British scientists must begin testing a treatment that is hoped to counter the effects of Covid-19 in the most seriously ill patients.
It has been found that those with the most severe form of the disease have an extremely low number of an immune cell called a T cell.
T cells clear the infection from the body.
The clinical trial will assess whether a drug called interleukin 7, which is known to increase the number of T cells, can help patients recover.
It involves scientists from the Francis Crick Institute, King’s College London and Guy’s and St Thomas ‘Hospital.
They examined the immune cells in the blood of 60 Covid-19 patients and found an apparent drop in the number of T cells.
Professor Adrian Hayday of the Crick Institute said it was a “big surprise” to see what was going on with the immune cells.
“They are trying to protect us, but the virus seems to be doing something that is pulling the rug under them, as their numbers have dropped considerably.
In one microliter (0.001 ml) of blood drop, normal healthy adults have between 2,000 and 4,000 T cells, also called T cells.
The Covid patients the team tested were between 200 and 1,200.
Researchers say these findings pave the way for developing a “fingerprint test” to check blood T-cell levels, which could provide early indications of people at risk of developing the disease worse.
But it also offers the possibility of a specific treatment to reverse this decline in immune cells.
Manu Shankar-Hari, an intensive care consultant at Guy’s and St Thomas ‘Hospital, said that about 70% of the patients he sees in intensive care with Covid-19 arrive with between 400 and 800 lymphocytes per microliter. “When they start to recover, their lymphocyte levels also start to go up,” he added.
Interleukin 7 has already been tested in a small group of patients and has been shown to safely increase the production of these specific cells.
In this trial, it will be given to patients with a low number of lymphocytes who have been in intensive care for more than three days.
Mr. Shankar-Hari said, “We hope that [when we increase the cell count] viral infections go away.
“As an intensive care doctor, I take care of patients who are extremely sick and, apart from supportive care, we have no direct active treatment for the disease.
“So a treatment like this coming in the context of a clinical trial is extremely encouraging for intensive care doctors across the UK. “
This research has also provided insight into the specific ways in which this disease interacts with the immune system, which Professor Hayday says will be vital as scientists around the world search for clinically valuable information.
“The virus that caused this earth-changing emergency is unique – it is different. It’s something unprecedented. “
“The exact reason for this disruption – the key to the work of the T-cell system – is not at all clear to us.
“This virus is really doing something distinct and future research – which we will start immediately – must find the mechanism by which this virus has these effects. “