BackgroundInfluenza A viruses have an envelope made of a lipid bilayer and two surface glycoproteins, the hemagglutinin and the neuraminidase. The structure of the virus is directly dependent on the genetic makeup of the viral genome except the glycosylation moieties and the composition of the lipid bilayer. They both depend on the host cell and are in direct contact with the environment, such as air or water. Virus survival is important for virus transmission from contaminated waters in the case of wild aquatic birds or from contaminated surface or air for humans.ObjectiveThe objective of this study was to check whether the origin species of the host cell has an influence on influenza A virus survival.MethodThe persistence in water at 35°C of viruses grown on either mammalian cells or avian cells and belonging to two different subtypes H1N1 and H5N1 was compared.ResultsBoth H5N1 and H1N1 viruses remained infectious for periods of time as long as 19–25 days, respectively. However, within the same subtype, viruses grown on mammalian cells were more stable in water at 35°C than their counterparts grown on avian cells, even for viruses sharing the same genetic background.ConclusionsThis difference in virus stability outside the host is probably connected to the nature of the lipid bilayer taken from the cell or to the carbohydrate side chains of the virus surface glycoproteins. Moreover, the long-lasting survival time might have a critical role in the ecology of influenza viruses, especially for avian viruses.

Influenza A viruses (IAVs) are a major cause of infectious respiratory human diseases and their transmission is dependent upon the environment. However, the role of environmental factors on IAV survival outside the host still raises many questions. In this study, we used lentiviral pseudotypes to study the influence of the hemagglutinin protein in IAV survival. High-titered and cleaved influenza-based lentiviral pseudoparticles, through the use of a combination of two proteases (HAT and TMPRSS2) were produced. Pseudoparticles bearing hemagglutinin proteins derived from different H1N1, H3N2 and H5N1 IAV strains were subjected to various environmental parameters over time and tested for viability through single-cycle infectivity assays. We showed that pseudotypes with different HAs have different persistence profiles in water as previously shown with IAVs. Our results also showed that pseudotypes derived from H1N1 pandemic virus survived longer than those derived from seasonal H1N1 virus from 1999, at high temperature and salinity, as previously shown with their viral counterparts. Similarly, increasing temperature and salinity had a negative effect on the survival of the H3N2 and H5N1 pseudotypes. These results showed that pseudotypes with the same lentiviral core, but which differ in their surface glycoproteins, survived differently outside the host, suggesting a role for the HA in virus stability.