This paper provides important information about the immune response to SARS-CoV-2. Three key findings. (1)
A. 'Circulating SARS-CoV-2-specific CD8+ and CD4+ T cells were identified in 70% and 100% of COVID-19 convalescent patients, respectively.' (2)
B. 'The M, spike, and N proteins each accounted for 11%–27% of the total CD4+ response.' This suggests vaccine candidates should not simply focus on the spike protein. (3)
C. They found reactive CD4+ T cells in 40%–60% of unexposed individuals from blood taken a year or more ago. This suggests crossreactive T cell recognition between circulating ‘‘common cold’’ coronaviruses and SARS-CoV-2. (4)
In regards to this last point, based on mouse models, they speculate that CD4+ T cells are of value in protective immunity. They also suggest 'the presence of cross-reactive T cells was found to correlate with less severe disease' in H1N1 flu(Sridhar, 2013; Wilkinson, 2012)(5)
'Any degree of cross-protective coronavirus immunity in the population could have a very substantial impact on the overall course of the pandemic, and the dynamics of the epidemiology for years to come' (Kissler et al., 2020). (6)
So just to provoke: could this cross-protective immunity be part of the 'dark matter' suggested by Karl Friston and implied by Sunetra Gupta? (7)
I have assumed that low antibody levels and a circulating virus means inevitable further outbreaks and a second winter surge. I'm sure we shall see outbreaks, as elsewhere, but do these cross-reactive T cells mean a second surge is less likely? Or is this over-speculation? (8)
