2021 BQ Journal Vol 42 - 18

December 15, 2020

Antibodies and T cells protect against SARS-CoV-2
At a Glance
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Monkeys with the highest levels of antibodies against SARS-CoV-2, the virus that causes COVID-19, were
best protected against reinfection.
Immune cells called T cells also helped prevent reinfection and may be especially important if antibody
levels are low or decline over time.

The tide in the global fight against COVID-19, the disease caused by the
SARS-CoV-2 virus, may soon begin to turn. Last month, three
pharmaceutical companies announced promising results from vaccine
trials. Countries around the world are now poised to begin the largest
mass vaccination campaigns since the 1950s.
But some questions remain about what types and amounts of immune
system components are needed to produce long-term immunity against
SARS-CoV-2. This information would be valuable both for tracking the
effectiveness of vaccines and designing new ones in the future.
Researchers led by Dr. Dan Barouch of Beth Israel Deaconess Medical
Center used monkeys called rhesus macaques to look at levels of
antibodies and immune cells required to prevent reinfection with the
virus.

The study examined what levels of
immune system components like
antibodies (shown here) are
needed to protect against SARSCoV-2 (center), the virus that
causes COVID-19.Dr_Microbe / iStock
/ Getty Images Plus

The study was funded in part by NIH's National Institute of Allergy and
Infectious Diseases (NIAID), Office of the Director (OD), and National
Cancer Institute (NCI). Results were published on December 4, 2020, in Nature.

The research team first collected antibodies from rhesus monkeys that had been exposed to SARS-CoV-2 and
recovered. When these antibodies were injected into unexposed monkeys, the monkeys were protected against
later exposure to the virus. The level of protection matched the amount of antibody received. All three
monkeys that were given the highest dose had no detectible virus in either their noses or lungs after exposure.
In contrast, only one out of three monkeys that received a medium dose of antibodies was completely
protected. All three monkeys that received the lowest dose got infected, although the length of infection was
shorter than in monkeys that weren't given any antibodies. Further modeling experiments estimated the
minimum level of antibodies needed in blood to confer protection against the virus.
The team also tested the antibodies in monkeys that had already been infected by the virus. As in the
experiments that used the antibodies to prevent infection, the highest dose proved to be most effective at
reducing levels of the virus.
People who've been infected with SARS-CoV-2 usually can't produce levels of effective antibodies like those
used in the monkeys that received the highest dose. Therefore, engineered antibodies produced in the lab-
called monoclonal antibodies-may be a better strategy than convalescent plasma for treating people, the
results suggest.

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A Henry Schein Publication

2021 BQ Journal Vol 42

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