In an animal model for COVID-19 that shares important features of human disease, scientists have shown that prior infection with the SARS-CoV-2 virus provides protection against reinfection, and treatment with convalescent serum limits virus replication in the lungs.
Syrian hamsters, commonly found as pets, have served critical roles in understanding human infectious diseases for decades. The new study—by a collaboration of scientists at the University of Wisconsin-Madison, the University of Tokyo and the Icahn School of Medicine at Mount Sinai and published in the Proceedings of the National Academy Sciences—demonstrates they are also a useful small animal model for researchers trying to understand SARS-CoV-2 and in evaluating vaccines, treatments and drugs against the disease it causes.
“Hamsters are good models for human influenza and SARS-CoV,” team leader Professor Yoshihiro Kawaoka said.
To determine whether hamsters developed antibodies against SARS-CoV-2 that protect them from reinfection, the researchers administered a round of the virus to a number of animals about three weeks following initial infection and were unable to detect virus in their respiratory tracts. They did find virus in the airways of control animals not previously infected.
“The animals all possessed antibodies and did not get sick again, which suggests they developed protective immunity,” Pete Halfmann said. “But we still can’t say how long this protection lasts.”
In early April, researchers initiated a clinical trial to examine whether the antibody-bearing component of blood—the plasma or sera—from recovered COVID-19 patients could be given to sick patients to assist in their recovery. While convalescent plasma has been used in other disease outbreaks, it remains poorly understood as a treatment.
So, Professor Kawaoka’s team extracted convalescent sera from previously sick hamsters and then pooled it together. They infected new hamsters with SARS-CoV-2 and then gave them this antibody-laden sera either one day or two days following infection.
The hamsters that received treatment within a day of infection had much lower amounts of infectious virus in their nasal passages and lungs than those given a mock treatment. Those that received sera on day two showed a less appreciable benefit, though they still had lower levels of virus in their respiratory organs compared to control animals.