New York – A lower supply of a certain type of immune cell in older people that is critical to fighting foreign invaders may help explain their vulnerability to severe Covid-19, scientists say.
When germs enter the body, the initial “innate” immune response generates inflammation not specifically targeted at the bacteria or virus.
Within days, the more precise “adaptive” immune response starts generating antibodies against the invader along with T cells that either assist in antibody production or seek out and attack infected cells.
In a small study published on Wednesday in Cell, Covid-19 patients with milder disease had better adaptive immune responses and, in particular, stronger T-cell responses to the coronavirus.
People over the age of 65 were much more likely to have poor T cell responses and a poorly coordinated immune response in general, co-author Shane Crotty of the La Jolla Institute for Immunology said.
As we age, our supply of “naive” T cells shrinks, he explained. Put another way, we have fewer “inexperienced” T cells available to be activated to respond to a new invader.
“Ageing and scarcity of naive T cells may be linked risk factors for failure to generate a coordinated adaptive immune response, resulting in increased susceptibility to severe COVID-19,” the researchers said.
Meanwhile, an antiseptic nasal spray containing povidone-iodine may help curb transmission of the coronavirus, preliminary research suggests.
In test tube experiments, a team of ear, nose and throat doctors found that a povidone-iodine nasal spray inactivated the virus in as little as 15 seconds. The nasal spray they tested is typically used to disinfect the inside of the nose before surgery.
Formulations designed for use on skin are not safe in the nose, the researchers note. They reported on Thursday in JAMA Otolaryngology – Head and Neck Surgery that they now have their patients use the spray before intranasal procedures, to reduce the risk of virus transmission through the air via droplets and aerosol spread.
They also suggest instructing patients to perform nasal decontamination before coming to appointments, to “further decrease intranasal viral load and… prevent spread in waiting areas and other common areas”.
They caution, however, that routine use of povidone-iodine would not be safe for some people, including pregnant women and patients with thyroid conditions.
Larger clinical trials have not yet proved that viral transmission is curbed by intranasal povidone-iodine solutions, but “these studies are already underway,” the researchers said.