Cellular non-membranous RNA-granules, P-bodies (RNA processing bodies, PB) and stress granules (SG), are important components of the innate immune response to virus invasion. Mechanisms governing how a virus modulates PB formation remain elusive. Here, we report the important roles of GW182 and DDX6, but not Dicer, Ago2 and DCP1A, in PB formation, and that Kaposi’s sarcoma-associated herpesvirus (KSHV) lytic infection reduces PB formation through several specific interactions with viral RNA-binding protein ORF57. The wild-type ORF57, but not its N-terminal dysfunctional mutant, inhibits PB formation by interacting with the N-terminal GW-domain of GW182 and the N-terminal domain of Ago2, two major components of PB. KSHV ORF57 also induces nuclear Ago2 speckles. Homologous HSV-1 ICP27, but not EBV EB2, shares this conserved inhibitory function with KSHV ORF57. By using time-lapse confocal microscopy of HeLa cells co-expressing GFP-tagged GW182, we demonstrated that viral ORF57 inhibits primarily the scaffolding of GW182 at the initial stage of PB formation. Consistently, KSHV-infected iSLK/Bac16 cells with reduced GW182 expression produced far fewer PB and SG, but 100-fold higher titer of infectious KSHV virions when compared to cells with normal GW182 expression. Altogether, our data provide the first evidence that a DNA virus evades host innate immunity by encoding an RNA-binding protein that promotes its replication by blocking PB formation.

Microtubules and their associated proteins play a prominent role in many physiological and morphological aspects of brain function. Abnormal deposition of the microtubule‐associated proteins (MAPs), MAP2 and γ, is a prominent aspect of Alzheimer's disease. MAP2 and γ are heat‐stable phosphoproteins subject to high rates of phosphorylation/dephosphorylation. The phosphorylation state of these proteins modulates their affinity for tubulin and thereby affects the structure of the neuronal cytoskeleton. The dinoflagellate toxin okadaic acid is a potent and specific inhibitor of protein phosphatases 1 and 2A. In cultured rat cortical neurons and a human neuroblastoma cell line (MSN), okadaic acid induces increased phosphorylation of MAP2 and γ concomitant with early changes in the neuronal cytoskeleton and ultimately leads to cell death. These results suggest that the diminished rate of MAP2 and γ dephosphorylation affects the stability of the neuronal cytoskeleton. The effect of okadaic acid was not restricted to neurons. Astrocytes stained with antibodies to glial fibrillary acidic protein (GFAP) showed increased GFAP staining and changes in astrocyte morphology from a flat shape to a stellate appearance with long processes.