Assessment of BCG vaccine immune response in a sample of Egyptian infants

Abstract

Background: In Egypt, tuberculosis (TB) is considered the third most important public health problem after schistosomiasis and hepatitis C. We sought to investigate the immune response induced by the currently used Bacillus Calmette-Guerin (BCG) vaccine in a sample of Egyptian infants . Methods: A cross sectional study comprising 25 healthy BCG vaccinated infants, 14-24 months old was carried out. They were 15 boys and 10 girls. These infants were subjected to clinical and laboratory evaluation including blood counts, tuberculin intradermal test and in-vitro assessment of T cell response to purified protein derivative (PPD) and phytohemagglutinin (PHA) stimulation with measurement of IFN-γ in the supernatant of cultured mononuclear cells using the AssayMax Human interferon-gamma (IFN-γ) ELISA Kit (Assaypro), USA. Results: Among enrolled infants, 76 % had BCG scar and 28% had positive tuberculin test. IFN γ levels after PPD stimulation (median (IQR): 0.13 (0.09-0.44) ng/ml) and after PHA stimulation (median (IQR): 1 (0.99-1) ng/ml) were significantly higher than basal levels (median (IQR): 0.08 (0.05-0.22) ng/ml), p= 0.001. Only five infants (20 %) had failed IFN γ response after PPD stimulation and these infants showed also lower PHA stimulated IFN γ response (z=-2.18, p=0.03), in comparison to those with PPD stimulated IFN γ response. BCG scar positive and negative groups were comparable in their immunological parameters. Infants with positive tuberculin test results (n=7) showed significantly higher IFN γ levels after PPD stimulation in comparison to the negative tuberculin group (n=18) (z=-2.09, p= 0.036). Conclusion: In this small cohort, it appears that the current BCG vaccination in Egypt results in an acceptable level of immune response. Absent BCG scar does not indicate failed immunization. Further longitudinal studies on a large number of infants are recommended to estimate the real clinical protection conferred by the currently used vaccine