Minerva Research Labs, a London-based company at the forefront of health and nutraceuticals, has recently focused its research and development team on COVID-19 serological tests, doing analysis and evaluations on various rapid testdevices in order to bring more clarity and insight to the subject.
Dr. David Reilly, Head of Science and Clinicals of Minerva Research Labs, who holds a PhD in biochemistry and has over 30 years of experience in biomedical research, sheds light on the principles, composition and use of rapid COVID-19immunodiagnostic tests.
Currently there are several strategies for the isolation and treatment of people who have been infected with the Sars-CoV-2 virus (or COVID-19). One proposed strategy, which is currently still in the development and validation phase, is the proposed use of biological tests to identify individuals who have been infected with the virus and have subsequently developed immunity.
Diagnostic kits and tests fall substantially into 2 categories. The first is a genetic test, the Nucleic Acid Amplification Test (NAAT), similar to that used for DNA analysis, which allows the detection of the presence of the virus.
The genetic material (viral particles containing RNA) is collected with a nasal or throat swab and then sent to a specialized laboratory that analyzes it to determine whether the virus is present, usually within 24 hours. A small number of machines are also available in hospitals to generate the data in only a hour, but these devices are limited in the number of samples they can routinely test. The NAAT is the most reliable test and the most useful for diagnostic purposes, where an infection is in progress. The difficulty with this method is that we will soon reach the limits of the structures capable of testing for the COVID-19, potentially causing a backlog of tests. This notwithstanding there is also a risk that there may also soon be a shortage of the chemical reagents needed for this type of testing.
Serological tests, explains Dr. Reilly, aim to detect the antibodies produced by the body to fight the virus, rather than directly testing for the virus itself. Serological tests require only a couple of drops of blood placed onto the test strip and a result can be observed in minutes.
The immune system has many mechanisms to fight the invading virus, including the production of antibodies by B lymphocytes. The development of diagnostic kits to measure antibodies in the blood potentially offers a relatively simple and accessible opportunity for mass testing. The main tests are often referred to as Lateral Flow Analysis (LFA) tests and are similar in design and principle to pregnancy testing kits.
Minerva is evaluating Lateral Flow Kits from 6 suppliers and assessing results based on tests administered to healthy volunteers, volunteers who tested positive for the virus and are currently asymptomatic, and finally volunteers who self-reported symptoms typically experienced following viral infection, but have not been tested for the virus. At the moment, access to volunteers is limited due to the lockdown, but we are working with clinical partners in the UK, including Dr. Hugh Coyne at the Coyne Medical Centre and Dr. Martin Godfrey at the Clapham Family Practice, in preparation to scale up the testing when restrictions are eased or lifted.
These serological tests require a blood sample to check for antibodies (also known as Immunoglobulins). Following a viral infection, 2 types of antibodies are produced in the body. Immunoglobulin M (IgM) is produced very quickly, in the first days of the immune response typically reaching its peak within a week, after which it subsides. The presence of IgM indicates that the infection is ongoing and that the body is reacting, but at this stage it is advisable to avoid contact and take the necessary measures recommended by the Health Authorities. Immunoglobulin G (IgG) is produced about a week later and is usually expressed at higher levels, with a more specific targeted mechanism that makes IgG antibodies more prominent in the fight against the virus. Those who test positive for the presence of IgG antibodies are at a more advanced stage of immune response or have now recovered. If already protected by the immune system, individuals may be able to return to work without risk of infecting others, in accordance with the measures of the Health Authorities.
Of the 6 COVID-19 antibody kit models tested, 3 are composed of individual test strips, one each for detection of IgM or IgG (Figure 1, A, C and D, either as individual strips or in a single cartridge). Another 2 models have a single band of nitrocellulose and reports both IgM and IgG with two separate indicator lines (Figure 1, B and F). The simplest device has a nitrocellulose band with a single indicator strip which does not distinguish between IgM an IgG (Figure 1, E).
How the test works
The design of each device is based on a cartridge, inside of which a strip of nitrocellulose containing specific reagents, allows the “capture” of IgM or IgG antibodies, if they are present in the blood. Each kit has a detection system that amplifies the signal. The typical amplification and detection system used in the kits we tested is based on the use of colloidal gold, which generates a chromatic reaction in the presence of the antibody.
To use the test, you must:
1. Extract a drop of blood from your fingertip by pricking finger with a 28 gauge lancet.
2. Place a drop of blood in the appropriate well of the device using a pipette / dropper.
3. Then, within 15 seconds, add 3 drops of diluent to promote the flow of antibodies along the nitrocellulose strip.
4. Wait up to 20 minutes until the specific indicator appears, confirming either the presence or absence of the antibodies.
The test results:
A small-scale, the Minerva Research Labs’ study included assessments of different test subjects. There are several groups which ideally need to be tested to be able to understand the reliability of the tests. Firstly, those who are asymptomatic and are apparently healthy. As a confirmation of diagnostic potential, the tests should also be administered to those who provided a swab sample and were diagnosed as positive for the presence of the Sars-CoV-2 virus. Finally, those who not been tested for the presence of the virus, but have experienced typical symptoms following infection, preferably confirmed by medical diagnosis, should also be tested.
Although the number of tests already carried out is not large enough to indicate the specificity, sensitivity, reliability, and reproducibility of the devices, the first results are encouraging, and several important considerations have emerged:
- All asymptomatic and presumably healthy subjects were negative for the presence of antibodies (as expected).
All symptomatic subjects were positive (for the presence of IgG, but not for IgM), suggesting that they had actually been infected with the coronavirus and were now recovering.
- 1 of the 6 kits was not effective, failing to signal the presence of antibodies found by the other devices.
Although potentially the kits could be made available for home-testing, the tests are not easy to use. Ideally, they would be administered by or with the help of professionals. For private use they must be optimized and potentially simplified. This in our view will limit their suitability for home use as:
- The use of the finger prick and pipette to take a blood sample from your finger and apply blood into the device requires user dexterity and precision.
- The indicator line that signals the presence of antibodies, in the case of our detections, was found to be weak and poorly defined. Therefore, it was often difficult to distinguish results. A professional would be able to judge whether the line is sufficiently visible or could repeat the test.
- A more valid and reliable response may require repeat testing in the following days, at a more advanced stage of immune response development, or it could be evaluated using laboratory equipment to study a serum or plasma sample.
The positive news from the Minerva Research Lab test is that the kits have been helpful in the identification of those subjects who appear to have been exposed to the virus. They can also give clarity to those who have either demonstrated mild symptoms, more serious symptoms as well as confirmation that healthy individuals have not been exposed to the SARS-CoV-2 virus.
The devices tested to date still require more work to be done to verify their specificity and validity. However, these could be of great help in the event that they accurately detect the presence of IgM and/or IgG to those who have shown symptoms but are not sure that they have been exposed to the virus.
The serological tests will help to understand how the virus has spread to certain geographical areas, demographic groups and different groups of workers. Without the serological test some of these people may never know if they have developed immunity.
With little known about how the virus behaves and evolves, the devices could also be useful in knowing who will be able to return to work, especially among those serving essential functions, such as frontline healthcare professional who are the most at risk of infection. A negative NAAT virus test result in combination with the presence of IgG antibodies, indicates a strengthening of the immune system and therefore for a certain period of time (it is not yet known if this will be measured in weeks, months or years) it is possible that the virus will not be contracted again. However, as SARS-CoV-2 is a new strain of virus we do not yet know if it is possible to contract the disease repeatedly.
LFA devices are not the only instruments used for the development of these antibody tests. Other tools such as microfluidic systems are currently being validated and offer the exciting prospect of increasing our ability to use specific, sensitive and reliable tests to help in the fight against COVID-19.