More on what the total adaptive immune system response to coronavirus looks like. (Nat. Med. Study) These researchers used 41 Australian patients with mild or moderate illness and 27 healthy controls. The healthy controls were tested for potential cross-reactivity antibodies from seasonal coronavirus and the 5 with the lowest and highest response were selected as ultimate controls. Antibody and B cell and T cell responses were studied, with the usual findings of a fairly robust response somewhat correlated with disease severity. The focus was on the presence of adaptive immune activity in blood, and I increasingly wonder if more research shouldn’t be done in peripheral tissues, where the virus actually attacks first.
And yet another publication on the role of T cells. (Science Article) The researchers studied the T cell response of ten patients who had acute respiratory distress syndrome. Helper T cells were found in all and killer T cells in 8. There were also healthy controls who showed some potential cross-reactivity. Now we are really getting in the weeds, but the sub-type of the helper T cells was a class referred to as central memory ones, which have high migratory capability and rapid proliferation capacity. That is good. The T killer cells also showed characteristics of being strong producers of chemicals that kill infected cells.
Yet another article by pediatricians about the limited role of children in the epidemic. (Ped. Article) (Ped. Study) The study comes from Geneva and described the experience of one large hospital system with coronavirus and children. Out of 4310 patients, 40 were under 16. The researchers traced their family and household contacts and dynamics. There were 111 total household contacts. Adults were confirmed or suspected with coronavirus infection before the child in 79% of the cases. In only 8% did the child develop symptoms before any adult member. 85% of adults in the households developed symptoms at some point compared to only 43% of children. Almost all the cases in children were mild and all resolved within 7 days.
And a comparison of Finland and Sweden in regard to schools and children. (Scand. Article) Finland closed schools, Sweden left them open for children up to age 15 initially and then for all. The researchers looked at case rates and found no difference between the two countries for these age groups (although at ages up to 15, Finland appeared to have a higher rate and for 16 to 19, Sweden did), although Sweden had a higher rate overall. and found that serious illness was very rare. Contact tracing in Finland found very little transmission in children. A Swedish analysis found no increased risk for teachers.
Yet more on antibody development to coronavirus. (Medrxiv Paper) This group was examining responses in mild and asymptomatic individuals, using 63 healthy people, 63 asymptomatic ones and 51 mild disease patients, all from China. In general, they found antibody response in most of the mild and asymptomatic patients, of varying types and levels, with stronger responses in those with mild disease. The asymptomatic patients diminished to below detectable levels in two months. Note the issue with sensitivity of assays to detect low levels and also, don’t forget the T cells. Ahh, but here is the real interesting finding, a number of the health contacts also had antibody responses to several of this coronavirus strain’s proteins.
Once more on the antibody response, in mild and severe patients. (Medrxiv Paper) This study focused on mild and severe patients’ development of antibodies. There were 47 total subjects, 15 of whom had severe disease. All but three of the patients with mild disease developed measurable antibodies by one test, but these three all had neutralizing antibodies by another one. These antibodies showed up much faster in patients with severe versus mild disease.
I think these studies cumulatively continue to show two things, one is that children are a low risk of getting infected and at even lower risk of being a transmitter of disease to others. The second is that everyone who has been infected likely develops an adaptive immune response to coronavirus, both from B cells, the producers of antibodies, and from T cells. But commercial assays aren’t sensitive to pick this up in people with asymptomatic or even mild illness.