Mucosal immunization with ChAd-SARS-CoV-2-S prevents sequential transmission of SARS-CoV-2 to unvaccinated hamsters.

COVID-19 vaccines have successfully reduced severe disease and death after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Nonetheless, COVID-19 vaccines are variably effective in preventing transmission and symptomatic SARS-CoV-2 infection. Here, we evaluated the impact of mucosal or intramuscular vaccine immunization on airborne infection and transmission of SARS-CoV-2 in Syrian hamsters. Immunization of the primary contact hamsters with a mucosal chimpanzee adenoviral-vectored vaccine (ChAd-CoV-2-S), but not intramuscular messenger RNA (mRNA) vaccine, reduced infectious virus titers ~100-fold and 100,000-fold in the upper and lower respiratory tract of the primary contact hamster following SARS-CoV-2 exposure. This reduction in virus titer in the mucosal immunized contact animals was sufficient to eliminate subsequent transmission to vaccinated and unvaccinated hamsters. In contrast, sequential transmission occurred after systemic immunization with the mRNA vaccine. Thus, immunization with a mucosal COVID-19 vaccine protects against cycles of respiratory transmission of SARS-CoV-2 and can potentially limit the community spread of the virus.

Vaccination reduces central nervous system IL-1ß and memory deficits after COVID-19 in mice.

Up to 25% of individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibit postacute cognitive sequelae. Although millions of cases of coronavirus disease 2019 (COVID-19)-mediated memory dysfunction are accumulating worldwide, the underlying mechanisms and how vaccination lowers risk are unknown. Interleukin-1 (IL-1), a key component of innate immune defense against SARS-CoV-2 infection, is elevated in the hippocampi of individuals with COVID-19. Here we show that intranasal infection of C57BL/6J mice with SARS-CoV-2 Beta variant leads to central nervous system infiltration of Ly6Chi monocytes and microglial activation. Accordingly, SARS-CoV-2, but not H1N1 influenza virus, increases levels of brain IL-1ß and induces persistent IL-1R1-mediated loss of hippocampal neurogenesis, which promotes postacute cognitive deficits. Vaccination with a low dose of adenoviral-vectored spike protein prevents hippocampal production of IL-1ß during breakthrough SARS-CoV-2 infection, loss of neurogenesis and subsequent memory deficits. Our study identifies IL-1ß as one potential mechanism driving SARS-CoV-2-induced cognitive impairment in a new mouse model that is prevented by vaccination.

Mucosal vaccine-induced cross-reactive CD8+ T cells protect against SARS-CoV-2 XBB.1.5 respiratory tract infection.

A nasally delivered chimpanzee adenoviral-vectored severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine (ChAd-SARS-CoV-2-S) is currently used in India (iNCOVACC). Here, we update this vaccine by creating ChAd-SARS-CoV-2-BA.5-S, which encodes a prefusion-stabilized BA.5 spike protein. Whereas serum neutralizing antibody responses induced by monovalent or bivalent adenoviral vaccines were poor against the antigenically distant XBB.1.5 strain and insufficient to protect in passive transfer experiments, mucosal antibody and cross-reactive memory T cell responses were robust, and protection was evident against WA1/2020 D614G and Omicron variants BQ.1.1 and XBB.1.5 in mice and hamsters. However, depletion of memory CD8+ T cells before XBB.1.5 challenge resulted in loss of protection against upper and lower respiratory tract infection. Thus, nasally delivered vaccines stimulate mucosal immunity against emerging SARS-CoV-2 strains, and cross-reactive memory CD8+ T cells mediate protection against lung infection by antigenically distant strains in the setting of low serum levels of cross-reactive neutralizing antibodies.

Durable immunity to SARS-CoV-2 in both lower and upper airways achieved with a gorilla adenovirus (GRAd) S-2P vaccine in non-human primates.

SARS-CoV-2 continues to pose a global threat, and current vaccines, while effective against severe illness, fall short in preventing transmission. To address this challenge, there's a need for vaccines that induce mucosal immunity and can rapidly control the virus. In this study, we demonstrate that a single immunization with a novel gorilla adenovirus-based vaccine (GRAd) carrying the pre-fusion stabilized Spike protein (S-2P) in non-human primates provided protective immunity for over one year against the BA.5 variant of SARS-CoV-2. A prime-boost regimen using GRAd followed by adjuvanted S-2P (GRAd+S-2P) accelerated viral clearance in both the lower and upper airways. GRAd delivered via aerosol (GRAd(AE)+S-2P) modestly improved protection compared to its matched intramuscular regimen, but showed dramatically superior boosting by mRNA and, importantly, total virus clearance in the upper airway by day 4 post infection. GrAd vaccination regimens elicited robust and durable systemic and mucosal antibody responses to multiple SARS-CoV-2 variants, but only GRAd(AE)+S-2P generated long-lasting T cell responses in the lung. This research underscores the flexibility of the GRAd vaccine platform to provide durable immunity against SARS-CoV-2 in both the lower and upper airways.

Vaccination prevents IL-1ß-mediated cognitive deficits after COVID-19.

Up to 25% of SARS-CoV-2 patients exhibit post-acute cognitive sequelae. Although millions of cases of COVID-19-mediated memory dysfunction are accumulating worldwide, the underlying mechanisms and how vaccination lowers risk are unknown. Interleukin-1, a key component of innate immune defense against SARS-CoV-2 infection, is elevated in the hippocampi of COVID-19 patients. Here we show that intranasal infection of C57BL/6J mice with SARS-CoV-2 beta variant, leads to CNS infiltration of Ly6Chi monocytes and microglial activation. Accordingly, SARS-CoV-2, but not H1N1 influenza virus, increases levels of brain IL-1ß and induces persistent IL-1R1-mediated loss of hippocampal neurogenesis, which promotes post-acute cognitive deficits. Breakthrough infection after vaccination with a low dose of adenoviral vectored Spike protein prevents hippocampal production of IL-1ß during breakthrough SARS-CoV-2 infection, loss of neurogenesis, and subsequent memory deficits. Our study identifies IL-1ß as one potential mechanism driving SARS-CoV-2-induced cognitive impairment in a new murine model that is prevented by vaccination.

A bivalent ChAd nasal vaccine protects against SARS-CoV-2 BQ.1.1 and XBB.1.5 infection and disease in mice and hamsters.

We previously described a nasally delivered monovalent adenoviral-vectored SARS-CoV-2 vaccine (ChAd-SARS-CoV-2-S, targeting Wuhan-1 spike [S]; iNCOVACC®) that is currently used in India as a primary or booster immunization. Here, we updated the mucosal vaccine for Omicron variants by creating ChAd-SARS-CoV-2-BA.5-S, which encodes for a pre-fusion and surface-stabilized S protein of the BA.5 strain, and then tested monovalent and bivalent vaccines for efficacy against circulating variants including BQ.1.1 and XBB.1.5. Whereas monovalent ChAd-vectored vaccines effectively induced systemic and mucosal antibody responses against matched strains, the bivalent ChAd-vectored vaccine elicited greater breadth. However, serum neutralizing antibody responses induced by both monovalent and bivalent vaccines were poor against the antigenically distant XBB.1.5 Omicron strain and did not protect in passive transfer experiments. Nonetheless, nasally delivered bivalent ChAd-vectored vaccines induced robust antibody and spike-specific memory T cell responses in the respiratory mucosa, and conferred protection against WA1/2020 D614G and Omicron variants BQ.1.1 and XBB.1.5 in the upper and lower respiratory tracts of both mice and hamsters. Our data suggest that a nasally delivered bivalent adenoviral-vectored vaccine induces protective mucosal and systemic immunity against historical and emerging SARS-CoV-2 strains without requiring high levels of serum neutralizing antibody.

Estrogen hormone is an essential sex factor inhibiting inflammation and immune response in COVID-19.

Although vaccines have been evaluated and approved for SARS-CoV-2 infection prevention, there remains a lack of effective treatments to reduce the mortality of COVID-19 patients already infected with SARS-CoV-2. The global data on COVID-19 showed that men have a higher mortality rate than women. We further observed that the proportion of mortality of females increases starting from around the age of 55 significantly. Thus, sex is an essential factor associated with COVID-19 mortality, and sex related genetic factors could be interesting mechanisms and targets for COVID-19 treatment. However, the associated sex factors and signaling pathways remain unclear. Here, we propose to uncover the potential sex associated factors using systematic and integrative network analysis. The unique results indicated that estrogens, e.g., estrone and estriol, (1) interacting with ESR1/2 receptors, (2) can inhibit SARS-CoV-2 caused inflammation and immune response signaling in host cells; and (3) estrogens are associated with the distinct fatality rates between male and female COVID-19 patients. Specifically, a high level of estradiol protects young female COVID-19 patients, and estrogens drop to an extremely low level in females after about 55 years of age causing the increased fatality rate of women. In conclusion, estrogen, interacting with ESR1/2 receptors, is an essential sex factor that protects COVID-19 patients from death by inhibiting inflammation and immune response caused by SARS-CoV-2 infection. Moreover, medications boosting the down-stream signaling of ESR1/ESR2, or inhibiting the inflammation and immune-associated targets on the signaling network can be potentially effective or synergistic combined with other existing drugs for COVID-19 treatment.

mRNA-1273 and Ad26.COV2.S vaccines protect against the B.1.621 variant of SARS-CoV-2.

BACKGROUND: Since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019, viral variants with greater transmissibility or immune-evasion properties have arisen, which could jeopardize recently deployed vaccine- and antibody-based countermeasures. METHODS: Here, we evaluated in mice and hamsters the efficacy of a pre-clinical version of the Moderna mRNA vaccine (mRNA-1273) and the Johnson & Johnson recombinant adenoviral-vectored vaccine (Ad26.COV2.S) against the B.1.621 (Mu) variant of SARS-CoV-2, which contains spike mutations T95I, Y144S, Y145N, R346K, E484K, N501Y, D614G, P681H, and D950N. FINDINGS: Immunization of 129S2 and K18-human ACE2 transgenic mice with the mRNA-1273 vaccine protected against weight loss, lung infection, and lung pathology after challenge with the B.1.621 or WA1/2020 N501Y/D614G SARS-CoV-2 strain. Similarly, immunization of 129S2 mice and Syrian hamsters with a high dose of Ad26.COV2.S reduced lung infection after B.1.621 virus challenge. CONCLUSIONS: Thus, immunity induced by the mRNA-1273 or Ad26.COV2.S vaccine can protect against the B.1.621 variant of SARS-CoV-2 in multiple animal models. FUNDING: This study was supported by the NIH (R01 AI157155 and U01 AI151810), NIAID Centers of Excellence for Influenza Research and Response [CEIRR] contracts 75N93021C00014 and 75N93021C00016, and the Collaborative Influenza Vaccine Innovation Centers [CIVIC] contract 75N93019C00051. It was also supported, in part, by the National Institutes of Allergy and Infectious Diseases Center for Research on Influenza Pathogenesis (HHSN272201400008C) and the Japan Program for Infectious Diseases Research and Infrastructure (JP21wm0125002) from the Japan Agency for Medical Research and Development (AMED).

Vaccine protection against the SARS-CoV-2 Omicron variant in macaques.

The rapid spread of the SARS-CoV-2 Omicron (B.1.1.529) variant, including in highly vaccinated populations, has raised important questions about the efficacy of current vaccines. In this study, we show that the mRNA-based BNT162b2 vaccine and the adenovirus-vector-based Ad26.COV2.S vaccine provide robust protection against high-dose challenge with the SARS-CoV-2 Omicron variant in cynomolgus macaques. We vaccinated 30 macaques with homologous and heterologous prime-boost regimens with BNT162b2 and Ad26.COV2.S. Following Omicron challenge, vaccinated macaques demonstrated rapid control of virus in bronchoalveolar lavage, and most vaccinated animals also controlled virus in nasal swabs. However, 4 vaccinated animals that had moderate Omicron-neutralizing antibody titers and undetectable Omicron CD8+ T cell responses failed to control virus in the upper respiratory tract. Moreover, virologic control correlated with both antibody and T cell responses. These data suggest that both humoral and cellular immune responses contribute to vaccine protection against a highly mutated SARS-CoV-2 variant.

Vaccine Protection Against the SARS-CoV-2 Omicron Variant in Macaques.

BACKGROUND: The rapid spread of the SARS-CoV-2 Omicron (B.1.1.529) variant, including in highly vaccinated populations, has raised important questions about the efficacy of current vaccines. Immune correlates of vaccine protection against Omicron are not known. METHODS: 30 cynomolgus macaques were immunized with homologous and heterologous prime-boost regimens with the mRNA-based BNT162b2 vaccine and the adenovirus vector-based Ad26.COV2.S vaccine. Following vaccination, animals were challenged with the SARS-CoV-2 Omicron variant by the intranasal and intratracheal routes. RESULTS: Omicron neutralizing antibodies were observed following the boost immunization and were higher in animals that received BNT162b2, whereas Omicron CD8+ T cell responses were higher in animals that received Ad26.COV2.S. Following Omicron challenge, sham controls showed more prolonged virus in nasal swabs than in bronchoalveolar lavage. Vaccinated macaques demonstrated rapid control of virus in bronchoalveolar lavage, and most vaccinated animals also controlled virus in nasal swabs, showing that current vaccines provide substantial protection against Omicron in this model. However, vaccinated animals that had moderate levels of Omicron neutralizing antibodies but negligible Omicron CD8+ T cell responses failed to control virus in the upper respiratory tract. Virologic control correlated with both antibody and T cell responses. CONCLUSIONS: BNT162b2 and Ad26.COV2.S provided robust protection against high-dose challenge with the SARS-CoV-2 Omicron variant in macaques. Protection against this highly mutated SARS-CoV-2 variant correlated with both humoral and cellular immune responses.

JIB-04 Has Broad-Spectrum Antiviral Activity and Inhibits SARS-CoV-2 Replication and Coronavirus Pathogenesis.

Pathogenic coronaviruses are a major threat to global public health. Here, using a recombinant reporter virus-based compound screening approach, we identified small-molecule inhibitors that potently block the replication of severe acute respiratory syndrome virus 2 (SARS-CoV-2). Among them, JIB-04 inhibited SARS-CoV-2 replication in Vero E6 cells with a 50% effective concentration of 695 nM, with a specificity index of greater than 1,000. JIB-04 showed in vitro antiviral activity in multiple cell types, including primary human bronchial epithelial cells, against several DNA and RNA viruses, including porcine coronavirus transmissible gastroenteritis virus. In an in vivo porcine model of coronavirus infection, administration of JIB-04 reduced virus infection and associated tissue pathology, which resulted in improved weight gain and survival. These results highlight the potential utility of JIB-04 as an antiviral agent against SARS-CoV-2 and other viral pathogens. IMPORTANCE The coronavirus disease 2019 (COVID-19), the disease caused by SARS-CoV-2 infection, is an ongoing public health disaster worldwide. Although several vaccines are available as a preventive measure and the FDA approval of an orally bioavailable drug is on the horizon, there remains a need for developing antivirals against SARS-CoV-2 that could work on the early course of infection. By using infectious reporter viruses, we screened small-molecule inhibitors for antiviral activity against SARS-CoV-2. Among the top hits was JIB-04, a compound previously studied for its anticancer activity. Here, we showed that JIB-04 inhibits the replication of SARS-CoV-2 as well as different DNA and RNA viruses. Furthermore, JIB-04 conferred protection in a porcine model of coronavirus infection, although to a lesser extent when given as therapeutic rather than prophylactic doses. Our findings indicate a limited but still promising utility of JIB-04 as an antiviral agent in the combat against COVID-19 and potentially other viral diseases.

Estrogen Hormone Is an Essential Sex Factor Inhibiting Inflammation and Immune Response in COVID-19.

Although vaccines have been evaluated and approved for SARS-CoV-2 infection prevention, there remains a lack of effective treatments to reduce the mortality of COVID-19 patients already infected with SARS-CoV-2. The global data of COVID-19 showed that men have a higher mortality rate than women. We further observed that the proportion of mortality of female increases starting from around the age of 55 significantly. Thus, sex is an essential factor associated with COVID-19 mortality, and sex related genetic factors could be interesting mechanisms and targets for COVID-19 treatment. However, the associated sex factors and signaling pathways remain unclear. Here, we propose to uncover the potential sex associated factors using systematic and integrative network analysis. The unique results indicated that estrogen hormones (ER), e.g., estrone and estriol, 1) interacting with ESR1/2 receptors, 2) can inhibit SARS-CoV-2 caused inflammation and immune response signaling in host cells; and 3) estrogen hormone is associated with the distinct fatality rates between male and female COVID-19 patients. Specifically, a high level of estradiol protecting young female COVID-19 patients, and estrogen loss to an extremely low level in females after about 55 years of age causing the increased fatality rate of women. In conclusion, estrogen hormone, interacting with ESR1/2 receptors, is an essential sex factor that protects COVID-19 patients by inhibiting inflammation and immune response caused by SARS-CoV-2 infection. Medications perturb the down-stream of ESR1/ESR2 to inhibit the inflammation and immune response can be effective or synergistic combined with other existing drugs for COVID-19 treatment.

6-Thioguanine blocks SARS-CoV-2 replication by inhibition of PLpro.

The emergence of SARS-CoV-2 has led to a global health crisis that, in addition to vaccines and immunomodulatory therapies, calls for the identification of antiviral therapeutics. The papain-like protease (PLpro) activity of nsp3 is an attractive drug target as it is essential for viral polyprotein cleavage and for deconjugation of ISG15, an antiviral ubiquitin-like protein. We show here that 6-Thioguanine (6-TG), an orally available and widely available generic drug, inhibits SARS-CoV-2 replication in Vero-E6 cells with an EC50 of approximately 2 µM. 6-TG also inhibited PLpro-catalyzed polyprotein cleavage and de-ISGylation in cells and inhibited proteolytic activity of the purified PLpro domain in vitro. We therefore propose that 6-TG is a direct-acting antiviral that could potentially be repurposed and incorporated into the set of treatment and prevention options for COVID-19.

A single intranasal or intramuscular immunization with chimpanzee adenovirus-vectored SARS-CoV-2 vaccine protects against pneumonia in hamsters.

The development of an effective vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the etiologic agent of coronavirus disease 2019 (COVID-19), is a global priority. Here, we compare the protective capacity of intranasal and intramuscular delivery of a chimpanzee adenovirus-vectored vaccine encoding a prefusion stabilized spike protein (chimpanzee adenovirus [ChAd]-SARS-CoV-2-S) in Golden Syrian hamsters. Although immunization with ChAd-SARS-CoV-2-S induces robust spike-protein-specific antibodies capable of neutralizing the virus, antibody levels in serum are higher in hamsters vaccinated by an intranasal compared to intramuscular route. Accordingly, against challenge with SARS-CoV-2, ChAd-SARS-CoV-2-S-immunized hamsters are protected against less weight loss and have reduced viral infection in nasal swabs and lungs, and reduced pathology and inflammatory gene expression in the lungs, compared to ChAd-control immunized hamsters. Intranasal immunization with ChAd-SARS-CoV-2-S provides superior protection against SARS-CoV-2 infection and inflammation in the upper respiratory tract. These findings support intranasal administration of the ChAd-SARS-CoV-2-S candidate vaccine to prevent SARS-CoV-2 infection, disease, and possibly transmission.

A single intranasal or intramuscular immunization with chimpanzee adenovirus vectored SARS-CoV-2 vaccine protects against pneumonia in hamsters.

The development of an effective vaccine against SARS-CoV-2, the etiologic agent of COVID-19, is a global priority. Here, we compared the protective capacity of intranasal and intramuscular delivery of a chimpanzee adenovirus-vectored vaccine encoding a pre-fusion stabilized spike protein (ChAd-SARS-CoV-2-S) in Golden Syrian hamsters. While immunization with ChAd-SARS-CoV-2-S induced robust spike protein specific antibodies capable or neutralizing the virus, antibody levels in serum were higher in hamsters immunized by an intranasal compared to intramuscular route. Accordingly, ChAd-SARS-CoV-2-S immunized hamsters were protected against a challenge with a high dose of SARS-CoV-2. After challenge, ChAd-SARS-CoV-2-S-immunized hamsters had less weight loss and showed reductions in viral RNA and infectious virus titer in both nasal swabs and lungs, and reduced pathology and inflammatory gene expression in the lungs, compared to ChAd-Control immunized hamsters. Intranasal immunization with ChAd-SARS-CoV-2-S provided superior protection against SARS-CoV-2 infection and inflammation in the upper respiratory tract. These findings support intranasal administration of the ChAd-SARS-CoV-2-S candidate vaccine to prevent SARS-CoV-2 infection, disease, and possibly transmission.

6-Thioguanine blocks SARS-CoV-2 replication by inhibition of PLpro protease activities.

A recently emerged betacoronavirus, SARS-CoV-2, has led to a global health crisis that calls for the identification of effective therapeutics for COVID-19 disease. Coronavirus papain-like protease (PLpro) is an attractive drug target as it is essential for viral polyprotein cleavage and for deconjugation of ISG15, an antiviral ubiquitin-like protein. We show here that 6-Thioguanine (6-TG) inhibits SARS-CoV-2 PLpro-catalyzed viral polyprotein cleavage and ISG15 deconjugation in cells and inhibits replication of SARS-CoV-2 in Vero-E6 cells and Calu3 cells at submicromolar levels. As a well-characterized FDA-approved orally delivered drug, 6-TG represents a promising therapeutic for COVID-19 and other emerging coronaviruses. ONE SENTENCE SUMMARY: A repurposed drug that targets an essential enzymatic activity of SARS-CoV-2 represents a promising COVID-19 therapeutic.

An Agonistic Anti-CD137 Antibody Disrupts Lymphoid Follicle Structure and T-Cell-Dependent Antibody Responses.

CD137 is a costimulatory receptor expressed on natural killer cells, T cells, and subsets of dendritic cells. An agonistic monoclonal antibody (mAb) against CD137 has been used to reduce tumor burden or reverse autoimmunity in animal models and clinical trials. Here, we show that mice treated with an agonistic anti-CD137 mAb have reduced numbers of germinal center (GC) B cells and follicular dendritic cells (FDCs) in lymphoid tissues, which impair antibody responses to multiple T-cell-dependent antigens, including infectious virus, viral proteins, and conjugated haptens. These effects are not due to enhanced apoptosis or impaired proliferation of B cells but instead correlate with changes in lymphoid follicle structure and GC B cell dispersal and are mediated by CD137 signaling in CD4+ and CD8+ T cells. Our experiments in mice suggest that agonistic anti-CD137 mAbs used in cancer and autoimmunity therapy may impair long-term antibody and B cell memory responses.

ZBTB32 restrains antibody responses to murine cytomegalovirus infections, but not other repetitive challenges.

ZBTB32 is a transcription factor that is highly expressed by a subset of memory B cells and restrains the magnitude and duration of recall responses against hapten-protein conjugates. To define physiological contexts in which ZBTB32 acts, we assessed responses by Zbtb32-/- mice or bone marrow chimeras against a panel of chronic and acute challenges. Mixed bone marrow chimeras were established in which all B cells were derived from either Zbtb32-/- mice or control littermates. Chronic infection of Zbtb32-/- chimeras with murine cytomegalovirus led to nearly 20-fold higher antigen-specific IgG2b levels relative to controls by week 9 post-infection, despite similar viral loads. In contrast, IgA responses and specificities in the intestine, where memory B cells are repeatedly stimulated by commensal bacteria, were similar between Zbtb32-/- mice and control littermates. Finally, an infection and heterologous booster vaccination model revealed no role for ZBTB32 in restraining primary or recall antibody responses against influenza viruses. Thus, ZBTB32 does not limit recall responses to a number of physiological acute challenges, but does restrict antibody levels during chronic viral infections that periodically engage memory B cells. This restriction might selectively prevent recall responses against chronic infections from progressively overwhelming other antibody specificities.

Interferon induced protein 35 exacerbates H5N1 influenza disease through the expression of IL-12p40 homodimer.

Pro-inflammatory cytokinemia is a hallmark of highly pathogenic H5N1 influenza virus (IAV) disease yet little is known about the role of host proteins in modulating a pathogenic innate immune response. The host Interferon Induced Protein 35 (Ifi35) has been implicated in increased susceptibility to H5N1-IAV infection. Here, we show that Ifi35 deficiency leads to reduced morbidity in mouse models of highly pathogenic H5N1- and pandemic H1N1-IAV infection. Reduced weight loss in Ifi35-/- mice following H5N1-IAV challenge was associated with reduced cellular infiltration and decreased production of specific cytokines and chemokines including IL-12p40. Expression of Ifi35 by the hematopoietic cell compartment in bone-marrow chimeric mice contributed to increased immune cell recruitment and IL-12p40 production. In addition, Ifi35 deficient primary macrophages produce less IL-12p40 following TLR-3, TLR-4, and TLR-7 stimulation in vitro. Decreased levels of IL-12p40 and its homodimer, IL-12p80, were found in bronchoalveolar lavage fluid of H5N1-IAV infected Ifi35 deficient mice. Specific antibody blockade of IL-12p80 ameliorated weight loss and reduced cellular infiltration following H5N1-IAV infection in wild-type mice; suggesting that increased levels of IL-12p80 alters the immune response to promote inflammation and IAV disease. These data establish a role for Ifi35 in modulating cytokine production and exacerbating inflammation during IAV infection.

Nucleotide resolution mapping of influenza A virus nucleoprotein-RNA interactions reveals RNA features required for replication.

Influenza A virus nucleoprotein (NP) association with viral RNA (vRNA) is essential for packaging, but the pattern of NP binding to vRNA is unclear. Here we applied photoactivatable ribonucleoside enhanced cross-linking and immunoprecipitation (PAR-CLIP) to assess the native-state of NP-vRNA interactions in infected human cells. NP binds short fragments of RNA (~12 nucleotides) non-uniformly and without apparent sequence specificity. Moreover, NP binding is reduced at specific locations within the viral genome, including regions previously identified as required for viral genome segment packaging. Synonymous mutations designed to alter the predicted RNA structures in these low-NP-binding regions impact genome packaging and result in virus attenuation, whereas control mutations or mutagenesis of NP-bound regions have no effect. Finally, we demonstrate that the sequence conservation of low-NP-binding regions is required in multiple genome segments for propagation of diverse mammalian and avian IAV in host cells.