Quality and not quantity of antibodies suggests if one may have severe COVID-19 or die of disease
Antibody development and neutralisation of the virus have been suggested to be some of the deciding factors that predict the outcomes of COVID-19. As a result, several studies have been conducted in the past few months to determine whether humans produce a robust immune response against SARS-CoV-2, the causative agent of novel coronavirus disease.
Antibody development and neutralisation of the virus have been suggested to be some of the deciding factors that predict the outcomes of COVID-19 .
As a result, several studies have been conducted in the past few months to determine whether humans produce a robust immune response against SARS-CoV-2, the causative agent of novel coronavirus disease.
So far, the researchers have found that those with severe COVID-19 generally form more antibodies than those with mild or asymptomatic disease. However, the antibody levels quickly start to dwindle and may not last more than a few months.
Now, a group of researchers at the Massachusetts General Hospital say that it is the quality, and not the number, of antibodies that determines who will have mild or severe COVID-19 and who may die of the disease.
The findings of the study have been published in the peer-reviewed journal Cell.
Antibodies are immune system molecules that identify and fight against antigens (foreign or potentially harmful substances). There are several types of antibodies that our body produces. Three of these include:
- IgM, the first antibodies that are produced during an infection
- IgG, antibodies that are formed later in the infection and are usually responsible for long term immunity
- IgA, antibodies that are mainly present in mucosal secretions including saliva and tears.
Each antibody is a Y-shaped molecule. This molecule has a hypervariable region on top, a variable region below that and then there is a constant region. The top two regions interact with the antigens and the constant region interacts with other molecules of the immune system and helps destroy pathogens.
The constant region binds to something called Fc receptors present on the surface of immune cells including B cells, macrophages and neutrophils.
The latest study
For the study, the researchers assessed the antibody profile of about 193 COVID-19 patients who were hospitalised following the diagnosis and compared the immune response of patients with moderate disease to those with severe disease or those who died of it.
Here is what they found:
- All three groups (moderate, severe disease and those who died) developed similar IgM and IgA antibody response.
- Individuals who died of the disease had comparatively lower IgG levels than the other two groups by the third week of the disease, suggesting a defective IgG production in the former.
- Antibodies in patients who died of COVID-19 did not develop the ability to bind strongly to Fc receptors and, hence, may not have been able to trigger a strong immune response against SARS-CoV-2.
- Most people who survived had antibodies against the S2 domain of the spike protein of SARS-CoV-2. Spike protein is the part of the COVID-19 causing virus that it uses to bind to and enter inside healthy cells. The authors of the study indicated that this domain is also present in other coronavirus es and hence patients may have some pre-existing immunity to SARS-CoV-2.
Explaining the importance of the finding, Tomer Zoher, lead author of the study said in a news release by the Massachusetts General Hospital, “If we can further understand the importance of cross- Coronavirus immunity,” he added, “researchers may be able to design vaccines able to counteract a much broader range of coronavirus es.”
For more information, read our article on COVID-19.
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