Chlamydia trachomatis is the most commonly reported sexually transmitted infection (STI) in Canada. In BC alone, there were 7000 cases reported in 2003. Although antibiotic treatment is effective, more than half of all infections escape detection and timely treatment because they are asymptomatic in the early stages. Left untreated, the infection can lead to chronic pain and infertility. The development of an effective vaccine to prevent C. trachomatis infection is an urgent public health priority. No vaccine has been developed for C. trachomatis since an inactivated whole cell vaccine failed in trials in the 1960s. In order to better understand how the immune system responds to the bacteria and to develop candidate vaccine preparations, Dr. Michelle Zaharik is using cutting edge immunological and gene array technologies to probe how the immune system responds to C. trachomatis. She is looking particularly at dendritic cells (DCs) which play a role in activating the immune system to mount a defence against invading pathogens and are the subject of intense interest for vaccine development. Michelle’s study will identify the specific DC responses necessary to develop protective immunity against C. trachomatis. Ultimately, this may contribute to the development of vaccines specifically targeted to preventing chlamydial infections.