Abstract: Flash-heat Inactivation of HIV-1 in Breast Milk

Background: Heat-treated expressed breast milk (EBM) is recommended by WHO as an option to reduce vertical transmission of HIV. The objective of this study was to evaluate the effect of Flash-heat (FH), on cell-free and cell-associated HIV in breast milk. Methods: Fresh EBM was collected from 5 healthy mothers in California and spiked with 6.6 log10 HIV copies per ml of cell-free HIV. Milk was aliquoted into unheated (UH) controls or FH (50mL EBM heated in 450mL water jacket until water boiled, then EBM removed), simulating field conditions with a glass peanut butter jar containing the heated milk in an aluminum pan over an open flame. We assayed for cell-free HIV by reverse-transcriptase (RT) and luciferase production in TZM-bl indicator cells. Cell-associated virus was studied by Peripheral Blood Mononuclear Cell (PBMC) assay. To assess HIV transmission via reactivation of latent provirus, lymphocytes were spiked into milk and cell survival after heating was evaluated by flow cytometry. Results: Cell-free HIV in FH EBM was reduced by more than two logs as detected by RT, and 7 logs by TZM-bl assay. RT and PBMC results have limited interpretation, however, due to false positive controls and residual inoculum artifacts, respectively. Lymphocyte viability was reduced to 0.3%. Conclusions: RT and TZM-bl results suggest inactivation of cell-free HIV in FH EBM. Cell- associated inactivation was seen in the PBMC assay and cell death seen by flow cytometry. FH may be a safe and affordable infant feeding option for HIV positive mothers in developing countries, especially during times of high risk, such as during mastitis or the transition from exclusive breastfeeding to replacement foods. Spiking studies are useful for demonstrating safety margins when treating samples with low naturally occurring levels of virus.