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As the COVID pandemic continues to sweep across the world, it has yet to be determined whether previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection provides long-lasting immunity. Although many studies have shown that people who have recovered from the infection develop antibodies that last for months, more research is imperative.
Now a new study published on the prepress server bioRxiv * shows that SARS-CoV-2 specific T cell functional responses are retained for six months after infection. However, the strength of this response depends on the clinical features of the primary infection.
The UK researchers aimed to determine the antibody responses against SARS-CoV-2 and how long they last.
The study
The immune response to SARS-CoV-2 is essential to control the primary infection and prevent reinfection, which has been observed in some cases during the pandemic. However, there is a growing concern that the immune responses that follow a natural infection are not maintained, predisposing a person to a recurrent infection.
To arrive at the study findings, the researchers studied the magnitude and phenotype of the cellular immune response to SARS-CoV2 in 100 donors six months after having a primary infection. The team related this to the antibody level profile against the spike, the nucleoprotein, and the receptor-binding domain (RBD) over the past six months.
What the study found
When a pathogen enters the body and causes an infection, the immune system works to fight it. An innate immune response occurs, in which the cells secrete interferons and other chemicals such as cytokines. Interferons interfere with viral replication, while cytokines conduct cell signaling to aid in communication and stimulate the movement of cells to the site of infection.
Meanwhile, an adaptive immune response is a specific response to infection, in which white blood cells such as T cells (cellular response) and B cells (antibody response) recognize whether cells are infected to increase the number of cells. to fight infection.
In the study, the researchers found that T-cell immune responses to SARS-CoV-2 were detected in all donors. In addition, all donors have predominant CD4 + T cell responses with expression of interleukin 2 (IL-2) chain cytokines.
The team also revealed that median T-cell responses were 50 percent higher in those who had experienced an initial symptomatic infection. This means that the severity of the primary infection provides a benchmark for cellular immunity that lasts for at least six months.
The pattern has also been seen in the first weeks after acute SARS-CoV-2 infection in patients recovering from severe or mild illness. The findings reveal that a response to higher viral loads and inflammatory mediators during acute infection can provide a higher antibody response.
“Our findings demonstrate that the vast majority of adults are likely to have strong cellular immunity to SARS-CoV-2 within six months of mild to moderate asymptomatic infection,” the team concluded.
“These characteristics are encouraging in relation to the longevity of cellular immunity against this new virus and are likely to contribute to the relatively low rates of reinfection that have been observed to date. More studies will be needed to assess how well these immune responses are maintained. long-term, “the team added.
Detecting how long immunity against SARS-CoV-2 is crucial in the development of effective vaccines. This may help in the response against the coronavirus pandemic, which has now infected more than 47.32 million people and killed at least 1.21 million.
So far, of all the recorded COVID-19 cases, 31.5 million have recovered.
*Important news
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be considered conclusive, guide clinical practice / health-related behavior, or be treated as established information.
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