The Emerging Role of Non-Coding RNAs in the Regulation of Virus Replication and Resultant Cellular Pathologies

Non-coding RNAs, particularly lncRNAs and miRNAs, have recently been shown to regulate different steps in viral infections and induction of immune responses against viruses. Expressions of several host and viral lncRNAs have been found to be altered during viral infection. These lncRNAs can exert antiviral function via inhibition of viral infection or stimulation of antiviral immune response. Some other lncRNAs can promote viral replication or suppress antiviral responses. The current review summarizes the interaction between ncRNAs and herpes simplex virus, cytomegalovirus, and Epstein–Barr infections. The data presented in this review helps identify viral-related regulators and proposes novel strategies for the prevention and treatment of viral infection.

Gain-of-function genetic screening identifies the antiviral function of TMEM120A via STING activation

Zika virus (ZIKV) infection can be associated with neurological pathologies, such as microcephaly in newborns and Guillain-Barre syndrome in adults. Effective therapeutics are currently not available. As such, a comprehensive understanding of virus-host interactions may guide the development of medications for ZIKV. Here we report a human genome-wide overexpression screen to identify host factors that regulate ZIKV infection and find TMEM120A as a ZIKV restriction factor. TMEM120A overexpression significantly inhibits ZIKV replication, while TMEM120A knockdown increases ZIKV infection in cell lines. Moreover, Tmem120a knockout in mice facilitates ZIKV infection in primary mouse embryonic fibroblasts (MEF) cells. Mechanistically, the antiviral activity of TMEM120A is dependent on STING, as TMEM120A interacts with STING, promotes the translocation of STING from the endoplasmic reticulum (ER) to ER-Golgi intermediate compartment (ERGIC) and enhances the phosphorylation of downstream TBK1 and IRF3, resulting in the expression of multiple antiviral cytokines and interferon-stimulated genes. In summary, our gain-of-function screening identifies TMEM120A as a key activator of the antiviral signaling of STING.

ILDR1 Promotes Influenza a Virus Replication Through Binding to PLSCR1

As a natural antiviral regulator, phospholipid scramblase 1 (PLSCR1) has been shown to inhibit influenza virus replication in infected cells through interacting with NP of influenza A virus (IAV). But its antiviral function as well as the underlying regulatory mechanism has not been examined in vivo. In the present work, we show that PLSCR1 expression is decreased in H1N1 SIV-infected mice, and Plscr1−/−mice are more susceptible to H1N1 SIV infection. By performing yeast two-hybrid screening, we identified immunoglobulin-like domain-containing receptor 1 (ILDR1) as a novel PLSCR1-binding partner. ILDR1 is highly expressed in the lungs, and its expression level is increased after virus infection. Interestingly, ILDR1 could not directly interact with virus NP protein, but could combine with PLSCR1 competitively. Our data indicates that there is a previously unidentified PLSCR1-ILDR1-NP regulatory pathway playing a vital role in limiting IAV infection, which provides novel insights into IAV-host interactions.

NAD+-consuming enzymes in immune defense against viral infection

The COVID-19 pandemic reminds us that in spite of the scientific progress in the past century, there is a lack of general antiviral strategies. In analogy to broad-spectrum antibiotics as antibacterial agents, developing broad spectrum antiviral agents would buy us time for the development of vaccines and treatments for future viral infections. In addition to targeting viral factors, a possible strategy is to understand host immune defense mechanisms and develop methods to boost the antiviral immune response. Here we summarize the role of NAD+-consuming enzymes in the immune defense against viral infections, with the hope that a better understanding of this process could help to develop better antiviral therapeutics targeting these enzymes. These NAD+-consuming enzymes include PARPs, sirtuins, CD38, and SARM1. Among these, the antiviral function of PARPs is particularly important and will be a focus of this review. Interestingly, NAD+ biosynthetic enzymes are also implicated in immune responses. In addition, many viruses, including SARS-CoV-2 contain a macrodomain-containing protein (NSP3 in SARS-CoV-2), which serves to counteract the antiviral function of host PARPs. Therefore, NAD+ and NAD+-consuming enzymes play crucial roles in immune responses against viral infections and detailed mechanistic understandings in the future will likely facilitate the development of general antiviral strategies.

3C protease of enterovirus 71 cleaves promyelocytic leukemia protein and impairs PML-NBs production

Background Enterovirus 71 (EV71) usually infects infants causing hand-foot-mouth disease (HFMD), even fatal neurological disease like aseptic meningitis. Effective drug for preventing and treating EV71 infection is unavailable currently. EV71 3C mediated the cleavage of many proteins and played an important role in viral inhibiting host innate immunity. Promyelocytic leukemia (PML) protein, the primary organizer of PML nuclear bodies (PML-NBs), can be induced by interferon and is involved in antiviral activity. PML inhibits EV71 replication, and EV71 infection reduces PML expression, but the molecular mechanism is unclear. Methods The cleavage of PMLIII and IV was confirmed by co-transfection of EV71 3C protease and PML. The detailed cleavage sites were evaluated further by constructing the Q to A mutant of PML. PML knockout cells were infected with EV71 to identify the effect of cleavage on EV71 replication. Immunofluorescence analysis to examine the interference of EV71 3C on the formation of PML-NBs. Results EV71 3C directly cleaved PMLIII and IV. Furthermore, 3C cleaved PMLIV at the sites of Q430–A431 and Q444–S445 through its protease activity. Overexpression of PMLIV Q430A/Q444A variant exhibited stronger antiviral potential than the wild type. PMLIV Q430A/Q444A formed normal nuclear bodies that were not affected by 3C, suggesting that 3C may impair PML-NBs production via PMLIV cleavage and counter its antiviral activities. PML, especially PMLIV, which sequesters viral proteins in PML-NBs and inhibits viral production, is a novel target of EV71 3C cleavage. Conclusions EV71 3C cleaves PMLIV at Q430–A431 and Q444–S445. Cleavage reduces the antiviral function of PML and decomposes the formation of PML-NBs, which is conducive to virus replication.

Controlling Strategies of Citrus to Increase The Yield in The Country: A step Towards The Fight Against COVID-19

Citrus (oranges, lemon, mandarin, limes and tangarines) has significant nutritional value in human foods. It is rich source of vitamin C, sugar, organic acids, amino acids, minerals like Ca, Mg and various other phytochemicals (flavonoids, hesperidin etc) compounds that are responsible for good health. Citrus is growing in more than one forty countries of the world including Pakistan, Brazil, China, Mexico, USA, Spain and India.Viral infection and inflammation triggers the production of oxygen free radicals and these radicals severely damage the cells, however hesperidin and vitamin C is reported to counteract these damages. Intake of plentiful citrus fruits is one of amongst the many possible approaches to prevent from COVID-19 role of nutrition. Citrus fruit are very rich in important substances with a potential beneficial for health such as modulating the immunity and in protecting cells from oxidative stress related with infection. Flavonoids and hesperidin two major key compound found in citrus have affinity to treat Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Hesperidin has a low binding energy, both with the coronavirus “spike” protein, and with the fundamental protease that alters the primary proteins of the virus (pp1a and ppa1b) into the complex liable for viral replication hence these compounds could work as an antiviral function. Pakistan is amongst top ten citrus producers in the world. Citrus is one of the best commercial fruits of Pakistan cultivated on a large area, however, in Pakistan yield of citrus has been affected due to attack of insects and pathogens (nematode, fungal, bacterial and viral) which causes heavy losses both in quality and quantity. The purpose of this article is to focusing on the controlling the pathogens of citrus to boost citrus production in country as these beneficial plants are well known for its essential vitamin and flavonoid contents to control COVID-19.

Enhanced Antiviral Function of Magnesium Chloride-Modified Heparin on a Broad Spectrum of Viruses

Previous studies reported on the broad-spectrum antiviral function of heparin. Here we investigated the antiviral function of magnesium-modified heparin and found that modified heparin displayed a significantly enhanced antiviral function against human adenovirus (HAdV) in immortalized and primary cells. Nuclear magnetic resonance analyses revealed a conformational change of heparin when complexed with magnesium. To broadly explore this discovery, we tested the antiviral function of modified heparin against herpes simplex virus type 1 (HSV-1) and found that the replication of HSV-1 was even further decreased compared to aciclovir. Moreover, we investigated the antiviral effect against the new severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) and measured a 55-fold decreased viral load in the supernatant of infected cells associated with a 38-fold decrease in virus growth. The advantage of our modified heparin is an increased antiviral effect compared to regular heparin.

m6A modifications regulate intestinal immunity and rotavirus infection

N6-methyladenosine (m6A) is an abundant mRNA modification and affects many biological processes. However, how m6A levels are regulated during physiological or pathological processes such as virus infections, and the in vivo function of m6A in the intestinal immune defense against virus infections are largely unknown. Here, we uncover a novel antiviral function of m6A modification during rotavirus (RV) infection in small bowel intestinal epithelial cells (IECs). We found that rotavirus infection induced global m6A modifications on mRNA transcripts by down-regulating the m6a eraser ALKBH5. Mice lacking the m6A writer enzymes METTL3 in IECs (Mettl3ΔIEC) were resistant to RV infection and showed increased expression of interferons (IFNs) and IFN-stimulated genes (ISGs). Using RNA-sequencing and m6A RNA immuno-precipitation (RIP)-sequencing, we identified IRF7, a master regulator of IFN responses, as one of the primary m6A targets during virus infection. In the absence of METTL3, IECs showed increased Irf7 mRNA stability and enhanced type I and III IFN expression. Deficiency in IRF7 attenuated the elevated expression of IFNs and ISGs and restored susceptibility to RV infection in Mettl3ΔIEC mice. Moreover, the global m6A modification on mRNA transcripts declined with age in mice, with a significant drop from 2 weeks to 3 weeks post birth, which likely has broad implications for the development of intestinal immune system against enteric viruses early in life. Collectively, we demonstrated a novel host m6A-IRF7-IFN antiviral signaling cascade that restricts rotavirus infection in vivo.