Some good news comes as researchers scramble for potential vaccine candidates amidst the global COVID-19 pandemic. Scientists from the La Jolla Institute for Immunology report that the human immune system is indeed capable of launching a full-fledged response when exposed to coronavirus. The report comes from a study of 20 adults who successfully recovered from COVID-19 without major problems.
The global search for SARS-CoV-19 vaccine candidates revolves around one big question: what is the human immune system capable of? Researchers know that in order to be successful with vaccination, the right candidate needs to be able to trigger an enduring, substantial immune response.
Another question also lingers: can exposure to other types of coronaviruses, like those that cause a mere cold, provide protective immunity? In the late 18th century, immunology pioneer Edward Jenner realized that infection with cowpox could provide an individual immunity against its more deadly and contagious cousin, smallpox, and the concept of vaccination was born. Perhaps scientists could make a similar connection in this 21st century pandemic.
"All efforts to predict the best vaccine candidates and fine-tune pandemic control measures hinge on understanding the immune response to the virus," explained La Jolla’s Shane Crotty, PhD.
The new study builds off of a previous bioinformatics study of how to predict which viral fragments could activate human T cells and initiate an immune response. In the most recent study, researchers analyzed samples from 20 adults who had recovered from COVID-19 without major problems, indicating a “normal” immune response.
In this analysis, researchers aimed to see if T cells isolated from these adults recognized the viral fragments identified in the bioinformatics study. They considered two main types of fragments, those from the coronavirus’s namesake, the “spike protein,” and those not from the spike protein. Promisingly, they observed a strong T cell response to all types of viral fragments, spike protein and others.
Researchers also saw a multi-faceted T cell response, both from CD4 “helper” T cells, which activate B cells and contribute to antibody production, and from CD8 “killer” T cells, which target and destroy cells the virus has already infected, preventing further infection.
Additionally, researchers analyzed T cells from blood samples collected years before the current coronavirus pandemic, observing that these immune responses also showed signs of T cell reactivity to the SARS-CoV-19, more likely than not because of exposure to common cold-causing coronaviruses that could initiate a similar immune response.
"People were really worried that COVID-19 doesn't induce immunity, and reports about people getting re-infected reinforced these concerns, but knowing now that the average person makes a solid immune response should largely put those concerns to rest,” Crotty said.
While the scientific community is still cautious and considering that in some cases, an excessive immune response may be harmful, the present study offers some promising conclusions. Going forward, scientists anticipate using their findings to look for differences in immune responses in different outcomes of COVID-19, i.e. hospitalization, asymptomatic cases, and mild infection cases. This understanding of the COVID-19 immune response also offers a way to test experimental vaccines for efficacy. Scientists still need to confirm the protective effect of previous exposure to common cold coronaviruses.