Week 3: ELISA – enzyme linked immunosorbent assay
Introduction
In the early days of the COVID-19 pandemic, a fair number of people thought that they had been infected with SARS-CoV2, but they had not had serious symptoms or typical symptoms of infection. But how could they know that it was COVID-19? Perhaps they had just had a regular cold. In the earliest months, qPCR and lateral flow tests for SARS-CoV2 were not widely available. By the time these tests were available, the virus would have long since gone from the body, and these tests would show a negative result. In fact, it was still possible to tell whether a person had come into contact with the virus because they would still have antibodies against it − antibodies last for many months.
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Transcript: Audio 1 Introduction to Week 3
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How can one tell if a person has been infected with a virus? An infection induces antibodies which persist for a lot longer than the virus itself. In effect, the infection leaves a signature of its presence – virus-specific antibodies. Anyone who has been infected, has antibodies against different components of the virus, and indeed they will be specific for the strain of virus that has infected them. Epidemiologists can use this information to track epidemics. A big problem with COVID-19 was that up to 40% of infected people were asymptomatic. But this only became apparent when random community testing for the virus or virus-specific antibodies was carried out.
This week you will learn how to measure antibodies against SARS-CoV2 using a versatile assay called ELISA – an enzyme-linked immunosorbent assay. Much of your time will be spent in a virtual laboratory which will prepare you to do epidemiological and immunological studies in later weeks.
Audio 1 Introduction to Week 3
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By the end of this week you should be able to:
- outline the theoretical background and steps used in an ELISA
- carry out an ELISA in a virtual laboratory to detect antibodies to SARS-CoV2 spike protein
- report antibody titres derived from your assay
- interpret your results.