Internal N 6 -methyladenosine (m 6 A) modification is one of the most common and abundant modifications of RNA. However, the biological role(s) of viral RNA m 6 A remains elusive. Using human metapneumovirus (hMPV) as a model, we demonstrate that m 6 A serves as a molecular marker for innate immune discrimination of self from nonself RNAs. We show that hMPV RNAs are m 6 A methylated and that viral m 6 A methylation promotes hMPV replication and gene expression. Inactivating m 6 A addition sites with synonymous mutations or demethylase resulted in m 6 A deficient recombinant hMPVs and virion RNAs that induced significantly higher expression of type I interferon (IFN) which was dependent on the cytoplasmic RNA sensor RIG-I, not MDA5. Mechanistically, m 6 A-deficient virion RNA induces higher expression of RIG-I, binds more efficiently to RIG-I, and facilitates the conformational change of RIG-I, leading to enhanced IFN expression. Furthermore, m 6 A-deficient rhMPVs triggered higher IFN in vivo and were significantly attenuated in cotton rats yet retained high immunogenicity. Collectively, our results highlight that (i) virus acquires m 6 A in their RNAs as a means of mimicking cellular RNA to avoid detection by innate immunity; and (ii) viral RNA m 6 A can serve as a target to attenuate hMPV for vaccine purposes.

The nonstructural protein 1 (NS1) of several flaviviruses, including West Nile, dengue, and yellow fever viruses, is capable of inducing variable degrees of protection against flavivirus infection in animal models. However, the immunogenicity of NS1 protein of Zika virus (ZIKV) is less understood. Here, we determined the efficacy of ZIKV NS1-based vaccine candidates using two delivery platforms, methyltransferase-defective recombinant vesicular stomatitis virus (mtdVSV) and a DNA vaccine. We first show that expression of ZIKV NS1 could be significantly enhanced by optimizing the signal peptide. A single dose of mtdVSV-NS1-based vaccine or two doses of DNA vaccine induced high levels of NS1-specfic antibody and T cell immune responses but provided only partial protection against ZIKV viremia in BALB/c mice. In Ifnar1-/- mice, neither NS1-based vaccine provided protection against a lethal high dose (105 PFU) ZIKV challenge, but mtdVSV-NS1-based vaccine prevented deaths from a low dose (103 PFU) challenge, though they experienced viremia and body weight loss. We conclude that ZIKV NS1 alone conferred substantial, but not complete, protection against ZIKV infection. Nevertheless, these results highlight the value of ZIKV NS1 for vaccine development. Importance Most Zika virus (ZIKV) vaccine research has focused on the E or prM-E proteins and the induction of high levels of neutralizing antibodies. However, these ZIKV neutralizing antibodies cross react with other flaviviruses, which may aggravate the disease via an Antibody Dependent Enhancement (ADE) mechanism. ZIKV NS1 protein may be an alternative antigen for vaccine development, as antibodies to NS1 do not bind to the virion, thereby eliminating the risk of ADE. Here we show that recombinant VSV and DNA vaccines expressing NS1, alone, confer partial protection against ZIKV infection in both immunocompetent and immunodeficient mice, highlighting the value of NS1 as a potential vaccine candidate.

Human noroviruses (HuNoVs) are responsible for more than 95% of the non-bacterial acute gastroenteritis epidemics in the world. The CDC estimates that every year 21 million individuals suffer from HuNoV-induced gastroenteritis in the United States. Currently, there is no FDA-approved vaccine for HuNoVs. Development of an effective vaccine has been hampered by the lack of an efficient cell culture system for HuNoVs and a suitable small animal model for pathogenesis study. In this study, we developed lactic acid bacteria (LAB) as a vector to deliver HuNoV antigen. A LAB strain (Lactococcus lactis) carrying VP1 gene of a HuNoV GII.4 virus (LAB-VP1) was constructed. It was found that HuNoV VP1 protein was highly expressed by LAB vector and was secreted into media supernatants. To test whether LAB-based HuNoV vaccine candidate is immunogenic, 4-day-old gnotobiotic piglets were orally inoculated with various doses of LAB-VP1. It was found that LABs were persistent in the small intestine of piglets and shed in pig feces for at least 25 days post inoculation. LAB DNA and VP1 were detected in mesenteric lymph nodes and spleen tissue in LAB-VP1 inoculated groups. HuNoV-specific IgG and IgA were detectable in serum and feces respectively at day 13 post-inoculation, and further increased at later time points. After being challenged with HuNoV GII.4 strain, a large amount of HuNoV antigens were observed in the duodenum, jejunum, and ileum sections of the intestine in the LAB control group. In contrast, significantly less, or no, HuNoV antigens were detected in the LAB-VP1 immunized groups. Collectively, these results demonstrate that a LAB-based HuNoV vaccine induces protective immunity in gnotobiotic piglets.

Background There is increasing evidence that students are completing medical school with insufficient surgical education. Near-peer tutoring and flipped classroom formatting may be used to enhance learning while simultaneously relieving faculty burden of teaching. Here, we qualitatively evaluate a 3-month course that integrates the use of near-peer teaching and flipped classroom formatting, with the goal of increasing first-year medical students’ self-perceived confidence in performing basic sutures and knot-ties as well as interest in surgery. Methods Twenty-one first-year medical students participated in a suturing and knot-tying course led by senior medical students. The course consisted of 2-h sessions held every 2 weeks for a total of five sessions. Students were sent publicly available videos prior to each session by which to learn the upcoming techniques and received live feedback from instructors during sessions. Questionnaires were completed pre-course and post-course. Results Compared to pre-course ratings, post-course ratings of self-perceived confidence to perform various knot-ties and sutures all increased significantly ( p < 0.05). All students stated that the course strengthened their desire to pursue a career in surgery. Student feedback of the course was overall positive. Conclusions Near-peer teaching can be used in conjunction with flipped classroom to increase first-year medical students’ self-perceived confidence in surgical suturing and knot-tying as well as interest in surgery. This curriculum may serve as an outline for student-led courses at other institutions.

Internal N6-methyladenosine (m6A) modification of RNA is one of the most abundant modifications in eukaryotic cells as well as in viruses. However, the biological role(s) of RNA m6A in virus-host interaction remains elusive. Using human metapneumovirus (hMPV), a medically important non-segmented negative-sense RNA virus as a model, we demonstrate that m6A serves as a molecular marker for innate immune discrimination of self from nonself RNAs. We show that hMPV RNAs are m6A methylated and that viral m6A methylation promotes hMPV replication and gene expression. Inactivating these m6A sites with synonymous mutations resulted in m6A deficient recombinant hMPVs that induced significantly higher expression of type I interferon (IFN) that restricted viral replication. Notably, the induction of type I IFN by m6A-deficient rhMPVs and virion RNA was dependent on the cytoplasmic RNA sensor RIG-I, not MDA5. Using RIG-I pull down and RIG-I limited digestion assay, we mechanistically demonstrated that m6A-deficient virion RNA exposed to cytoplasm has much high accessibility to the binding of RIG-I, which allows RIG-I’s translocation along the RNA strand and subsequential conformational change, oligomerization, activation of IFN signaling cascade, and then even higher RIG-I expression during anti-virus status. Furthermore, m6A-deficient rhMPVs triggered higher type I IFN in vivo and were significantly attenuated in the lower respiratory tract yet retained high immunogenicity in cotton rats. Collectively, our results highlight that (i) virus acquires m6A in their RNAs as a means of mimicking cellular RNA to avoid the detection by innate immunity; and (ii) viral m6A RNA can serve as a novel target to attenuate hMPV for vaccine purposes.