Fear of the COVID-19 pandemic is sweeping the globe, fueled in part by how little we know so far about the virus and how to fight it. One worry, arising from some isolated reports from China and Japan, was that patients who recovered from the viral disease could be reinfected and fall ill again. But according to a report in. GEN: Genetic Engineering & Biotechnology News, Chinese scientists who did a small study with monkeys conclude that there may be no reason to worry about reinfection.

The study used four, adult Chinese rhesus macaques. After intratracheal infection, the monkeys were analyzed on schedule, including measurements such as body weight, body temperature, lung x-rays, sampling of sera, nasal/throat/anal swabs, and primary tissues.

The rhesus monkeys were successfully infected, as measured by weight loss, viral replication mainly in the nose, pharynx, lung, and gut, as well as moderate interstitial pneumonia.

In order to identify the distribution of the virus in the body, and to analyze histopathological changes in the infected monkeys, one of the monkeys was euthanized seven days after infection. Lesions occurred mainly in the lung, confirmed by H&E and anti-spike protein of SARS-CoV-2 staining. The monkey was determined to have mild to moderate interstitial pneumonia. In addition, the chest x-ray at seven days post-infection showed that the upper lobe of the right lung had varying degrees of the localized infiltration and interstitial markings, showing the mild to bilateral ground-glass opacification.

The team then waited until the remaining three monkeys’ symptoms were alleviated. The monkeys were cleared of the infection by meeting the clinical discharge evaluation criteria (absence of clinical symptoms and two negative RT-PCR test results).

Two of the three remaining monkeys were rechallenged at 29 days post-infection with the same dose of the SARS-CoV-2 strain. One monkey was untreated and monitored as a control.

The team measured the amount of virus in the monkeys at five days post-reinfection. The viral loads in 96 nasopharyngeal and anal swabs tested negative.

One of the two reexposed monkeys was euthanized to analyze the viral replication and histological changes. No viral replication in all tissues was observed. In addition, no pathological damage and viral antigen in lung tissues were found in the sacrificed monkey.

Taken together, the monkeys that had been reexposed to SARS-CoV-2 were like the control monkey—with no recurrence of COVID-19. Further, these data suggest that primary SARS-CoV-2 infection could protect from subsequent exposures which will have important implications for vaccine design.

Read more from GEN: Genetic Engineering & Biotechnology News and find the study at www.biorxiv.org.

Featured image: Macaques hug Guiyang, China. Photo © Sean Pavone, courtesy Dreamstime (ID 42179728).