MALDI Mass Spectrometry Imaging Reveals Heterogeneous Distribution of Tenofovir and Tenofovir Diphosphate in Colorectal Tissue of Subjects Receiving a Tenofovir-Containing Enema

Efforts to prevent human immunodeficiency virus (HIV) infection via pre-exposure prophylaxis (PrEP) include the development of anti-HIV drugs as microbicides for topical application to the mucosal sites of infection; however, although understanding the distribution profiles of these drugs in target mucosal tissues is of critical importance to guiding their optimization, data in this regard are largely lacking. With this in mind, we developed a matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) approach to visualize tenofovir (TFV), an HIV nucleotide analog reverse-transcriptase inhibitor under investigation for use as a topical microbicide, and its active metabolite TFV-diphosphate (TFV-DP) in colorectal biopsies obtained from healthy volunteers who received TFV-containing enemas. Application of MALDI MSI resulted in sufficient spatial resolution to visualize both TFV and TFV-DP and revealed heterogeneity in the distribution profiles of both analytes, including the presence of regions in which TFV and TFV-DP were undetectable, in colorectal tissue at two different time points and concentrations. Cell-specific staining for CD4 T and CD11c dendritic cells, which are important to the establishment of HIV infection, demonstrated that the TFV and TFV-DP distributions were independent of these cell types. MALDI MSI of endogenous lipids demonstrated that the heterogeneity observed for TFV and TFV-DP was not a function of tissue composition or processing. These data provide unique insight into the spatial distribution of TFV and TFV-DP in human colorectal tissue. In addition, this work establishes an approach that can be leveraged to directly detect and visualize these clinically important analytes more broadly in tissue.