EP_056. T-cell response induced by the Pfizer-BioNTech COVID-19 vaccine after primary immunization in Malaysia

Shuwahida Shuib¹, Chong Zhuo Lin², Nurul Najwa Ainaa Alias¹, Azwin Farhin Yaakob¹, Mastura Mat Sani¹, Nurain Nadiah Jaafar¹, Najwa Syahirah Roslan¹, Siti Fatimah Abdullah¹, Masita Arip^3*

1. Autoimmune Unit, Allergy and Immunology Research Centre, Institute for Medical Research, National Institutes of Health, Ministry of Health Malaysia, 40170 Shah Alam, Malaysia

2. Centre for Communicable Disease Epidemiology Research, Institute for Public Health, National Institutes of Health, Ministry of Health Malaysia,40170 Shah Alam, Malaysia

3. Allergy and Immunology Research Centre, Institute for Medical Research, National Institutes of Health, Ministry of Health Malaysia, 40170 Shah Alam, Malaysia

*Corresponding author: Masita Arip. This email address is being protected from spambots. You need JavaScript enabled to view it.

ABSTRACT

INTRODUCTION: The COVID-19 pandemic has accelerated the development and evaluation of next-generation vaccines, including messenger ribonucleic acid (mRNA) platform technologies. Vaccination aims to protect against SARS-CoV-2 infection by eliciting antibodies and T-cell-mediated immunity. While extensive research has predominantly focused on antibody-mediated immunity, a comprehensive understanding of T-cell immunity remains imperative. T-cells play a central role in identifying and eliminating infected cells, establishing durable immune memory and contributing to robust cellular immunity.

OBJECTIVE(S): This study attempted to assess the T-cell response among Pfizer-BioNTech vaccine recipients in Malaysia after completion of the primary dose.

MATERIALS & METHODS: Blood samples were collected before receiving the first dose (T0), 21 days after the first dose (T1) and 14 days after the second dose (completed dose) (T2). We employed the enzyme-linked immunospot (ELISpot) assay to assess the T-cell response in a cohort of 22 healthy subjects. The ELISpot assay enables the detection of individual T cells that secrete interferon gamma (IFN-γ), allowing analysis of immune responses at the single-cell level. Peripheral blood mononuclear cells (PBMCs) were isolated, cryopreserved and subsequently stimulated with SARS-CoV-2 peptides. The secretion of IFN-γ from primed T-cells was quantified as spot-forming units (SFU) per 10⁶ PBMCs using the EliSpot plate reader.

 RESULTS: Findings showed that T-cell responses were undetectable above the positivity threshold of 33 SFU per 10⁶ PBMCs at T0. However, a significant increase (p < 0.001) in T-cell reactivity was observed at both T1 and T2, with median (interquartile range, IQR) values of 246 (149) and 550 (386), respectively.

CONCLUSION: These results indicate that the Pfizer-BioNTech vaccine can elicit a robust T-cell response among the recipients. These findings highlight the importance of considering T-cell immunity, in addition to antibody-mediated immunity, when evaluating the efficacy of COVID-19 vaccines.

KEYWORDS: SARS-CoV-2, COVID-19 Vaccination, Cell-Mediated Immunity, ELISpot Assay