5 Summary

This week, we introduced the wide range of viruses that produce disease in humans, before focusing on two respiratory viruses − influenza-A and SARS-CoV2. Both are enveloped viruses with an RNA genome that produce acute infections that are spread by aerosol droplets.

Distinctive components of virus infection can be recognised by the immune system. The adaptive immune system recognises virus antigens, whereas the innate immune system recognises pathogen-associated molecular patterns. In the case of influenza-A and SARS-CoV2 the PAMPs are the ssRNA of the viral genome or the dsRNA, which is an intermediate of virus replication. TLRs recognise viral RNA in endosomes, while RLHs recognise dsRNA of replicating virus in the cytoplasm.

After recognising the virus, infected cells secrete interferon, a cytokine which signals to neighbouring cells, to slow virus spread. Other cytokines induce inflammation, which normally helps control infection, but can contribute to host tissue damage.

The actions of the innate immune system hold the line against the virus until the adaptive immune response gets into action, but that takes several days… And that is what you will learn about next week.

You should now go to Week 2 [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] .