Accumulation of human-adapting mutations during circulation of A(H1N1)pdm09 influenza virus in humans in the United Kingdom

The influenza pandemic that emerged in 2009 provided an unprecedented opportunity to study adaptation of a virus recently acquired from an animal source during human transmission. In the United Kingdom, the novel virus spread in three temporally distinct waves between 2009 and 2011. Phylogenetic analysis of complete viral genomes showed that mutations accumulated over time. Second- and third-wave viruses replicated more rapidly in human airway epithelial (HAE) cells than did the first-wave virus. In infected mice, weight loss varied between viral isolates from the same wave but showed no distinct pattern with wave and did not correlate with viral load in the mouse lungs or severity of disease in the human donor. However, second- and third-wave viruses induced less alpha interferon in the infected mouse lungs. NS1 protein, an interferon antagonist, had accumulated several mutations in second- and third-wave viruses. Recombinant viruses with the third-wave NS gene induced less interferon in human cells, but this alone did not account for increased virus fitness in HAE cells. Mutations in HA and NA genes in third-wave viruses caused increased binding to alpha-2,6-sialic acid and enhanced infectivity in human mucus. A recombinant virus with these two segments replicated more efficiently in HAE cells. A mutation in PA (N321K) enhanced polymerase activity of third-wave viruses and also provided a replicative advantage in HAE cells. Therefore, multiple mutations allowed incremental changes in viral fitness, which together may have contributed to the apparent increase in severity of A(H1N1)pdm09 influenza virus during successive waves. IMPORTANCE: Although most people infected with the 2009 pandemic influenza virus had mild or unapparent symptoms, some suffered severe and devastating disease. The reasons for this variability were unknown, but the numbers of severe cases increased during successive waves of human infection in the United Kingdom. To determine the causes of this variation, we studied genetic changes in virus isolates from individual hospitalized patients. There were no consistent differences between these viruses and those circulating in the community, but we found multiple evolutionary changes that in combination over time increased the virus's ability to infect human cells. These adaptations may explain the remarkable ability of A(H1N1)pdm09 virus to continue to circulate despite widespread immunity and the apparent increase in severity of influenza over successive waves of infection

Nicotinic acetylcholine receptor signaling regulates inositol‐requiring enzyme 1α activation to protect β‐cells against terminal unfolded protein response under irremediable endoplasmic reticulum stress

Aims/introductionUnder irremediable endoplasmic reticulum (ER) stress, hyperactivated inositol-requiring enzyme 1α (IRE1α) triggers the terminal unfolded protein response (T-UPR), causing crucial cell dysfunction and apoptosis. We hypothesized that nicotinic acetylcholine receptor (nAChR) signaling regulates IRE1α activation to protect β-cells from the T-UPR under ER stress.Materials and methodsThe effects of nicotine on IRE1α activation and key T-UPR markers, thioredoxin-interacting protein and insulin/proinsulin, were analyzed by real-time polymerase chain reaction and western blotting in rat INS-1 and human EndoC-βH1 β-cell lines. Doxycycline-inducible IRE1α overexpression or ER stress agents were used to induce IRE1α activation. An α7 subunit-specific nAChR agonist (PNU-282987) and small interfering ribonucleic acid for α7 subunit-specific nAChR were used to modulate nAChR signaling.ResultsNicotine inhibits the increase in thioredoxin-interacting protein and the decrease in insulin 1/proinsulin expression levels induced by either forced IRE1α hyperactivation or ER stress agents. Nicotine attenuated X-box-binding protein-1 messenger ribonucleic acid site-specific splicing and IRE1α autophosphorylation induced by ER stress. Furthermore, PNU-282987 attenuated T-UPR induction by either forced IRE1α activation or ER stress agents. The effects of nicotine on attenuating thioredoxin-interacting protein and preserving insulin 1 expression levels were attenuated by pharmacological and genetic inhibition of α7 nAChR. Finally, nicotine suppressed apoptosis induced by either forced IRE1α activation or ER stress agents.ConclusionsOur findings suggest that nAChR signaling regulates IRE1α activation to protect β-cells from the T-UPR and apoptosis under ER stress partly through α7 nAChR. Targeting nAChR signaling to inhibit the T-UPR cascade may therefore hold therapeutic promise by thwarting β-cell death in diabetes

Penetration of infectious prion protein in the intestine during the lactation period.

Prion diseases are fatal neurodegenerative zoonotic foodborne disorders, which are caused by an abnormal isoform of prion protein (PrPSc) derived from the cellular isoform of prion protein (PrPC). According to epidemiological surveillance and in vivo experiments, exposure to the PrPSc during the weaning period is fraught with risk, suggesting that, during development, the intestinal defenses and the immune system are involved in PrPSc infection susceptibility. Although it remains unclear how PrPSc passes through the natural biological barriers during its invasion of intestinal cells, the 37 kDa/67 kDa laminin receptor is suspected to be one of the receptors involved in PrPSc-incorporation. In addition, we have recently shown that the neonatal Fc receptor (nFcR), which contributes to the uptake of maternal antibodies into the intestine, may play an important role in PrPSc incorporation. In this review, recent studies on PrPSc uptake and models of PrPSc incorporation into the intestine via the laminin and Fc receptors are described

Intrathoracic injection of the Ho Chi Minh (HCM), Patilas (PAT) and Orlando (ORL) strains of <i>Ae</i>. <i>aegypti</i> with ZIKV results in robust infection of mosquitoes.

HCM, PAT and ORL strains of Ae. aegypti were infected by intrathoracic injection with 103 PFU of ZIKV, and after 7 or 10 days allowed to feed on naïve mice. (A) Experimental workflow for the ZIKV injection experiments. (B) QRT-PCR analysis was performed on the salivary gland (SG) and midgut (MG) of ORL, PAT and HCM mosquitoes 7 or 10 days after injection with ZIKV. ZIKV RNA levels were normalized to mosquito Rp49 RNA levels. (C) Infection rate of each strain infected for 7 and 10 days was calculated by comparing infected vs. uninfected mosquitoes in each experiment. Data shown are pooled from at least two independent experiments. (n = 19/group for ORL-Day 7; n = 18/group for ORL-Day 10; n = 14/group for PAT-Day 7; n = 17/group for PAT-Day 10; n = 18/group for HCM-Day 7; n = 11/group for HCM-Day 10.) Significance was calculated using one-way ANOVA.</p

Altered vector competence in an experimental mosquito-mouse transmission model of Zika infection

<div><p>Few animal models of Zika virus (ZIKV) infection have incorporated arthropod-borne transmission. Here, we establish an <i>Aedes aegypti</i> mosquito model of ZIKV infection of mice, and demonstrate altered vector competency among three strains, (Orlando, ORL, Ho Chi Minh, HCM, and Patilas, PAT). All strains acquired ZIKV in their midguts after a blood meal from infected mice, but ZIKV transmission only occurred in mice fed upon by HCM, and to a lesser extent PAT, but not ORL, mosquitoes. This defect in transmission from ORL or PAT mosquitoes was overcome by intrathoracic injection of ZIKV into mosquito. Genetic analysis revealed significant diversity among these strains, suggesting a genetic basis for differences in ability for mosquito strains to transmit ZIKV. The intrathoracic injection mosquito-mouse transmission model is critical to understanding the influence of mosquitoes on ZIKV transmission, infectivity and pathogenesis in the vertebrate host, and represents a natural transmission route for testing vaccines and therapeutics.</p></div

Infection of inbred BALB/c and C57BL/6 and outbred Institute of Cancer Research mice with the emerging H7N9 avian influenza virus

A new avian-origin influenza virus A (H7N9) recently crossed the species barrier and infected humans; therefore, there is an urgent need to establish mammalian animal models for studying the pathogenic mechanism of this strain and the immunological response. In this study, we attempted to develop mouse models of H7N9 infection because mice are traditionally the most convenient models for studying influenza viruses. We showed that the novel A (H7N9) virus isolated from a patient could infect inbred BALB/c and C57BL/6 mice as well as outbred Institute of Cancer Research (ICR) mice. The amount of bodyweight lost showed differences at 7 days post infection (d.p.i.) (BALB/c mice 30%, C57BL/6 and ICR mice approximately 20%), and the lung indexes were increased both at 3 d.p.i. and at 7 d.p.i.. Immunohistochemistry demonstrated the existence of the H7N9 viruses in the lungs of the infected mice, and these findings were verified by quantitative real-time polymerase chain reaction (RT-PCR) and 50% tissue culture infectious dose (TCID(50)) detection at 3 d.p.i. and 7 d.p.i.. Histopathological changes occurred in the infected lungs, including pulmonary interstitial inflammatory lesions, pulmonary oedema and haemorrhages. Furthermore, because the most clinically severe cases were in elderly patients, we analysed the H7N9 infections in both young and old ICR mice. The old ICR mice showed more severe infections with more bodyweight lost and a higher lung index than the young ICR mice. Compared with the young ICR mice, the old mice showed a delayed clearance of the H7N9 virus and higher inflammation in the lungs. Thus, old ICR mice could partially mimic the more severe illness in elderly patients

Viral titers in brains of mice engorged upon by ZIKV-infected mosquitoes.

Viral titers in brains of mice engorged upon by ZIKV-infected mosquitoes.</p