As part of its role in the World Health Organization (WHO) Global Influenza Surveillance and Response System (GISRS), the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne received 12,180 human influenza-positive samples during 2024. Viruses were analysed for their antigenic, genetic, and antiviral susceptibility properties. Selected viruses were propagated in qualified cells or embryonated hens' eggs for potential use in seasonal influenza virus vaccines. During 2024, influenza A(H1N1)pdm09 and A(H3N2) viruses predominated, accounting for 33% and 42%, respectively, of all viruses received, compared to 5% for influenza B/Victoria. Of note, one influenza A(H5N1) virus was also received in 2024. The majority of A(H1N1)pdm09 (98%), A(H3N2) (88%) and influenza B (100%) viruses analysed at the Centre were found to be antigenically and genetically similar to the respective WHO recommended vaccine strains for the Southern Hemisphere in 2024. Of 4,007 samples tested for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir, twelve A(H1N1)pdm09 viruses and one B/Victoria virus showed highly reduced inhibition against oseltamivir or zanamivir. Of 3,294 total samples sequenced for baloxavir susceptibility, 18 of the 1,825 A(H3N2) samples were identified with genetic evidence of reduced susceptibility to baloxavir marboxil in the PA gene.

As part of its role in the World Health Organization (WHO) Global Influenza Surveillance and Response System (GISRS), the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne (the Centre) received 13,817 human influenza-positive samples during 2025. Viruses were analysed for their antigenic, genetic, and antiviral susceptibility properties. Selected viruses were propagated in qualified cells or embryonated hens' eggs for potential use in seasonal influenza virus vaccines. Of the 13,817 samples received or processed, influenza A(H1N1)pdm09 viruses predominated, accounting for 46.1% of samples, compared to 21.2% for A(H3N2) viruses and 19.5% for influenza B viruses; one influenza C virus was received. Among viruses analysed at the Centre, the majority of A(H1N1)pdm09 (> 99%) and influenza B (98%) viruses were antigenically similar to their respective WHO recommended vaccine strains for the Southern Hemisphere in 2025. In contrast, only 43% of A(H3N2) viruses were antigenically similar to their respective WHO recommended vaccine strains. Of 3,307 samples tested for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir, 37 A(H1N1)pdm09 viruses showed highly reduced inhibition by oseltamivir and no influenza viruses tested showed highly reduced inhibition by zanamivir. Of 5,080 samples with sequencing of the polymerase acidic (PA) gene, no genetic markers associated with highly reduced susceptibility to baloxavir marboxil were identified.

Nipah virus (NiV) and Hendra virus (HeV) are highly pathogenic henipaviruses without approved human vaccines or therapies. Here, we report on a highly potent bispecific therapeutic that combines an anti-fusion (F) nanobody with an anti-receptor binding protein (RBP) antibody to deliver a dual-targeting biologic that is resistant to viral escape. We show that the nanobody, DS90, engages a unique, conserved site within prefusion F of NiV and HeV, and provides neutralization and complete protection from NiV disease. Bispecific engineering of DS90 with the anti-RBP mAb m102.4 results in neutralization, elimination of viral escape and superior protection from NiV disease compared to leading monovalent approaches. These findings carry implications for the development of cross-neutralizing immunotherapies that limit the emergence of henipaviral escape mutants. ### Competing Interest Statement The authors have declared no competing interest.

Severe respiratory syndrome coronavirus 2 (SARS-CoV-2) infections are associated with significant morbidity and mortality worldwide. Identification and characterization of intracellular proteins with antiviral activity (known as restriction factors) is a key first step towards the future development of novel host-directed antiviral therapies. In this study, we investigated the antiviral activity of 14 different interferon-stimulated gene (ISG) proteins against SARS-CoV-2. Overexpression of human guanylate binding protein (GBP) 1 resulted in potent inhibition of the ancestral SARS-CoV-2 strain, as well as against Alpha, Beta, Delta, Omicron BA.1, and Omicron BA.2 variants of concern (VOCs). Moreover, knockdown or knockout of endogenous human GBP1 resulted in enhanced titers of SARS-CoV-2. While hGBP1 can restrict some viruses via actin remodeling, our data indicate that this is not the mechanism here. Moreover, we show that unlike GBP2 and GBP5, which impair spike protein processing, GBP1 did not reduce infectivity of spike-pseudotyped viruses following titration on Caco-2 cells. Multiple human GBPs have been reported to inhibit SARS-CoV-2 in vitro; however, we report no significant differences in virus titers recovered from the upper or lower airways of SARS-CoV-2-infected wild-type mice compared to from mice lacking the chromosome 3 cluster of mouse GBPs (GBP1/2/3/5/7). Together, our studies describe the ability of human GBP1 to inhibit SARS-CoV-2 replication, highlighting this host protein as a potential target for the development of host-directed antiviral therapies against this virus.IMPORTANCEViruses like SARS-CoV-2 can cause widespread illness and death. While currently licensed antiviral drugs are critical tools, drug resistance can develop. Our immune system produces intracellular proteins called "restriction factors" that can limit virus replication within cells. These proteins are promising targets for developing new antiviral therapies. In this study, we identified one such protein, human GBP1, which inhibited a range of SARS-CoV-2 variants in vitro, including Delta and Omicron. Interestingly, GBP1 inhibited SARS-CoV-2 through a different mechanism to that of other human GBPs as it did not interfere with prosessing of the viral spike protein. Of interest, a cluster of mouse GBPs, including GBP1, did not demontrate significant antiviral activity in a mouse model of infection. Overall, our findings suggest that human GBP1 could be a valuable target for host-directed antiviral strategies and highlight the limitations of using mouse models to study certain aspects of human innate immunity.

Host cell restriction factors are intracellular proteins that target and inhibit virus replication. Membrane-associated RING-CH finger (MARCHF) proteins are a family of intracellular E3-ubiquitin ligases and some, including MARCHF8, have been implicated in restricting the replication of diverse RNA viruses. However, little is currently known as to whether MARCHF proteins mediate antiviral activity against DNA viruses. Herein, we used a doxycycline-inducible overexpression system to demonstrate that human MARCHF1 and MARCHF8 potently restrict productive HSV-1 replication and assessed MARCHF8-mediated restriction of HSV-1 in detail. A functional RING-CH domain and a tyrosine-based motif, located in the N- and C-terminal cytoplasmic tail of MARCHF8, respectively, were required for HSV-1 restriction. For many RNA viruses, MARCHF8-mediated restriction has been associated with downregulation of viral envelope glycoproteins from the cell surface, thereby limiting their subsequent incorporation into nascent virions. However, while MARCHF8 expression did not affect virus entry, translocation of viral genome to the nucleus and immediate early (IE) gene expression, it did inhibit HSV-1 genomic replication, and therefore subsequent late gene expression and release of infectious virions. MARCHF8-mediated restriction of HSV-1 occurred independent of other cellular factors known to impact genomic replication of HSV-1, namely SAMHD1 and CD81, and could also proceed efficiently in cells expressing a functional cGAS-STING pathway. To our knowledge, these studies are the first to demonstrate MARCHF8-mediated restriction against a human DNA virus. Moreover, inhibition of HSV-1 genomic replication represents a novel mechanism of MARCHF8-mediated virus restriction that is distinct to its reported antiviral activity against different RNA viruses.

Nipah virus (NiV) and Hendra virus (HeV) are highly pathogenic henipaviruses without approved human vaccines or therapies. Here, we report on a highly potent bispecific therapeutic that combines an anti-fusion glycoprotein nanobody with an anti-receptor-binding glycoprotein (RBP) antibody to deliver a dual-targeting biologic that is resistant to viral escape. We show that the nanobody, DS90, engages a unique, conserved site within the fusion glycoprotein of NiV and HeV and provides neutralization and complete protection from NiV disease. Bispecific engineering of DS90 with the anti-RBP monoclonal antibody m102.4 results in neutralization, elimination of viral escape and superior protection from NiV disease compared to leading monovalent approaches. These findings carry implications for the development of cross-neutralizing immunotherapies that limit the emergence of henipaviral escape mutants.

The European domestic ferret ( Mustela putorius furo ) is considered the gold standard small animal model for studying human and avian influenza virus infections. However, experimental characterisation of the transcriptomic response to interferon (IFN) stimulation and/or influenza virus infection has been limited, particularly in defining the induction of interferon-stimulated genes (ISGs), with most being computationally predicted. In this study, we present a comprehensive transcriptome-wide assessment of the ferret transcriptome following IFN-α treatment of a ferret lung (FRL) cell line, as well as in nasal turbinates from influenza A virus (IAV)-infected ferrets using long-read RNA sequencing. We have identified a panel of ferret genes orthologous to human ISGs that are upregulated both in response to IFN-α stimulation in vitro and IAV infection in vivo. We have also identified novel IFN-stimulated genes and transcripts. Furthermore, we observed elongation of the poly(A) tails of genes in the ribosome and Coronavirus Disease-19 pathways in response to IFN-α treatment in vitro, suggesting a relationship between poly(A) elongation and the antiviral responses of the host. These results illuminate the dynamics of the transcriptional innate immune response of the domestic ferret and provide an important resource for better utilising ferrets as a small animal model to study influenza virus infections.

Dynamin-like GTPase proteins, including myxoma (Mx) and guanylate-binding proteins (GBPs), are among the many interferon stimulated genes induced following viral infections. While studies report that human (h)GBPs inhibit different viruses in vitro, few have convincingly demonstrated that mouse (m)GBPs mediate antiviral activity, although mGBP-deficient mice have been used extensively to define their importance in immunity to diverse intracellular bacteria and protozoa. Herein, we demonstrate that individual (overexpression) or collective (knockout (KO) mice) mGBPs of the chromosome 3 cluster (mGBPchr3) do not inhibit replication of five viruses from different virus families in vitro, nor do we observe differences in virus titres recovered from wild type versus mGBPchr3 KO mice after infection with three of these viruses (influenza A virus, herpes simplex virus type 1 or lymphocytic choriomeningitis virus). These data indicate that mGBPchr3 do not appear to be a major component of cell-intrinsic antiviral immunity against the diverse viruses tested in our studies. Mouse guanylate binding proteins of the chromosome 3 cluster (mGBPchr3) do not mediate potent antiviral activity against different human or mouse viruses in vitro and in vivo.

In vitro three-dimensional organoid models simulate key aspects of the structure and function of in vivo organs and have been used to study physiology, host-pathogen interactions, pathogenesis and pharmacodynamics. Although most organoid studies have been developed using human or mouse tissues, recent advancements have enabled the establishment of intestinal and respiratory tract organoids from domestic animal samples. Mycoplasma bovis causes chronic respiratory tract infections in cattle with significant health and economic consequences. The pathogenesis and virulence factors of M. bovis have been studied in several in vitro infection models, but the use of organoids has not been examined previously. In this study, we assessed the feasibility of using a matrix-embedded bovine tracheal organoid system to study respiratory infections with M. bovis. Bovine tracheal organoids were inoculated with M. bovis strain MbovMil and incubated for 72hours to investigate the ability of M. bovis to proliferate, attach and invade the organoids. M. bovis was able to infect the organoids, resulting in a mean 260-fold increase in the titre of viable M. bovis by 72hours post-inoculation. Examination of the infected organoids using transmission electron microscopy revealed the presence of mycoplasmas within the organoid cells and membrane bound clusters of M. bovis inside the intercellular junctions. Our findings indicate that bovine tracheal organoids can be used as a model system for studying respiratory tract infections caused by M. bovis.

Respiratory infections cause significant morbidity and mortality, yet it is unclear why some individuals succumb to severe disease. In patients hospitalized with avian A(H7N9) influenza, we investigated early drivers underpinning fatal disease. Transcriptomics strongly linked oleoyl-acyl-carrier-protein (ACP) hydrolase (OLAH), an enzyme mediating fatty acid production, with fatal A(H7N9) early after hospital admission, persisting until death. Recovered patients had low OLAH expression throughout hospitalization. High OLAH levels were also detected in patients hospitalized with life-threatening seasonal influenza, COVID-19, respiratory syncytial virus (RSV), and multisystem inflammatory syndrome in children (MIS-C) but not during mild disease. In olah-/-- /- mice, lethal influenza infection led to survival and mild disease as well as reduced lung viral loads, tissue damage, infection-driven pulmonary cell infiltration, and inflammation. This was underpinned by differential lipid droplet dynamics as well as reduced viral replication and virus-induced inflammation in macrophages. Supplementation of oleic acid, the main product of OLAH, increased influenza replication in macrophages and their inflammatory potential. Our findings define how the expression of OLAH drives life-threatening viral disease.

Influenza A virus (IAV) is a common respiratory pathogen and a global cause of significant and often severe morbidity. Although inflammatory immune responses to IAV infections are well described, little is known about how neuroimmune processes contribute to IAV pathogenesis. In the present study, we employed surgical, genetic, and pharmacological approaches to manipulate pulmonary vagal sensory neuron innervation and activity in the lungs to explore potential crosstalk between pulmonary sensory neurons and immune processes. Intranasal inoculation of mice with H1N1 strains of IAV resulted in stereotypical antiviral lung inflammation and tissue pathology, changes in breathing, loss of body weight and other clinical signs of severe IAV disease. Unilateral cervical vagotomy and genetic ablation of pulmonary vagal sensory neurons had a moderate effect on the pulmonary inflammation induced by IAV infection, but significantly worsened clinical disease presentation. Inhibition of pulmonary vagal sensory neuron activity via inhalation of the charged sodium channel blocker, QX-314, resulted in a moderate decrease in lung pathology, but again this was accompanied by a paradoxical worsening of clinical signs. Notably, vagal sensory ganglia neuroinflammation was induced by IAV infection and this was significantly potentiated by QX-314 administration. This vagal ganglia hyperinflammation was characterized by alterations in IAV-induced host defense gene expression, increased neuropeptide gene and protein expression, and an increase in the number of inflammatory cells present within the ganglia. These data suggest that pulmonary vagal sensory neurons play a role in the regulation of the inflammatory process during IAV infection and suggest that vagal neuroinflammation may be an important contributor to IAV pathogenesis and clinical presentation. Targeting these pathways could offer therapeutic opportunities to treat IAV-induced morbidity and mortality.

Myxovirus resistance (Mx) proteins are products of interferon stimulated genes (ISGs) and Mx proteins of different species have been reported to mediate antiviral activity against a number of viruses, including influenza A viruses (IAV). Ferrets are widely considered to represent the 'gold standard' small animal model for studying pathogenesis and immunity to human IAV infections, however little is known regarding the antiviral activity of ferret Mx proteins. Herein, we report induction of ferret (f)Mx1/2 in a ferret lung cell line and in airway tissues from IAV-infected ferrets, noting that fMx1 was induced to higher levels that fMx2 both in vitro and in vivo. Overexpression confirmed cytoplasmic expression of fMx1 as well as its ability to inhibit infection and replication of IAV, noting that this antiviral effect of fMx1was modest when compared to cells overexpressing either human MxA or mouse Mx1. Together, these studies provide the first insights regarding the role of fMx1 in cell innate antiviral immunity to influenza viruses. Understanding similarities and differences in the antiviral activities of human and ferret ISGs provides critical context for evaluating results when studying human IAV infections in the ferret model.

Background: Human natural killer (NK) cells and gamma delta (gamma delta) T cells may impact outcomes of solid organ transplantation (SOT) such as lung transplantation (LTx) following the differential engagement of an array of activating and inhibitory receptors. Amongst these, CD16 may be particularly important due to its capacity to bind IgG to trigger antibody-dependent cellular cytotoxicity (ADCC) and the production of proinflammatory cytokines. While the use of immunosuppressive drugs (ISDs) is an integral component of SOT practice, their relative impact on various immune cells, especially gamma delta T cells and CD16-induced functional responses, is still unclear.Methods: The ADCC responses of peripheral blood NK cells and gamma delta T cells from both healthy blood donors and adult lung transplant recipients (LTRs) were assessed by flow cytometry. Specifically, the degranulation response, as reflected in the expression of CD107a, and the capacity of both NK cells and gamma delta T cells to produce IFN-gamma and TNF-alpha was assessed following rituximab (RTX)-induced activation. Additionally, the effect of cyclosporine A (CsA), tacrolimus (TAC), prednisolone (Prdl) and azathioprine (AZA) at the concentration of 1 ng/ml, 10 ng/ml, 100 ng/ml, and 1000 ng/ml on these responses was also compared in both cell types.Results: Flow cytometric analyses of CD16 expresion showed that its expression on gamma delta T cells was both at lower levels and more variable than that on peripheral blood NK cells. Nevertheless functional analyses showed that despite these differences, gamma delta T cells like NK cells can be readily activated by engagement with RTX to degranulate and produce cytokines such as IFNg and TNF-a. RTX-induced degranulation by either NK cells or gamma delta T cells from healthy donors was not impacted by co-culture with individual ISDs. However, CsA and TAC but not Prdl and AZA did inhibit the production of IFN-gamma and TNF-alpha by both cell types. Flow cytometric analyses of RTX-induced activation of NK cells and gamma delta T cells from LTRs suggested their capacity to degranulate was not markedly impacted by transplantation with similar levels of cells expressing CD107 pre- and post-LTx. However an impairment in the ability of NK cells to produce cytokines was observed in samples obtained post LTx whereas gamma delta T cell cytokine responses were not significantly impacted.Conclusions: In conclusion, the findings show that despite differences in the expression levels of CD16, gamma delta T cells like NK cells can be readily activated by engagement with RTX and that in vitro exposure to CsA and TAC (calcineurin inhibitors) had a measurable effect on cytokine production but not degranulation by both NK cells and gdT cells from healthy donors. Finally the observation that in PBMC obtained from LTx recipients, NK cells but not gamma delta T cells exhibited impaired cytokine reponses suggests that transplantation or chronic exposure to ISDs differentially impacts their potential to respond to the introduction of an allograft and/or transplant-associated infections.

Moraxella catarrhalis is an important human respiratory pathogen and a major causative agent of otitis media and chronic obstructive pulmonary disease. Toll-like receptors contribute to, but cannot fully account for, the complexity of the immune response seen in M. catarrhalis infection. Using primary mouse bone marrow-derived macrophages to examine the host response to M. catarrhalis infection, our global transcriptomic and targeted cytokine analyses revealed activation of immune signalling pathways by both membrane-bound and cytosolic pattern-recognition receptors. We show that M. catarrhalis and its outer membrane vesicles or lipooligosaccharide (LOS) can activate the cytosolic innate immune sensor caspase-4/11, gasdermin-D-dependent pyroptosis, and the NLRP3 inflammasome in human and mouse macrophages. This pathway is initiated by type I interferon signalling and guanylate-binding proteins (GBPs). We also show that inflammasomes and GBPs, particularly GBP2, are required for the host defence against M. catarrhalis in mice. Overall, our results reveal an essential role for the interferon-inflammasome axis in cytosolic recognition and immunity against M. catarrhalis, providing new molecular targets that may be used to mitigate pathological inflammation triggered by this pathogen.

Bovine respiratory disease (BRD) is the leading cause of morbidity and mortality in feedlot cattle. Bovine herpesvirus-1 (BHV-1) is one of the main culprits of BRD; however, research on BHV-1 is hampered by the lack of suitable models for infection and drug testing. In this study, we established a novel bovine tracheal organoid culture grown in a basement membrane extract type 2 (BME2) matrix and compared it with the air–liquid interface (ALI) culture system. After differentiation, the matrix-embedded organoids developed beating cilia and demonstrated a transcriptomic profile similar to the ALI culture system. The matrix-embedded organoids were also highly susceptible to BHV-1 infection and immune stimulation by Pam2Cys, an immunomodulator, which resulted in robust cytokine production and tracheal antimicrobial peptide mRNA upregulation. However, treatment of bovine tracheal organoid cultures with Pam2Cys was not sufficient to inhibit viral infection or replication, suggesting a role of the non-epithelial cellular microenvironment in vivo.

BACKGROUND:We previously demonstrated the safety and immunogenicity of an MF59-adjuvanted COVID-19 vaccine based on the SARS-CoV-2 spike glycoprotein stabilised in a pre-fusion conformation by a molecular clamp using HIV-1 glycoprotein 41 sequences. Here, we describe 12-month results in adults aged 18-55 years and ≥56 years. METHODS:Phase 1, double-blind, placebo-controlled trial conducted in Australia (July 2020-December 2021; ClinicalTrials.govNCT04495933; active, not recruiting). Healthy adults (Part 1: 18-55 years; Part 2: ≥56 years) received two doses of placebo, 5 μg, 15 μg, or 45 μg vaccine, or one 45 μg dose of vaccine followed by placebo (Part 1 only), 28 days apart (n = 216; 24 per group). Safety, humoral immunogenicity (including against virus variants), and cellular immunogenicity were assessed to day 394 (12 months after second dose). Effects of subsequent COVID-19 vaccination on humoral responses were examined. FINDINGS:All two-dose vaccine regimens were well tolerated and elicited strong antigen-specific and neutralising humoral responses, and CD4+ T-cell responses, by day 43 in younger and older adults, although cellular responses were lower in older adults. Humoral responses waned by day 209 but were boosted in those receiving authorised vaccines. Neutralising activity against Delta and Omicron variants was present but lower than against the Wuhan strain. Cross-reactivity in HIV diagnostic tests declined over time but remained detectable in most participants. INTERPRETATION:The SARS-CoV-2 molecular clamp vaccine is well tolerated and evokes robust immune responses in adults of all ages. Although the HIV glycoprotein 41-based molecular clamp is not being progressed, the clamp concept represents a viable platform for vaccine development. FUNDING:This study was funded by the Coalition for Epidemic Preparedness Innovations, the National Health and Medical Research Council of Australia, and the Queensland Government.

Airway epithelial cells and macrophages (MΦ) represent cellular targets of infection by influenza A virus (IAV). Epithelial cells support IAV infection and replication by enabling the generation and release of new viral particles (productive replication). In contrast, MΦ are susceptible to initial IAV infection but the release of infectious viral particles is inhibited through abortive replication. Despite the lack of infectious virions released from infected MΦ, we detected newly synthesised viral RNA and nucleoprotein (NP) in MΦ supernatants. We show that viral RNA is released from infected MΦ as viral ribonucleoprotein (vRNP) complexes which elicits potent inflammatory responses when exposed to uninfected cells. These vRNPs specifically induced IL-1β, CXCL13, IL-32, CCL4 and CXCL10 in uninfected cells and were at least partially sensed through the RIG-I/MDA5 pathway. While MΦ represent a dead-end for IAV infection through abortive replication, the release of vRNPs shapes immune repsonses of uninfected cells in the local microenvironment.### Competing Interest StatementThe authors have declared no competing interest.

Host cell restriction factors are intracellular proteins that can inhibit virus replication. Characterisation of novel host cell restriction factors can provide potential targets for host-directed therapies. In this study, we aimed to assess a member of the Tripartite-motif family protein (TRIM) family, TRIM16, as a putative host cell restriction factor. To this end, we utilized constitutive or doxycycline-inducible systems to overexpress TRIM16 in HEK293T epithelial cells and then tested for its ability to inhibit growth by a range of RNA and DNA viruses. In HEK293T cells, overexpression of TRIM16 resulted in potent inhibition of multiple viruses, however, when TRIM16 was overexpressed in other epithelial cell lines (A549, Hela, or Hep2), virus inhibition was not observed. When investigating the antiviral activity of endogenous TRIM16, we report that siRNA-mediated knockdown of TRIM16 in A549 cells also modulated the mRNA expression of other TRIM proteins, complicating the interpretation of results using this method. Therefore, we used CRISPR/Cas9 editing to knockout TRIM16 in A549 cells and demonstrate that endogenous TRIM16 did not mediate antiviral activity against the viruses tested. Thus, while initial overexpression in HEK293T cells suggested that TRIM16 was a host cell restriction factor, alternative approaches did not validate these findings. These studies highlight the importance of multiple complementary experimental approaches, including overexpression analysis in multiple cell lines and investigation of the endogenous protein, when defining host cell restriction factors with novel antiviral activity.

Many interferon (IFN)-stimulated genes are upregulated within host cells following infection with influenza and other viruses. While the antiviral activity of some IFN-stimulated genes, such as the IFN-inducible GTPase myxoma resistance (Mx)1 protein 1, has been well defined, less is known regarding the antiviral activities of related IFN-inducible GTPases of the guanylate-binding protein (GBP) family, particularly mouse GBPs, where mouse models can be used to assess their antiviral properties in vivo. Herein, we demonstrate that mouse GBP1 (mGBP1) was upregulated in a mouse airway epithelial cell line (LA-4 cells) following pretreatment with mouse IFN alpha or infection by influenza A virus (IAV). Whereas doxycycline-inducible expression of mouse Mx1 (mMx1) in LA-4 cells resulted in reduced susceptibility to IAV infection and reduced viral growth, inducible mGBP1 did not. Moreover, primary cells isolated from mGBP1-deficient mice (mGBP1(-/-)) showed no difference in susceptibility to IAV and mGBP1(-/-) macrophages showed no defect in IAV-induced NLRP3 (NLR family pyrin domain containing 3) inflammasome activation. After intranasal IAV infection, mGBP1(-/-) mice also showed no differences in virus replication or induction of inflammatory responses in the airways during infection. Thus, using complementary approaches such as mGBP1 overexpression, cells from mGBP1(-/-) mice and intranasal infection of mGBP1(-/-) we demonstrate that mGBP1 does not play a major role in modulating IAV infection in vitro or in vivo.

Influenza virus–specific tissue-resident memory (Trm) CD8 + T cells located along the respiratory tract provide cross-strain protection against a breadth of influenza viruses. We show that immunization with a single-cycle influenza virus vaccine candidate (S-FLU) results in the deposition of influenza virus nucleoprotein (NP)–specific CD8 + Trm along the respiratory tract that were more cross-reactive against viral variants and less likely to drive the development of cytotoxic T lymphocyte (CTL) escape mutants, as compared to the lung memory NP-specific CD8 + T cell pool established following influenza infection. This immune profile was linked to the limited inflammatory response evoked by S-FLU vaccination, which increased TCR repertoire diversity within the memory CD8 + T cell compartment. Cumulatively, this work shows that S-FLU vaccination evokes a clonally diverse, cross-reactive memory CD8 + T cell pool, which protects against severe disease without driving the virus to rapidly evolve and escape, and thus represents an attractive vaccine for use against rapidly mutating influenza viruses.