The pathogenic Neisseria, Neisseria meningitidis and Neisseria gonorrhoeae, are closely related bacteria that cause a significant burden of disease worldwide. N. meningitidis asymptomatically colonizes the human nasopharynx of up to 20% of the population but can cause severe invasive disease including meningococcal sepsis and meningitis. There are estimated to be >82 million N. gonorrhoeae infections per year worldwide, which if left untreated can cause adverse pregnancy outcomes, infertility and increased HIV transmission. Control of gonorrhoea is becoming increasingly difficult due to widespread antibiotic resistance. While vaccines are routinely used for N. meningitidis, no vaccine is available for N. gonorrhoeae. My research has focused on understanding how these bacteria infect and adapt to their human host, with an aim to exploit this knowledge for vaccine development.