Repetitive mRNA vaccination is required to improve the quality of broad-spectrum anti-SARS-CoV-2 antibodies in the absence of CXCL13.

Since the initial spread of severe acute respiratory syndrome coronavirus 2 infection, several viral variants have emerged and represent a major challenge for immune control, particularly in the context of vaccination. We evaluated the quantity, quality, and persistence of immunoglobulin G (IgG) and IgA in individuals who received two or three doses of messenger RNA (mRNA) vaccines, compared with previously infected vaccinated individuals. We show that three doses of mRNA vaccine were required to match the humoral responses of preinfected vaccinees.

Post-acute sequelae of COVID-19 is characterized by diminished peripheral CD8β7 integrin T cells and anti-SARS-CoV-2 IgA response.

Several millions of individuals are estimated to develop post-acute sequelae SARS-CoV-2 condition (PASC) that persists for months after infection. Here we evaluate the immune response in convalescent individuals with PASC compared to convalescent asymptomatic and uninfected participants, six months following their COVID-19 diagnosis. Both convalescent asymptomatic and PASC cases are characterised by higher CD8 T cell percentages, however, the proportion of blood CD8 T cells expressing the mucosal homing receptor β7 is low in PASC patients.

Low quantity and quality of anti-spike humoral response is linked to CD4 T-cell apoptosis in COVID-19 patients.

In addition to an inflammatory reaction, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)-infected patients present lymphopenia, which we recently reported as being related to abnormal programmed cell death. As an efficient humoral response requires CD4 T-cell help, we hypothesized that the propensity of CD4 T cells to die may impact the quantity and quality of the humoral response in acutely infected individuals. In addition to specific immunoglobulins (Ig)A, IgM, and IgG against SARS-CoV-2 nucleocapsid (N), membrane (M), and spike (S1) proteins, we assessed the quality of IgG response by measuring the avidity index.