Summary / Abstract I am applying for a K24 award with the goals of expanding the scope of two NIH-funded research studies in Botswana and creating a combined dataset to maximally utilize existing data and specimens from clinical cohorts. In the past 18 years, I have built a successful research program in Botswana with a focus on the prevention of mother-to-child HIV transmission (PMTCT), understanding adverse birth outcomes among infants exposed to antiretrovirals in utero, and improving survival among HIV-infected and HIV-exposed children. I have successfully mentored or co-mentored over 30 young investigators in my career, but through a K24 mechanism I can improve my mentoring expertise and expand opportunities for mentees. My K24-supported research will have the following aims: 1) to expand analyses of the virologic and immunologic predictors of successful outcomes following use of a broadly neutralizing monoclonal antibody as an ART-sparing intervention in a cohort of early-treated HIV-infected children; 2) to expand the objectives of existing NIH- funded nationwide birth surveillance in Botswana by adding first-ever birth outcomes surveillance of Dolutegravir-exposed infants and marginal structural modeling to simulate a clinical trial comparing birth outcomes by ART regimens used in pregnancy; and 3) to combine data from 6 large research cohorts to evaluate the reasons for declining mortality among HIV-exposed uninfected children in Botswana. My training plan will specifically expand my expertise in maternal-fetal medicine, and my mentoring plan will involve a team approach in Boston and Botswana to efficiently utilize opportunities within both large clinical trials and existing datasets and specimens.