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People Mount Strong Immune Responses to Coronavirus, Boding Well for a Vaccine

MONDAY, May 18, 2020 (HealthDay News) -- As the drive towards a vaccine against the new coronavirus accelerates, there's some good news: People with COVID-19 have robust immune responses against the virus, scientists say.

The researchers based their conclusions after testing immune T-cell counts in 20 patients who recovered from the infection.

"If we had seen only marginal immune responses, we would have been concerned," explained researcher Alessandro Sette. "But what we see is a very robust T-cell response against the spike protein [on the virus' outer shell], which is the target of most ongoing COVID-19 efforts, as well as other viral proteins. These findings are really good news for vaccine development."

Sette is a professor in the Center for Infectious Disease and Vaccine Research at the La Jolla Institute for Immunology in California.

Uncertainties as to the nature of the human immune system response to the coronavirus have troubled experts searching for an effective coronavirus vaccine.

"All efforts to predict the best vaccine candidates and fine-tune pandemic control measures hinge on understanding the immune response to the virus," Center co-researcher Shane Crotty said in an institute news release.

"People were really worried that COVID-19 doesn't induce immunity, and reports about people getting reinfected reinforced these concerns," he said.

However, "knowing now that the average person makes a solid immune response should largely put those concerns to rest," Crotty believes.

Trials 'look pretty promising'

Indeed, efforts towards a vaccine have shown promise.

A number of coronavirus vaccines under development "look pretty promising" and one or two could be ready for large-scale testing by July, the director of the U.S. National Institutes of Health said.

"Your big challenge now is to go big and everybody is about ready for that. And we want to be sure that happens in a coordinated way," Dr. Francis Collins told the Associated Press.

And on Monday, the New York Times reported that an experimental vaccine against the new coronavirus appears to be safe and to trigger an immune response, according to results of the first human clinical trial.

The findings from the early-stage trial that started in March included eight healthy people who each received two doses of the vaccine, the Times reported.

The volunteers made antibodies that were able to stop the coronavirus from replicating, and the levels of the antibodies were similar to those in people who've recovered after contracting the virus, according to vaccine maker Moderna.

The company said the next phase of the testing will involve 600 people and is scheduled to begin soon, but U.S. officials have cautioned that it could take a year to 18 months to produce a vaccine that would be widely available, according to the Times.

The La Jolla research does seem to solidify the notion that effective vaccines are possible.

In their research, Sette's group found that all the patients had a strong CD4, or "helper," T-cell response to the new coronavirus. Almost all of them had made CD8, or "killer," T-cells specifically against COVID-19. "Our data show that the virus induces what you would expect from a typical, successful antiviral response," Crotty said.

"We have a solid starting foundation to now ask whether there's a difference in the type of immune response in people who have severe outcomes and require hospitalization versus people who can recover at home or are even asymptomatic," Sette noted.

"But not only that, we now have an important tool to determine whether the immune response in people who have received an experimental vaccine resembles what you would expect to see in a protective immune response to COVID-19, as opposed to an insufficient or detrimental response," he said.

Help from the common cold?

Sette and his team also looked at T-cell responses in blood samples taken before this coronavirus began circulating. They found that many people had a strong immune response even though they had never been exposed.

Because nearly everyone has been exposed to common cold coronaviruses, this might explain this immune response, they said.

It's not clear, however, if this "cross-reactivity" confers some preexisting immunity to COVID-19. But if it does, that might explain why some people or areas are hit harder by COVID-19 than others, the researchers said.

"Given the severity of the ongoing COVID-19 pandemic, any degree of cross-reactive coronavirus immunity could have a very substantial impact on the overall course of the pandemic and is a key detail to consider for epidemiologists as they try to scope out how severely COVID-19 will affect communities in the coming months, Crotty said.

Dr. Amesh Adalja is senior scholar at the Johns Hopkins Center for Health Security. Reading over the La Jolla findings, he said they "establish that the cell-mediated arm of the immune system does provide substantial immunity after infection.

"It also shows that some of the cells that respond to the other, endemic, coronaviruses have cross-reactive potential against this coronavirus," Adalja said. "Vaccine studies will have to look at both antibody generation as well as cell-mediated immunity."

The report was published online May 14 in the journal Cell.

More information

For more on COVID-19, see the U.S. Centers for Disease Control and Prevention.

SOURCES: Amesh Adalja,M.D., senior scholar, Johns Hopkins Center for Health Security, Baltimore; May 14, 2020, press release, La Jolla Institute for Immunology; Associated Press; New York Times

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