Given the rising number of coronavirus cases, scientists across the world are working round the clock to find a vaccine against the virus which has killed over 1 million people across the globe. According to a latest study, the novel coronavirus which causes COVID-19 blocks body's pain signalling pathways, which could explain why nearly 50 per cent of the infected people experience few or no symptoms, even though they spread the disease.
As per the scientists, including Rajesh Khanna from the University of Arizona in the US, nearly half of coronavirus transmission occurs prior to the onset of symptoms, and 40 per cent of COVID-19 infections are asymptomatic.
"It made a lot of sense to me that perhaps the reason for the unrelenting spread of COVID-19 is that in the early stages, you're walking around all fine as if nothing is wrong because your pain has been suppressed," Khanna said.
In a research paper published in the journal PAIN, the scientists raised the possibility that pain, as an early symptom of COVID-19, may be reduced by the coronavirus spike protein as it silences the "body's pain signalling pathways."
Earlier scientists had established that the novel coronavirus SARS-CoV-2 spike protein uses the human cells' angiotensin-converting enzyme 2 (ACE2) receptor to enter the body. Later in June, two studies pointed to neuropilin-1 as a second receptor for SARS-CoV-2, the researchers said.
"That caught our eye because for the last 15 years my lab has been studying a complex of proteins and pathways that relate to pain processing that are downstream of neuropilin," said Khanna.
"So we stepped back and realised this could mean that maybe the spike protein is involved in some sort of pain processing," he added.
One of the biological pathways signal through which the body feels pain is via a protein named vascular endothelial growth factor-A (VEGF-A) that plays an essential role in blood vessel growth but also has been linked to diseases such as cancer, and rheumatoid arthritis, the scientists said.
They added that most recently this protein has been linked to COVID-19.
Like a key in a lock, when VEGF-A binds to the receptor neuropilin, it initiates a cascade of events resulting in the hyperexcitability of neurons, which leads to pain, the study noted.
Khanna and his research team found that the SARS-CoV-2 spike protein binds to neuropilin in exactly the same location as VEGF-A.
Although several attempts have been made to develop vaccines against human coronavirus infections, there is no vaccine available as of now. Many pharma companies are working on protein-based vaccines for COVID-19 and the most advanced one is from Novavax, based on the entire Sars-CoV-2 spike protein plus an immune system-activating adjuvant.
With PTI inputs