Scientists claim signs of persistent SARS-CoV-2 immunity

In the past few months, coronavirus pandemics have spread worldwide, affecting more than 21.67 million people. New details are gradually emerging about the new coronavirus, now called Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), although some people who have been infected in the past are getting the virus again. The report indicates that it has been infected.

Many health care professionals have asked if immunity with SARS-CoV-2 persists. Now, scientists have found strong persistent immunity signs, even with mild COVID-19 illness.

Published studies that have not yet been peer-reviewed medRxiv *, Revealed that antibodies and immune cells capable of fighting the virus were present in previously infected individuals, preventing the possibility of reinfection.

Coronavirus binding Spike proteinThe ACE2 receptor (blue) in human cells (red) causes the virus to enter the cells, as depicted in the background. Illustration credit: Juan Gaertner / Shutterstock

What is immunity?

Immunity is the body’s ability to resist certain infections and toxins by using antibodies and sensitized white blood cells. Adaptive immunity occurs after exposure to an antigen such as a pathogen or vaccination. When the innate immune response is insufficient to control the infection, it is triggered and stimulated.

The adaptive immune response involves cells that produce targeted antibodies that can bind and kill the virus. From there, the immune cells develop memory for a particular antigen, which effectively kills it whenever the body encounters it again, reducing the risk of reinfection.

Other diseases such as chicken pox, Mumps, measles, etc. trigger the body’s adaptive immune system. Therefore, if a person is infected with the virus for these diseases a second time, the body can eradicate the infection.

The memory of the immune system may remember infections efficiently, but may forget others. For example, a person with measles should have lifelong immunity with just one attack. However, illnesses, such as colds and respiratory syncytial virus, that children repeatedly develop in the same winter can also recur.

Currently, SARS-CoV-2 has not been long enough for scientists to judge how long their immunity lasts.

Persistent immunity

In a new study, scientists have shown that SARS-CoV-2 infection can provide long-term immunity to people who are already infected. The first study wasEvidence for a persistent mucosal and systemic antibody response to the SARS-CoV-2 antigen in COVID-19 patientsShows that anti-SARS-CoV-2 antibody responses were detected in the blood and saliva of people infected with the virus compared to the control virus.

To reach their findings, a Canadian research team detected the presence of immunoglobulin A (IgA) and immunoglobulin B (IgB) antibodies to the SARS-CoV-2 spike protein and its receptor binding domain (RBD). We have developed an enzyme-linked immunosorbent assay for COVID-19 in the blood and saliva of acute and convalescent patients.

The team also found that the antibody was found at peak IgG levels achieved by 16-30 days post-symptom onset. In addition, IgA antibody denatured rapidly, whereas IgG antibody persisted and remained stable in both blood and saliva samples until 115 days post-symptom onset.

“Importantly, the IgG responses in saliva and serum are correlated, suggesting that salivary antibodies may serve as surrogate markers for systemic immunity,” the team reported.

“Our finding that the IgG response to the SARS-CoV-2 antigen was stable for three months was consistent with two other studies that also pointed to the durability of the IgG response to spike trimers. They agree,” they added.

The team concluded that this study provided evidence that IgG responses to the novel coronavirus persist in saliva and blood.

“Given that SARS-CoV-2 is first replicated in the oropharynx and nasopharyngeal canal, future characterization of salivary antibody properties and kinetics at the earliest time after contact-followed infection in individuals “There is a correlation between virus settings and defenses that affect COVID-19 disease progression,” said a team from the University of Toronto, Canada.

Immunity even after mild COVID-19

Another study published in medRxiv*, A team of researchers has shown that functional SARS-CoV-2 specific immune memory persists even after mild COVID-19 development.

In a study by researchers at the University of Washington in the United States, the team longitudinally evaluated people who had recovered from a mild COVID-19 infection to determine if their immunity to the virus was developing and persistent.

Researchers found that people who recovered from SARS-CoV-2 infection had specific IgG antibodies and neutralizing plasma, and increased numbers of virus-specific memories B and T that persisted for more than 3 months after the onset of symptoms. I discovered that I developed a cell.

“In addition, SARS-CoV-2-specific memory lymphocytes have demonstrated properties associated with potent antiviral immunity: memory T cells secrete IFN-γ and expand upon antigen re-encounter, but memory B cells expressed a receptor that, when expressed as an antibody, could neutralize the virus,” the researchers wrote in a paper.

“These findings indicate that mild COVID-19 persists and induces memory lymphocytes that display functional features associated with antiviral protective immunity,” they added.

Possible protective immunity

Third study not peer reviewed or published medRxiv* Provides evidence that antibodies targeting RBD show previous and recent infections among people who develop symptomatic COVID-19. Also, they have IgG antibodies Neutralizing antibody And probably linked to protective immunity.

To reach the results of the study, the team will measure the kinetics of the initial antibody response to the RBD of the SARS-CoV-2 spike protein among 259 infected people with symptoms. They compared antibody levels with more than 1,500 blood samples taken before the appearance of the coronavirus pandemic.

They found that between 14 and 28 days after the onset of symptoms, all IgG, IgA, or IgM antibody responses to RBD were all accurate in determining recently infected individuals, with 100% specificity and 97%. %, 91% sensitivity. 81% each.

The IgA and IgM antibodies remained short-circuited, and it was predicted that infected individuals would become seronegative by 51 and 47 days after the onset of symptoms, respectively. However, IgG antibody persisted for 75 days long after the onset of symptoms.

*Important Notices

medRxiv It publishes preliminary, non-peer reviewed scientific reports and should not be considered conclusive and should not guide clinical practice/health-related behavior or be treated as established information.