When it comes to COVID-19, many questions still remain unanswered. Among them: when do antibodies develop and how long do they last? A team of researchers in Sweden is trying to provide some answers.

Every time our body comes into contact with a foreign substance, the immune system reacts; sometimes it tolerates this substance and other times it interprets it as an “invader” and attacks it.

This is what happens with infectious agents, and SARS-CoV-2 is no exception. However, little is known (still) about when the antibody response of our body begins and especially how long it can last.

To summarize, the first signal from our immune system is initiated by the activation of B lymphocytes, a sort of sentinel that detects the invader and responds by producing antibodies that are called Immunoglobulin M (IgM), after a certain period of time; this varies, but after approximately two weeks, our body develops other antibodies — Immunoglobulin G (IgG). These antibodies remain in our body and guard over us for years. They’re called “neutralizing antibodies” and are what every infectious diseases specialist would like to see in the analysis of their patients, as they prevent further infections by the same pathogen.

Little is known about the immune response to SARS-CoV-2 because it’s still a new coronavirus. Above all, little is known about the immune response and how long the acquired immunity can last.

A group of Swedish researchers at Danderyd University Hospital, in collaboration with the Royal Institute of Technology (KTH) and SciLifeLab, both in Stockholm, collected 2149 SARS-CoV-2 positive samples in April and re-analyzed the patients after four months.

What did the Swedish scientists’ research uncover?

They found that 82% of SARS-CoV-2 positive patients in April still had measurable levels of neutralizing antibodies (IgG) after four months (i.e. they had developed some degree of immunity to COVID-19).

Another important result of the Swedish study was that researchers were able to link the presence of neutralizing antibodies with the severity of symptoms during infection. That is, patients who had mild symptoms over the course of the disease had no measurable neutralizing antibodies after four months.

There’s more: many patients displayed the antibody response, even during the infection, and to further confirm the above, those who had even mild symptoms also demonstrated a low-immune response.

Why is it important to study the immune response?

Continuing to study this group of patients, their immune response, and the body’s ability to produce neutralizing antibodies capable of fighting SARS-CoV-2, is important to understand how our immune system reacts over the long-term and consequently also how to develop an effective vaccine.

In addition, the Swedish study not only analyzed the antibody response but also studied various proteins of SARS-CoV-2 that may be responsible for the success of the infection. Understanding which parts of the virus’ surface proteins trigger the immune response is critical in understanding why patients respond differently to the infection and why many exhibit more mild symptoms. Finally, knowing the most important virus proteins is crucial for the development of a useful and safe vaccine.

This post is also available in: Italiano

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