Mouse-adapted Influenza Virus Research Articles

Ventricular-subventricular zone stem cell niche adaptations in a mouse model of post-infectious hydrocephalus.

Congenital post-infectious hydrocephalus (PIH) is a condition characterized by enlargement of the ventricular system, consequently imposing a burden on the associated stem cell niche, the ventricular-subventricular zone (V-SVZ). To investigate how the V-SVZ adapts in PIH, we developed a mouse model of influenza virus-induced PIH based on direct intracerebroventricular injection of mouse-adapted influenza virus at two distinct time points: embryonic day 16 (E16), when stem cells line the ventricle, and postnatal day 4 (P4), when an ependymal monolayer covers the ventricle surface and stem cells retain only a thin ventricle-contacting process. Global hydrocephalus with associated regions of astrogliosis along the lateral ventricle was found in 82% of the mice infected at P4. Increased ependymogenesis was observed at gliotic borders and throughout areas exhibiting intact ependyma based on tracking of newly divided cells. Additionally, in areas of intact ependyma, stem cell numbers were reduced; however, we found no significant reduction in new neurons reaching the olfactory bulb following onset of ventriculomegaly. At P4, injection of only the non-infectious viral component neuraminidase resulted in limited, region-specific ventriculomegaly due to absence of cell-to-cell transmission. In contrast, at E16 intracerebroventricular injection of influenza virus resulted in death at birth due to hypoxia and multiorgan hemorrhage, suggesting an age-dependent advantage in neonates, while the viral component neuraminidase resulted in minimal, or no, ventriculomegaly. In summary, we tracked acute adaptations of the V-SVZ stem cell niche following onset of ventriculomegaly and describe developmental changes that help mitigate the severity of congenital PIH.

Immunoregulatory functions of natural killer cells in avian influenza virus infection

The avian influenza virus (AIV) has a great pandemic potential both in animals, and in human population. For effective struggle against this virus, it is important to study the immune response against AIV, and, in particular, the features of T cell immunity. At the period of early immune response, when the activation of adaptive immunity factors has not yet occurred, the natural killers, which have both cytotoxic and immunoregulatory functions, are known to play a key role in the fight against the influenza virus. In this study, we investigated the interaction between natural killers and T helpers in the process of antiviral response. The aim of this study was to study immunoregulatory functions of NK cells in BALB/c mice vaccinated with different doses of avian influenza virus.We used a strain of mouse-adapted avian influenza virus (AIV) of the H5N2 serotype (A/duck/ Pennsylvania/10218/1984). The determination of the virus titer in the mice lung tissue was performed by infecting 10-day-old chicken embryos (SPF) with lung extracts at various decimal dilutions, followed by the immune agglutination test. Quantitative determination of natural killers and T helpers (Th) in the mice spleen tissue was carried out by flow cytometry. The amount of Th cells in mice spleens increased at low infectious dose (2.5 EID50) which is explained by active clonal expansion of this cell subpopulation. The infectious disease process ended upon complete virus elimination from the lungs. The amounts of Th cells were also increased in a group of mice infected with intermediate infectious dose (25 EID50), however, being accompanied by virus replication in lungs. When the mice were infected with a high dose of the virus (250 EID50), there was a decrease in the Th cells number versus control group of animals, whereas replication of AIV was noted throughout the entire observation period in the lung tissue.The amounts of helper T cells at high doses of viral infection could be decreased due to activation of NK cells. The activated NK cells may then eliminate exhausted helper T cells. Thus, NK cells immunoregulatory function represents an important immunological factor which keeps balance between the pathogen destruction and excessive inflammation of the lung tissue affected by the avian influenza virus.

Aggregation of Enveloped Viruses By Platelet Factor 4 (PF4) and Neutrophil Extracellular Traps (NETs): Implications for the Anti-Viral Properties of NETs

As part of the innate immune response, neutrophils release neutrophil extracellular traps (NETs), webs of DNA coated with histones that ensnare and kill bacteria. A growing body of literature suggests that NETs can also capture and inactivate enveloped viruses. The ability of NETs to limit the systemic spread of pathogens occurs at the expense of collateral organ damage induced when high concentrations of NETs are digested by DNases to release toxic NET degradation products (NDPs) including cell free DNA and histones. Our group has shown that the positively charged platelet-specific chemokine (PF4, CXCL4), compacts NETs by forming tetramers that electrostatically cross-bind two polyanionic fragments of DNA, similarly to the way it aggregates heparans. PF4 complexed to NETs induces NET resistance to nuclease digestion, preventing the release of toxic NDPs while enhancing NET-bacterial capture by bridging anionic DNA to the negatively charged microbial surface. PF4 has also been shown limit pulmonary injury and enhance survival in mice infected with PR8, a mouse-adapted H1N1 influenza virus. Our group and others have found that both PF4 and NETs are elevated in the setting of SARS-CoV-2, leading us to hypothesize that they may act synergistically to combat the proliferation of enveloped viruses. To investigate the effect of PF4 on the pathogenicity of enveloped viruses, we studied PR8 and murine hepatitis virus (MHV)-1, a betacoronavirus that induces severe pulmonary disease. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) were used to assess the ability of PF4 and human-derived NETs to aggregate MHV-1 and PR8 virions. ChAdOx1, a replication-deficient adenovirus was used as a non-enveloped viral control. The DLS and SEM studies showed that PF4 (5-20 µg/ml) aggregated MHV-1 and PR8, forming complexes with an average diameter of 500nm, the width of 4-5 virions (Figure 1). In contrast, PF4 did not aggregate non-enveloped adenovirus. DLS studies showed that PF4 does not form complexes with coronavirus spike protein. However, the anti-PF4-polyanion antibody KKO, bound to PF4-viral complexes, leading to an additional 50% increase in viral aggregate size, an effect not seen with an isotype control antibody TRA (Figure A). These results suggest that PF4 binds to polyanions on the viral envelop via electrostatic interaction, much in the same way that it binds to heparans and DNA. We preformed subsequent DLS studies in which MHV-1 virions were incubated with both intact and digested NETs, and viral-NET aggregation was only observed in the presence of PF4. To determine if PF4 aggregates virus in vivo, IHC studies were performed on lungs harvested from MHV-1-infected A/J mice inoculated intranasally with 5 x 103 PFU of virus and sacrificed at 48h. The lungs were prepared for immunohistochemistry (IHC), and labeled with antibodies directed against PF4 and the MHV-1 nucleocapsid protein. We calculated the average Pearson's coefficient in 4 randomly selected 20x confocal images of the lungs of MHV-1 infected animals (n=4 mice, 16 images analyzed) using the FIJI JaCoP colocalization plugin. We observed co-localization of PF4 and MHV-1 within the cytoplasm of a subset of cells (r= 0.70225, p<0.0001), suggesting that PF4-MHV-1 aggregation occurs in vivo (Figure B) Lastly, the plaque forming unit assay was used to measure the effect of PF4 on MHV-1 infectivity of L2 cells. We found that incubating MHV-1 with PF4 (0-100µg/ml), leads to a 50% decrease in infectivity(n=5, p=0.023). Our studies demonstrate that PF4 binds to and aggregates MHV-1 and PR8 in vitro likely through electrostatic interactions with the viral envelop rather than adhesion to the viral spike protein. These results also suggest that PF4-mediated aggregation enhances viral capture by NETs to form NETs:PF4:viral complexes that may limit viral spread. IHC studies of lungs from MHV-1 infected mice demonstrate that PF4 colocalizes with the virus, suggesting that aggregation also occurs in vivo. In ongoing studies, we are investigating whether PF4 and NETs act synergistically to reduce coronavirus and influenza infectivity and enhance immune recognition and subsequent clearance of viral aggregates. These findings will help to define the anti-viral properties of NETs and may generate insights relevant to the treatment of coronavirus, influenza, and other enveloped viruses. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Angiogenic role of lung pericytes in experimental viral lung injury

Lung pericytes are perivascular stromal cells that surround microvascular endothelial cells. While their roles in fibrogenesis have been explored, their angiogenic functions in experimental lung injury and repair have not been characterized. RNAseq analysis of primary lung pericytes activated ex vivoreveals upregulation of novel angiogenic pathways. One gene of interest we identified is angiopoietin‐L4 (Angptl4). Stromal cells, particularly pericytes, are the primary sources of angiopoietin‐L4 in the lung. ANGPTL4 has been shown to regulate angiogenesis in cancer biology and retinal diseases. We have shown that lung pericyte‐derived ANGPTL4 promotes network formation and monolayer permeability in endothelial cells in vitro. We hypothesize that knockdown of ANGPTL4 in vivo is protective in acute viral lung injury by promoting endothelial integrity and decreasing microvascular leak during injury and resolution. Transgenic mice with inducible genetic deletion of Angptl4 and littermate controls were inoculated with mouse‐adapted human influenza virus (A/PR/8). Mice lacking Angptl4 showed decreased measures of lung injury and protein leak during the acute and resolution phases of lung injury. Future directions include identification of ANGPTL4 signaling pathways and cellular targets in the lung, and characterization of the mechanisms by which pericyte‐derived ANGPTL4 leads to persistence of endothelial dysfunction or activation in viral lung injury.

The features of the course of virus-associated acute lung injury in mice with induced immunosuppression

BACKGROUND: Among all groups of patients with virus-associated acute lung injury with influenza infection, the most severe course is observed in patients with immunosuppression. In this case, despite the studied mechanism of the course of combined pathology, the question of therapy in this group of patients remains unclear.&#x0D; AIM: To study the features of the course of acute lung injury in influenza infection with secondary immunosuppression in an experiment for the possibility of searching for experimental therapy for this combined pathology.&#x0D; MATERIALS AND METHODS: The study was performed on 115 outbred female mice. The mouse-adapted pandemic influenza virus A/California/7/09MA (H1N1)pdm09 was used for modeling viral acute lung injury. Experimental immunosuppression was reproduced by administration of methotrexate (1.25 mg/kg intraperitoneally, once every 3 days during 3 weeks before infection). During the experiment, mortality, blood oxygen saturation, the concentration of pro-inflammatory cytokines in the lungs, and the severity of lung injury were measured.&#x0D; RESULTS: The presence of experimental immunosuppression led to an exacerbation of acute lung injury in infected animals in terms of mortality and lung damage. Changes in the dynamics of proinflammatory cytokines (TNF-, IL-6, IL-1) in the lungs were observed during acute lung injury. Retarded recovery of the lungs functional activity was noted.&#x0D; CONCLUSIONS: The experimental immunosuppression contributed to the exacerbation of acute lung injury and to an increase in the duration of the pathology. These changes could be associated with an altered process of elimination of the pathogen. The reproduced model of combined pathology was used for searching a therapy for these complications.

DNA vaccine targeting the ectodomain of influenza M2 protein to endolysosome pathway enhances anti-M2e protective antibody response in mice.

A promising candidate for developing the universal influenza vaccine is the ectodomain of the M2 protein (M2e). We designed and prepared an experimental DNA vaccine with an improved potential to induce anti-M2e immune response. The sequence for truncated NS1 protein followed by 4xM2e was inserted into the expression vector pTriEx-4 (pEx). M2e repeats were fused to the transmembrane domain and cytoplasmic tail of lysosome-associated membrane glycoprotein 2 isoform A (LAMP-2a) to target the M2e to the endo-lysosome pathway, facilitating increased antigen presentation by MHC II. Using confocal microscope immunofluorescence analysis, we confirmed a strong colocalization of pEx 4M2e-LAMP-2a with early endosomes and a weaker colocalization with late endosomes. BALB/c mice immunized with three doses of pEx 4M2e-LAMP-2a DNA vaccine and challenged with 2LD50 mouse-adapted influenza virus developed significantly (up to 16 times) higher anti-M2e antibody response in comparison to mice immunized with pEx 4M2e vaccine using the same immunization protocol. This was in correlation with the increased survival rate (near to 67% vs 50%) observed in animals immunized with pEx 4M2e-LAMP-2a DNA in comparison to mice immunized with pEx 4M2e. Keywords: influenza A; matrix protein 2 ectodomain; NS1; LAMP-2a; DNA vaccine.

Evaluating the Immune Response of Recombinant H1N1 Hemagglutinin with MF59 Adjuvant in Animal Model as a Novel Alternative to the Influenza Vaccine.

The H1N1 influenza virus is known as a serious pandemic threat across the globe. Vaccination is one of the most effective methods of protection against this virus and the way to reduce the seasonal pandemic risk. The commercial vaccine does not adequately respond to pandemic strains. This study examines the potential function of formulated H1N1 hemagglutinin with MF59 adjuvant against A/PR/8/34 (H1N1). To this end, a recombinant hemagglutinin (rHA) gene of influenza A virus was designed and expressed in SF9 cell by the Baculovirus expression system. Four groups of mice were immunized by rHA in combination with MF59, Alum adjuvant, and virus split only. The immunized mice subsequently used for the humoral immune assay and the results compared with untreated mice (negative group). Besides, both treated and control mice groups were challenged with mouse-adapted influenza virus A/PR/8/34(H1N1) through the intranasal drop. Bodyweight, survival, temperature variation, and the medical conditions of the samples were assessed. Mice immunized with the recombinant protein demonstrated a humoral response to the influenza A virus. Upon virus challenging, co-administration of rHA with MF59 adjuvant could lead to 92% survival of the vaccinated mice within 10 days. The MF59-treated group showed slight weight loss and high-temperature body two weeks after infection. This group also displayed a higher hemagglutination inhibition (HI) antibody titer as compared to the group vaccinated with virus split, and Alum adjuvant. Altogether, the results showed that the recombinant protein with the MF59 adjuvant created better safety than the Alum adjuvant, thereby can be considered as a safe and reliable vaccine against the H1N1 virus for further investigations.

The effect of aminoguanidine on acute lung injury induced by influenza A/H1N1/PDM09

Background. Acute lung injury is one of severe course of influenza infection with mortality up to 40% of patients, despite on etiological and pathogenetic therapy.&#x0D; The aim of the article to study of the effects of aminoguanidine on correcting on acute lung injury induced by influenza virus A/California/7/09MA (mouse-adapted) (H1N1)pdm09, collection Smorodintsev Research Institute of Influenza.&#x0D; Materials and methods. The study was performed on 95 outbred female mice. The mouse-adapted pandemic influenza virus A/California/7/09MA (H1N1)pdm09 was used for modeling viral infection at a dose of 1 LD50. The mortality was analysed. Levels of advanced glycation end-products (AGEs), proinflammatory cytokines in lung; saturation index and leukocytes marker parameters in blood; pathological and histological studies of lung were performed on 4 and 7 days post infection.&#x0D; Results. Aminoguanidine led to 2-fold decrease in mortality in mice with virus-induced acute lung injury; significantly suppressed the growth of AGEs and proinflammatory cytokine levels in lung; reduced decrease of saturation index and hematological inflammatory markers; decreased level of inflammatory injury in lung tissue.&#x0D; Conclusion. Aminoguanidine relieved virus-induced acute lung injury in mice. These AGEs inhibitor reduced the proinflammatory response and structural changes in respiratory tract epithelial cells induced by reactive carbonyl compounds on cell membrane.

Gut microbiota manipulation during the prepubertal period shapes behavioral abnormalities in a mouse neurodevelopmental disorder model

Previous studies demonstrate an association between activation of the maternal immune system during pregnancy and increased risk of neurodevelopmental psychiatric conditions, such as schizophrenia and autism, in the offspring. Relatively recent findings also suggest that the gut microbiota plays an important role in shaping brain development and behavior. Here we show that maternal immune activation (MIA) accomplished by infection with a mouse-adapted influenza virus during pregnancy induced up-regulation of frontal cortex serotonin 5-HT2A receptor (5-HT2AR) density in the adult offspring, a phenotype previously observed in postmortem frontal cortex of schizophrenic subjects. 5-HT2AR agonist-induced head-twitch behavior was also augmented in this preclinical mouse model. Using the novel object recognition (NOR) test to evaluate cognitive performance, we demonstrate that MIA induced NOR deficits in adult offspring. Oral antibiotic treatment of prepubertal mice prevented this cognitive impairment, but not increased frontal cortex 5-HT2AR density or psychedelic-induced head-twitch behavior in adult MIA offspring. Additionally, gut microbiota transplantation from MIA mice produced behavioral deficits in antibiotic-treated mock mice. Adult MIA offspring displayed altered gut microbiota, and relative abundance of specific components of the gut microbiota, including Ruminococcaceae, correlated with frontal cortex 5-HT2AR density. Together, these findings provide a better understanding of basic mechanisms by which prenatal insults impact offspring brain function, and suggest gut-brain axis manipulation as a potential therapeutic approach for neurodevelopmental psychiatric conditions.

Mouse-adapted H9N2 avian influenza virus causes systemic infection in mice

BackgroundH9N2 influenza viruses continuously circulate in multiple avian species and are repeatedly transmitted to humans, posing a significant threat to public health. To investigate the adaptation ability of H9N2 avian influenza viruses (AIVs) to mammals and the mutations related to the host switch events, we serially passaged in mice two H9N2 viruses of different HA lineages — A/Quail/Hong Kong/G1/97 (G1) of the G1-like lineage and A/chicken/Shandong/ZB/2007 (ZB) of the BJ/94-like lineage —and generated two mouse-adapted H9N2 viruses (G1-MA and ZB-MA) that possessed significantly higher virulence than the wide-type viruses.FindingZB-MA replicated systemically in mice. Genomic sequence alignment revealed 10 amino acid mutations coded by 4 different gene segments (PB2, PA, HA, and M) in G1-MA compared with the G1 virus and 23 amino acid mutations in 5 gene segments (PB1, PA, HA, M, and NS) in ZB-MA compared to ZB virus, indicating that the mutations in the polymerase, HA, M, and NS genes play critical roles in the adaptation of H9N2 AIVs to mammals, especially, the mutations of M1-Q198H and M1-A239T were shared in G1-MA and ZB-MA viruses. Additionally, several substitutions showed a higher frequency in human influenza viruses compared with avian viruses.ConclusionsDifferent lineages of H9N2 could adapt well in mice and some viruses could gain the ability to replicate systemically and become neurovirulent. Thus, it is essential to pay attention to the mammalian adaptive evolution of the H9N2 virus.

Lack of selective resistance of influenza A virus in presence of host-targeted antiviral, UV-4B

Development of antiviral drug resistance is a continuous concern for viruses with high mutation rates such as influenza. The use of antiviral drugs targeting host proteins required for viral replication is less likely to result in the selection of resistant viruses than treating with direct-acting antivirals. The iminosugar UV-4B is a host-targeted glucomimetic that inhibits endoplasmic reticulum α-glucosidase I and II enzymes resulting in improper glycosylation and misfolding of viral glycoproteins. UV-4B has broad-spectrum antiviral activity against diverse viruses including dengue and influenza. To examine the ability of influenza virus to develop resistance against UV-4B, mouse-adapted influenza virus was passaged in mice in the presence or absence of UV-4B and virus isolated from lungs was used to infect the next cohort of mice, for five successive passages. Deep sequencing was performed to identify changes in the viral genome during passaging in the presence or absence of UV-4B. Relatively few minor variants were identified within each virus and the ratio of nonsynonymous to synonymous (dN/dS) substitutions of minor variants confirmed no apparent positive selection following sustained exposure to UV-4B. Three substitutions (one synonymous in PB2, one nonsynonymous in M and PA each) were specifically enriched (>3%) in UV-4B-treated groups at passage five. Recombinant viruses containing each individual or combinations of these nonsynonymous mutations remained sensitive to UV-4B treatment in mice. Overall, these data provide evidence that there is a high genetic barrier to the generation and selection of escape mutants following exposure to host-targeted iminosugar antivirals.

Multiple amino acid substitutions involved in the adaption of three avian-origin H7N9 influenza viruses in mice

BackgroundAvian influenza A H7N9 virus has caused five outbreak waves of human infections in China since 2013 and posed a dual challenge to public health and poultry industry. The number of reported H7N9 virus human cases confirmed by laboratory has surpassed that of H5N1 virus. However, the mechanism for how H7N9 influenza virus overcomes host range barrier has not been clearly understood.MethodsTo generate mouse-adapted H7N9 influenza viruses, we passaged three avian-origin H7N9 viruses in mice by lung-to-lung passages independently. Then, the characteristics between the parental and mouse-adapted H7N9 viruses was compared in the following aspects, including virulence in mice, tropism of different tissues, replication in MDCK cells and molecular mutations.ResultsAfter ten passages in mice, MLD50 of the H7N9 viruses reduced >750-3,160,000 folds, and virus titers in MDCK cells increased 10-200 folds at 48 hours post-inoculation. Moreover, the mouse-adapted H7N9 viruses showed more expanded tissue tropism and more serious lung pathological lesions in mice. Further analysis of the amino acids changes revealed 10 amino acid substitutions located in PB2 (E627K), PB1 (W215R and D638G), PA (T97I), HA (H3 numbering: R220G, L226S, G279R and G493R) and NA (P3Q and R134I) proteins. Moreover, PB2 E627K substitution was shared by the three mouse-adapted viruses (two viruses belong to YRD lineage and one virus belongs to PRD lineage), and PA T97A substitution was shared by two mouse-adapted viruses (belong to YRD lineage).ConclusionsOur result indicated that the virulence in mice and virus titer in MDCK cells of H7N9 viruses significantly increased after adapted in mouse model. PB2 E627K and PA T97A substitutions are vital in mouse adaption and should be monitored during epidemiological study of H7N9 virus.

Intranasal coinfection model allows for assessment of protein vaccines against nontypeable Haemophilus influenzae in mice.

Nontypeable Haemophilus influenzae (NTHi) is a commensal in the human nasopharynx and the cause of pneumonia, meningitis, sinusitis, acute exacerbations of chronic obstructive pulmonary disease and acute otitis media (AOM). AOM is the most common ailment for which antibiotics are prescribed in the United States. With the emergence of new strains of antibiotic-resistant bacteria, finding an effective and broad coverage vaccine to protect against AOM-causing pathogens has become a priority. Mouse models are a cost-effective and efficient way to help determine vaccine efficacy. Here, we describe an NTHi AOM model in C57BL/6J mice, which also utilizes a mouse-adapted H1N1 influenza virus to mimic human coinfection. We tested our coinfection model using a protein vaccine formulation containing protein D, a well-studied NTHi vaccine candidate that can be found in the 10-valent Streptococcus pneumoniae conjugate vaccine. We verified the usefulness of our mouse model by comparing bacterial loads in the nose and ear between protein D-vaccinated and control mice. While there was no measurable difference in nasal bacterial loads, we did detect significant differences in the bacterial loads of ear washes and ear bullae between vaccinated and control mice. The results from this study suggest that our NTHi AOM coinfection model is useful for assessing protein vaccines.

Differential Redox State Contributes to Sex Disparities in the Response to Influenza Virus Infection in Male and Female Mice.

Influenza virus replicates intracellularly exploiting several pathways involved in the regulation of host responses. The outcome and the severity of the infection are thus strongly conditioned by multiple host factors, including age, sex, metabolic, and redox conditions of the target cells. Hormones are also important determinants of host immune responses to influenza and are recently proposed in the prophylaxis and treatment. This study shows that female mice are less susceptible than males to mouse-adapted influenza virus (A/PR8/H1N1). Compared with males, PR8-infected females display higher survival rate (+36%), milder clinical disease, and less weight loss. They also have milder histopathological signs, especially free alveolar area is higher than that in males, even if pro-inflammatory cytokine production shows slight differences between sexes; hormone levels, moreover, do not vary significantly with infection in our model. Importantly, viral loads (both in terms of viral M1 RNA copies and tissue culture infectious dose 50%) are lower in PR8-infected females. An analysis of the mechanisms contributing to sex disparities observed during infection reveals that the female animals have higher total antioxidant power in serum and their lungs are characterized by increase in (i) the content and biosynthesis of glutathione, (ii) the expression and activity of antioxidant enzymes (peroxiredoxin 1, catalase, and glutathione peroxidase), and (iii) the expression of the anti-apoptotic protein Bcl-2. By contrast, infected males are characterized by high expression of NADPH oxidase 4 oxidase and phosphorylation of p38 MAPK, both enzymes promoting viral replication. All these factors are critical for cell homeostasis and susceptibility to infection. Reappraisal of the importance of the host cell redox state and sex-related effects may be useful in the attempt to develop more tailored therapeutic interventions in the fight against influenza.

Enhanced pathogenicity and neurotropism of mouse-adapted H10N7 influenza virus are mediated by novel PB2 and NA mutations.

The H10 subtype of avian influenza viruses (AIVs) circulates globally in wild birds and poultry, and this subtype has been shown to be increasingly prevalent in China. Among the various H10 viruses, H10N7 AIVs have caused repeated mammal and human infections. To investigate their genetic adaptation in mammals, we generated a mouse-adapted avian H10N7 variant (A/mallard/Beijing/27/2011-MA; BJ27-MA) which exhibited increased virulence in mice compared to wild-type virus and acquired neurotropism. Sequencing showed the absence of the widely recognized mammalian adaptation markers of E627K and D701N in PB2 in the mouse-adapted strain; instead, five amino acid mutations were identified: E158G and M631L in PB2; G218E in haemagglutinin (H3 numbering); and K110E and S453I in neuraminidase (NA). The neurovirulence of the BJ27-MA virus necessitated the combined presence of the PB2 and NA mutations. Mutations M631L and E158G of PB2 and K110E of NA were required to mediate increased virus replication and severity of infection in mice and mammalian cells. PB2-M631L was functionally the most dominant mutation in that it strongly upregulated viral polymerase activity and played a critical role in the enhancement of virus replication and disease severity in mice. K110E mutation in NA, on the other hand, significantly promoted NA enzymatic activity. These results indicate that the novel mutations in PB2 and NA genes are critical for the adaptation of H10N7 AIV in mice, and they could serve as molecular signatures of virus transmission to mammalian hosts, including humans.

Estradiol and progesterone influence on influenza infection and immune response in a mouse model.

Influenza infection severity may be mediated by estradiol and/or progesterone. An exploratory study was designed to evaluate 17-β-estradiol and progesterone on influenza infection and examine immune-mediated response in a mouse model. Inoculation with placebo or mouse-adapted H1N1 influenza virus occurred. Treatment groups included 17-β-estradiol, progesterone, ovariectomy, and pregnancy. Mice were assessed for morbidity and mortality. Toll-like receptor gene studies and airspace cell differentials were performed. Onset of morbidity was earlier and morbidity duration greater for progesterone. Absence of morbidity/mortality and overall survival was greater for 17-β-estradiol. Airspace cell differentials suggest improved immune cell recruitment for 17-β-estradiol. Pregnant mouse data demonstrate significant mortality during the period of increased progesterone. Select immune cell markers demonstrate patterns of regulation that may promote proper immune response to influenza infection for 17-β-estradiol. Estradiol may play a protective and progesterone a detrimental role in the pathophysiology of influenza infection.

A small-molecule IRF3 agonist functions as an influenza vaccine adjuvant by modulating the antiviral immune response

Vaccine adjuvants are essential to drive a protective immune response in cases where vaccine antigens are weakly immunogenic, where vaccine antigen is limited, or where an increase in potency is needed for a specific population, such as the elderly. To discover novel vaccine adjuvants, we used a high-throughput screen (HTS) designed to identify small-molecule agonists of the RIG-I-like receptor (RLR) pathway leading to interferon regulatory factor 3 (IRF3) activation. RLRs are a group of cytosolic pattern-recognition receptors that are essential for the recognition of viral nucleic acids during infection. Upon binding of viral nucleic acid ligands, the RLRs become activated and signal to transcription factors, including IRF3, to initiate an innate immune transcriptional program to control virus infection. Among our HTS hits were a series of benzothiazole compounds from which we designed the lead analog, KIN1148. KIN1148 induced dose-dependent IRF3 nuclear translocation and specific activation of IRF3-responsive promoters. Prime-boost immunization of mice with a suboptimal dose of a monovalent pandemic influenza split virus H1N1 A/California/07/2009 vaccine plus KIN1148 protected against a lethal challenge with mouse-adapted influenza virus (A/California/04/2009) and induced an influenza virus-specific IL-10 and Th2 response by T cells derived from lung and lung-draining lymph nodes. Prime-boost immunization with vaccine plus KIN1148, but not prime immunization alone, induced antibodies capable of inhibiting influenza virus hemagglutinin and neutralizing viral infectivity. Nevertheless, a single immunization with vaccine plus KIN1148 provided increased protection over vaccine alone and reduced viral load in the lungs after challenge. These findings suggest that protection was at least partially mediated by a cellular immune component and that the induction of Th2 and immunoregulatory cytokines by a KIN1148-adjuvanted vaccine may be particularly beneficial for ameliorating the immunopathogenesis that is associated with influenza viruses.

In vitro and in vivo effects of Peganum harmala L. seeds extract against influenza A virus.

Influenza A virus infections are still a major health problem and the choices available for the control and treatment of the disease are limited. This research evaluated in vitro and in vivo antiviral effects of Peganum harmala L. seeds (PHS) extract against influenza A virus. In this research, in vitro anti-influenza A virus activity of the extract was assessed in Madin-Darby canine kidney (MDCK) cells. In order to evaluate anti-influenza activity of PHS extract in vivo, BALB/c mice were infected with 5LD50 of mouse-adapted influenza virus (H1N1; PR8) and received 200 mg/kg/day of PHS extract or 20 mg/kg/day oseltamivir. Lungs of seven mice per group were removed on day 3 post-infection and lung virus titers were determined by qRT-PCR. Mice survival, body weights and general conditions were observed for up to 14 days post-infection. The results demonstrated that, the ethanolic extract of PHS possesses high activity against influenza virus with IC50 value of 15.7 (CI95%:11.7-21) μg/ml in MDCK cells. Our results also showed that, oral administration of PHS extract (200 mg/kg/day) or oseltamivir (20 mg/kg/day) to infected mice, increased the survival rate, reduced body weight loss, and decreased lung virus titer. Based on our findings, P. harmala seeds extract can inhibit influenza A virus replication in vitro and in vivo. Therefore, isolation and characterization of the plant's active compounds and investigation of the underlying mechanisms of its antiviral action are highly suggested.

Interleukin 37 expression in mice alters sleep responses to inflammatory agents and influenza virus infection

Multiple interactions between the immune system and sleep are known, including the effects of microbial challenge on sleep or the effects of sleep loss on facets of the immune response. Cytokines regulate, in part, sleep and immune responses. Here we examine the role of an anti-inflammatory cytokine, interleukin-37 (IL-37) on sleep in a mouse strain that expresses human IL-37b (IL37tg mice). Constitutive expression of the IL-37 gene in the brains of these mice under resting conditions is low; however, upon an inflammatory stimulus, expression increases dramatically. We measured sleep in three conditions; (a) under baseline conditions and after 6h of sleep loss, (b) after bolus intraperitoneal administration of lipopolysaccharide (LPS) or IL-1β and (c) after intranasal influenza virus challenge. Under baseline conditions, the IL37tg mice had 7% more spontaneous non-rapid eye movement sleep (NREMS) during the light period than wild-type (WT) mice. After sleep deprivation both WT mice and IL37tg mice slept an extra 21% and 12%, respectively, during the first 6h of recovery. NREMS responses after sleep deprivation did not significantly differ between WT mice and IL37tg mice. However, in response to either IL-1β or LPS, the increases in time spent in NREMS were about four-fold greater in the WT mice than in the IL37tg mice. In contrast, in response to a low dose of mouse-adapted H1N1 influenza virus, sleep responses developed slowly over the 6day recording period. By day 6, NREMS increased by 10% and REMS increased by 18% in the IL37tg mice compared to the WT mice. Further, by day 4 IL37tg mice lost less weight, remained more active, and retained their body temperatures closer to baseline values than WT mice. We conclude that conditions that promote IL-37 expression attenuate morbidity to severe inflammatory challenge.

Cross-protective efficacy of dendritic cells targeting conserved influenza virus antigen expressed by Lactobacillus plantarum.

Avian influenza virus (AIV) can infect birds and mammals, including humans, and are thus a serious threat to public health. Vaccination is vital for controlling AIV circulation. In this study, we generated a recombinant lactobacillus expressing the NP-M1-DCpep of H9N2 avian influenza virus and evaluated the activation effect of NC8-pSIP409-NP-M1-DCpep on dendritic cells (DCs) in a mouse model. The specific mucosal antibody responses and B and T cell responses in lymphoid tissues were also characterized. Importantly, we confirmed that specific CD8 T cells presented in vitro and antigen-specific cytotoxicity (activated the expression of CD107a) and in vivo antigen-specific cytotoxicity after vaccination. The adoptive transfer of NC8-pSIP409-NP-M1-DCpep-primed CD8+ T cells into NOD-SCID mice resulted in effective protection against mouse-adapted AIV infection. In addition, we observed protection in immunized mice challenged with mouse-adapted H9N2 AIV and H1N1 influenza virus, as evidenced by reductions in the lung virus titers, improvements in lung pathology, and weight loss and complete survival. Our data are promising for the generation of effective, non-traditional influenza vaccines against AIVs.