Coronaviruses responsible for Middle East Respiratory Syndrome (MERS-CoV), related to SARS-CoV-2 the agent responsible for COVID-19, continue to maintain a high level of alert from the World Health Organization (WHO) for the ‘high lethality rate (35%) associated with human infection: 1 death for every three infected. Autochthonous cases mainly concern Middle Eastern countries (85% in Saudi Arabia), but imported cases have been reported in other countries around the world, including Italy. The disease begins with respiratory symptoms which can worsen to severe clinical pictures of pneumonia. To date, no specific vaccines or treatments are available. The infection is mainly transmitted by person-to-person contact in the family or hospital (nosocomial infections), but current scientific evidence suggests that the dromedary and its products (e.g. milk) play a key role in the transmission of the virus from the animal to the humans (zoonosis), while bats are widely regarded as the evolutionary source and next ancestor.
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For entry into the host cell the MERS-CoV virus does not use the ACE2 receptor as SARS-CoV and SARS-CoV-2 do, but the DPP4 receptor. However, there are other viruses of its cousins, such as the bat coronavirus NeoCoV and other close relatives viruses, which use the ACE2 receptor instead. The NeoCoV virus, discovered in 2011 in South Africa in bats of the Neoromicia Capensis species, shares 85% similarity in the genome with the MERS-CoV virus, but has a difference in the component of the Spike protein, called the receptor binding domain that attaches the virus to the host cell. So far, no worries. The problem was created with a mutation (T510F), artificially induced by some Chinese researchers (https://lnkd.in/d-gbwmyw) on the Spike protein, which allows the NeoCoV virus to efficiently infect human cells that express ACE2. Even more singular is the fact that the infection is not blocked by neutralizing antibodies directed to SARS-CoV-2 and MERS-CoV.
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However, we are talking about a mutation never detected in any of the naturally obtained NeoCoV viral samples. If, on the other hand, we consider the natural phenomena of spillover or jumps of the virus from one species to another, a hypothetical passage to humans of the NeoCoV virus with a natural mutation similar to that obtained in the laboratory, would give rise to an infection with a high transmissibility, linked to the use of the ACE2 receptor (as SARS-CoV-2 does) and the high lethality rate that characterizes the MERS-CoV infection.
If to date no cases of human NeoCoV infection have been reported and therefore there is still no cause for panic, its zoonotic potential must still be assessed in the event of an evolutionary adaptation in humans. It is a scenario that signals the importance in a One Health perspective of the monitoring and genomic sequencing of these viruses to prepare health systems for possible outbreaks of MERS-CoV with greater affinity for the human ACE2 receptor. The WHO, in an official statement calls for further studies to be conducted to understand if the NeoCoV virus represents a significant threat to humans, also in light of the extensive mutations in the SARS-CoV-2 Spike protein, particularly in the Omicron variant. strongly changed compared to the previous ones.
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