Crystal structures of the DExH-box RNA helicase DHX9.

DHX9 is a DExH-box RNA helicase with versatile functions in transcription, translation, RNA processing and regulation of DNA replication. DHX9 has recently emerged as a promising target for oncology, but to date no mammalian structures have been published. Here, crystal structures of human, dog and cat DHX9 bound to ADP are reported. The three mammalian DHX9 structures share identical structural folds. Additionally, the overall architecture and the individual domain structures of DHX9 are highly conserved with those of MLE, the Drosophila orthologue of DHX9 previously solved in complex with RNA and a transition-state analogue of ATP. Due to differences in the bound substrates and global domain orientations, the localized loop conformations and occupancy of dsRNA-binding domain 2 (dsRBD2) differ between the mammalian DHX9 and MLE structures. The combined effects of the structural changes considerably alter the RNA-binding channel, providing an opportunity to compare active and inactive states of the helicase. Finally, the mammalian DHX9 structures provide a potential tool for structure-based drug-design efforts.

Development of assays to support identification and characterization of modulators of DExH-box helicase DHX9.

DHX9 is a DExH-box RNA helicase that utilizes hydrolysis of all four nucleotide triphosphates (NTPs) to power cycles of 3' to 5' directional movement to resolve and/or unwind double stranded RNA, DNA, and RNA/DNA hybrids, R-loops, triplex-DNA and G-quadraplexes. DHX9 activity is important for both viral amplification and maintaining genomic stability in cancer cells; therefore, it is a therapeutic target of interest for drug discovery efforts. Biochemical assays measuring ATP hydrolysis and oligonucleotide unwinding for DHX9 have been developed and characterized, and these assays can support high-throughput compound screening efforts under balanced conditions. Assay development efforts revealed DHX9 can use double stranded RNA with 18-mer poly(U) 3' overhangs and as well as significantly shorter overhangs at the 5' or 3' end as substrates. The enzymatic assays are augmented by a robust SPR assay for compound validation. A mechanism-derived inhibitor, GTPγS, was characterized as part of the validation of these assays and a crystal structure of GDP bound to cat DHX9 has been solved. In addition to enabling drug discovery efforts for DHX9, these assays may be extrapolated to other RNA helicases providing a valuable toolkit for this important target class.

Antimicrobial resistance of commensal Escherichia coli and Enterococcus faecalis isolated from clinically healthy captive wild animals in Seoul zoo.

Despite the importance of antimicrobial resistance, only a few studies on the antimicrobial susceptibility on wild animals have been conducted owing to their population, accessibility, and characteristics. The objective of this study was to investigate the prevalence and characteristics of antimicrobial resistance pattern in Escherichia coli and Enterococcus faecalis isolated from the feces of captive wild animals in a zoo. A total of 61 captive wild animals were included in this study. E. coli was isolated from 58 of the 61 animals and E. faecalis was isolated from 29 animals. Among the isolated E. coli strains, ampicillin exhibited the highest resistance rate (27/29, 93.1%). Of these, 18 strains (18/29, 62%) showed multidrug resistance. The multilocus sequence typing (MLST) test showed that only ST155 was detected twice, while the other 16 strains showed different ST types. Among the E. faecalis strains, two were susceptible to all tested antimicrobials, whereas the remaining 27 strains showed resistance to one or more antimicrobials. Nine strains (9/27, 31%) showed multidrug resistance. Among the E. faecalis strains, resistance to quinupristin/dalfopristin was the highest at 96.3% (26/27), while the MLST of the nine MDR strains showed no predominant ST. Genetic association with human isolates or livestock products was observed in the isolated ST types. This indicates that antibiotic resistance in the zoo is responsible for the use of antibiotics and the partial horizontal transmission between humans and animals through feeding or contact.

Safety and tolerability of bone marrow-derived mesenchymal stem cells in lupus animal models and a phase I clinical trial in humans.

OBJECTIVE: Several clinical trials aimed at treating various autoimmune diseases, including systemic lupus erythematosus (SLE), by introducing mesenchymal stem cells (MSCs) have been conducted. However, with refractory lupus nephritis (LN), the outcomes of MSC transplantation are not well known, and further validation is required. In particular, data concerning the safety and efficacy of LN treatment using bone marrow-derived MSCs (BM-MSCs) are still lacking. METHODS: We identified characteristics of BM-MSCs in terms of cell morphology, chromosomal stability, differentiation capacity, and phenotype through cell passages. The in vivo stability of BM-MSCs was evaluated by single-dose and repeated-dose toxicity tests, tumorigenicity tests, and biodistribution tests using lupus mouse models. Based on the encouraging nonclinical results, we conducted a nonrandomized, open-label, single-arm phase I clinical trial to evaluate the tolerability and safety of a single administration of haploidentical allogeneic BM-MSCs (CS20AT04) in seven LN patients (NCT03174587). We used a classical three + three design to find the optimal dosage. The starting dose was 2.0×106 cells/kg and escalated to 3.0×106 cells/kg if there was no dose-limiting toxicity (DLT). Evaluation of the safety and tolerability was assessed 28 days after the infusion, and the maximum tolerated dose was determined. RESULTS: Properly cultured BM-MSCs showed high proliferation and multipotency, but chromosomal changes were not found. There were two deaths by a rapid administration rate in the high-dose group (2.0×106 cells/head) in a single administration test. BM-MSCs were distributed in the kidneys until Day 7. In the phase I clinical trial, seven LN patients were enrolled. Participants received BM-MSCs through intravenous infusion. There was no DLT at both initial dose (2.0×106 cells/kg) and escalated dose (3.0×106 cells/kg). One patient was not administered the full 2.0×106 cells/kg dose because of a technical error during infusion. This patient did not show DLT. Three adverse events were reported, namely, one diarrhea, one toothache, and one arthralgia, and all were considered NCI-CTC grade I events. CONCLUSION: We defined the characteristics of BM-MSCs and identified their safety and tolerability in both animal models and a phase I clinical trial. The maximum tolerated dose was determined to be 3.0×106 cells/kg in patients with LN.

Regulation of MLL1 Methyltransferase Activity in Two Distinct Nucleosome Binding Modes.

Cryo-EM structures of the KMT2A/MLL1 core complex bound on nucleosome core particles (NCPs) suggest unusual rotational dynamics of the MLL1 complex approaching its physiological substrate. However, the functional implication of such dynamics remains unclear. Here, we show that the MLL1 core complex also shows high rotational dynamics bound on the NCP carrying the catalytically inert histone H3 lysine 4 to methionine (K4M) mutation. There are two major binding modes of the MLL1 complex on the NCPK4M. Importantly, disruption of only one of the binding modes compromised the overall MLL1 activity in an NCP-specific manner. We propose that the MLL1 core complex probably exists in an equilibrium of poised and active binding modes. The high rotational dynamics of the MLL1 complex on the NCP is a feature that can be exploited for loci-specific regulation of H3K4 methylation in higher eukaryotes.

Clinical application of protein-enhanced diet using mealworms in patients undergoing hepato-pancreato-biliary surgery.

OBJECTIVE: Patients with or without cancers who undergo major gastrointestinal surgery experience malnutrition owing to their catabolic status during the postoperative period. In this study, we evaluated the effect of the clinical application of protein-enhanced diet using mealworms in patients who underwent hepato-pancreato-biliary surgeries. METHODS: This study was designed as a prospective, two-armed, and double-blinded phase III study. The target number of enrolled patients was 216, and the patients were randomized on a 1:1 basis, either to the trial group (consuming mealworms) or to the control group (consuming grain powder). The primary endpoint was to examine the changes in body composition, including phase angle. For secondary outcomes, the activities of immune cells were evaluated using the patients' blood samples. RESULTS: No difference in the demographic characteristics of patients was observed. The ratio of the actual protein intake to the recommended daily intake in the trial group was significantly higher than that in the control group (110.03% vs. 98.80%, P = 0.023). In the data on body composition measured by InBody S-10 (Biospace, Seoul, South Korea), the ratios in body cell mass, fat free mass, muscle mass, and phase angle at the study endpoint compared with those at admission showed no statistically significant difference between the two groups. Immune cell analyses suggested that cytotoxic T cells in the trial group had higher activity than in the study group (1.192 vs. 0.974, P = 0.028). CONCLUSIONS: In this study, protein-enhanced diet using mealworms clinically improved the activity of immune cells. However, it did not significantly improve the patients' nutritional status after they experienced hepato-pancreato-biliary surgeries.

Therapeutic effiacy of T cells expressing chimeric antigen receptor derived from a mesothelin-specific scFv in orthotopic human pancreatic cancer animal models.

Novel CAR T cells targeting mesothelin (MSLN) expressed on pancreatic cancer cells were developed to overcome the limit of the clinical efficacy of CAR T cell therapy for pancreatic cancer patients. Optimal single-chain variable fragments (scFv) binding to MSLN were selected based on the binding activity and the functional effectiveness of various scFv containing CAR-expressing T cells. Engineered MSLN CAR T cells showed successful anti-tumor activity specific to MSLN expression level. Furthermore, MSLN CAR T cells were evaluated for the anti-cancer efficacy in orthotopic mouse models bearing pancreatic cancer cells, MIA Paca-2, MSLN-overexpressed MIA Paca-2 or endogenously MSLN-expressing AsPC-1. Mice were randomized into control, mock treated, MS501 BBz treated, MS501 28z treated or MS501 28BBz treated group. Mice were monitored by weekly IVIS imaging and tumors were harvested and analyzed by immunohistochemical analyses. MSLN CAR T cells produced the therapeutic effect in orthotopic animal models with complete remission in significant number of mice. Histopathological analysis indicated that CD4+ and CD8+ MSLN CAR T cells infiltrated pancreatic tumor tissue and led to cancer cell eradication. Our results demonstrated the anti-tumor efficacy of MSLN CAR T cell therapy against pancreatic cancer, suggesting its therapeutic potential.

BCG Cell Wall Skeleton As a Vaccine Adjuvant Protects Both Infant and Old-Aged Mice from Influenza Virus Infection.

Bacillus Calmette-Guerin (BCG) and the cell wall skeleton (CWS) derived from BCG are known to enhance nonspecific immune activation and anti-cancer immunity; however, their roles as a vaccine adjuvant are largely unknown. Here, we report that BCG-CWS acts as a strong immune adjuvant by promoting the protective immune responses in mouse models with influenza vaccination. The different aged mice immunized with inactivated split vaccine with or without BCG-CWS were challenged with an influenza pandemic virus. When protective immune responses were compared, even a single immunization of adult mice with a BCG-CWS-adjuvanted vaccine showed significantly enhanced humoral immune responses with increased IgG1 and IgG2a isotype antibodies. Importantly, the protective effects by the BCG-CWS adjuvant for influenza vaccination upon humoral and cellular immunogenicity were comparable between infants (6 days and 2 weeks old) and aged (20 months old) mice. Moreover, BCG-CWS dramatically augmented vaccine-mediated protective responses, including decreased viral loads, lung damage, and airway resistance, as well as increased mouse survival, amelioration of weight loss, and proinflammatory cytokine expression in all experimental groups including infant, adults, and old aged mice. We further provided the evidence that the BCG-CWS adjuvant effects were mediated through Toll-like receptors (TLR) 2 and TLR4 signaling pathways. Together, these data suggest that BCG-CWS can be promising as a potential influenza vaccine adjuvant in both young and old aged population through TLR2/4-mediated immune-boosting activities.

Mechanism for DPY30 and ASH2L intrinsically disordered regions to modulate the MLL/SET1 activity on chromatin.

Recent cryo-EM structures show the highly dynamic nature of the MLL1-NCP (nucleosome core particle) interaction. Functional implication and regulation of such dynamics remain unclear. Here we show that DPY30 and the intrinsically disordered regions (IDRs) of ASH2L work together in restricting the rotational dynamics of the MLL1 complex on the NCP. We show that DPY30 binding to ASH2L leads to stabilization and integration of ASH2L IDRs into the MLL1 complex and establishes new ASH2L-NCP contacts. The significance of ASH2L-DPY30 interactions is demonstrated by requirement of both ASH2L IDRs and DPY30 for dramatic increase of processivity and activity of the MLL1 complex. This DPY30 and ASH2L-IDR dependent regulation is NCP-specific and applies to all members of the MLL/SET1 family of enzymes. We further show that DPY30 is causal for de novo establishment of H3K4me3 in ESCs. Our study provides a paradigm of how H3K4me3 is regulated on chromatin and how H3K4me3 heterogeneity can be modulated by ASH2L IDR interacting proteins.

Natural killer cells contribute to enhanced respiratory disease after oil-in-water emulsion adjuvanted vaccination against respiratory syncytial virus and infection.

Respiratory syncytial virus (RSV) infection caused severe acute respiratory disease in children and the elderly. There is no licensed vaccine. It has been a challenging problem to avoid vaccine enhanced respiratory disease in developing a safe and effective RSV vaccine. Here, we investigated the impact of MF59-like oil-in-water emulsion adjuvant Addavax on the vaccine efficacy of inactivated split RSV (sRSV) and the roles of natural killer (NK) cells in enhanced respiratory disease in sRSV vaccinated mice after RSV infection. Addavax-adjuvanted sRSV vaccination induced higher levels of IgG1 isotype antibodies and more effective lung viral clearance upon RSV infection but promoted enhanced respiratory disease of weight loss, pulmonary inflammation, and NK and NK T (NKT) cell infiltrations in the lungs. Antibody treatment depleting NK cells prior to RSV infection resulted in preventing severe weight loss and histopathology, as well as attenuating infiltration of dendritic cell subsets and TNF-α+ T cells in the lungs. This study demonstrated the impacts of oil-in-water emulsion adjuvant on sRSV vaccination and the potential roles of NK and NKT cells in protection and respiratory disease after adjuvanted RSV vaccination and infection in a mouse model.

Roles of the Fc Receptor γ-Chain in Inducing Protective Immune Responses after Heterologous Vaccination against Respiratory Syncytial Virus Infection.

The roles of the Fc receptor (FcR) in protection or inflammatory disease after respiratory syncytial virus (RSV) vaccination and infection remain unknown. Virus-like particles containing RSV fusion proteins (RSV F-VLPs) induce T-helper type 1 antibody responses and protection against RSV. Heterologous RSV F-VLP prime and formalin-inactivated RSV (FI-RSV) boost vaccination has been reported to be effective in providing protection without inflammatory disease. Here, we investigated whether the FcRγ-chain is important for immune protection by the heterologous F-VLP and FI-RSV vaccination using FcRγ-chain knockout (-/-) mice. RSV F-VLP-primed and FI-RSV-boosted FcRγ -/- mice displayed less protective efficacy, as shown by higher lung viral titers upon RSV challenge, compared to RSV F-VLP-primed and FI-RSV-boosted immunized wild-type mice. RSV F-VLP and FI-RSV immunization induced lower levels of neutralizing activity and interferon-γ-producing CD8 T-cells in the bronchoalveolar lavage cells of FcRγ -/- mice than in those of wild-type mice. In addition, FcRγ -/- mice displayed a trend of enhancing lung histopathology after RSV vaccination and infection. This study suggests that the FcRγ-chain plays an important role in inducing antiviral protection and CD8 T-cell responses in RSV F-VLP prime and FI-RSV boost vaccination after RSV infections.

Changes in the bony alignment of the foot after tendo-Achilles lengthening in patients with planovalgus deformity.

BACKGROUND: This study was performed to investigate the change in the bony alignment of the foot after tendo-Achilles lengthening (TAL) and the factors that affect these changes in patients with planovalgus foot deformity. METHODS: Consecutive 97 patients (150 feet; mean age 10 years; range 5.1-35.7) with Achilles tendon contracture (ATC) and planovalgus foot deformity who underwent TAL were included. All patients underwent preoperative and postoperative weight-bearing anteroposterior (AP) or lateral (LAT) foot radiographics. Changes in AP talo-1st metatarsal angle, AP talo-2nd metatarsal angle, LAT talo-1st metatarsal angle, and calcaneal pitch angle and the factors affecting such changes after TAL were analyzed using lineal mixed model. RESULTS: There were no significant change in AP talo-1st metatarsal angle and AP talo-2nd metatarsal angle after TAL in patients with cerebral palsy (CP) (p = 0.236 and 0.212). However, LAT talo-1st metatarsal angle and calcaneal pitch angle were significantly improved after TAL (13.0°, p < 0.001 and 4.5°, p < 0.001). Age was significantly associated with the change in LAT talo-1st metatarsal angle after TAL (p = 0.028). The changes in AP talo-1st metatarsal angle, AP talo-2nd metatarsal angle, and calcaneal pitch angle after TAL were not significantly associated with the diagnosis (p = 0.879, 0.903, and 0.056). However, patients with CP showed more improvement in LAT talo-1st metatarsal angle (- 5.0°, p = 0.034) than those with idiopathic cause. CONCLUSION: This study showed that TAL can improve the bony alignment of the foot in patients with planovalgus and ATC. We recommend that physicians should consider this study's findings when planning operative treatment for such patients.

Adjuvant effects of killed Lactobacillus casei DK128 on enhancing T helper type 1 immune responses and the efficacy of influenza vaccination in normal and CD4-deficient mice.

Lactic acid bacteria Lactobacillus casei DK128 isolated from fermented vegetable foods was suggested to stimulate innate immune responses. Here, we investigated whether heat-killed DK128 would exhibit adjuvant effects on enhancing the efficacy of influenza vaccination. Immunization of mice with split influenza virus vaccine in the presence of heat-killed DK128 induced significantly higher levels of both IgG1 and IgG2c isotype antibodies than those by vaccine only. A single dose DK128-adjuvanted influenza vaccination conferred higher efficacy of protection, as evidenced by intact lung function, less weight loss, enhanced clearance of lung viral loads, and lower levels of inflammatory cytokines and infiltrates. Immunization of CD4 T cell-knockout (CD4KO) mice with influenza vaccine and DK128, but not with vaccine alone, induced isotype-switched IgG antibodies and protection against lethal challenge in CD4KO mice. The results in this study suggest heat-killed DK128 as a potential vaccine adjuvant, promoting the induction of IgG isotype switching in CD4-deficient condition and enhancing protective efficacy of split influenza vaccination in immunocompromised and immune-competent subjects.

Publisher Correction: Cryo-EM structure of the human MLL1 core complex bound to the nucleosome.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Identification of DOT1L inhibitors by structure-based virtual screening adapted from a nucleoside-focused library.

Disruptor of Telomeric Silencing 1-Like (DOT1L), the sole histone H3 lysine 79 (H3K79) methyltransferase, is required for leukemogenic transformation in a subset of leukemias bearing chromosomal translocations of the Mixed Lineage Leukemia (MLL) gene, as well as other cancers. Thus, DOT1L is an attractive therapeutic target and discovery of small molecule inhibitors remain of high interest. Herein, we are presenting screening results for a unique focused library of 1200 nucleoside analogs originally produced under the aegis of the NIH Pilot Scale Library Program. The complete nucleoside set was screened virtually against DOT1L, resulting in 210 putative hits. In vitro screening of the virtual hits resulted in validation of 11 compounds as DOT1L inhibitors clustered into two distinct chemical classes, adenosine-based inhibitors and a new chemotype that lacks adenosine. Based on the developed DOT1L ligand binding model, a structure-based design strategy was applied and a second-generation of non-nucleoside DOT1L inhibitors was developed. Newly synthesized compound 25 was the most potent DOT1L inhibitor in the new series with an IC50 of 1.0 µM, showing 40-fold improvement in comparison with hit 9 and exhibiting reasonable on target effects in a DOT1L dependent murine cell line. These compounds represent novel chemical probes with a unique non-nucleoside scaffold that bind and compete with the SAM binding site of DOT1L, thus providing foundation for further medicinal chemistry efforts to develop more potent compounds.

Natural Killer and CD8 T Cells Contribute to Protection by Formalin Inactivated Respiratory Syncytial Virus Vaccination under a CD4-Deficient Condition.

Respiratory syncytial virus (RSV) causes severe pulmonary disease in infants, young children, and the elderly. Formalin inactivated RSV (FI-RSV) vaccine trials failed due to vaccine enhanced respiratory disease, but the underlying immune mechanisms remain not fully understood. In this study, we have used wild type C57BL/6 and CD4 knockout (CD4KO) mouse models to better understand the roles of the CD4 T cells and cellular mechanisms responsible for enhanced respiratory disease after FI-RSV vaccination and RSV infection. Less eosinophil infiltration and lower pro-inflammatory cytokine production were observed in FI-RSV vaccinated CD4KO mice after RSV infection compared to FI-RSV vaccinated C57BL/6 mice. NK cells and cytokine-producing CD8 T cells were recruited at high levels in the airways of CD4KO mice, correlating with reduced respiratory disease. Depletion studies provided evidence that virus control was primarily mediated by NK cells whereas CD8 T cells contributed to IFN-γ production and less eosinophilic lung inflammation. This study demonstrated the differential roles of effector CD4 and CD8 T cells as well as NK cells, in networking with other inflammatory infiltrates in RSV disease in immune competent and CD4-deficient condition.

Cryo-EM structure of the human MLL1 core complex bound to the nucleosome.

Mixed lineage leukemia (MLL) family histone methyltransferases are enzymes that deposit histone H3 Lys4 (K4) mono-/di-/tri-methylation and regulate gene expression in mammals. Despite extensive structural and biochemical studies, the molecular mechanisms whereby the MLL complexes recognize histone H3K4 within nucleosome core particles (NCPs) remain unclear. Here we report the single-particle cryo-electron microscopy (cryo-EM) structure of the NCP-bound human MLL1 core complex. We show that the MLL1 core complex anchors to the NCP via the conserved RbBP5 and ASH2L, which interact extensively with nucleosomal DNA and the surface close to the N-terminal tail of histone H4. Concurrent interactions of RbBP5 and ASH2L with the NCP uniquely align the catalytic MLL1SET domain at the nucleosome dyad, thereby facilitating symmetrical access to both H3K4 substrates within the NCP. Our study sheds light on how the MLL1 complex engages chromatin and how chromatin binding promotes MLL1 tri-methylation activity.

Developmental ROS individualizes organismal stress resistance and lifespan.

A central aspect of aging research concerns the question of when individuality in lifespan arises1. Here we show that a transient increase in reactive oxygen species (ROS), which occurs naturally during early development in a subpopulation of synchronized Caenorhabditis elegans, sets processes in motion that increase stress resistance, improve redox homeostasis and ultimately prolong lifespan in those animals. We find that these effects are linked to the global ROS-mediated decrease in developmental histone H3K4me3 levels. Studies in HeLa cells confirmed that global H3K4me3 levels are ROS-sensitive and that depletion of H3K4me3 levels increases stress resistance in mammalian cell cultures. In vitro studies identified SET1/MLL histone methyltransferases as redox sensitive units of the H3K4-trimethylating complex of proteins (COMPASS). Our findings implicate a link between early-life events, ROS-sensitive epigenetic marks, stress resistance and lifespan.

Respiratory Syncytial Virus Fusion Protein-encoding DNA Vaccine Is Less Effective in Conferring Protection against Inflammatory Disease than a Virus-like Particle Platform.

Formalin-inactivated respiratory syncytial virus (RSV) vaccination causes vaccine-enhanced disease (VED) after RSV infection. It is considered that vaccine platforms enabling endogenous synthesis of RSV immunogens would induce favorable immune responses than non-replicating subunit vaccines in avoiding VED. Here, we investigated the immunogenicity, protection, and disease in mice after vaccination with RSV fusion protein (F) encoding plasmid DNA (F-DNA) or virus-like particles presenting RSV F (F-VLP). F-DNA vaccination induced CD8 T cells and RSV neutralizing Abs, whereas F-VLP elicited higher levels of IgG2a isotype and neutralizing Abs, and germinal center B cells, contributing to protection by controlling lung viral loads after RSV challenge. However, mice that were immunized with F-DNA displayed weight loss and pulmonary histopathology, and induced F specific CD8 T cell responses and recruitment of monocytes and plasmacytoid dendritic cells into the lungs. These innate immune parameters, RSV disease, and pulmonary histopathology were lower in mice that were immunized with F-VLP after challenge. This study provides important insight into developing effective and safe RSV vaccines.

Neuraminidase expressing virus-like particle vaccine provides effective cross protection against influenza virus.

Neuraminidase is the second major surface antigen on influenza virus. We investigated the immunogenicity and cross protective efficacy of virus-like particle containing neuraminidase derived from 2009 pandemic H1N1 influenza virus (N1 VLP) in comparison with inactivated split influenza vaccine. Immunization of mice with N1 VLP induced antibody responses specific for virus and cross-reactive neuraminidase inhibition activity whereas an inactivated split vaccine induced strain-specific hemagglutination inhibition activity. N1 VLP-immunized mice developed cross protective immunity against antigenically different influenza viruses, as determined by body weight changes, lung viral titers, infiltrating innate immune cells, and cytokines, and antibody secreting cells, and germinal center B cells. Also, N1 VLP-immune sera provided cross-protection in naïve mice. Immunity by N1 VLP vaccination was not compromised in Fc receptor γ-chain deficient mice. These results suggest that neuraminidase-presenting VLP can be developed as an effective cross-protective vaccine candidate along with current influenza vaccination.