Finnish researchers conducted a study showing that neutralizing bodies generated as a result of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) – the agent that causes coronavirus disease 2019 (COVID- 19) – usually persist for at least a year.
“Studies of people who have recovered from natural infection with SARS-CoV-2 are crucial in determining how long antibodies persist and whether these antibodies might protect against reinfection,” write Anu Haveri and colleagues at the Finnish Institute for Health and Welfare in Helsinki. .
Now the team has shown that in a cohort of more than 360 individuals recovered, immunoglobulin G (IgG) antibodies binding to the wild-type SARS-CoV-2 spike protein persisted in 97%. patients for at least twelve months.
The viral spike protein is the main structure that the virus uses to infect host cells and a main target for antibodies after infection or vaccination.
In addition, neutralizing antibodies against SARS-CoV-2 also persisted in 89% of individuals for at least a year.
“This strongly suggests that the protection against reinfection is long lasting,” the researchers write.
In contrast, the neutralization capability was significantly reduced compared to the worrying variants B.1.1.7 (alpha), B.1.351 (beta) and B.1.617.2 (delta) which occurred in the UK respectively, in South Africa and India. .
However, the team points out that although reinfection can occur in the absence of neutralizing antibodies, cellular immunity has been shown to be less affected by mutations present in these variants and will likely provide long-term protection against a serious illness.
A pre-printed version of the research paper is available on the site medRxiv* server, while the article is subject to peer review.
Learn more about the antibodies generated by SARS-CoV-2 infection
Infection with SARS-CoV-2 induces antibodies against the spike protein and another surface structure called a nucleoprotein which plays a vital role in packaging the viral genome.
Neutralizing antibodies generated against SARS-CoV-2 target the receptor binding domain (RBD) of the tip and prevent it from binding to the host cell’s receptor, the angiotensin-converting enzyme 2.
Neutralizing antibody titers, which are highly predictive of protection against infection and clinical disease, have been reported to persist for at least six to twelve months after infection.
“However, a protective threshold for humans is still under debate and subject to standardization of serological methods,” explains Haveri and his colleagues.
Additionally, SARS-CoV-2 has developed certain mutations that raise concerns about viral transmissibility and the potential escape of infection and vaccine-induced immunity.
“Evidence from convalescent sera from individuals who have recovered from natural infection can help determine how long antibodies and immunity persist and whether antibodies can protect against reinfection,” the team writes.
What did the researchers do?
Researchers assessed the persistence of serum antibodies in 367 people who had recovered from wild-type SARS-CoV-2 infection six and twelve months after diagnosis. Thirteen percent of the participants had recovered from a serious illness requiring hospitalization.
The team determined the proportion of individuals with anti-spike IgG (S-IgG), anti-nucleoprotein IgG (N-IgG) and neutralizing antibodies (NAb). In a subset of 78 participants, they also measured NAb titers against wild-type SARS-CoV-2 virus (B.1) and variants of concern B.1.1.7, B.1.351 and B.1.617 .2.
What did they find?
The study found that S-IgG, N-IgG, and NAb were detected in 91%, 98%, and 67% of participants, respectively, six months after infection was diagnosed.
The proportion of samples positive for S-IgG and Nab was still high twelve months after diagnosis, at 97% and 89%, respectively, but decreased to 36% for N-IgG.
The proportion of positive, weak positive (borderline) and negative subjects for neutralizing antibodies twelve months after infection against four strains of the SARS-CoV-2 virus (n = 78). A. Wild type virus (B.1). B. Alpha variant (B.1.1.7). C. Beta variant (B.1.351). D. Delta variant (B.1.617.2).
“We have shown that S-IgG antibodies and, more importantly, NAbs persist in most people for at least a year after infection with SARS-CoV-2,” Haveri and colleagues explain. “This strongly suggests that the protection against reinfection is long lasting.”
The mean concentration of IgG and NAb levels was higher six months after infection in those who had recovered from severe illness compared to mild illness. The difference was 2.0 to 7.4 times depending on the age group and persisted for at least twelve months after diagnosis.
“Consistent with previous observations, subjects with severe infection had higher concentrations of N-IgG, S-IgG and NAb titers than subjects with mild infection and are expected to remain seropositive longer,” the team explains.
NAb titers were significantly lower compared to variants of concern
Among the 78 individuals selected to compare neutralization of the wild-type virus and the three variants of concern, the NAb titers were significantly lower for all three variants.
Compared to the wild-type virus, the geometric mean titers were 1.2 to 2.2 times lower for the B.1.1.7 variant, 3.3 to 6.6 times lower for B.1.351 and 2, 6 to 3.5 times lower for B.1.617. 2.
“The results of our study support previous findings indicating that protection against neutralizing antibody-mediated infections may be impaired against the variants of concern, especially after mild illness,” says Haveri and colleagues.
However, the team states that “although in the absence of neutralizing antibodies reinfection is possible, cellular immunity is not affected in the same way by mutations at the RBD site and is likely to provide long-term protection against serious illness “.
medRxiv publishes preliminary scientific reports which are not peer reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.