A Systematic Molecular Pathology Study of a Laboratory Confirmed H5N1 Human Case

Abstract

Autopsy studies have shown that human highly pathogenic avian influenza virus (H5N1) can infect multiple human organs other than just the lungs, and that possible causes of organ damage are either viral replication and/or dysregulation of cytokines and chemokines. Uncertainty still exists, partly because of the limited number of cases analysed. In this study, a full autopsy including 5 organ systems was conducted on a confirmed H5N1 human fatal case (male, 42 years old) within 18 hours of death. In addition to the respiratory system (lungs, bronchus and trachea), virus was isolated from cerebral cortex, cerebral medullary substance, cerebellum, brain stem, hippocampus ileum, colon, rectum, ureter, aortopulmonary vessel and lymph-node. Real time RT-PCR evidence showed that matrix and hemagglutinin genes were positive in liver and spleen in addition to positive tissues with virus isolation. Immunohistochemistry and in-situ hybridization stains showed accordant evidence of viral infection with real time RT-PCR except bronchus. Quantitative RT-PCR suggested that a high viral load was associated with increased host responses, though the viral load was significantly different in various organs. Cells of the immunologic system could also be a target for virus infection. Overall, the pathogenesis of HPAI H5N1 virus was associated both with virus replication and with immunopathologic lesions. In addition, immune cells cannot be excluded from playing a role in dissemination of the virus in vivo.

Predicting Disease Severity and Viral Spread of H5N1 Influenza Virus in Ferrets in the Context of Natural Exposure Routes

“…2, where only the cerebrum was examined. Our findings support the idea that thorough sampling of the brain lobes, brainstem, and cerebellum is important to understand the complete extent of human CNS infection (21). In the absence of thorough sampling, CNS infection in humans exposed to virus via the URT route may also remain undetected, and neurological infection may, perhaps inappropriately, be considered a rare outcome of H5N1.…”

“…Fatal infection with H5N1 has been associated with acute respiratory distress syndrome (ARDS) (9)(10)(11), multiple organ failure (12)(13)(14)(15)(16)(17)(18), and encephalitis (19), but overall, few human autopsies have been conducted and it is difficult to determine the contribution of systemic infection to case fatality rates. Some autopsy reports indicate that infection was limited to the respiratory and gastrointestinal tracts (9,20), while others have isolated virus from the brain and gastrointestinal tract (21) or serum and cerebrospinal fluid (CSF) (22)(23)(24) or detected viral mRNA in the brain (21,25). Measurements from blood samples taken early during the infectious period link severe disease outcomes with lymphopenia and hypercytokinemia (2,10,14,26), while the presence of high loads of negative-sense viral RNA (vRNA) in plasma is indicative of systemic infection (24).…”

“…However, some differences between the two species in response to H5N1 have been noted. Infected humans frequently show progression to ARDS, but neurological disease is rarely manifested (2,13,14,19,21,26,32,33), while detection of virus in the brain and neurological disease are common in ferrets experimentally infected by the total respiratory tract (TRT) route (34,35). H5N1 virus spread outside the respiratory tract in ferrets has enabled this model to be employed as a means to study the anatomical pathways of viral dissemination.…”

Neuraminidase-Inhibiting Antibody Is a Correlate of Cross-Protection against Lethal H5N1 Influenza Virus in Ferrets Immunized with Seasonal Influenza Vaccine

“…An influenza pandemic due to highly pathogenic H5N1 could be significantly more severe than that recently experienced with pandemic H1N1/09 virus of swine origin, in part due to its capacity to infect beyond the respiratory tract in animal models (3,4) and humans (5,6). Unlike the pandemic H1N1/09 virus, the emergence of which was not predicted, we are alert to the potential threat from avian H5N1 and need to develop appropriate control measures to reduce morbidity and mortality in the event that this virus will gain the ability for efficient humanto-human spread.…”

Comparative Virus Replication and Host Innate Responses in Human Cells Infected with Three Prevalent Clades (2.3.4, 2.3.2, and 7) of Highly Pathogenic Avian Influenza H5N1 Viruses

“…Thus, all three clades of H5N1 viruses appeared to possess similarly low binding affinity for the human upper respiratory epithelium but higher binding ability to the alveolar lining. Type II alveolar epithelial cells and macrophages are major cell targets of H5N1 virus in infected human patients (13,14). To ascertain viable virus production of each virus clade, human A549 cells, a cell line widely used as an in vitro model for type II pulmonary epithelial cells (15), were infected with H5N1 viruses at a multiplicity of infection (MOI) of 0.001 and virus titers were analyzed over 72 h of infection.…”