No abstract

Accumulating data suggest that tripartite-motif-containing (TRIM) proteins participate in host responses to viral infections, either by acting as direct antiviral restriction factors or through regulating innate immune signaling of the host. Of >70 TRIMs, TRIM56 is a restriction factor of several positive-strand RNA viruses, including three members of the family Flaviviridae (yellow fever virus, dengue virus, and bovine viral diarrhea virus) and a human coronavirus (OC43), and this ability invariably depends upon the E3 ligase activity of TRIM56. However, the impact of TRIM56 on negative-strand RNA viruses remains unclear. Here, we show that TRIM56 puts a check on replication of influenza A and B viruses in cell culture but does not inhibit Sendai virus or human metapneumovirus, two paramyxoviruses. Interestingly, the anti-influenza virus activity was independent of the E3 ligase activity, B-box, or coiled-coil domain. Rather, deletion of a 63-residue-long C-terminal-tail portion of TRIM56 abrogated the antiviral function. Moreover, expression of this short C-terminal segment curtailed the replication of influenza viruses as effectively as that of full-length TRIM56. Mechanistically, TRIM56 was found to specifically impede intracellular influenza virus RNA synthesis. Together, these data reveal a novel antiviral activity of TRIM56 against influenza A and B viruses and provide insights into the mechanism by which TRIM56 restricts these medically important orthomyxoviruses. IMPORTANCE Options to treat influenza are limited, and drug-resistant influenza virus strains can emerge through minor genetic changes. Understanding novel virus-host interactions that alter influenza virus fitness may reveal new targets/approaches for therapeutic interventions.We show here that TRIM56, a tripartite-motif protein, is an intrinsic host restriction factor of influenza A and B viruses. Unlike its antiviral actions against positive-strand RNA viruses, the anti-influenza virus activity of TRIM56 was independent of the E3 ligase activity. Rather, expression of a short segment within the very C-terminal tail of TRIM56 inhibited the replication of influenza viruses as effectively as that of full-length TRIM56 by specifically targeting viral RNA synthesis. These data reveal the remarkable multifaceted activity of TRIM56, which has developed multiple domains to inhibit multiple viral families. They also raise the possibility of developing a broad-spectrum, TRIM56-based antiviral approach for addition to influenza prophylaxis and/or control strategies.

Immature function of the alveolar macrophage increases the risk of pulmonary infections in premature newborns. In utero alcohol increases fetal systemic oxidative stress. Because the premature lung is deficient in glutathione (GSH), we hypothesized that chronic in utero alcohol (ethanol) exposure exacerbates the oxidative stress within the developing lung, thereby impairing alveolar macrophage function. Additionally, we evaluated the effects of in vivo and in vitro GSH availability on ethanol-exposed macrophage function. Using a guinea pig model of chronic in utero ethanol exposure, fetal epithelial lining fluid (ELF) and alveolar macrophage GSH were decreased with increased markers of oxidative stress. Ethanol-exposed macrophage exhibited impaired phagocytosis and increased apoptosis compared with gestational control. When the GSH precursor S-adenosyl-methionine (SAM) was added to the maternal drinking water containing ethanol, fetal ELF and macrophage GSH were maintained and ELF oxidative stress diminished. In vivo maternal SAM therapy maintained macrophage phagocytosis and decreased apoptosis. In vitro GSH supplements also improved phagocytosis and viability in both premature and ethanolexposed macrophage. This suggested that in utero ethanol impaired premature macrophage function and viability via decreased GSH availability. Furthermore, GSH supplementation during and after ethanol exposure improved fetal macrophage function and viability. These results add a new dimension to the detrimental effects of fetal alcohol exposure on the developing alveolar macrophage, raising the possibility of GSH therapy to augment premature alveolar macrophage function. Fetal alcohol exposure remains a significant problem in our society. Alcohol abuse and binge drinking by pregnant women has been estimated at an alarming 35% of pregnancies (1-3). Fetal alcohol syndrome or alcohol-related neurodevelopmental disorder has been estimated to occur in ‫0001/1ف‬ pregnancies (4). Because there is a strong relationship between cocaine abuse and concurrent alcohol ingestion (5-7), and both substances may increase the risk of premature delivery (7,8), a significant population of premature infants is exposed to alcohol in utero.In animal models of fetal alcohol exposure, alcohol increases systemic oxidative stress in the developing fetus (9 -14). A decrease in the antioxidant GSH has been demonstrated, particularly in the alcohol-exposed fetal liver (9,15,16). As an essential antioxidant in the body, GSH is normally present in high concentrations in the ELF of the lung (17). The fetal lung is at risk for increased oxidative stress during development, because maturation of antioxidant systems, including GSH, is gestationally dependent (18,19). A reduction in alveolar GSH, as seen in the premature infant, leaves the preterm lung susceptible to increased pulmonary oxidative injury (20,21) and chronic lung disease (18,22). The impact of the oxidative stress of fetal alcohol exposure superimposed on the low GSH environment of the developing lu...

Currently, infections with SARS-Coronavirus-2 (SARS-CoV-2), the causative agent of the COVID-19 pandemic, are responsible for substantial morbidity and mortality worldwide. Older adults subjects > 60 years of age account for > 95% of the over one million fatal cases reported to date. It is unclear why in this age group SARS-CoV-2 infection causes more severe disease than in young adults. We hypothesized that differences in SARS-CoV-2 cross-reactive cellular immunity induced after infection with human coronaviruses (HCoVs), like OC43 and NL63, were at the basis of the differential mortality (and morbidity) observed after SARS-CoV-2 infection, because a small proportion of HCoV-specific T cells cross-react with SARS-CoV-2. Our data demonstrate that pre-existing T cell immunity induced by circulating human alpha- and beta-HCoVs is present in young adult individuals, but virtually absent in older adult subjects. Consequently, the frequency of cross-reactive T cells directed to the novel pandemic SARS-CoV-2 was minimal in most older adults. To the best of our knowledge, this is the first time that the presence of cross-reactive T cells to SARS-CoV-2 is compared in young and older adults. Our findings provide at least a partial explanation for the more severe clinical outcome of SARS-CoV-2 infection observed in the elderly. Moreover, this information could help to design efficacious vaccines for this age group, aiming at the induction of cell-mediated immunity.

Influenza A viruses (IAVs) are a major cause of respiratory illness and are responsible for yearly epidemics associated with more than 500,000 annual deaths globally. Novel IAVs may cause pandemic outbreaks and zoonotic infections with, for example, highly pathogenic avian influenza virus (HPAIV) of the H5N1 and H7N9 subtypes, which pose a threat to public health. Treatment options are limited and emergence of strains resistant to antiviral drugs jeopardize this even further. Like all viruses, IAVs depend on host factors for every step of the virus replication cycle. Host kinases link multiple signaling pathways in respond to a myriad of stimuli, including viral infections. Their regulation of multiple response networks has justified actively targeting cellular kinases for anti-cancer therapies and immune modulators for decades. There is a growing volume of research highlighting the significant role of cellular kinases in regulating IAV infections. Their functional role is illustrated by the required phosphorylation of several IAV proteins necessary for replication and/or evasion/suppression of the innate immune response. Identified in the majority of host factor screens, functional studies further support the important role of kinases and their potential as host restriction factors. PKC, ERK, PI3K and FAK, to name a few, are kinases that regulate viral entry and replication. Additionally, kinases such as IKK, JNK and p38 MAPK are essential in mediating viral sensor signaling cascades that regulate expression of antiviral chemokines and cytokines. The feasibility of targeting kinases is steadily moving from bench to clinic and already-approved cancer drugs could potentially be repurposed for treatments of severe IAV infections. In this review, we will focus on the contribution of cellular kinases to IAV infections and their value as potential therapeutic targets.