Year: 2009
Type: article
Abstract: Relatively little is known about the viral factors contributing to the lethality of the 1918 pandemic, although its unparalleled virulence was likely due in part to the newly discovered PB1-F2 protein. This protein, while unnecessary for replication, increases apoptosis in monocytes, alters viral polymerase activity in vitro, and produces enhanced inflammation and increased secondary pneumonia in vivo. However, the effects the PB1-F2 protein have in vivo remain unclear. To address the mechanisms involved, we intranasally infected groups of mice with either influenza A virus PR8 or a genetically engineered virus that expresses the 1918 PB1-F2 protein on a PR8 background, PR8-PB1-F2(1918). Mice inoculated with PR8 had viral concentrations peaking at 72 hours, while those infected with PR8-PB1-F2(1918) reached peak concentrations earlier, 48 hours. Mice given PR8-PB1-F2(1918) also showed a faster decline in viral loads. We fit a mathematical model to these data to estimate parameter values and select the best model. This model supports a lower viral clearance rate and higher infected cell death rate with the PR8-PB1-F2(1918) virus, although the viral production rate may also be higher. We hypothesize that the higher PR8-PB1-F2(1918) viral titers early in an infection are due to both an increase in viral production with decreased viral clearance, and that the faster decline in the later stages of infection result from elevated cell death rates. We discuss the implications these mechanisms have during an infection with a virus expressing a virulent PBI-F2 on the possibility of a pandemic and on the importance of antiviral treatments.
Language: English
Subfield: Epidemiology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W1522396702