HIV-infected Breast Milk Cells Play a More Important Role in Transmission of HIV Via Breast-feeding Than Does Cell-free Virus

Understanding how the level of HIV-1 infected breast milk cells (BMCs) affects HIV transmission via breast-feeding can shed light on the mechanism of infection and aid in establishing effective interventions.

The proportion of infected cells to total cells was measured in serial breast milk samples collected from 291 HIV-1 infected women in Nairobi, Kenya, by use of real-time DNA polymerase chain reaction (RT-PCR) amplification of BMCs.

The number of infected BMCs per million cells was associated with levels of cell-free viral RNA in breast milk (R = .144; P = .032), levels of cell-free virus in blood plasma (R = .365; P < .001), and the detection of proviral DNA in cervical and vaginal secretions (P < .001 and P = .030, respectively).

The number of infected BMCs per million cells was lower in colostrum or early milk than in mature milk (P < .001).

Previous studies demonstrated that the concentration of BMCs varies throughout lactation, and the researchers used these data to transform infected BMCs per million cells to infected BMCs per milliliter.

The estimated concentration of infected BMCs per milliliter was higher in colostrum or early milk than in mature milk (P < .001).
Each log10 increase in infected BMCs per milliliter was associated with a 3.19-fold increased risk of transmission (P = .002), after adjustment for cell-free virus in plasma (hazard ratio [HR], 2.09; P = .03) and breast milk (HR, 1.01; P = 1.00).

"This suggests that infected BMCs may play a more important role in transmission of HIV via breast-feeding than does cell-free virus," conclude the authors.

Divisions of Human Biology and Public Health Sciences, Fred Hutchinson Cancer Research Center, and Departments of Biostatistics, Medicine, and Epidemiology, University of Washington, Seattle; Department of Pediatrics, University of Nairobi, Nairobi, Kenya.

10/25/04

Reference
C M Rousseau and others. Association of Levels of HIV-1 Infected Breast Milk Cells and Risk of Mother-to-Child Transmission. The Journal of Infectious Diseases 190(10): 1880-1888. November 15, 2004.