PB1-F2 Proteins from H5N1 and 20th Century Pandemic Influenza Viruses Cause Immunopathology

With the recent emergence of a novel pandemic strain, there is presently intense interest in understanding the molecular signatures of virulence of influenza viruses. PB1-F2 proteins from epidemiologically important influenza A virus strains were studied to determine their function and contribution to virulence. Using 27-mer peptides derived from the C-terminal sequence of PB1-F2 and chimeric viruses engineered on a common background, we demonstrated that induction of cell death through PB1-F2 is dependent upon BAK/BAX mediated cytochrome c release from mitochondria. This function was specific for the PB1-F2 protein of A/Puerto Rico/8/34 and was not seen using PB1-F2 peptides derived from past pandemic strains. However, PB1-F2 proteins from the three pandemic strains of the 20th century and a highly pathogenic strain of the H5N1 subtype were shown to enhance the lung inflammatory response resulting in increased pathology. Recently circulating seasonal influenza A strains were not capable of this pro-inflammatory function, having lost the PB1-F2 protein's immunostimulatory activity through truncation or mutation during adaptation in humans. These data suggest that the PB1-F2 protein contributes to the virulence of pandemic strains when the PB1 gene segment is recently derived from the avian reservoir

Cell death regulation during influenza A virus infection by matrix (M1) protein: a model of viral control over the cellular survival pathway

During early infection, viruses activate cellular stress-response proteins such as heat-shock proteins (Hsps) to counteract apoptosis, but later on, they modulate these proteins to stimulate apoptosis for efficient viral dissemination. Hsp70 has been attributed to modulate viral entry, transcription, nuclear translocation and virion formation. It also exerts its anti-apoptotic function by binding to apoptosis protease-activating factor 1 (Apaf-1) and disrupting apoptosome formation. Here, we show that influenza A virus can regulate the anti-apoptotic function of Hsp70 through viral protein M1 (matrix 1). M1 itself did not induce apoptosis, but enhanced the effects of apoptotic inducers. M1-small-interfering RNA inhibits virus-induced apoptosis in cells after either virus infection or overexpression of the M1 protein. M1 binds to Hsp70, which results in reduced interaction between Hsp70 and Apaf-1. In a cell-free system, the M1 protein mediates procaspase-9 activation induced by cytochrome c/deoxyadenosine triphosphate. A study involving deletion mutants confirmed the role of the C-terminus substrate-binding domain (EEVD) of Hsp70 and amino acids 128–165 of M1 for this association. The M1 mutants, which did not co-immunoprecipitate with Hsp70, failed to induce apoptosis. Overall, the study confirms the proapoptotic function of the M1 protein during influenza virus infection

Consensus guidelines for the definition, detection and interpretation of immunogenic cell death.

Cells succumbing to stress via regulated cell death (RCD) can initiate an adaptive immune response associated with immunological memory, provided they display sufficient antigenicity and adjuvanticity. Moreover, multiple intracellular and microenvironmental features determine the propensity of RCD to drive adaptive immunity. Here, we provide an updated operational definition of immunogenic cell death (ICD), discuss the key factors that dictate the ability of dying cells to drive an adaptive immune response, summarize experimental assays that are currently available for the assessment of ICD in vitro and in vivo, and formulate guidelines for their interpretation

Effect of D222G Mutation in the Hemagglutinin Protein on Receptor Binding, Pathogenesis and Transmissibility of the 2009 Pandemic H1N1 Influenza Virus

Influenza viruses isolated during the 2009 H1N1 pandemic generally lack known molecular determinants of virulence associated with previous pandemic and highly pathogenic avian influenza viruses. The frequency of the amino acid substitution D222G in the hemagglutinin (HA) of 2009 H1N1 viruses isolated from severe but not mild human cases represents the first molecular marker associated with enhanced disease. To assess the relative contribution of this substitution in virus pathogenesis, transmission, and tropism, we introduced D222G by reverse genetics in the wild-type HA of the 2009 H1N1 virus, A/California/04/09 (CA/04). A dose-dependent glycan array analysis with the D222G virus showed a modest reduction in the binding avidity to human-like (α2-6 sialylated glycan) receptors and an increase in the binding to avian-like (α2-3 sialylated glycan) receptors in comparison with wild-type virus. In the ferret pathogenesis model, the D222G mutant virus was found to be similar to wild-type CA/04 virus with respect to lethargy, weight loss and replication efficiency in the upper and lower respiratory tract. Moreover, based on viral detection, the respiratory droplet transmission properties of these two viruses were found to be similar. The D222G virus failed to productively infect mice inoculated by the ocular route, but exhibited greater viral replication and weight loss than wild-type CA/04 virus in mice inoculated by the intranasal route. In a more relevant human cell model, D222G virus replicated with delayed kinetics compared with wild-type virus but to higher titer in human bronchial epithelial cells. These findings suggest that although the D222G mutation does not influence virus transmission, it may be considered a molecular marker for enhanced replication in certain cell types.Centers for Disease Control and Prevention (U.S.)United States. National Institutes of Health (merit award R37 GM057073-13)Singapore-MIT Alliance for Research and Technolog

Experimental Infection of Mice with Avian Paramyxovirus Serotypes 1 to 9

The nine serotypes of avian paramyxoviruses (APMVs) are frequently isolated from domestic and wild birds worldwide. APMV-1, also called Newcastle disease virus, was shown to be attenuated in non-avian species and is being developed as a potential vector for human vaccines. In the present study, we extended this evaluation to the other eight serotypes by evaluating infection in BALB/c mice. Mice were inoculated intranasally with a prototype strain of each of the nine serotypes and monitored for clinical disease, gross pathology, histopathology, virus replication and viral antigen distribution, and seroconversion. On the basis of multiple criteria, each of the APMV serotypes except serotype 5 was found to replicate in mice. Five of the serotypes produced clinical disease and significant weight loss in the following order of severity: 1, 2>6, 9>7. However, disease was short-lived. The other serotypes produced no evident clinical disease. Replication of all of the APMVs except APMV-5 in the nasal turbinates and lungs was confirmed by the recovery of infectious virus and by substantial expression of viral antigen in the epithelial lining detected by immunohistochemistry. Trace levels of infectious APMV-4 and -9 were detected in the brain of some animals; otherwise, no virus was detected in the brain, small intestine, kidney, or spleen. Histologically, infection with the APMVs resulted in lung lesions consistent with broncho-interstitial pneumonia of varying severity that were completely resolved at 14 days post infection. All of the mice infected with the APMVs except APMV-5 produced serotype-specific HI serum antibodies, confirming a lack of replication of APMV-5. Taken together, these results demonstrate that all APMV serotypes except APMV-5 are capable of replicating in mice with minimal disease and pathology

Transcriptomic Analysis of Host Immune and Cell Death Responses Associated with the Influenza A Virus PB1-F2 Protein

Airway inflammation plays a major role in the pathogenesis of influenza viruses and can lead to a fatal outcome. One of the challenging objectives in the field of influenza research is the identification of the molecular bases associated to the immunopathological disorders developed during infection. While its precise function in the virus cycle is still unclear, the viral protein PB1-F2 is proposed to exert a deleterious activity within the infected host. Using an engineered recombinant virus unable to express PB1-F2 and its wild-type homolog, we analyzed and compared the pathogenicity and host response developed by the two viruses in a mouse model. We confirmed that the deletion of PB1-F2 renders the virus less virulent. The global transcriptomic analyses of the infected lungs revealed a potent impact of PB1-F2 on the response developed by the host. Thus, after two days post-infection, PB1-F2 invalidation severely decreased the number of genes activated by the host. PB1-F2 expression induced an increase in the number and level of expression of activated genes linked to cell death, inflammatory response and neutrophil chemotaxis. When generating interactive gene networks specific to PB1-F2, we identified IFN-γ as a central regulator of PB1-F2-regulated genes. The enhanced cell death of airway-recruited leukocytes was evidenced using an apoptosis assay, confirming the pro-apoptotic properties of PB1-F2. Using a NF-kB luciferase adenoviral vector, we were able to quantify in vivo the implication of NF-kB in the inflammation mediated by the influenza virus infection; we found that PB1-F2 expression intensifies the NF-kB activity. Finally, we quantified the neutrophil recruitment within the airways, and showed that this type of leukocyte is more abundant during the infection of the wild-type virus. Collectively, these data demonstrate that PB1-F2 strongly influences the early host response during IAV infection and provides new insights into the mechanisms by which PB1-F2 mediates virulence

Antigenic Fingerprinting of H5N1 Avian Influenza Using Convalescent Sera and Monoclonal Antibodies Reveals Potential Vaccine and Diagnostic Targets

Using whole-genome-fragment phage display libraries, Hana Golding and colleagues identify the viral epitopes recognized by serum antibodies in humans who have recovered from infection with H5N1 avian influenza

Global economic burden of unmet surgical need for appendicitis

Background: There is a substantial gap in provision of adequate surgical care in many low-and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods: Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results: Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion: For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

IRE1α–XBP1 controls T cell function in ovarian cancer by regulating mitochondrial activity

Tumours evade immune control by creating hostile microenvironments that perturb T cell metabolism and effector function 1?4 . However, it remains unclear how intra-tumoral T cells integrate and interpret metabolic stress signals. Here we report that ovarian cancer?an aggressive malignancy that is refractory to standard treatments and current immunotherapies 5?8 ?induces endoplasmic reticulum stress and activates the IRE1α?XBP1 arm of the unfolded protein response 9,10 in T cells to control their mitochondrial respiration and anti-tumour function. In T cells isolated from specimens collected from patients with ovarian cancer, upregulation of XBP1 was associated with decreased infiltration of T cells into tumours and with reduced IFNG mRNA expression. Malignant ascites fluid obtained from patients with ovarian cancer inhibited glucose uptake and caused N-linked protein glycosylation defects in T cells, which triggered IRE1α?XBP1 activation that suppressed mitochondrial activity and IFNγ production. Mechanistically, induction of XBP1 regulated the abundance of glutamine carriers and thus limited the influx of glutamine that is necessary to sustain mitochondrial respiration in T cells under glucose-deprived conditions. Restoring N-linked protein glycosylation, abrogating IRE1α?XBP1 activation or enforcing expression of glutamine transporters enhanced mitochondrial respiration in human T cells exposed to ovarian cancer ascites. XBP1-deficient T cells in the metastatic ovarian cancer milieu exhibited global transcriptional reprogramming and improved effector capacity. Accordingly, mice that bear ovarian cancer and lack XBP1 selectively in T cells demonstrate superior anti-tumour immunity, delayed malignant progression and increased overall survival. Controlling endoplasmic reticulum stress or targeting IRE1α?XBP1 signalling may help to restore the metabolic fitness and anti-tumour capacity of T cells in cancer hosts.Fil: Song, Minkyung. Weill Cornell Medicine; Estados UnidosFil: Sandoval, Tito A.. Weill Cornell Medicine; Estados UnidosFil: Chae, Chang-Suk. Weill Cornell Medicine; Estados UnidosFil: Chopra, Sahil. Weill Cornell Medicine; Estados UnidosFil: Tan, Chen. Weill Cornell Medicine; Estados UnidosFil: Rutkowski, Melanie R.. University of Virginia; Estados UnidosFil: Raundhal, Mahesh. Dana Farber Cancer Institute; Estados Unidos. Harvard Medical School; Estados UnidosFil: Chaurio, Ricardo A.. H. Lee Moffitt Cancer Center & Research Institute; Estados UnidosFil: Payne, Kyle K.. H. Lee Moffitt Cancer Center & Research Institute; Estados UnidosFil: Konrad, Csaba. Weill Cornell Medicine; Estados UnidosFil: Bettigole, Sarah E.. Quentis Therapeutics Inc.; Estados UnidosFil: Shin, Hee Rae. Quentis Therapeutics Inc.; Estados UnidosFil: Crowley, Michael J. P.. Weill Cornell Graduate School of Medical Sciences; Estados UnidosFil: Cerliani, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; ArgentinaFil: Kossenkov, Andrew V.. The Wistar Institute; Estados UnidosFil: Motorykin, Ievgen. Weill Cornell Medicine,; Estados UnidosFil: Zhang, Sheng. Weill Cornell Medicine,; Estados UnidosFil: Manfredi, Giovanni. Weill Cornell Medicine,; Estados UnidosFil: Zamarin, Dmitriy. Memorial Sloan Kettering Cancer Center; Estados UnidosFil: Holcomb, Kevin. Weill Cornell Medicine,; Estados UnidosFil: Rodriguez, Paulo C.. H. Lee Moffitt Cancer Center & Research Institute; Estados UnidosFil: Rabinovich, Gabriel Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Conejo Garcia, Jose R.. H. Lee Moffitt Cancer Center & Research Institute; Estados UnidosFil: Glimcher, Laurie H.. Dana Farber Cancer Institute; Estados Unidos. Harvard Medical School; Estados UnidosFil: Cubillos-Ruiz, Juan R.. Weill Graduate School Of Medical Sciences; Estados Unidos. Weill Graduate School Of Medical Sciences; Estados Unido