Evaluation of anti-SARS-CoV-2 RBD antibody response after booster dose of SpikoGen® in individuals with two previous doses of Sinopharm and its association with HLA-DR and -DQ alleles.

BACKGROUND: It has been demonstrated that COVID-19 vaccines confer significant protection, but temporal decay in the vaccine-induced antibodies has been reported; therefore, a third booster dose was considered. Human leukocyte antigen (HLA) class II molecules act as antigen presenting structures, play critical roles in the formation of an efficient antibody response. The current study aimed to evaluate the anti-receptor binding domain (RBD) antibody response after the booster dose of SpikoGen® vaccine in individuals with a history of Sinopharm primary vaccination series and its association with HLA-DQB1 and -DRB alleles.

METHODS: Whole blood samples were drawn from 95 eligible individuals before and three weeks after the booster dose of SpikoGen®. Quantitative measurement of anti-RBD IgG and qualitative assessment of anti-RBD IgA was performed using the ELISA method and HLA-DQB1 and -DRB loci were genotyped by low-resolution SSP-PCR method.

RESULTS: A significant increase was observed in the anti-RBD IgG antibodies after the booster dose of SpikoGen® (baseline: 1.82 ± 0.55 GMT, after: 2.28 ± 0.36 GMT)(P < 0.0001). The median fold change of anti-RBD IgG antibodies for DRB1*14 positive individuals (3.96 (1.47-31.75)) was significantly higher than DRB1*14 negative people (1.18 (1.08-1.34))(P = 0.008). In addition, the median fold change of anti-RBD IgG antibodies for DQB1*04 positive individuals (1.39 (1.21-3.43)) was higher than those which were DQB1*04 negative (1.18 (1.08-1.34)), however it was marginally significant (P = 0.060). The seroconversion incidence for anti-RBD IgA antibodies was 68.42 %.

CONCLUSION: In conclusion, our study showed that the booster dose of SpikoGen® can elicit a robust anti-RBD antibody response which was positively associated with DRB1*14 allele.