All about Covid -19 Antibodies

Dr Harleen Kaur
The year 2020 has been attributed to as the year of Covid -19. Starting from the city of Wuhan in last months of 2019 and spreading to each and every corner of the world, it has played havoc with the human society ranging from morbidity, mortality to economic crisis leading to loss of life and job for millions of people across the globe . The world has seen many ups and downs since the first case was reported from Wuhan and when Dr Li Wenliang, the virus whistleblower doctor was punished by Chinese police for sharing posts on social media warning of SARS- like virus spreading in the city and very unfortunately Dr Li himself succumbed to the virus in February 2020. Li’s Death prompted a National outrage in China compelling the police authorities to apologies to his family for the mistake; it is rare for the Chinese authorities to admit such mistakes. As the virus engulfed more and more Nations there was worldwide demand for hydroxy chloroquinine from India and even Trump warned of retaliation if India doesn’t export Hydroxychloroquinine to U.S. and on other hand, Brazilian President Jair Messias Bolsonaro thanked Indian Prime Minister Narendra Modi for easing restrictions on export of hydroxychloroquinine and compared India’s move to Lord Hanuman and Sanjeevani Booti of the epic Ramayana.
Apart from political and social ups and downs in the pandemic, the medical field has also learned a lot in handling the pandemic in last one year. Starting from RT-PCR for diagnosing the virus, the medical science travelled through different techniques like NAAT (Nucleic acid amplification testing) RAT (Rapid antigen testing), making diagnosis simple and easier to perform. Government Medical college Jammu has taken a leap by starting Covid Biomarkers to follow up the path disease may take and further moving one step ahead have now started Covid Antibodies testing to assess the development of immunity in the patients who have recovered from the disease or to do the serosurveillance of population to understand the development of herd immunity.
Antibodies are also known as immunoglobulin and are protective proteins produced by our immune system in response to any infecting agent like virus, bacteria or any other foreign product. Antibodies are Body’s defense mechanism or in simpler words these are the army inside our body to fight the invaders like viruses and other disease causing pathogens. Even a little child is now aware about the shape and look of Corona virus, a round particle with spikes all over its surface, but how does a antibody looks like? The antibody or immunoglobulin molecule is a Y shaped, made up of four chains, consisting of two identical light (L) chains and two identical Heavy (H) chains, These chains are held together by disulfide bonds to form a flexible Y shaped structure having variable and constant portion capable of holding the virus and neutralizing it like the security forces neutralizes the invading enemies. There are five main types of antibodies or immunoglobulin, IgG , IgA, IgM, IgE and IgD. In SARS Co-V infection, antibodies can develop against mainly four structural proteins like Protein spike(S), envelop(E), membrane(M) and nucleo capsid (N) out of these N and S proteins are considered more immunogenic. Ideally IgM antibody indicates acute or recent infection and IgG, a past or chronic infection. But this does not hold true for Corona infection, it is because of variable time of appearance of IgM and IgG antibodies in relation to each other, IgG can appear later, at the same time or even earlier than IgM in SARS-CoV-2 infection. Antibody testing is again of two type, Rapid antibody test, which is point of care test and can be done on patients bed side and second is laboratory based test done by high end electrochemiluminescence techniques on fully auto analyzers. The Electro chemiluminescence technology has 99.8% specificity and 99.5% sensitivity and has shown no cross reactivity with the common corona virus and till date is the most accurate and effective method to detect covid-19 antibodies and is now available in Government Medical College Jammu also.
As everyone is talking of vaccine and are eagerly waiting for the one to come into the market and all hopes are on vaccine to get rid of this pandemic. The efficacy of the vaccine will be tested by the potency or capability of vaccine antigen to stimulate the production of SARS-CoV-2 antibodies in the recipient’s blood. Anti body testing can be used for:
* To assess the spread of covid infection in the community and to check the development of Herd immunity in the population.
* To check the effectiveness of any vaccine
* To identify the right donor for convalescent plasma therapy to needy patients
* Prioritization of people to receive vaccine.
* To identify the people who are still susceptible to infection.
* It can be a part of testing algorithm for return to work strategy to minimize the risk of spread of infection.
The antibody testing is widely being used in global sero- surveys, mass testing and testing protocols in many countries like Singapore (Migrant worker testing), UK (Health care worker testing) and Switzerland ( Corporate worker testing). Even in Jammu and Kashmir, a serosurvey was conducted by the department of community medicine in collaboration with Department of Biochemistry GMC Srinagar, and it was found that 39% of Kashmir’s population has developed Covid antibodies, In other words it can be said that two out of every five people in the valley have developed antibodies against the corona virus.
The sero surveillance was conducted in ten districts of Kashmir and Pulwama recorded highest prevalence of antibodies in 43.1% followed by 43% in Budgam, 42.3% in Kupwara, 40.7% in Srinagar, 30.8% in Bandipora and 39.0% in Ganderbal. Very interestingly the first survey conducted in Srinagar in June showed the presence of antibodies in 3.8% of population. , The trend has been encouraging, said Dr Muhammad Salim Khan, the principal investigator of the survey, but emphasized the need of vaccine in order to develop herd immunity to defeat corona virus.
With the facility of Covid antibody testing available in Jammu, there is urgent need to carry on similar sero survey in all districts of Jammu to assess the ground reality of present pandemic and is critical to the implementation of crucial health policies for the pandemic to minimize the adverse impact of pandemic
(The author is Associate Professor in the Department of Microbiology, Government Medical College Jammu)