Published on Thursday in PAIN, The Journal of the International Association for the Study of Pain, the study may help scientists understand why nearly half of those who get infected with the novel coronavirus don't experience symptoms, but can spread it and infect others.
Prior research suggests that the virus that causes COVID-19 uses the angiotensin-converting enzyme 2 to enter the human body. However, some studies have shown that neuropilin-1 also serves as a receptor for coronavirus.
The researchers found that the SARS-CoV-2 spike protein binds to neuropilin in the same location as the vascular endothelial growth factor-A, which has been linked to cancer and other serious diseases.
As corresponding author Dr. Rajesh Khanna explained, "we stepped back and realized this could mean that maybe the spike protein is involved in some sort of pain processing."
Khanna and his team performed various lab experiments on rodents, using VEGF-A to induce pain. Then, they added the SARS-CoV-2 protein.
"[This] completely reversed the VEGF-induced pain signaling. It didn't matter if we used very high doses of spike or extremely low doses -- it reversed the pain completely," said Khanna.
The results could have major implications for the future of COVID-19 research and explain the "unrelenting spread" of the novel coronavirus by asymptomatic individuals, according to Khanna.
"If we can prove that this pain relief is what is causing COVID-19 to spread further, that's of enormous value."
"We have a pandemic, and we have an opioid epidemic. They're colliding. Our findings have massive implications for both," Khanna concluded.
Per NPR, according to data from the CDC, as much as 45 percent of those who get coronavirus experience no difficulties.
However, it remains unclear why some people experience no symptoms.
Science suggests that those who don't feel any symptoms have exceptionally strong immune systems, capable of fighting off the virus. According to some studies, so-called disease tolerance could be behind this phenomenon.
It could end sooner if a vaccine is developed and available for widespread use. According to experts, one could be ready by the middle of 2021.