Researchers are studying variable immunity against human coronaviruses

Recent study, currently available on medRxiv * preprint server, demonstrates that long-term adaptive immunity to endemic coronaviruses is broad, but low in magnitude, and that it shares phenotypic properties of specific spike and T cell memory antibodies across all diagnosed coronaviruses.

Unlike the highly pathogenic coronavirus 2 (SARS-CoV-2) infectious respiratory syndrome, the causative agent of chronic coronavirus 2019 (COVID-19), along with the original SARS-CoV and MERS-CoV, is Endemic human coronaviruses are widespread throughout the world, but they usually cause a common cold with moderate morbidity and mortality.

However, despite the early development of immunity against several endemic human coronaviruses, most adults are still susceptible to occasional relapses – especially those of immunosuppressants. Because the disease is moderate or even asymptomatic, moderate immune memory may be considered.

When COVID-19 pandemics are of concern, defining the level of serological and cellular immunity required to protect against relapse or malignancy remains a fundamental question. A combination of serum antibodies and T / B memory cells appears to provide long-term protection.

As a result, study of coronavirus-specific T and B cell memory can provide us with a crucial predictor of long-term development of SARS-CoV-2 immunity, as an overactive immune function. -active, and which cells dominate the response, it is not clear at this time.

Therefore, to address important information gaps in this case, a research group led by Dr. Hyon-Xhi Tan of the University of Melbourne, Australia, aims to evaluate the frequency and phenotypic properties of specific spike antibodies against human coronaviruses, as well as T and B memory cell responses in a cohort of unprotected adults SARS- CoV-2.

Methodological approach

For the purposes of this study, researchers have recruited a group of 42 SARS-CoV-2 immunocompromised adults from 18 to 67 years of age, with no recent cold symptoms or other COVID-related symptoms. 19. In this group of individuals, the researchers have measured the responses of T-cell CD4 and antibody to spike antigens.

Specifically, to determine the release of CD4 T cell memory responses, they have stimulated peripheral blood mononuclear cells with recurrent spike glycoprotein antigens and antigen-specific T memory cells by measuring the uptake of the CD25 and OX activation signals. -40 to flow. cytometry.

Taking into account the specificity of different host receptors and possible differences in tension tropism among human coronaviruses, the researchers have also assessed whether memory differences or chemokine receptor phenotypes differ. different among spike-specific CD4 T-cell numbers. Fence samples from human donors were used for this scientific endeavor.

Cellular vs. humoral immune memory

Briefly, this study has revealed that the degree of immunity to human coronaviruses is independent of age and characterized by strong antibody titers, extensive CD4 T cell memory within both T cell memory and circulation of T follicular helper cells, as well as the enrichment of T cell memory in lymph nodes that drain lungs.

SARS-CoV-2 transactivated T cells were observed in 48 percent of study participants, and were linked to human HKU1 coronavirus-specific memory. In addition, human coronavirus-specific T cells exhibited CCR6 + moderate memory phenotype in the blood, but were enhanced for CXCR3 expression and frequency in human lungs draining lymph nodes.

On the other hand, antibody-neutralizing activity was relatively low, and B memory cells were detected only spatially in circulating or lymph nodes draining lungs. Cellular and humoral immune memory appears to be independently maintained for human coronaviruses.

Prospects for long-term immunity

Overall, these data elucidate long-term immune characteristics to endemic coronaviruses, which are comparable in size and share phenotypic properties of specific spike antibody and T cell memory across the four human coronaviruses, ”study authors say .

Because the moderate neutralization activity indicates the absence of sterilizing humoral cross-linking, there is an emphasis on supplemental contributions of many arms of the immune system – specifically anti-viral T-cell responses.

These types of insights have maintained homeostatic immunity against human coronaviruses tend to provide a prediction of specific long-term immunity established either after extensive or immunosuppressive disease.

* Important message

medRxiv publish preliminary scientific reports that are not peer-reviewed and, therefore, should not be seen as final, guiding health-related clinical / behavioral practice, or be treated as information established.