THE CYTOKINE RESPONSE TO BACILLE-CALMETTE-GUERIN VACCINATION IN SOUTH-INDIA

SETTING: Evaluation of immune response after BCG vaccination in a popu lation from South India where BCG vaccination was a failure. OBJECTIVE : TO study the cell-mediated immune responses (CMI) in vitro by assess ing skin test conversion, lymphocyte proliferation and cytokine patter ns before and after BCG vaccination in 20 Mantoux negative subjects, a nd to compare this with that of 20 naturally Mantoux positive subjects . DESIGN: In vitro lymphocyte proliferation and cytokine responses to various mycobacterial antigens were studied in 12 subjects from each g roup. The cytokines interferon gamma (IFN-gamma), interleukin (IL)-4 a nd IL-10 were measured by both reverse transcriptase polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assay (ELISA). RESUL TS: All Of those who were initially Mantoux negative but one subject c onverted to positivity following vaccination, confirming that BCG vacc ination does cause skin test conversion. However, in vitro proliferati ve responses to phytohaemagglutinin (PHA), purified protein derivative (PPD) and Mycobacterium tuberculosis remained largely unaltered by va ccination. The production of IFN-gamma was significantly higher in PPD -positive individuals compared to the PPD-negative group, and BCG vacc ination of the latter did not change the levels of IFN-gamma, IL-4 or IL-10. CONCLUSIONS: The finding that PPD-negative individuals did not produce IFN-gamma even following vaccination and skin test conversion suggests that BCG had little effect in driving the immune response tow ards a protective Th1 type.