In the second study, scientists led by Tao Dong, an immunologist at the Medical Research Council
(MRC), in Britain, went hunting for T-cells. These get less press than antibodies, but play
an equally vital role in battling infections and securing long-term protection.
(Their importance is vividly demonstrated by HIV, which targets and kills them. ) As described in
Nature Immunology, the researchers compared blood samples from 28 mild
and 14 severely ill covid-19 patients, as well as 16 healthy donors. The paper describes a "robust"
T-cell response in infected people and, as with the Icelandic work,
different responses in those who developed mild and severe cases of the
illness. Specifically, mild cases were characterised by more CD8 cells, which kill infected cells
directly, rather than CD4 ones,
which regulate the immune response more generally. The MRC study found T-cells that could
recognise eight separate parts of the virus, including the spike protein that allows it
to penetrate human cells. That target list could offer useful hints for refining vaccines in future.
Al Edwards, an immunologist turned biochemical engineer at the University of Reading (who was
not involved with either paper), is cautiously optimistic. The immune response to the disease
seems to be working roughly as expected, he says.
If that continues, then vaccines developed to trigger long-lasting immunity should work-at least in
theory. In practice, it is still too early to celebrate. Dr Edwards warns that immunology has never
been a predictive science.
There is no test that can show definitively that a vaccine will work short of actually trying it in
the real world.