Entry of the monocytotropic strains of HIV into the mononuclear cells is mediated in part by chemokine receptors such as CXCR-4 and CCR-5. Thus far, the expression of these receptors has been analyzed on adult monocytes. Determination of the expression of these receptors on cord monocytes may be useful in understanding their role in the perinatal transmission of HIV infection.

In the present study, using fluorescence flow cytometry, the relative expression of CCR-5 on monocytes was evaluated by analysis of binding of macrophage inflammatory protein-1α (MIP-1α), a chemokine ligand for CCR-5. Overall, it was assumed that MIP-1α receptor (MIP-1αR) expression represented CCR-5 expression. Cord blood samples (n=16) were compared with an equal number of paired healthy adult blood samples. The newborn donors of the cord samples were born at term and had no perinatal complications.

Cord blood contained a higher percentage of monocytes (CD14+; mean 44.40%) than adult blood (25.66%); P=0.001. However, less cord monocytes expressed MIP-1αR than adult monocytes (36.9% v/s 74.4%); P=0.001. Furthermore, The mean fluorescence intensity of MIP-1αR was greater on adult samples as compared to cord samples (27.91 v/s 14.20; P=0.032). Analysis of MIP-1αR expression on CD4+ monocytes and T lymphocytes is ongoing.

In summary, our results suggest that cord blood monocytes have a developmental delay in the expression of MIP-1αR, a coreceptor for HIV. Further studies are needed to evaluate the effect of the relatively low levels of chemokine receptors in the newborn on perinatal HIV transmission and subsequent clinical progression.