Perturbations in spike specific peripheral T follicular helper cells in
SARS-CoV2 breakthrough convalescent individuals immunized by BBV152
vaccine.
Abstract
SARS-CoV2 infection has caused an increase in mortality and morbidity
but with vaccination, the disease severity has significantly reduced.
But with emergence of various variants of concerns (VOCs), the vaccine
breakthrough infection has also increased. Here, we studied circulating
spike specific T follicular response (cTfh) in infection naïve vaccinees
and convalescent vaccinees (individuals who got delta breakthrough
infection after 2 doses of BBV152 vaccine) to understand their response
as they are the most crucial cells that are involve in vaccine mediated
protection by helping in B-cell maturation. Our results indicated that
cTfh cells in both the groups recognized wild type and delta spike
protein but memory response to wild type spike was superior in infection
naïve than in convalescent group. The cytokine response particularly
IL-21 from cTfh cells was also higher in infection naïve than
convalescent vaccines indicating a dampened cTfh response in
convalescent vaccines after breakthrough infection. Also, there was
positive correlation between IL-21 from cTfh cells and neutralizing
antibodies of infection naïve vaccinees. Multiple cytokine analysis also
revealed higher inflammation in convalescent vaccinees. Our data
indicated necessity of third booster dose may be individual specific
depending in the steady state functional phenotype of immune cells.