In a new study conducted aimed at understanding protective immunity to SARS-CoV-2, researchers have found that SARS-CoV-2 infection induced protective immunity against re-exposure in non-human primates.
An understanding of protective immunity to SARS-CoV-2 is critical for vaccine and public health strategies aimed at ending the global COVID-19 pandemic. A key unanswered question is whether infection with SARS-CoV-2 results in protective immunity against re-exposure. The researchers developed a rhesus macaque model of SARS-CoV-2 infection and observed that macaques had high viral loads in the upper and lower respiratory tract, humoral and cellular immune responses, and pathologic evidence of viral pneumonia. Following initial viral clearance, the animals were re-challenged with SARS-CoV-2 and showed reductions in median viral loads in bronchoalveolar lavage and nasal mucosa as compared with primary infection. Anamnestic immune responses following rechallenge suggested that protection was mediated by immunologic control. These data shows that SARS-CoV-2 infection induced protective immunity against re-exposure in nonhuman primates. However, rigorous clinical studies will be required to determine whether SARS-CoV-2 infection effectively protects against SARS-CoV-2 re-exposure in humans.
In another study, researchers developed a series of DNA vaccine candidates expressing different forms of the SARS-CoV-2 Spike (S) protein and evaluated them in 35 rhesus macaques. The vaccinated animals developed humoral and cellular immune responses, including neutralizing antibody titers comparable to those found in convalescent humans and macaques infected with SARS-CoV-2. Following vaccination, all animals were challenged with SARS-CoV-2, and the vaccine encoding the full-length S protein resulted in reductions in median viral loads in bronchoalveolar lavage and nasal mucosa, respectively, as compared with sham controls. Vaccine-elicited neutralizing antibody titers correlated with protective efficacy, suggesting an immune correlate of protection. These data demonstrated vaccine protection against SARS-CoV-2 in non-human primates.