A Tat/Rev Induced Limiting Dilution Assay to Measure Viral Reservoirs in Non-Human Primate Models of HIV Infection.

The establishment of latent infection and poorly characterized viral reservoirs in tissues represent major obstacles to a definitive cure for HIV. Non-human primate (NHP) models of HIV infection are critical to elucidate pathogenic processes and an essential tool to test novel therapeutic strategies. Thus, the availability of novel assays to measure residual viral replication and reservoirs in NHP models may increase their utility in the search for an HIV cure. We developed a tat/rev induced limiting dilution assay to measure the frequency of CD4+ T cells that express multiply-spliced(ms)_SIV RNA in presence and absence of stimulation. We validated the assay using cell lines and cells from blood and lymph nodes of SIV infected macaques. In vitro, SIV/SHIV TILDA detects only cells expressing viral proteins. In SIV/SHIV-infected macaques, CD4+ T cells that express msSIV/SHIV RNA (TILDA data) were detected also in the setting of very low/undetectable viremia. TILDA data were significantly higher after stimulation and correlated with plasma viral load (pVL). Interestingly, TILDA data from early cART initiation correlated with peak and AUC pVL post-cART interruption. In summary, we developed an assay that may be useful in characterizing viral reservoirs and determining the effect of HIV interventions in NHP models.

A novel sorting technology allows for highly efficient selection of sperm without chromatin damage.

Sperm chromatin damage has been associated with male infertility, increased risk for spontaneous abortion, and poor embryo development. Available methods for detecting chromatin damage render the sperm no longer suitable for clinical use. Early apoptotic events resulting in chromatin damage are associated with increased permeability of the cell membrane to large ions. We propose the use of a large fluorescent organic cation, proprietary fluorochrome (PF-1), for fluorescence-activated cell sorting (FACS) for negative selection of sperm without chromatin damage. Sperm with chromatin damage are PF-1 positive. Performance of cell sorting by PF-1 was verified with terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) after FACS on PF-1(+) and PF-1(-) subpopulations. Whereas 19.5% of PF-1 positive sperm were TUNEL positive only 1.5% sperm in the PF-1(-) fraction were TUNEL positive (p < 0.00001). TUNEL values below 1.9% were considered background fluorescence. Post-sorting motility and vitality were 49.4% (SD: 12.5) and 65.0% (SD: 14.99), respectively. Proprietary fluorochrome activated sperm sorting may decrease or most likely eliminate all of TUNEL positive sperm without adverse effects on viability, providing a new therapeutic avenue for men with a high percentage of TUNEL positive sperm. Further research is needed to determine if the reduction in TUNEL positive sperm using PF-1 will improve in vitro fertilization (IVF) outcomes.

Flow cytometric characterization of apoptosis and chromatin damage in spermatozoa.

Apoptosis has been implicated in sperm chromatin damage; it is unclear whether apoptosis occurs through cytoplasmic or mitochondrial pathways. Sperm has minimal volume of cytoplasm but prominent mitochondria. Propidium iodide (PI), annexin V (AV), DiIC1(5) and proprietary fluorochrome (PF-1) were used to investigate apoptosis activation in human sperm using multichannel flow cytometry. There was a time-dependent increase in staining of spermatozoa with both AV and PF-1 and decrease in mitochondrial staining with DiIC1(5). These results strongly suggest that the drop in mitochondrial potential precedes changes in membrane phospholipids, and thus suggest apoptotic activation through mitochondrial pathway in human spermatozoa.