HIV-1 persists in breast milk cells despite antiretroviral treatment to prevent mother-to-child transmission

Abstract

Background: The effects of short-course antiretrovirals given to reduce mother-to-child transmission (MTCT) on temporal patterns of cell-associated HIV-1 RNA and DNA in breast milk are not well defined.

Methods: Women in Kenya received short-course zidovudine (ZDV), single-dose nevirapine (sdNVP), combination ZDV/sdNVP or short-course highly active antiretroviral therapy (HAART). Breast milk samples were collected two to three times weekly for 4-6 weeks. HIV-1 DNA was quantified by real-time PCR. Cell-free and cell-associated RNA levels were quantified by the Gen-Probe HIV-1 viral load assay.

Results: Cell-free HIV-1 RNA levels in breast milk were significantly suppressed by sdNVP, ZDV/sdNVP or HAART therapy compared with ZDV between day 3 and week 4 postpartum (P < or = 0.03). Breast milk HIV-1 DNA levels (infected cell levels) were not significantly different between treatment arms at any timepoint during the 4-6-week follow-up. At 3 weeks postpartum, when the difference in cell-free RNA levels was the greatest comparing HAART directly with ZDV (P = 0.0001), median log10 HIV-1 DNA copies per 1 x 10 cells were 2.78, 2.54, 2.69, and 2.31 in the ZDV, sdNVP, ZDV/sdNVP and HAART arms, respectively (P = 0.23). Cell-associated HIV-1 RNA levels were modestly suppressed in HAART versus ZDV/sdNVP during week 3 (3.37 versus 4.02, P = 0.04), as well as over time according to a linear mixed-effects model.

Conclusion: Cell-free and, to a lesser extent, cell-associated HIV-1 RNA levels in breast milk were suppressed by antiretroviral regimens used to prevent MTCT. However, even with HAART, there was no significant reduction in the reservoir of infected cells, which could contribute to breast milk HIV-1 transmission.

Fig. 1. Cell-free HIV-1 RNA levels in breast milk over time postpartum: Nairobi, Kenya, 2003–2005

(a) Weekly medians and interquartile ranges of log₁₀ cell-free HIV-1 RNA per milliliter. P values on the basis of Kruskal–Wallis test. (b) Individual data points and lowess curves for the four treatment arms: ZDV (× symbol), sdNVP (square symbol), ZDV/sdNVP —— (circle symbol), and HAART (triangle symbol).

Fig. 2. HIV-1 DNA levels in breast milk over time postpartum: Nairobi, Kenya, 2003–2005

(a) Weekly medians and interquartile ranges of log₁₀ HIV-1 DNA copies per million breast milk cells. P values on the basis of Kruskal–Wallis test. (b) Individual data points and lowess curves for the four treatment arms: ZDV (× symbol), sdNVP (square symbol), ZDV/sdNVP —— (circle symbol), HAART (triangle symbol). BMC, breast milk cell.

Fig. 3. Cell-associated HIV-1 RNA levels in breast milk over time postpartum: Nairobi, Kenya, 2003–2005

(a) Weekly medians and interquartile ranges of log₁₀ cell-associated HIV-1 RNA per million breast milk cells. P values on the basis of Mann–Whitney U test. (b) Individual data points and lowess curves for the four treatment arms: ZDV/sdNVP (——, solid line), HAART (, long-dash dotted line). BMC, breast milk cell.

Fig. 4. A model of how treatment affects cell-free and cell-associated HIV-1 levels in breast milk

Left panel: levels of HIV-1 DNA (infected cells) and HIV-1 RNA (cell-free virus) prior to treatment. The majority of cell-free virus is produced by activated T cells, whereas macrophages and resting T cells contribute less cell-free virus. Right panel: following treatment to prevent MTCT, where virus spread is impaired, levels of infected activated T cells decrease due to normal cell turnover of infected cells, whereas levels of infected resting T cells and macrophages are only minimally reduced. The levels of cell-free virus are significantly reduced due to the reduction of infected activated T cells.