"Even after recovering from the infection, you have damage that prevents you from fully regaining your capacity to produce CD8+ cells. Therefore, something occurred during infection to stop that and harm your response "Professor Mark Davis of Stanford University and director of the institute's Center for Immunity, Transplantation, and Infection. The paper, which was released this month in the journal Immunity, has Davis as its lead author.
CD4+ T cells, commonly nicknamed "helper T cells" for their involvement in marshaling other aspects of the immune response, looked to be unharmed. However, Davis and his team discovered that in individuals who had survived an infection, both the quantity and quality of CD8+ T cells—also known as "killer T cells" for their function in destroying infected cells—were significantly worse. Even after these individuals received the Pfizer-BioNTech vaccine, a disparity persisted.
"Looking at the broader swath of data, we came up with a seven-fold average reduction. Yet in a few of the instances, it was far bigger. So that's a major problem," Davis added.
While researchers frequently look to antibodies first to gauge the body's early protection against an infection, an array of T cells also make up a crucial portion of the body's defenses. Davis and his team built a new technique of measure this reaction, utilizing a reagent they produced to essentially identify a precise picture of the T cells.
"Technology-wise, looking at the T cell response and quantitatively assessing it is tougher than antibody detection. That's why there's a need to better that technology and also tie it to vaccine research," said Chao Jiang, a program officer at the National Institutes of Health. Jiang oversaw the research, which was financed by the agency.
According to Davis, the decrease may cause the immune system to take longer to eliminate diseased cells. It might also make it more difficult for them to benefit fully from the vaccine they received and ward against new variants when compared to others who don't have the harm. "Saying that this might impede reactions to other viruses would, in my opinion, be too much of a guess. SARS-CoV-2 variations, however, are still present. There are them "said him.
The dysfunction, which persisted even after infections were treated, was compared by the study's authors to that observed in their earlier research with viruses like hepatitis C or HIV.
"After all these years of research, we now know that SARS-CoV-2 did in fact modify our host immune response. Moreover, the malfunction of CD8 T cells may only be one element of it "Jiang stated.
According to Jiang, not all infectious diseases have been associated with this particular persistent dysfunction. However she emphasized that this does not imply that SARS-CoV-2 causes the same type of havoc on the immune system that HIV may.
"There may be long-term immunological effects of this malfunction. We don't sure whether it's connected to extended COVID, but it might be. And a lot of study is being done, so I believe we will comprehend the mechanism more "Jiang remarked.
It will be crucial to research how this damage fits with other aspects of the intricate immune response of the body. Jiang pointed out that studies conducted in other countries have revealed evidence of greater antibody defense from patients who were both infected and immunized.
In order to be able to correlate that with other clinical symptoms, Jiang said it is crucial to continue a study like this. This is especially true as the clinical cohort ages.
The Davis research has the drawback of relying on "peripheral" T cells found in the blood. It is impossible to collect samples from other parts of the body, such as the lungs, where the immunological response might be most pronounced.
Davis emphasized that their measurements did reveal different types of T cells for the virus in the blood at levels that appeared to be acceptable. "This issue has basically been brought up a million times. In essence, I would suggest that everything eventually finds its way into circulation "Davis stated.
Some of the phenomena they saw might also be specific to the group of persons the researchers studied: those who received the COVID-19 mRNA vaccine after contracting the disease. In particular, Davis said that persons who mix-and-match their booster shots with various immunizations may experience varied outcomes years after their original infection.
"Can we possibly restore those damaged CD8 responses as we continue to examine them? Or do people bounce back later?" said he.
