HIV coreceptor and chemokine ligand gene expression in the male urethra and female cervix.

OBJECTIVE: Isolates with a tropism for the coreceptor CCR5 are the predominant viral strain transmitted following heterosexual transmission. We have investigated coreceptor expression levels within male and female genital epithelia to assess whether selective transmission can be explained by elevated CCR5 expression within the genital epithelia per se. DESIGN: Individuals attending a local genitourinary medicine unit were recruited, and samples of genital epithelia obtained using either a cytobrush (females) or urethral swab (males). Expression of coreceptor and cell marker mRNAs was then determined by reverse transcription (RT)-PCR. METHODS: RNA was recovered from the epithelial cell samples then used as templates in competitive quantitative RT-PCR to measure mRNA expression of key chemokines, coreceptors and cell-type markers in the epithelial cell samples. Cell-surface coreceptor expression was also assessed in a sample of patients using fluorescent cell staining. RESULTS: CXCR4 and CCR3 coreceptors were expressed at significantly higher levels than CCR5 within the female endo- and ectocervix and distal end of the male urethra. Increased levels of cell surface expressed CXCR4 compared to CCR5 was confirmed in samples obtained from the female genital tract by FACS analysis. CONCLUSIONS: The selective transmission of CCR5-tropic viral variants is unlikely to result simply from differential coreceptor abundance at the genital epithelia.

The effect of hematocrit and leukocyte adherence on flow direction in the microcirculation.

We sought to characterize how adherent leukocytes at the vessel wall, and the presence of erythrocytes, alter the streamlines (paths) of blood flow in the postcapillary venules. We directly visualized blood flow and leukocyte-endothelial cell interactions in postcapillary venules located in the cremaster muscle of anesthetized mice. Fluid streamlines were visualized by perfusing the cremaster muscle tissue with 0.5-micron fluorescent beads suspended in either buffer or whole blood, to examine the effect that erythrocytes have on the directionality of flow. Acute inflammation was induced in some animals by pretreatment of the vessels with tumor necrosis factor-alpha. To quantify the flow direction, the average deflection angle was defined as a scalar metric. Tracer bead trajectories were measurably altered by the presence of systemic levels of hematocrit, determined in each animal to be about 45%. Deviation from undirectional flow was also found to: (i) decrease with increasing vessel diameter, and (ii) increase with the number of adherent leukocytes. Fluid streamlines in the presence or absence of leukocyte adhesion or red cells agreed qualitatively with those obtained from theoretical calculations of blood flow using multiparticle adhesive dynamics. The microscale characteristics of venular flow are significantly altered during inflammation or changes in local hematocrit.