1918 H1N1 Influenza Virus Replicates and Induces Proinflammatory Cytokine Responses in Extrarespiratory Tissues of Ferrets

Abstract

1918 H1N1 virus spread to and induced cytokine responses in tissues outside the respiratory tract, which likely contributed to the severity of infection. Moreover, our data support the suggested link between 1918 H1N1 infection and central nervous system disease.

Mini viral RNAs act as innate immune agonists during influenza virus infection

“…Ferret experiments with IN05 and NL09 were described previously 29 and conducted in the Biosafety Level-3 laboratory of the Erasmus Medical Centre in compliance with European guidelines (EU directive on animal testing 86/609/EEC) and Dutch legislation (Experiments on Animals Act, 1997), after approval by the independent animal experimentation ethical review committee of the Netherlands Vaccine Institute (permit number 200900201). Ferret experiments with BM18 were described previously 30 and approved by Institutional Animal Care and Use Committee of Rocky Mountain Laboratories, National Institutes of Health, and conducted in an Association for Assessment and Accreditation of Laboratory Animal Care international-accredited facility according to the guidelines and basic principles in the United States Public Health Service Policy on Humane Care and Use of Laboratory Animals, and the Guide for the Care and Use of Laboratory Animals. Sample inactivation and shipment was performed according to standard operating procedures for the removal of specimens from high containment and approved by the Institutional Biosafety Committee.…”

“…RNA was extracted 8 hours post infection and analysed using deep sequencing or qualitative RT-PCR. Ferret lung tissue was obtained from ferrets infected with A/Indonesia/5/2005 (H5N1) or A/Netherlands/602/2009 (H1N1) 29 , or A/Brevig Mission/1/1918 (H1N1) 30 . A single ferret (lung titre = 7.6×10 1 log 10 TCID 50 /g) was excluded from analysis on the basis of its apparent lack of infection.…”

“…mvRNA levels were determined by deep sequencing using universal influenza virus primers, as detailed above. Viral load or titre was determined by segment 6 qRT-PCR or by using previously published values 29,30 . Subsequent enrichment analysis of Gene Ontology terms specifically affected by mvRNA levels was carried out using Parametric Analysis of Gene Set Enrichment 49 via the GAGE package in R, with data from the above genome annotations, accessed via the biomaRt package 50 .…”

“…To address whether mvRNAs are also produced in infection of animal models, we investigated mvRNA generation in ferrets, which are regarded as the gold-standard model for influenza virus infection studies. Specifically, we analysed RNA samples from ferret lungs one and three days after infection with highly pathogenic avian A/Indonesia/5/2005 (H5N1) (abbreviated as IN05), 2009 swine-origin pandemic A/Netherlands/602/2009 (H1N1) (abbreviated as NL09) or the BM18 pandemic virus 29,30 . mvRNAs were present in all infected lung samples one day after infection, with mvRNA levels particularly high in the BM18 infected ferret lungs (Fig.…”

Influenza in High-Risk Hosts—Lessons Learned from Animal Models

“…2). The 1918 pandemic induced high morbidity among all ages, but young adults had a disproportionately higher rate of mortality (Morens et al 2008;Walters et al 2016;Taubenberger et al 2019) potentially attributed to the virus's ability to induce a dysregulated pro-inflammatory immune response, as shown in mice, ferrets, and cynomolgus macaques (Kobasa et al 2004(Kobasa et al , 2007Kash et al 2006;Memoli et al 2009;de Wit et al 2018;Short et al 2018). During the influenza virus seasons immediately after pandemics, there tends to be a flattening of the young adult hump in the age-specific mortality curve back into the "U-shape" (Fig.…”