COVID-19: Monkeys Develop Immunity to SARS-CoV-2

A new study reveals that macaques develop protective antibodies against SARS-CoV-2, which protect them from reinfection.

Developing immunity to SARS-CoV-2 after an initial infection is of particular interest in the fight against the recent COVID-19 pandemic. Researchers have turned to monkeys for answers.

After administering a dose of SARS-CoV-2 into the tracheas of four adult rhesus macaques, the researchers detected high concentrations of the virus in the animals’ noses and throats, which peaked three days after the initial infection. This was accompanied by a decrease in appetite, weight loss, and an increased respiratory rate.

One week after infection, traces of the virus are detected in many body tissues, and the animals develop interstitial pneumonia—characterized by inflammation of the pulmonary alveoli— one of the main symptoms of COVID-19 in humans.

By collecting blood serum from primates, researchers are identifying antibodies capable of targeting the SARS-CoV-2 surface protein, which the virus uses to enter human cells. Antibody levels remain relatively low during the first week after infection but increase at three and four weeks. Protective neutralizing antibodies appear to be produced during the recovery process following SARS-CoV-2 infection.

Indeed, after the primary infection had cleared in the macaques, reinfection with the coronavirus did not result in detectable viral replication in the tissues, despite a slight fever. The results show that rhesus macaques infected with SARS-CoV-2 do not develop a secondary infection after recovering from an initial exposure to the coronavirus and being re-exposed to SARS-CoV-2. The primates therefore appear to develop at least short-term immunity against the pathogen.

While this is only a preliminary study, it marks the beginning of a response that could have a major impact on pandemic management. Based on these results, the team is questioning the observations of reinfection in humans. The authors suspect that false-negative PCR tests may have failed to detect a persistent virus, rather than an actual inability to develop immunity in humans.