This version is largely dedicated to the ongoing research on immune response to coronavirus.
This paper is an updated version of one that appeared in May, with a larger group of patients. (Medrxiv Paper) It was one of the first pieces of research to identify pre-existing defenses against coronavirus. The revised version confirms the findings that persons uninfected with the current strain of coronavirus had antibodies against portions of it. The authors note that even people infected with the current strain may have had some level of antibodies against it that caused the infection to be asymptomatic or mild. They cautioned that prevalence surveys needed to take the pre-existing antibodies into account. And they also warned that the restrictive lockdowns of children in particular could be hindering development of seasonal coronavirus defenses.
Another study showing strong and sustained immune response to CV infection. (Medrxiv Paper) The study comes from China and the researchers looked for spike and nucleocapsid antibodies among around 350 patients. Since China had the first epidemic outbreak, they were able to study responses over a long period of time. Antibodies developed over the course of the disease. Certain types, more central to fighting acute infection, waned over time, but up to six months later there were strong responses from certain antibodies. Only two patients had anomalous antibody development, indicating that for almost everyone, there will be a strong and lasting immune response. The authors also found that the response was similar for symptomatic and asymptomatic people.
This piece of research comes from Japan and also studies immune response to CV. (Medrxiv Paper) In looking at 13 patients, they identified common antibody targets, which were in the spike protein (recall that spike is where the part of the virus used to get into a cell is located) but not in the actual receptor binding region of the spike.
This paper came from New York and similarly involved identifying B cell and antibody targets. (Medrxiv Paper) They examined 26 infected but not hospitalized patients and 21 persons who had not been exposed. They found broad memory B cell existence in the unexposed subjects and even if circulating antibody levels were low in infected persons, they also had applicable memory B cells, which are capable of producing antibodies quickly. 86% of the unexposed group had memory B cells against a portion of the spike protein.
So the big picture that continues to evolve is that infected patients are developing a strong immune response, that persists over time. This response consists of antibodies, memory B cells and T cells. In addition, many people, as a result of prior infection by other strains of coronavirus, have pre-existing and cross-reactive immune responses to the current strain, including via T cells and memory B cells.