Determinants of innate immune responses to mycobacteria

Innate cells such as macrophages, monocytes, myeloid dendritic cells and granulocytes recognise mycobacteria and initiate immune responses such as phagocytosis, cytokine production and expression of maturation markers. The type and magnitude of innate responses to mycobacteria may determine the subsequent adaptive responses generated. Our aims were to determine maturational changes in innate immune responses to mycobacteria over the first 9 months of life, and to assess effects of genetic variations in toll-like receptors on host responses to mycobacteria. This knowledge is important for designing rational strategies for vaccination against tuberculosis. We collected blood from newborns, 10and 36-week old infants, and adults. We stimulated blood with mycobacteria for 6 hours and determined expression of intracellular cytokines, or for 18-20 hours and determined expression of maturation markers and secretion of cytokines in supernatants. Different innate cell subsets were identified through expression of specific surface markers expressed on these cells. The toll-like receptor 6 coding region was sequenced to identify polymorphisms occurring in this gene in our local population, and associate these with host responses to mycobacteria. We showed that pro-inflammatory cytokine production and co-stimulatory molecule expression increased over the first 9 months of life, while antiinflammatory cytokine production did not change. We described a novel tolllike receptor 6 polymorphism, and demonstrated an association between tolllike receptor 6 variations and responsiveness to mycobacteria. These findings suggest that immaturity of innate immune cells may result in sub-optimal immune responses to vaccination against tuberculosis at birth. These results also suggest that genetic variations between individuals should be considered when designing vaccination strategies to control tuberculosis. Un ive rsi ty of Ca pe To wn II Acknowledgements I would like to thank everyone who supported me academically, financially, emotionally and socially throughout my studies. Without your support, I would not have accomplished this mission. I apologise I may not be able to list every single individual who contributed to the success of this work. 1. I would like to thank my supervisor Prof Willem Hanekom for giving me the opportunity to pursue my postgraduate studies at the South African Tuberculosis Vaccine Initiative (SATVI) and for his excellent mentorship and support academically, financially and otherwise. His willingness to share his vast knowledge of TB immunology/vaccinology with me and his encouragement and emphasis on teamwork made me a mature scientist that I am today. The vast knowledge I gained from him and his guidance will continue to influence my career and future endeavours. Thank you boss! 2. I would like to thank my co-supervisors Dr Mark Bowmarker, Dr Elizabeth Smith and Dr Thomas Scrib . Despite the short time I spent with Dr Bowmarker and Dr Smith, I learned a lot from them. Special thanks go to Dr Scriba who guided me through my Ph.D work. He provided good advice, excellent ideas and stimulating discussions that helped me to go through my Ph.D work with relative ease. Baie Dankie! 3. I like to thank Prof Thomas Hawn and his laboratory team at the University of Washington School of Medicine, for accepting me in the laboratory and enriching me with a lot of immunogenetics knowledge. 4. I would like to thank the SATVI team in Cape Town and Worcester for their excellent support throughout my studies. I cannot name all but special thanks go to Dr Brian Abel, Dr Benjamin Kagina, Lesedi Lerumo, Asley Veldsman, Jane Hughes, Sarojini Pillay, the technical team in Worcester headed by Marwou de Kock, and the phlebotomy team including Charlene Barnard, Deborah Abrahams, Lynette Stone, Michele van Rooyen and Terrence O’rie who enrolled the participants and collected blood from them. Un ive rsi ty of Ca pe To wn III 5. I would like to thank all the participants in the study including mothers, infants, and adult volunteers. Without them, this project would not have been completed. 6. I would like to thank my family and friends for the financial and moral support. Special thanks go to my parents who, despite the fact that they never saw the four walls of a classroom, still supported me, and my siblings, to get a good education. Even though my dad could not live to see this day, he will always remain in my thoughts. I am also grateful to my brother Dr Charles Wiysonge for the financial support throughout my studies. Without you, I would not have accomplished this work. Merci Beaucoup! I also like to thank my beautiful wife Eunice Kinyuy, and gorgeous daughter, Burinyuy Eillis Nabia, for their constant support and motivation to complete this work. 7. Special thanks to the following funders who provided funding to enable successful completion of this work: SATVI, South African Tuberculosis and AIDS Training (SATBAT), National Research Foundation (NRF), Carnegie Corporation of New York, Marcus Rubin Postgraduate Scholarship, Twamley Postgraduate Bursary, and the University of Cape Town. 8. Last but not least, I would like to thank the almighty God for protecting me and giving me the strength to acquire this knowledge and to reach this point. Help and guide me to implement all I have learnt over the years to help and make the lives and health of people better. Un ive rsi ty of Ca pe To wn