Why Does SARS-CoV-2 Not Only Infect Humans: Understanding the ACE-2 Receptor

It is widely believed that SARS-CoV-2 primarily targets humans due to the presence of the ACE-2 receptor. However, recent research and observations have shown that the virus can infect a range of other animals as well. This article delves into the reasons behind these findings and explains the role of the ACE-2 receptor.

Introduction to the ACE-2 Receptor

Angiotensin-converting enzyme 2 (ACE-2) is a receptor protein that is widely expressed in various tissues and organs in both humans and animals. It plays a crucial role in the regulation of blood pressure and the renin-angiotensin system. The SARS-CoV-2 virus enters host cells by binding to ACE-2, which makes the receptor a critical target for understanding viral entry and infection.

The Role of ACE-2 in SARS-CoV-2 Infection

The receptor binding domain (RBD) of the SARS-CoV-2 spike protein specifically binds to the ACE-2 receptor with high affinity, effectively allowing the virus to gain entry into host cells. The high degree of similarity between the human ACE-2 receptor and that found in bats explains why bats can be intermediate hosts for the virus. However, this does not mean that the virus targets only humans. Other animals, including cats, dogs, minks, and even deer, can also be infected due to the presence of similar ACE-2 receptors.

Animal Infections of SARS-CoV-2

Recent studies have documented that SARS-CoV-2 can infect a variety of domestic and wild animals. For instance, cats, dogs, minks, and bats have all been reported to be hosts for the virus. These findings are significant because they highlight the potential for the virus to spread beyond humans and into the animal population, which can lead to multiple infections and complications.

One of the key reasons why SARS-CoV-2 can infect various animals is the presence of the highly conserved ACE-2 receptor in these species. The virus has evolved to target this specific receptor, making it a highly effective entry point for the virus. Experiments have shown that the virus can successfully infect cells with similar ACE-2 receptors in other animals, indicating that the receptor alone is a key determinant of susceptibility to the virus.

Case Studies and Observations

A noteworthy case study involves the infection of zoo animals by the warden who was infected with SARS-CoV-2. Reports suggest that the warden passed the virus to various animals in the zoo, highlighting the potential for human-to-animal transmission. Similarly, cats and dogs that cohabit with infected individuals have also been found to be infected, although the exact transmission routes remain unclear.

Further evidence of the virus's ability to infect other animals comes from experimental attempts to grow the virus in fertilized chicken eggs. These attempts were unsuccessful, indicating that the virus has lower affinity for other avian species compared to mammals.

To date, the list of animals known to be infected with SARS-CoV-2 includes mink, ferrets, cats, dogs, and bats. However, the comprehensive list of vulnerable species is still being determined as more research is ongoing. The focus remains on better understanding the precise mechanisms of viral entry and potential treatments that can address infections in both humans and animals.

Conclusion

While SARS-CoV-2 primarily affects humans due to the presence of the ACE-2 receptor, the virus can infect other animals as well. The ACE-2 receptor plays a crucial role in the viral infection process, and its presence in various species explains why the virus can spread beyond humans into the animal kingdom. Continued research is necessary to fully understand the complexities of viral transmission and to develop effective strategies to mitigate the impact of SARS-CoV-2 on both humans and animals.