Response to Comment on "The Origins of Sexually Transmitted HIV Among Men Who Have Sex with Men".

In this investigation, we evaluated explanations for the unusual degree of genetic diversity in HIV populations within the sampled seminal cell and plasma compartments observed in our previous study. These analyses included clonal sequencing of HIV DNA in peripheral blood mononuclear cells, ultradeep sequencing of HIV RNA in blood plasma, human leukocyte antigen (HLA) haplotyping of previously used samples, and a BLAST screen against both a local and public repository of HIV-1 sequences, and the investigations to determine whether these observations were secondary to contamination or artifact were unsuccessful. As there are very few HIV sequences from seminal cell tissues and transmission pairs described in the literature, future studies that evaluate more transmission pairs with sampling from multiple anatomic compartments and at multiple time points will most likely be required to resolve this controversy.