Pathogenesis of influenza in the Ferret Model : a basis for improved intervention

Although clinical disease and associated lesions of the respiratory tract due to IAV infections are well known, the exact pathogenesis of acute respiratory distress syndrome (ARDS) is not yet fully understood. ARDS is a fatal complication of influenza virus infection, and accounts for many influenza-­‐related mortalities. At the starting point of this thesis, the mechanism of pulmonary oedema formation, as one of the hallmarks

The neuropathogenesis of highly pathogenic avian influenza H5Nx viruses in mammalian species including humans

Circulation of highly pathogenic avian influenza (HPAI) H5Nx viruses of the A/Goose/Guangdong/1/96 lineage in birds regularly causes infections of mammals, including humans. In many mammalian species, infections are associated with severe neurological disease, a unique feature of HPAI H5Nx viruses compared with other influenza A viruses. Here, we provide an overview of the neuropathogenesis of HPAI H5Nx virus infection in mammals, centered on three aspects: neuroinvasion, neurotropism, and neurovirulence. We focus on in vitro studies, as well as studies on naturally or experimentally infected mammals. Additionally, we discuss the contribution of viral factors to the neuropathogenesis of HPAI H5Nx virus infections and the efficacy of intervention strategies to prevent neuroinvasion or the development of neurological disease.</p

Infection with Pythium flevoense in a harbour porpoise (Phocoena phocoena) as a novel cause of dermatitis in marine mammals

The oomycete Pythium flevoense was diagnosed as the cause of dermatitis in a young adult female harbour porpoise (Phocoena phocoena) that had been trapped in a pound net in a temperate saltwater environment. Disease from Pythium sp. infection-pythiosis-is infrequently diagnosed in humans, horses, dogs, cattle, and few other mammalian species. Pythiosis is typically associated with exposure to tropical or subtropical freshwater conditions, and typically caused by Pythium insidiosum. However, until now, pythiosis has been reported in neither marine mammals nor temperate saltwater conditions, and P. flevoense is not known as a cause of pythiosis in mammals. This porpoise developed generalised dermatitis despite treatment and euthanasia was necessary. Histopathological evaluation revealed a chronic active erosive dermatitis, with intralesional hyphae morphologically consistent with a Pythium sp. PCR analysis and sequencing of affected skin matched Pythium flevoense with a 100% similarity to the reference strain. Additional diagnostics excluded other pathogens. Based on this case report, P. flevoense needs to be considered as a mammalian pathogen. Furthermore, harbour porpoises and possibly other marine mammals may be at risk of infection with P. flevoense, and pythiosis should be included in the differential diagnosis of dermatitis in marine mammals.</p

Seoul Virus Tropism and Pathology in Naturally Infected Feeder Rats

Seoul virus (SEOV) is a zoonotic orthohantavirus carried by black and brown rats, and can cause hemorrhagic fever with renal syndrome in humans. Human cases of SEOV virus infection have most recently been reported in the USA, United Kingdom, France and the Netherlands and were primarily associated with contact with pet rats and feeder rats. Infection of rats results in an asymptomatic but persistent infection. Little is known about the cell tropism of SEOV in its reservoir and most available data is based on experimental infection studies in which rats were inoculated via a route which does not recapitulate virus transmission in nature. Here we report the histopathological analysis of SEOV cell tropism in key target organs following natural infection of a cohort of feeder rats, comprising 19 adults and 11 juveniles. All adult rats in this study were positive for SEOV specific antibodies and viral RNA in their tissues. One juvenile rat was seropositive, but negative in the rRT-PCR. Of the 19 adult rats of which subsequently additional organs were tested, SEOV RNA was detected in all lungs, followed by kidney (79%) and liver (74%). Histopathologic changes associated with SEOV infection were primarily found in the liver, consistent with a pathological diagnosis of a mild hepatitis. In conclusion, natural SEOV infection results in mild inflammation of the liver in the absence of clinical disease

Ferrets as a novel animal model for studying human respiratory syncytial virus infections in immunocompetent and immunocompromised hosts

Human respiratory syncytial virus (HRSV) is an important cause of severe respiratory tract disease in immunocompromised patients. Animal models are indispensable for evaluating novel intervention strategies in this complex patient population. To complement existing models in rodents and non-human primates, we have evaluated the potential benefits of an HRSV infection model in ferrets (Mustela putorius furo). Nine- to 12-month-old HRSV-seronegative immunocompetent or immunocompromised ferrets were infected with a low-passage wild-type strain of HRSV subgroup A (105 TCID50) administered by intra-tracheal or intra-nasal inoculation. Immune suppression was achieved by bi-daily oral administration of tacrolimus, mycophenolate mofetil, and prednisolone. Throat and nose swabs were collected daily and animals were euthanized four, seven, or 21 days post-infection (DPI). Virus loads were determined by quantitative virus culture and qPCR. We observed efficient HRSV replication in both the upper and lower respiratory tract. In immunocompromised ferrets, virus loads reached higher levels and showed delayed clearance as compared to those in immunocompetent animals. Histopathological evaluation of animals euthanized 4 DPI demonstrated that the virus replicated in the respiratory epithelial cells of the trachea, bronchi, and bronchioles. These animal models can contribute to an assessment of the efficacy and safety of novel HRSV intervention strategies

Pulmonary pathology of pandemic influenza A/H1N1 virus (2009)-infected ferrets upon longitudinal evaluation by computed tomography

We investigated the development of pulmonary lesions in ferrets by means of computed tomography (CT) following infection with the 2009 pandemic A/H1N1 influenza virus and compared the scans with gross pathology, histopathology and immunohistochemistry. Ground-glass opacities observed by CT scanning in all infected lungs corresponded to areas of alveolar oedema at necropsy. These areas were most pronounced on day 3 and gradually decreased from days 4 to 7 post-infection. This pilot study shows that the non-invasive imaging procedure allows quantification and characterization of influenza-induced pulmonary lesions in living animals under biosafety level 3 conditions and can thus be used in pre-clinical pharmaceutical efficacy studies

Intranasal H5N1 vaccines, adjuvanted with chitosan derivatives, protect ferrets against highly pathogenic influenza intranasal and intratracheal challenge

We investigated the protective efficacy of two intranasal chitosan (CSN and TM-CSN) adjuvanted H5N1 Influenza vaccines against highly pathogenic avian Influenza (HPAI) intratracheal and intranasal challenge in a ferret model. Six groups of 6 ferrets were intranasally vaccinated twice, 21 days apart, with either placebo, antigen alone, CSN adjuvanted antigen, or TM-CSN adjuvanted antigen. Homologous and intra-subtypic antibody cross-reacting responses were assessed. Ferrets were inoculated intratracheally (all treatments) or intranasally (CSN adjuvanted and placebo treatments only) with clade 1 HPAI A/Vietnam/1194/2004 (H5N1) virus 28 days after the second vaccination and subsequently monitored for morbidity and mortality outcomes. Clinical signs were assessed and nasal as well as throat swabs were taken daily for virology. Samples of lung tissue, nasal turbinates, brain, and olfactory bulb were analysed for the presence of virus and examined for histolopathological findings. In contrast to animals vaccinated with antigen alone, the CSN and TM-CSN adjuvanted vaccines induced high levels of antibodies, protected ferrets from death, reduced viral replication and abrogated disease after intratracheal challenge, and in the case of CSN after intranasal challenge. In particular, the TM-CSN adjuvanted vaccine was highly effective at eliciting protective immunity from intratrache

Functional properties of measles virus proteins derived from a subacute sclerosing panencephalitis patient who received repeated remdesivir treatments

Subacute sclerosing panencephalitis (SSPE) is a rare but fatal late neurological complication of measles, caused by persistent measles virus (MeV) infection of the central nervous system. There are no drugs approved for the treatment of SSPE. Here, we followed the clinical progression of a 5-year-old SSPE patient after treatment with the nucleoside analog remdesivir, conducted a post-mortem evaluation of the patient’s brain, and characterized the MeV detected in the brain. The quality of life of the patient transiently improved after the first two courses of remdesivir, but a third course had no further clinical effect, and the patient eventually succumbed to his condition. Post-mortem evaluation of the brain displayed histopathological changes including loss of neurons and demyelination paired with abundant presence of MeV RNA-positive cells throughout the brain. Next-generation sequencing of RNA isolated from the brain revealed a complete MeV genome with mutations that are typically detected in SSPE, characterized by a hypermutated M gene. Additional mutations were detected in the polymerase (L) gene, which were not associated with resistance to remdesivir. Functional characterization showed that mutations in the F gene led to a hyperfusogenic phenotype predominantly mediated by N465I. Additionally, recombinant wild-type-based MeV with the SSPE-F gene or the F gene with the N465I mutation was no longer lymphotropic but instead efficiently disseminated in neural cultures. Altogether, this case encourages further investigation of remdesivir as a potential treatment of SSPE and highlights the necessity to functionally understand SSPE-causing MeV.</p