The Role of Transplacental Microtransfusions of Maternal Lymphocytes in In Utero HIV Transmission

Abstract

The mechanisms of HIV transmission from mothers to infants are poorly understood. A possible mechanism of in utero transmission is transplacental transfer of HIV-infected maternal leukocytes into the fetal circulation during pregnancy. To determine if the frequency of in utero HIV infection correlates with presence or levels of maternal cells (MCs) in placenta-derived cord blood. DNA was extracted from dried cord blood spots (DBS) from newborns born to HIV+ mothers and corresponding maternal DBS specimens. Paired mother-infant samples were probed to identify unique maternal sequences targeted by 24 allele-specific real-time polymerase chain reaction assays. Infant DBS-derived DNA was then probed in replicate analyses for noninherited maternal allelic sequences. Rates of detection and levels of MCs in DBS samples of HIV(+) and HIV(-) newborns were compared. Of 114 mother-infant pairs with informative alleles, 38 newborns were HIV(+) and 76 HIV(-), based on detection of HIV DNA/RNA at birth. MC were detected in 23 of 38 HIV(+) newborns (60.5%) and in 47 of 76 HIV(-) newborns (61.8%). The mean and median concentrations of nucleated MCs in DBS for the HIV(+)/MC(+) newborns (n = 23) were 0.33% and 0.27%, respectively, compared with 0.09% and 0.10% for the HIV(-)/MC(+) newborns (n = 47) (2-sample T test for means: P = 0.78). There was no significant difference in rates of detection or concentrations of MC in DBS between HIV(+) and HIV(-) newborns. Therefore, we could not demonstrate a correlation between MC in DBS, assumed to reflect levels of in utero maternal-fetal cell trafficking, and the risk of in utero HIV transmission.