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Flash-Heat Inactivation of HIV-1 in Human Milk: A Potential Method to Reduce Postnatal Transmission in Developing Countries
Global Health Sciences Literature Digest
Published August 14, 2007
Journal Article

Israel-Ballard K, Donovan R, Chantry C, Coutsoudis A, Sheppard H, Sibeko L, et al. Flash-Heat Inactivation of HIV-1 in Human Milk: A Potential Method to Reduce Postnatal Transmission in Developing Countries. J Acquir Immune Defic Syndr 2007 Jul 1;45(3):318-323.

Study Design

Experiment, primarily laboratory-based.

Setting

Women providing breast milk were recruited from postnatal clinics in a peri-urban settlement in Durban, South Africa. Laboratory analyses of sera and breast milk were performed at the University of KwaZulu-Natal (KZN), Durban, and at the California Department of Health Services, Richmond, California, USA.

Participants

From October 2004 to July 2005, 84 HIV-infected breastfeeding mothers not currently receiving ART or antibiotics were enrolled, and provided 98 breast milk samples for testing. Mean age was 25.8 years, and mean CD4 cell count was 502 cells/mm3.

Experiment

Participants washed their hands with soap and water and manually expressed 75 to 150 mL of breast milk into sterile, locally obtained glass jars. Breast milk samples were immediately placed in an ice-water bath and transported to the KZN laboratory. 50 µL of each sample was aliquoted for flash-heating in the same glass jar, and the remaining volume was used as an unheated control. The glass jar was placed in a locally purchased one-quart aluminum pan filled with 450 µL of water and heated over a single-burner butane stove (ostensibly imitating the intense heat of a fire) until the water reached 100 ºC and was at a rolling boil. The breast milk jar was then immediately removed from the water, and breast milk allowed to cool to 37 ºC. Flash-heated and unheated breast milk were divided into 1.5 µL aliquots and stored at -80 ºC. Samples were shipped frozen on dry ice to the California Department of Health Services Laboratory for viral analysis.

Primary Outcomes

Presence of detectable HIV in heated and unheated breast milk. Quantitative measurement of HIV reverse-transcriptase (RT) activity (sensitivity of 400 copies/µL), was used as a marker for viable HIV in treated and untreated breast milk. The presence of HIV in unheated samples was also detected using a TaqMan real-time RNA-PCR (sensitivity of 50 copies/µL).

Results

Detectable (viable) HIV was found in 31% (26 of 84) of the unheated breast milk samples using the reverse transcriptase assay. Detectable HIV was associated with a lower maternal CD4 count (mean 338 vs. 551 cells/µL), older maternal age (mean age 27.8 vs. 24.9 years), taking multivitamins, and lower breast milk volume. Thirty of 98 total unheated samples (some mothers provided more than one sample) were positive by both real-time PCR and RT. Prior to heating, the mean viral load in these samples was 8266 copies/µL (SD 15,376); after flash heating, none of the samples showed detectable levels of HIV by RT assay.

Conclusions

The authors conclude that these findings indicate that flash-heating is capable of inactivating cell-free HIV in naturally infected breast milk. Field studies are still needed to determine the feasibility of flash-heating in the home setting to reduce postnatal HIV transmission.

Quality Rating

There is no widely accepted quality rating tool for experimental studies such as this.

In Context

The same authors have previously shown that flash-heating can inactivate higher concentrations of HIV (obtained by "spiking" samples with cell-free HIV) than are found in naturally infected breast milk.(1) Other studies have shown that using TaqMan real-time PCR is not appropriate for assessing HIV activity after heating;(2,3) co-culture, sometimes considered a gold standard, is also insensitive. The study here only detected cell-free virus, but recent data indicate that cell-associated virus may play a more important role in HIV transmission through breast milk.(4) A study in Zambia found a significant increase in breast milk viral load during the weaning period, suggesting that breastfeeding during this time may be particularly risky.(5) There is some preliminary data on the safety of flash-heated milk.(2,6)

Programmatic Implications

This study provides additional support for the possibility of reducing HIV transmission through breast milk by flash-heating, a technique that could be used in the field. This method may be most useful during times of increased risk of transmission, such as during weaning or if a mother has mastitis. However, before this method is introduced, considerable field and laboratory research are still needed. This includes the need to confirm the nutritional and immunologic adequacy, and the ability to prevent contamination of breast milk during expression, heating, and subsequent feeding. The current standardized heating protocol needs to be strictly adhered to until additional field tests and thermal inactivation studies are completed to determine the margin of heating error allowable to ensure HIV destruction. Finally, information is still needed on the impact of flash-heat on cell-associated HIV-1, which may be more important than free virus in transmission of HIV through breast milk.

References

  1. Israel-Ballard K, Chantry C, Dewey K, Lonnerdal B, Sheppard H, Donovan R, et al. Viral, nutritional, and bacterial safety of flash-heated and pretoria-pasteurized breast milk to prevent mother-to-child transmission of HIV in resource-poor countries: a pilot study. J Acquir Immune Defic Syndr 2005 Oct 1;40(2):175-81.
  2. Piatak M Jr, Saag MS, Yang LC, et al. Determination of plasma viral load in HIV-1 infection by quantitative competitive polymerase chain reaction. AIDS. 1993;7(Suppl 2):S65-S71.
  3. Nuanualsuwan S, Cliver DO. Infectivity of RNA from inactivated poliovirus. Appl Environ Microbiol 2003 Mar;69(3):1629-32.
  4. Rousseau CM, Nduati RW, Richardson BA, John-Stewart GC, Mbori-Ngacha DA, Kreiss JK, et al. Association of levels of HIV-1-infected breast milk cells and risk of mother-to-child transmission. J Infect Dis 2004 Nov 15;190(10):1880-8.
  5. Thea DM, Aldrovandi G, Kankasa C, Kasonde P, Decker WD, Semrau K, et al. Post-weaning breast milk HIV-1 viral load, blood prolactin levels and breast milk volume. AIDS 2006 Jul 13;20(11):1539-47.
  6. Israel-Ballard K, Coutsoudis A, Chantry CJ, Sturm AW, Karim F, Sibeko L, et al. Bacterial safety of flash-heated and unheated expressed breastmilk during storage. J Trop Pediatr 2006 Dec;52(6):399-405.