ELISA, or enzyme-linked immunosorbent assay, is a widely applicable test used for detecting the presence of antibodies in a biological sample. ELISA test kits have become a staple tool for both medical diagnosis and laboratory research and can be used to reliably detect a wide range of diseases like HIV, Lyme disease, and Covid-19.
Because the ELISA method can be set up to detect a vast number of different antibodies, its potential uses are extremely broad. A few common applications for ELISA testing include:
- Monitoring the progression of autoimmune diseases – a reliable method of evaluating antibody levels is crucial to tracking autoimmune diseases and verifying whether treatment is effective
- Determining the effectiveness of vaccines or other medications – ELISA can offer critical insight as to the levels of antibody production occurring in our bodies after vaccination
- Research – such as in the development of new drugs
- Medical diagnosis – usually in the context of eliminating possibilities or confirming an existing diagnosis
- Public health/pandemic response – ELISA testing can help differentiate between variants of Covid-19, for example
ELISA and the African Swine Fever Virus
One emergent use of ELISA testing has been in the response to an outbreak of African Swine Fever Virus (ASFV) in Europe and Asia. ASFV is a serious concern because it is the only known DNA arbovirus. Arbovirus is a term referring to a class of viruses transmitted by mosquitoes or other biting arthropods — in this case, ticks.
ASFV had been effectively eradicated in the mid-1990s, but a new, highly resistant strain was identified around 2007. There is currently no vaccine for ASFV, and it has the ability to decimate populations of swine, potentially leading to dire nutritional and economic consequences in the areas hardest hit by the virus.
In a 2021 paper by a team of American scientists and academics from several universities, ELISA testing for ASFV was rapidly developed using a recombinant protein antigen. The particular type of ELISA testing that was developed in response to ASFV is known as “blocking” ELISA, or bELISA. This involves an ELISA process that uses an additional blocking reaction to keep unwanted materials from impacting the test, thus increasing the accuracy of results.
To validate the ASFV bELISA assay, samples from 810 uninfected animals and 106 inoculated animals were used. The results indicated that this method had a diagnostic sensitivity of 98.11% and a diagnostic specificity of 99.42%. In layman’s terms, the tests were found to be highly reliable. Further research showed that ELISA could detect reliable precursors of the ASFV infection as soon as seven days after inoculation.
The Versatility of ELISA Testing
ELISA is a versatile and responsive tool because it can be set up to detect a huge range of different antibodies. This modular nature, wherein the same basic test method can be used to detect so many different antibodies, is inherent to the way ELISA works.
Each ELISA test uses highly specialized enzymes that have been designed to bind to specific antibodies in the sample (which is typically derived from blood in the case of human testing). The sample is mixed with a compound and placed on a plate. If the antibodies being searched for exist in the sample, they will bind to the plate, resulting in a positive test. This is typically indicated by the plate itself changing color.
That being said, the theoretical number of conditions ELISA can detect is limited merely by the speed at which researchers can develop effective binding enzymes for the antibodies associated with those conditions.