Researchers define immune system requirements for protection against COVID-19

Since the novel coronavirus emerged late last year, scientists around the world – including Beth Israel Deaconess Medical Center (BIDMC) immunologist Dan Barouch, MD, Ph.D. – have developed vaccines to protect against COVID-19 and to end the global pandemic. In November 2020, three pharmaceutical companies released preliminary data showing high rates of protection in phase 3 human trials for their vaccines, but questions remain about how the body develops and maintains immunity after vaccination or l ‘infection.

In a new newspaper article Nature, Barouch, director of the BIDMC Virology and Vaccine Research Center, and colleagues shed light on the role of antibodies and immune cells in protecting against SARS-CoV-2, the virus responsible for COVID-19, in rhesus macaques. “In this study, we define the role of antibodies to T cells in protecting against COVID-19 in monkeys. We report that a relatively low antibody titer (the concentration of antibodies in the blood) is necessary for protection, ”Barouch said. “This knowledge will be important in the development of next-generation vaccines, antibody-based therapies and public health strategies for COVID-19.”

Building on previous findings that infection with SARS-CoV-2 protects rhesus monkeys from re-exposure, Barouch and his colleagues purified and collected antibodies from animals that had recovered from the infection. They administered the antibodies at various concentrations to 12 uninfected macaques and observed that protection against SARS-CoV-2 challenge was dose dependent. Animals which received higher amounts of antibody were protected more completely, while animals which received lower amounts of antibody were less well protected. Likewise, when researchers administered varying concentrations of the purified antibodies to 6 macaques with active SARS-CoV-2 infection, those who received higher doses demonstrated faster viral control.

In a second set of experiments, Barouch and his colleagues evaluated the role of specific immune cells – CD8 + T cells – in contributing to protection against the virus by removing these cells from animals that had recovered from the virus. infection with SARS-CoV-2. The elimination of these immune cells made animals vulnerable to infection after further exposure to SARS-CoV-2.

“Our data define the role of antibodies and T cells in protecting against COVID-19 in monkeys. Antibodies alone can protect, even at relatively low levels, but T cells are also useful if antibody levels are insufficient, ”said Barouch, who is also Professor of Medicine at Harvard Medical School and a member of Ragon. Institute of MGH, MIT and Harvard. “These correlates of protection are important given the recent positive vaccine results in human trials and the likelihood that these and other vaccines will become widely available in the spring;” therefore, future vaccines may need to be licensed on the basis of immune rather than clinical correlates. efficiency.”