Mathematical and computational models for infectious diseases are increasingly used to support public-health decisions; however, their reliability is currently under debate. Real-time forecasts of ...epidemic spread using data-driven models have been hindered by the technical challenges posed by parameter estimation and validation. Data gathered for the 2009 H1N1 influenza crisis represent an unprecedented opportunity to validate real-time model predictions and define the main success criteria for different approaches.
We used the Global Epidemic and Mobility Model to generate stochastic simulations of epidemic spread worldwide, yielding (among other measures) the incidence and seeding events at a daily resolution for 3,362 subpopulations in 220 countries. Using a Monte Carlo Maximum Likelihood analysis, the model provided an estimate of the seasonal transmission potential during the early phase of the H1N1 pandemic and generated ensemble forecasts for the activity peaks in the northern hemisphere in the fall/winter wave. These results were validated against the real-life surveillance data collected in 48 countries, and their robustness assessed by focusing on 1) the peak timing of the pandemic; 2) the level of spatial resolution allowed by the model; and 3) the clinical attack rate and the effectiveness of the vaccine. In addition, we studied the effect of data incompleteness on the prediction reliability.
Real-time predictions of the peak timing are found to be in good agreement with the empirical data, showing strong robustness to data that may not be accessible in real time (such as pre-exposure immunity and adherence to vaccination campaigns), but that affect the predictions for the attack rates. The timing and spatial unfolding of the pandemic are critically sensitive to the level of mobility data integrated into the model.
Our results show that large-scale models can be used to provide valuable real-time forecasts of influenza spreading, but they require high-performance computing. The quality of the forecast depends on the level of data integration, thus stressing the need for high-quality data in population-based models, and of progressive updates of validated available empirical knowledge to inform these models.
IL-33, a novel IL-1 family member, is crucially expressed and involved in pulmonary diseases, but its regulation in viral diseases such as influenza A virus (IAV) remains unclear. This study aimed to ...characterize the expression and release of IL-33 in lungs of IAV-infected mice in vivo and in murine respiratory epithelial cells (MLE-15) in vitro. Our results provide evidence of up-regulation of IL-33 mRNA in IAV-infected murine lungs, compared with noninfected control mice. The overexpression of IL-33 was positively correlated with a significant increase in mRNA encoding the proinflammatory cytokines TNF-α, IFN-γ, IL-1β, and IL-6, and was also associated with an increase in IFN-β mRNA. A profound overexpression of IL-33 protein was evident in IAV-infected murine lungs and bronchoalveolar lavages of influenza-infected mice, compared with low concentrations in naive lungs in vivo. Immunolocalization highlighted the cellular expression of IL-33 in alveolar epithelial and endothelial cells, along with increased infiltrate cells in virus-infected lungs. Further in vitro experiments showed an induction of IL-33 transcript-in MLE-15 cells and human epithelial cells (A549) infected with different strains of IAV in comparison with noninfected cells. In conclusion, our findings evidenced a profound expression of IL-33 in lungs during both in vivo and in vitro IAV infections, suggesting a role for IL-33 in virus-induced lung infections.
As an effective antiviral agent, the clinical application of oseltamivir (OTV) is limited by the appearance of drug-resistant viruses. Due to their low toxicity and excellent activity, the antiviral ...capabilities of selenium nanoparticles (SeNPs) has attracted increasing attention in recent years. To overcome the limitation of drug resistance, the use of modified NPs with biologics to explore novel anti-influenza drugs is developing rapidly. In this study, OTV surface-modified SeNPs with superior antiviral properties and restriction on drug resistance were synthesized. OTV decoration of SeNPs (Se@OTV) obviously inhibited H1N1 infection and had less toxicity. Se@OTV interfered with the H1N1 influenza virus to host cells through inhibiting the activity of hemagglutinin and neuraminidase. The mechanism was that Se@OTV was able to prevent H1N1 from infecting MDCK cells and block chromatin condensation and DNA fragmentation. Furthermore, Se@OTV inhibited the generation of reactive oxygen species and activation of p53 phosphorylation and Akt. These results demonstrate that Se@OTV is a promising efficient antiviral pharmaceutical for H1N1.
The objective of this report was to characterize the enhanced clinical disease and lung lesions observed in pigs vaccinated with inactivated H1N2 swine δ-cluster influenza A virus and challenged with ...pandemic 2009 A/H1N1 human influenza virus. Eighty-four, 6-week-old, cross-bred pigs were randomly allocated into 3 groups of 28 pigs to represent vaccinated/challenged (V/C), non-vaccinated/challenged (NV/C), and non-vaccinated/non-challenged (NV/NC) control groups. Pigs were intratracheally inoculated with pH1N1and euthanized at 1, 2, 5, and 21 days post inoculation (dpi). Macroscopically, V/C pigs demonstrated greater percentages of pneumonia compared to NV/C pigs. Histologically, V/C pigs demonstrated severe bronchointerstitial pneumonia with necrotizing bronchiolitis accompanied by interlobular and alveolar edema and hemorrhage at 1 and 2 dpi. The magnitude of peribronchiolar lymphocytic cuffing was greater in V/C pigs by 5 dpi. Microscopic lung lesion scores were significantly higher in the V/C pigs at 2 and 5 dpi compared to NV/C and NV/NC pigs. Elevated TNF-α, IL-1β, IL-6, and IL-8 were detected in bronchoalveolar lavage fluid at all time points in V/C pigs compared to NV/C pigs. These data suggest H1 inactivated vaccines followed by heterologous challenge resulted in potentiated clinical signs and enhanced pulmonary lesions and correlated with an elevated proinflammatory cytokine response in the lung. The lung alterations and host immune response are consistent with the vaccine-associated enhanced respiratory disease (VAERD) clinical outcome observed reproducibly in this swine model.
The H1N1 Eurasian avian-like swine (EAsw) influenza viruses originated from an avian H1N1 virus. To characterize potential changes in the membrane fusion activity of the hemagglutinin (HA) during ...avian-to-swine adaptation of the virus, we studied EAsw viruses isolated in the first years of their circulation in pigs and closely related contemporary H1N1 viruses of wild aquatic birds. Compared to the avian viruses, the swine viruses were less sensitive to neutralization by lysosomotropic agent NH4Cl in MDCK cells, had a higher pH optimum of hemolytic activity, and were less stable at acidic pH. Eight amino acid substitutions in the HA were found to separate the EAsw viruses from their putative avian precursor; four substitutions-T492S, N722D, R752K, and S1132F-were located in the structural regions of the HA2 subunit known to play a role in acid-induced conformational transition of the HA. We also studied low-pH-induced syncytium formation by cell-expressed HA proteins and found that the HAs of the 1918, 1957, 1968, and 2009 pandemic viruses required a lower pH for fusion induction than did the HA of a representative EAsw virus. Our data show that transmission of an avian H1N1 virus to pigs was accompanied by changes in conformational stability and fusion promotion activity of the HA. We conclude that distinctive host-determined fusion characteristics of the HA may represent a barrier for avian-to-swine and swine-to-human transmission of influenza viruses.
Continuing cases of human infections with zoonotic influenza viruses highlight the necessity to understand which viral properties contribute to interspecies transmission. Efficient binding of the HA to cellular receptors in a new host species is known to be essential for the transmission. Less is known about required adaptive changes in the membrane fusion activity of the HA. Here we show that adaptation of an avian influenza virus to pigs in Europe in 1980s was accompanied by mutations in the HA, which decreased its conformational stability and increased pH optimum of membrane fusion activity. This finding represents the first formal evidence of alteration of the HA fusion activity/stability during interspecies transmission of influenza viruses under natural settings.
Influenza infection causes severe disease and death in humans. In traditional vaccine research and development, a single high-dose virus challenge of animals is used to evaluate vaccine efficacy. ...This type of challenge model may have limitations. In the present study, we developed a novel challenge model by infecting mice repeatedly in short intervals with low doses of influenza A virus. Our results show that compared to a single high-dose infection, mice that received repeated low-dose challenges showed earlier morbidity and mortality and more severe disease. They developed higher vial loads, more severe lung pathology, and greater inflammatory responses and generated only limited influenza A virus-specific B and T cell responses. A commercial trivalent influenza vaccine protected mice against a single high and lethal dose of influenza A virus but was ineffective against repeated low-dose virus challenges. Overall, our data show that the repeated low-dose influenza A virus infection mouse model is more stringent and may thus be more suitable to select for highly efficacious influenza vaccines.
Influenza epidemics and pandemics pose serious threats to public health. Animal models are crucial for evaluating the efficacy of influenza vaccines. Traditional models based on a single high-dose virus challenge may have limitations. Here, we describe a new mouse model based on repeated low-dose influenza A virus challenges given within a short period. Repeated low-dose challenges caused more severe disease in mice, associated with higher viral loads and increased lung inflammation and reduced influenza A virus-specific B and T cell responses. A commercial influenza vaccine that was shown to protect mice from high-dose challenge was ineffective against repeated low-dose challenges. Overall, our results show that the low-dose repeated-challenge model is more stringent and may therefore be better suited for preclinical vaccine efficacy studies.
•IFNAR KO mice exhibited increased mortality after infection with influenza A/FM/1/47.•The level of proinflammatory cytokines increased in IFNAR KO mice after infection.•The production of IL-10 was ...impaired in IFNAR KO mice after infection.•IFNAR signaling was critical to induce IL-10 production.•Restoration of IL-10 to IFNAR KO mice alleviated cytokine storm and improved mortality.
Antiviral immune responses play as a double edged sword in resolution of infection and pathogenesis of acute lung injury caused by infection with highly pathogenic influenza A viruses. Here we show that type I interferons (IFNs) are important in protection against acute influenza A virus infection not only via their antiviral activity but also via their anti-inflammatory activity. IFN α receptor (IFNAR) knock-out (KO) mice exhibited increased mortality and morbidity with higher viral load after infection with influenza virus A/FM/1/47 (H1N1, a mouse-adapted strain) compared with wild-type (WT) mice, though the viruses were finally eliminated in both groups. The levels of proinflammatory cytokines in the lungs were significantly higher, while the level of IL-10 in the lungs was significantly lower in IFNAR KO mice than in WT mice during the course of infection. Restoration of IL-10 during an ongoing virus infection significantly reduced the levels of proinflammatory cytokines and improved mortality of IFNAR KO mice. These results suggest that type I IFNs are responsible not only for direct resolution of viral load but also for suppression of immunopathology caused by influenza A virus through IL-10 production.
The reassortment between avian H9N2 and Eurasian avian-like (EA) H1N1 viruses may have potentially changed from avian-to-mammals adaptation. This study generated 20 reassortant viruses with the ...introduction of H1N1/2009 internal genes from EA H1N1 virus into H9N2 virus. 12 of these recovered the replication capability both in the lungs and turbinate samples. 10 of 12 obtained PA gene segments from the ribonucleoprotein (RNP) complexes of the EA H1N1 virus, and 3 exhibited extreme virulence. Specially, the combination of PB2, PA and NP genes could overcome the species-specific restriction in human cells. Analysis of the polymerase activities found that introduction of the PA gene resulted in increased polymerase activity. These findings indicated that RNP complexes from EA H1N1 virus could confer an adaptation advantage and high compatibility to avian H9N2 virus. This raises new concerns for public health due to the possible coexistence of H9N2 and EA H1N1 viruses in dogs.
Influenza virus neuraminidase (NA)-targeting antibodies are an independent correlate of protection against influenza. Antibodies against the NA act by blocking enzymatic activity, preventing virus ...release and transmission. As we advance the development of improved influenza virus vaccines that incorporate standard amounts of NA antigen, it is important to identify the antigenic targets of human monoclonal antibodies (mAbs). Here, we describe escape mutants generated by serial passage of A/Netherlands/602/2009 (H1N1)pdm09 in the presence of human anti-N1 mAbs. We observed escape mutations on the head domain of the N1 protein around the enzymatic site (S364N, N369T, and R430Q) and also detected escape mutations located on the sides and bottom of the NA (N88D, N270D, and Q313K/R). This work increases our understanding of how human antibody responses target the N1 protein.
As improved influenza virus vaccines are being developed, the influenza virus neuraminidase (NA) is becoming an important new target for immune responses. By identifying novel epitopes of anti-NA antibodies, we can improve vaccine design. Additionally, characterizing escape mutations in these epitopes aids in identifying NA antigenic drift in circulating viruses.
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