Rapid evolution of SARS-CoV-2 in domestic cats

Preliminary Study on the Efficacy of a Recombinant, Subunit SARS-CoV-2 Animal Vaccine against Virulent SARS-CoV-2 Challenge in Cats

The objective of this work was to evaluate the safety and efficacy of a recombinant, subunit SARS-CoV-2 animal vaccine in cats against virulent SARS-CoV-2 challenge. Two groups of cats were immunized with two doses of either a recombinant SARS-CoV-2 spike protein vaccine or a placebo, administered three weeks apart. Seven weeks after the second vaccination, both groups of cats were challenged with SARS-CoV-2 via the intranasal and oral routes simultaneously. Animals were monitored for 14 days post-infection for clinical signs and viral shedding before being humanely euthanized and evaluated for macroscopic and microscopic lesions. The recombinant SARS-CoV-2 spike protein subunit vaccine induced strong serologic responses post-vaccination and significantly increased neutralizing antibody responses post-challenge. A significant difference in nasal and oral viral shedding, with significantly reduced virus load (detected using RT-qPCR) was observed in vaccinates compared to mock-vaccinated controls. Duration of nasal, oral, and rectal viral shedding was also significantly reduced in vaccinates compared to controls. No differences in histopathological lesion scores were noted between the two groups. Our findings support the safety and efficacy of the recombinant spike protein-based SARS-CoV-2 vaccine which induced high levels of neutralizing antibodies and reduced nasal, oral, and rectal viral shedding, indicating that this vaccine will be efficacious as a COVID-19 vaccine for domestic cats.

Assessing the Potential Role of Cats (Felis catus) as Generators of Relevant SARS-CoV-2 Lineages during the Pandemic

Several questions regarding the evolution of SARS-CoV-2 remain poorly elucidated. One of these questions is the possible evolutionary impact of SARS-CoV-2 after the infection in domestic animals. In this study, we aimed to evaluate the potential role of cats as generators of relevant SARS-CoV-2 lineages during the pandemic. A total of 105 full-length genome viral sequences obtained from naturally infected cats during the pandemic were evaluated by distinct evolutionary algorithms. Analyses were enhanced, including a set of highly related SARS-CoV-2 sequences recovered from human populations. Our results showed the apparent high susceptibility of cats to the infection SARS-CoV-2 compared with other animal species. Evolutionary analyses indicated that the phylogenomic characteristics displayed by cat populations were influenced by the dominance of specific SARS-CoV-2 genetic groups affecting human populations. However, disparate dN/dS rates at some genes between populations recovered from cats and humans suggested that infection in these two species may suggest a different evolutionary constraint for SARS-CoV-2. Interestingly, the branch selection analysis showed evidence of the potential role of natural selection in the emergence of five distinct cat lineages during the pandemic. Although these lineages were apparently irrelevant to public health during the pandemic, our results suggested that additional studies are needed to understand the role of other animal species in the evolution of SARS-CoV-2 during the pandemic.