Imaging and tracking HIV viruses in human cervical mucus

Abstract. We describe a systematic approach to image, track, and quantify the movements of HIV viruses embedded in human cervical mucus. The underlying motivation for this study is that, in HIV-infected adults, women account for more than half of all new cases and most of these women acquire the infection through heterosexual contact. The endocervix is believed to be a susceptible site for HIV entry. Cervical mucus, which coats the endocervix, should play a protective role against the viruses. Thus, we developed a methodology to apply time-resolved confocal microscopy to examine the motion of HIV viruses that were added to samples of untreated cervical mucus. From the images, we identified the viruses, tracked them over time, and calculated changes of the statistical mean-squared displacement (MSD) of each virus. Approximately half of tracked viruses appear constrained while the others show mobility with MSDs that are proportional to an exponential model, over time range {tau}, depicting a combination of anomalous diffusion and flow-like behavior. The MSD data also reveal plateaus attributable to possible stalling of the viruses. Although a more extensive study is warranted, these results support the assumption of mucus being a barrier against the motion of these viruses.