London, Apr 20 (IANS): Our guts may not provide long-lasting systemic immunity from Covid-19, which is where immune cells circulate through the body to provide protection to other organs, finds a new study that may have implications for oral coronavirus vaccines.

A team of researchers from the University Hospital Erlangen, Germany, studied the role of the gut in providing systemic immunity to this virus.

An analysis of blood samples from patients infected with SARS-CoV-2 revealed that immune cells circulating in the blood, which were triggered by the gut's response to infection, were limited in number when compared to immune cells that had been triggered elsewhere in the body.

"Although the gut is considered an important portal of entry for the virus, the immune response in the blood of Covid-19 patients is dominated by lymphocytes, cells that protect the body from infection, that have been triggered by other areas of the body," said Sebastian Zundler, from the varsity's Department of Medicine.

The team used a technique called flow cytometry to detect and measure the different types of immune cells that were found in the blood samples of patients currently with Covid-19, patients recovered from Covid-19 and those free of the virus.

There is a special mechanism in the lymphoid tissue of the gut that triggers the production of an imprint marker called "a4b7 integrin". This marker causes T cells to head towards the gut to fight infection.

"We found relatively few immune cells with this marker in the blood of patients with Covid-19. This could be because of the "dilution" by cells generated at other sites of infection, most probably the lung, or alternatively by the selective attraction of these gut-imprinted immune cells to organs other than the gut, since there was no difference between patients with and without symptoms that suggested an intestinal element to their infection," explained lead author Tanja Muller, from the varsity.

The researchers speculate that if the gut-imprinted immune cells are diluted in comparison to immune cells triggered by other parts of the body, there could be implications for the oral-based Covid-19 vaccines currently under development.