PERSISTENCE OF SPECIFIC IMMUNE RESPONSE AFTER HEPATITIS B VACCINATION IN EGYPT: RELATION TO HLA-DRB1 ALLELES AND SCHEDULE OF VACCINATION

Abstract

Background: Hepatitis B (HB) is one of the world's major health problems.HB vaccination is the most effective way to prevent transmission of hepatitis B virus (HBV).
Objective: Evaluation of persistence of each of humoral and cellular immunity against HBV after HB vaccination & studying some factors that affect persistence of immune response after HB vaccination including: Human Leukocyte antigens-DRB1 (HLA-DRB1) and Schedule of vaccination.
Methods: The study included three groups with different HB vaccination schedules with time since vaccination ranging from 6 to 16 years. They were investigated for their immunological memory. To evaluate humoral immunity the antibody to hepatitis B surface antigen (anti-HBs) titres were measured. Cellular immunity was determined by enzyme-linked immunosorbent spot assay (ELISpot) to detect HBV specific interferon (IFN)-gamma producing cells.
Results: 65% of participants who displayed unprotected anti-HBs titre were positive HBV specific interferon (IFN)-gamma producing cells and 90% of participants who displayed protective anti-HBs titre were also positive for IFN-gamma producing cells. The most prevalent HLA-DRB1 alleles in those with anti-HBs ≥10 milli-international units per milliliter (mIU/ml) were HLA-DRB1*15.
Conclusion: Primed immune cells to hepatitis B surface antigen (HBsAg) still exist for years even after loss of the protective anti-HBs titre.There is association between HLA-DRB1*15 allele with long term humoral memory to HB vaccine.
Key words: HBV, HB Vaccination, Humoral immunity, Cellular immunity, Human leukocyte antigen.
Abbreviations: Antibody to hepatitis B surface antigen (anti-HBs); Antibody to HB core antigen (anti-HBc); Bacillus Calmette - Guērin (BCG); 5-bromo-4-chloro-3-indolyl-phosphate/ nitroblue tetrazolium (BCIP/NBT); Diphtheria, tetanus, pertussis and oral polio(DTP-OPV); Enzyme-linked immunosorbent assay (ELISA);Enzyme-linked immunosorbent spot assay (ELISpot); Expanded Program of Immunization (EPI); Hepatitis B (HB); Hepatitis B surface antigen (HBsAg);Hepatitis B virus (HBV); Human Leukocyte antigens-DRB1 (HLA-DRB1); Interferon (IFN);Intracellular cytokine staining (ICS); Milli-international units per milliliter (mIU/ml); Peripheral blood mononuclear cells (PBMCs); Phosphate buffered saline (PBS); Phosphate buffered saline- Tween 20 (PBS-T); Phytohaemagglutinin (PHA); Polyvinylidene fluoride (PVDF); Spot forming units (SFCs); World health organization (WHO).