Sima Fischl-Debaroncelli, 73, a COVID-19 patient, watches as infusion coordinator Michelle Tzec checks the temperature of Dr. Peter Fischl, 72, at Desert Valley Hospital in Victorville, California, US, on December 17, 2020. Both were given Regeneron's Casirivimab and Imdevimab antibody cocktail infusion. Image Credit: Los Angeles Times

The vaccines have arrived, and that gives us hope of reining in the spread of coronavirus. COVID-19 consumed much of last year, killing people and battering economies. If 2021 has to be an improvement, a sizeable part of the world’s population should be vaccinated.

We have at least five proven vaccines. And all of them have been found to be effective in priming our immune system to fight the coronavirus. They help create antibodies, which are the ammunition for our body to eliminate pathogens.

There are antibody drugs too. They are given to vulnerable patients in the early days of infection. It has prevented them from being hospitalised and enabled them to return to active life soon. But these medicines are yet to catch on, although US President Donald Trump was one of the recipients. Several Trump administration officials were also treated with monoclonal antibody medicines.

Let’s get to know antibodies, antigens, the tests and the antibody drugs.

What is an antibody?

An antibody is a protein produced by the immune system in response to the presence of a foreign substance in the body. The foreign substance is called an antigen, but more of that later. Antibodies recognise foreign substance and eliminate it from the body.

An antibody is also generally called an immunoglobulin. All antibodies are immunoglobulins, but all immunoglobulins are not antibodies. 

These antibodies are found in blood plasma and tissue fluids, and they are disease-specific.

How antibodies react to coronavirus

Exposure to the coronavirus triggers the production of two types of antibodies in the human body. Immunoglobulin M (IgM) is the first antibody generated by the immune system, and this occurs in the acute infection phase.

IgG antibodies are created as the secondary immune response, and these are specific to the virus. They are produced about 14 days after symptoms start. IgG antibodies can circulate in the blood for several months after recovery, and their presence indicates a past infection.

What are antibody tests?

Antibody tests, called immunity tests or serology tests, search for antibodies in the blood. They look for IgM and IgG antibodies to detect whether your immune system has responded to coronavirus infection.

The presence of IgM antibodies means the individual has COVID-19 (active phase of infection). It can also mean that the person has recently recovered from an infection.

Serology tests are reported to be accurate in indicating that an individual has been exposed to the virus, and is likely to have immunity to the infection compared to a person who tests negative.

These tests are not used to detect the presence of a virus. A PCR (polymerase chain reaction) test is best suited for that since it can detect the coronavirus’ genetic material in the human body.

What is an antigen?

An antigen is a foreign substance that has entered the body. Several substances are regarded as antigens, including pathogens (disease-causing microorganisms such as bacteria and viruses), toxins such as insect venom, chemicals, allergens and pollens.

Typically, any substance that provokes the immune system to produce antibodies is called an antigen. It can enter the body from outside through ingestion, inhalation, or injection. Since they come from outside the body, they are called heteroantigens, but antigens that originate in the body are autoantigens.

What’s an antigen test?

Antigen tests — also referred to as rapid tests — look for proteins on the virus’ surface to ascertain the presence of pathogens like the coronavirus. Using a nasal swab fluid sample, antigen tests can produce results in minutes. Like a home pregnancy test, the result is reflected on a paper strip. These tests are reliable when an individual has a high viral load.

How long will antibodies last?

All antibodies don’t have the same lifespan. Antibodies that fight a flu virus has a short life, while antibodies against meningitis last around three years. Hepatitis B immunisation lasts a lifetime.

Coronavirus is a new pathogen, so the lifespan of antibodies triggered by an infection or vaccination is yet to be ascertained. After all, the virus has been around for little over a year.

What is a monoclonal antibody?

Monoclonal antibodies are proteins produced in the laboratory using cloned immune cells. They can serve as substitute antibodies to enhance or mimic the immune system’s ability to fight off harmful pathogens such as viruses.

They are used to treat certain types of cancer and arthritis, multiple sclerosis, heart disease, lupus, inflammatory bowel disease, psoriasis, and transplant rejection, according to MedicineNet.

Can antibody drugs treat COVID-19?

The US Food and Drug Administration has granted emergency authorisation to two monoclonal antibody formulations — bamlanivimab, produced by Eli Lilly, and a two-antibody combination (casirivimab and imdevimab) developed by Regeneron.

These drugs are designed to prevent the coronavirus from invading cells so that the patients are not hospitalised.

How does it work?

Casirivimab and imdevimab are specifically directed against the spike protein of SARS-CoV-2 so that the virus is prevented from entering the human cells. In US clinical trials, the two-medicine combination reduced the hospitalisations of COVID-19 patients whose conditions were at high risk of worsening.

The drugs are not effective in treating critically ill patients, but studies suggest that they can help keep a new infection in check.

Why is the treatment not popular?

These drugs are in the form of a liquid that must be administered intravenously. Hospitals find it cumbersome since the process takes at least two hours.

Some doctors have not been enthusiastic about prescribing it since the benefits are uncertain. It could also be partly due to the US National Institutes of Health’s treatment guidelines, which say there isn’t enough evidence to show whether the drugs actually work, an NPR report said.

Did the antibody drugs help President Trump?

US President Trump was given the Regeneron product, but it’s not known whether he benefited from it. Trump’s lawyer Rudy Giuliani and former New Jersey governor Chris Christie were among the other recipients, according to the New York Times. Other reports hinted at celebrities’ preferential treatment, saying that the drugs were available only to the elite.

US Housing Secretary Ben Carson said the antibody-drug saved him. Carson, a retired neurosurgeon, wrote on Facebook: “[Trump] cleared me for the monoclonal antibody therapy that he had previously received, which I am convinced saved my life”.

Many other patients, who have undergone therapy with antibody drugs, also attest to its efficacy,