- Several coronavirus vaccine candidates that are approaching the final stage of human trials have shown promising results, being able to safely generate the immune response that could prevent the infection.
- The neutralizing antibodies that can prevent or cure COVID-19 might disappear after a few months. However, the immune response would still have a memory of the pathogen and could mount future defenses upon reinfection.
- A new study looked at the other immunity parameters that can be measured in COVID-19 survivors, and the research could be used to find the best, most effective coronavirus vaccines from the various candidates that will hopefully be approved.
The novel coronavirus pandemic is still out of control, with several regions of the world still dealing with massive surges in cases. It now takes the virus roughly five days to infect a million new people, and that’s just the number of cases that end up being confirmed via testing. The increased availability of PCR tests certainly helps countries discover patients much faster than before, but the infectivity rate is still much higher than a few months ago.
There is some good news in all of this. We now have a couple of medications that are known to work in coronavirus patients, and we know which drugs aren’t effective. On top of that, several vaccine candidates have shown promising results in clinical trials, inducing the desired immune response without any significant side effects. The vaccines will give communities immunity and curb the spread. The object of these drugs is to generate the same immune response that can be obtained by surviving COVID-19, which is the creation of neutralizing antibodies that can stop the virus from binding to cells, thus killing its capacity to replicate. On top of that, additional immune responses ensure the body can remember its interaction with the pathogen, and kill it again upon reinfection.
A new study now delivers more good news. Researchers think they can measure the immune response of various vaccine candidates and determine which are the most effective at neutralizing SARS-CoV-2.
A series of studies in the past few weeks questioned our ability to attain herd immunity to COVID-19. With any infectious disease, the more people in a community that become immunized, the less likely it is for the virus to spread easily. The protection comes from surviving the illness or from receiving a vaccine.
Some studies say coronavirus immunity will be short-lived, lasting anywhere from 6 to 12 months, similar to other human coronaviruses that induce common colds. Other researchers found that antibody tests might fail to detect antibodies as soon as two to three months after the person recovers from COVID-19. But other tests can measure the immune response. Antibodies don’t have to be circulating in the bloodstream for a person who had the disease recently to resist a secondary infection. Specialized white blood cells have the role of registering the body’s interactions with various pathogens and inducing an appropriate response upon a subsequent encounter. That’s apparently what can happen with COVID-19.
Researchers from The Doherty Institute published a paper in Nature Medicine where they discuss how the immune system reacts to SARS-CoV-2 and what these discoveries might mean for the future coronavirus vaccines.
The researchers didn’t just look for neutralizing antibodies in COVID-19 survivors. They also looked at how B and T cells operate in response to the coronavirus infection. The researchers studied patients who developed mild symptoms, or who had no signs at all. They were looking for an immune response that mimics the behavior of a vaccine. The B cells produce the antibodies that can block the virus’s spike protein from hooking up to the ACE receptors of the human cells. The T cells assist with the development of the B cell response.
“We found that those who showed strong neutralizing antibody activity had a robust B cell response,” Dr. Jennifer Juno told Royal Australian College of General Practitioners (RACGP). But most surprisingly, we also found that a particular subset of T cells, called T-follicular helper cells, was a great predictor of an effective immune response.”
The researchers think the “immune parameters” it identified can be used in vaccine trials. The same science can be applied to various vaccine candidates to study the strength of the immune response.
“Now we know how the immune system responds to the spike protein, and we have these biomarkers or predictors of what elicits a good or poor immune response to COVID-19, we can look at the vaccine candidates and see what will offer the best protection,” Juno said.
A single vaccine candidate will not be enough to meet global demand. Most clinical trials studied vaccine protocols that involve two inoculations over the span of two to four weeks. Pharmaceutical companies think they might need some 15 billion vials to manufacture vaccines for the world’s population.
While several drugs showed effectiveness in clinical research so far, some could deliver a more robust immune response than others. The research from the Doherty Institute could help scientists involved in the other studies measure the immune responses their drugs induce and fine-tune them to increase the efficacy.
The study could also help with further COVID-19 herd immunity work. The new research shows that high titers of antibodies and memory T cells of the HKU1 human coronavirus are present in those who have recovered from COVID-19. One theory says that immunity to colds caused by other coronaviruses could provide some sort of protection against COVID-19.
It’s still unclear whether T cells that recognize HKU1 and other human coronaviruses can generate a response against COVID-19 and eliminate the virus. Monash University biomedical scientist Dr. Emily Edwards told newsGP that it’s not known whether conventional cold antibodies could neutralize SARS-CoV-2 and whether the killer T cells can eliminate the SARS-CoV-2 virus.
