Circulating CTLA-4 Level and CTLA-4 rs733618 Gene Polymorphism Role in Immunological Response to Pfizer BioNTech (BNT162b2) COVID-19 Vaccine in Iraq

Background and Aim: Immune response to BNT162b2 COVID-19 vaccine among people is not the same. Genetic polymorphism in inhibitory immune checkpoints may have an important role in immune response after vaccination; therefore, we aimed to demonstrate the role of CTLA-4 rs733618 gene polymorphism and the amount of circulating CTLA-4 in individuals vaccinated with the BNT162b2 vaccine following the booster dose. Materials and Methods: This research is a cross-sectional study performed on 180 healthy adults (above 18 years old) vaccinated with the BNT162b2 COVID-19 vaccine 21-30 days after the second dose at the community dwelling from December 2021 to April 2022. After DNA extraction from the sample’s blood, Allele-specific polymerase chain reaction (ASPCR) was developed to detect single nucleotide polymorphisms of CTLA-4 rs733618. The levels of IgG in the serum, which are directed towards the spike protein-1 and soluble CTLA-4, were quantified using an Enzyme-linked Immunosorbent Assay (ELISA). Results: The current study showed no significant association in CTLA-4 rs733618 genotype distribution and immune response to the BNT162b2 vaccine, Furthermore, there was a highly significant difference between CTLA-4 serum levels and CTLA-4 rs733618 genotype frequency. Conclusion: CTLA-4 -1722 T/C rs733618 is not significantly related to immunological response to the BNT162b2 vaccine. The level of s-CTLA-4 production may be affected by CTLA-4rs733618 polymorphism. rs733618 (T/C) and rs733618(C/C) genotypes significantly related with high level of s-CTLA-4, while rs733618 T/T genotype related with low level of s-CTLA-4.