Heterogeneity and Hierarchy of Immune Response to Primary Immunization in HIV-Infected Children on HAART and the Impact of an Additional Dose of Vaccine

The nature of vaccine response inferiority is not well studied in children living with HIV (CLHIV). The authors investigated Hepatitis B Virus (HBV) and Diphtheria/Pertussis/Tetanus toxoid (DPT) vaccination responses following primary immunization in CLHIV (n = 42) and healthy controls (HC) (n = 38) and the effect of an additional vaccine dose. Antibody responses, CD4 and HBV-specific T/B cells were analysed using CMIA/ELISA and flow-cytometry. CLHIV had significantly lower baseline median antibody titres for all vaccines than HC (p <0.02). Differential seroprotection rates observed in CLHIV were, 4.8% for pertussis; 9.5% for HBV; 26.2% for diphtheria and 66.7% for tetanus. WHO staging significantly influenced anti-HBs levels (p = 0.0095). HBsAg-specific CD4+T-cells were significantly higher in CLHIV than HC (p = 0.042). An additional vaccine dose (HBV and Tdap) conferred a higher protection rate for tetanus and diphtheria (p <0.040) in CLHIV. These findings suggest that CLHIV exhibit a hierarchy of vaccine responses affecting antibody levels and protection rate, which was rescued by administering additional vaccine dose.