Aaron Harris at APHA

The theme of American Public Health Association’s 136th annual meeting in San Diego, CA was ‘Public Health Without Borders’ and was a congregation of public health experts all over the world sharing their insights into global health.

I had the opportunity to present some of the results from my main project in Bangladesh, ‘Memory B cell responses in patients with dehydrating diarrhea caused by Vibrio cholerae O1.’ Bangladesh lies in the largest delta in the world, and is thus susceptible to severe flooding following the annual monsoons. While cholera is endemic in the country, cholera becomes epidemic during the flooding periods and a serious threat to public health in the region. The treatment for dehydrating diarrhea, which is responsible for the increased mortality during this time, is simple; oral rehydration solution, which is essentially a mixture of salts and sugars. We know from volunteer studies that infection with cholera elicits long-term immunity for at least three years. The best vaccine is a oral whole cell vaccine that provides protection for up to 2 years with about a 50% efficacy. The goal of my study was to search for markers that demonstrate evidence of protective immunity in patients infected with culture confirmed Vibrio cholerae. The results of the study showed that key cholera virulent factors, cholera toxin B subunit (CTB) and toxin co-regulated pilus (TcpA), give rise to both systemic and mucosal memory B cell responses that can be detected for at least one year following infection. We used a novel method to detect memory B cells that involved culture if peripheral blood mononuclear cells in vitro for 5-6 days followed by an ELISPOT assay to detect antibody secreting cells. This is the first study to describe evidence of immunity to a non-invasive pathogen such as cholera for up to one year, and may have important vaccine implications.