The Impact of Helminthic Infection on the Efficacy of the Bacille Calmette-Guérin (BCG) Vaccine Against Pulmonary Tuberculosis Sadie Forrester Department of Biological Sciences, York College of Pennsylvania PROJECT SUMMARY The efficacy of bacille Calmette-Guérin (BCG), the only vaccine prescribed against tuberculosis, varies from 0% to 80%. That variability has not been explained, although low protection characterizes regions endemic for helminths. This proposal intends to test the impact of helminthic infection on BCG efficacy through a two-phase study. Rhesus monkeys in phase one will be infected with the helminth Schistosoma mansoni before or after BCG vaccination, and subsequently challenged with Mycobacterium tuberculosis. If clinical assessments, cellular proliferation analyses, cytokine assays, bacterial counts, and pathologic examinations indicate that helminthic infection reduces efficacy, phase two will be conducted. Monkeys in phase two will be infected with S. mansoni and treated with the antihelminthic drug praziquantel before or after BCG vaccination, followed by exposure to M. tuberculosis. Should pretreatment with praziquantel appear to improve immune responsiveness to BCG, administering antihelminthics before vaccination may be a cost-effective way to protect worm-burdened peoples from tuberculosis. INTRODUCTION  Bacille Calmette-Guérin (BCG) is the only vaccine administered against tuberculosis.  Cases of pulmonary tuberculosis infection continue to rise in developing countries because the vaccine’s efficacy is highly variable.  The reason for the variability is not understood.  Examination of the impact of helminthic infections, which are common in areas where efficacy is low, has largely been overlooked.  Helminthic infections may reduce the efficacy of the BCG vaccine because they alter the underlying immune profile.  The proposed study will determine whether the helminthic infection Schistosoma mansoni alters the underlying immune profile of rhesus monkeys and whether that shift in turn reduces the efficacy of the BCG vaccine.  The study will also test the ability of the antihelminthic drug praziquantel to restore the immune profile and improve the efficacy of the BCG vaccine upon eradication of helminthic infection. GroupPrimary Treatment Secondary a Treatment ISaline-- IIS. mansoni-- IIIBCG-- IVS. mansoniBCG V S. mansoni GroupPrimary Treatment Secondary Treatment Tertiary a Treatment VIPraziquantelS. mansoni-- VIIS. mansoniPraziquantel-- VIIIBCGPraziquantel-- IXPraziquantelBCG-- XS. mansoniBCGPraziquantel XIS. mansoniPraziquantelBCG  Clinical assessments will be conducted daily to monitor for signs of tuberculosis such as coughing  Cellular proliferation analysis will be executed regularly to measure the response to tuberculin PPD  Trap ELISA and flow cytometry will detect cytokine levels in regularly collected unstimulated venous blood samples  Pathologic examinations upon sacrifice will verify S. mansoni and tuberculosis infections  Bacterial counts from lung tissue samples will indicate the intensity of tuberculosis infections OBJECTIVES  To conduct a controlled study that characterizes the effect of schistosomiasis on the cytokine profile of the immune system  To determine how the efficacy of the BCG vaccine is impacted by an altered immune response  To test whether antihelminthic treatment is able to restore the immune response and improve the efficacy of the BCG vaccine against challenge RESEARCH DESIGN AND METHODS Acknowledgements: Carolyn Mathur, PhD, YCP Research Mentor Deborah Ricker, PhD EXPECTED RESULTS  A prominent Th2 immune profile in monkeys with schistosomiasis  Reduced cellular proliferation in monkeys with schistosomiasis at the time of BCG vaccination  Increased cellular proliferation and a restored Th1 immune profile in S. mansoni-infected monkeys treated with praziquantel prior to vaccination (Figure 3)  Vaccinated monkeys never infected with S. mansoni or that were infected but received praziquantel prior to vaccination will be more resistant to challenge with M. tuberculosis REVIEW OF LITERATURE  The immune system is dominated by one of two divergent responses during the course of an infection.  One response is primarily cell-mediated and is induced by T helper type 1 (Th1) cytokines.  The other is primarily humoral and is induced by T helper type 2 (Th2) cytokines (Gallagher 1997).  Ethiopian immigrants to Israel with helminthic infections had highly activated immune systems characterized by a Th2 cytokine profile (Borkow et al. 2000) (Figure 1).  The Th1 response to tetanus toxoid is suppressed in humans with schistosomiasis (Sabin et al. 1996).  A short-term study revealed that humans treated with antihelminthics before BCG vaccination had elevated in vitro responses compared to vaccinated individuals infected with helminths (Elias et al. 2001) (Figure 2). Table 1. Phase I summary protocol Table 2. Phase II summary protocol LITERATURE CITED Bentwich, Z., Kalinkovich, A., Weisman, Z., Borkow, G., Beyers, N. and Beyers, A.D Can eradication of helminthic infections change the face of AIDS and tuberculosis? Trends in Immunology Today 20: Borkow, G., Leng, Q., Weisman, Z., Stein, M., Galai, N., Kalinkovich, A. and Bentwich, Z Chronic immune activation associated with intestinal helminth infections results in impaired signal transduction and anergy. Journal of Clinical Investigation [serial online] 106: Available from: HighWire Press. Elias, D., Wolday, D., Akuffo, H., Petros, B., Bronner, U. and Britton, S Effect of deworming on human T cell responses to mycobacterial antigens in helminth-exposed individuals before and after bacille Calmette-Guérin (BCG) vaccination. Clinical and Experimental Immunology 123: Gallagher, R Tagging T cells Th1 or Th2? Science 275: Sabin, E.A., Araujo, M.I., Carvalho, E.M. and Pearce, E.J Impairment of tetanus toxoid-specific Th1-like immune responses in humans infected with Schistosoma mansoni. Journal of Infectious Diseases 173: a Three of the six monkeys in each group will be challenged with M. tuberculosis after tertiary treatments. IL-2 IFN-γ Helminths Cytokine network Th2 cytokines Th1 cytokines Figure 1. Figure 2. Figure 2. Proliferative responses (a) and IFN-γ secretion (b) to mycobacterial antigen in humans treated with antihelminthics prior to vaccination with BCG. Peripheral blood mononuclear cells (PBMC) obtained 8 weeks after the first dose of placebo ( ) or antihelminthic ( ) were stimulated with phytohaemagglutinin (PHA) or tuberculin purified protein derivative (PPD). Data are means + s.e.m. *P<0.001 **P<0.05 (Reproduced from Elias et al. 2001). (a)(b) * ** Figure 3. Expected proliferative response to PPD in S. mansoni infected (S) and praziquantel treated (P) groups before and after BCG vaccination (+BCG). Unstimulated PBMC will be analyzed 1 week before ( ) and 8 weeks after ( ) vaccination. Data are means (Adapted from Elias et al. 2001). Figure 3. a Three of the six monkeys in each group will be challenged with M. tuberculosis after secondary treatments Stimulation index PHA PPD IFN- γ (pg/ml) PHA PPD Figure 1. The shift of the immune system towards a Th2 cytokine profile as a result of helminthic infection (Adapted from Bentwich et al. 1999). S S+BCG P P+BCG IL-4 IL-10 Stimulation index