This is a copy of the slides presented at the meeting but not formally written up for the volume.

One proposed approach to reduce the spread of HIV is to prevent transmission of the virus through the use of a topical microbicide. One microbicide strategy is a charge inhibition based approach using polyanionic compounds designed to interfere with the process of HIV-1 attachment to potential target cells. This strategy however, is predicated on further understanding the charge characteristics of whole virions and the relative contribution of viral and host-cell proteins to such charge. Electrokinetic methods (i.e. ζ-potential) provide information on the surface structure of biological cells without producing significant alteration of the cellular organization. Electrophoretic fingerprinting (EF) is obtained from 3D templates of the mean electrophoretic mobility (the raw data from which ζ-potential is calculated) of a given particle versus pH and solution conductivity at a fixed temperature. The EF thus represents a surface, described by isomobility lines, over all pertinent electrochemical conditions. These initial electrophoretic analyses have been performed using human CD4+ T cell lines. The cell lines are derived from human white blood cells which are the principle targets of the HIV-1 virus. Tissue culture work was carried out under Class II aseptic conditions. Cell types were maintained in RPMI growth medium supplemented with 10% heat inactivated foetal calf serum, 2mM glutamine, 100 i.u./ml penicillin and 100 μg/ml streptomycin at 37°C in a humidified 5% CO2 incubator. The cells were routinely passaged every 3-4 days in 75 cm3 fillter cap tissue culture flasks, by the addition of 4 mls of cells to 16 mls of fresh growth medium.Electrophoretic mobility (ζ-potential) was measured as a function of pH and ionic strength over a range chosen to cover that known for fluids found in the lower female reproductive tract, including vaginal fluid and semen. Measurements were made using a Malvern ZetaSizer NanoZS operating in the fast field reversal mode (PALS). Data was analyzed using SURFER™ software and the results validated from the covariance matrix of the linear fit. Challenges in the measurement and characterization of the cells include the difficulty of the cell preparation, cleanliness of the samples and sample handling required to maintain cell vitality.Overall, the EF’s analyzed under environments characteristic of physiological conditions for each CD4 T cell line resulted in similar zwitterionic surface charge features. These results suggest that the best candidate for a microbicide active needs, itself, to be zwitterionic so as to be able to mirror-image the shift in sign of surface charge as the pH of the vaginal tract changes. Current results suggest that HIV interaction with target cells is enhanced by physiological fluids. The data provides core information on the physico-chemical properties of model cellular targets for HIV-1 infection and pave the way for rational development of charge-based intervention strategies.