Evaluation of the Sars-Cov-2 immune response of a large group of UZ-Brussels staff after both infection and vaccination.

Project Details


Mid-December 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel zoonotic coronavirus, was discovered in Wuhan (China) and rapidly spread to the rest of the world. It particularly affects the respiratory system, generating Coronavirus disease
2019 (COVID-19) (Zhou P, et al. 2020, Nature). Despite appropriate personal protective
equipment (PPE), health care workers (HCW) are at high risk of infection as they work in close contact with COVID-19 patients. In the presence of symptoms suggestive of COVID-19, real-time PCR on nasopharyngeal swabs is considered as the gold standard for diagnosis of COVID-19. The sensitivity of that technique is however not 100% (Yang Y, et al. 2020, Innovation). Detection of antibodies against SARS-CoV-2 has been proposed as a diagnostic test for patients suspected of COVID-19 in whom no respiratory sample was taken at the time of acute illness (Li Z, et al. 2020, J Med Virol). Fortunately, several SARS-CoV-2 vaccines have recently been developed. In Belgium, vaccination campaign was initiated at the beginning of 2021.

While the strongest correlate of protection against most viral infections, including SARS-CoV-
2, is the robust and long-lasting establishment of strongly, neutralizing antibodies, produced by plasma cells, T cells are indispensable for several reasons. First, B-cell memory, as well as antibody affinity (affinity maturation) and functionality (isotype), is highly dependent on functional T follicular helper (Tfh) cells present in the lymph node follicles. Thus, a disbalance in T helper cell phenotypes towards Th2 or Th17 or a defect in Tfh cells, has been associated with poor prognosis (Kaneko, et al. 2020, Cell). Second, whereas neutralizing Abs are important to block infection and to transmit immune signals via Fc receptor signals, cytotoxic T cells are important to clear virally infected cells, especially when type I interferon signaling is hampered, as is the case in SARS-CoV-2 infection. Third, it is becoming more and more clear that T-cell memory exceeds B-cell memory in a natural SARS-CoV-2 infection (Reynolds, et al. 2020, Sci Immunol; Bonifacius, et al. 2021, Immunity). Finally, several studies report T-cell responses against SARS-CoV-2 in PCR negative individuals, probably cross-reacting because of previous infections with other coronaviruses, whereas this is not the case for antibody responses (Le Bert, et al. 2021, J Exp Med). This begs the question whether this might also be the case in vaccinated individuals, where both robust B-cell and T-cell responses have been measured, and which type of vaccine offers the longest protection.
Effective start/end date15/06/2131/12/22

Flemish discipline codes

  • Vaccinology