Influenza virus: a look at cell culture

Abstract

We know the flu for its annual seasonal epidemics and occasional pandemics. The highest morbidity from this infection is seen in children, but the highest mortality is reserved for patients over 65 years of age with associated comorbidities.

There are three known types of influenza viruses: Influenzavirus A, B, and C. All belong to the Orthomyxoviridae family and have a single-stranded, negative-polarity RNA genome. The lipid envelope contains two surface glycoproteins: hemagglutinin (HA) and neuraminidase (NA), which allow the influenza A virus to be subtyped. The last pandemic recorded in 2009 was caused by the AH1N1pdm (pdm: pandemic) variant.

Clinical symptoms begin abruptly with fever, general malaise, headache, and respiratory symptoms ranging from mild to pneumonia.

The diagnosis can be direct (detection of viral antigen, molecular diagnosis, or viral culture) or indirect (serology). In this review, we focus on viral culture. The influenza virus can be isolated in cell lines: MDCK (Madin-Darby Canine Kidney) or hCK (a cell line derived from the former, which are humanized MDCK cells). After infecting the cells, the cytopathic effect of the virus on them is observed by immunofluorescence. Viral culture demonstrates the presence of the virus, its viability, and infectivity, allowing for studies of sensitivity to antivirals. However, it has a limitation of approximately 50% sensitivity due to the meticulous nature of the cultivation procedure.

The entire population is susceptible to influenza, although immunity may exist due to previous contact with identical or antigenically similar viruses or through immunization (annual vaccination).

The World Health Organization (WHO) maintains a global influenza surveillance program, but the changing nature of the virus defies prediction and the onset of a pandemic is unpredictable.