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Human Immunodeficiency Virus-specific B cells in human breast milk

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Background

Breast milk is a component of the mucosal immune system, and contains specific antibodies and lymphocytes that may modulate the infectivity of milk, and therefore the risk of HIV-1 transmission via breastfeeding. While secretory antibodies (Ab) have been extensively explored in human breast milk, the existence, features, and function of B lymphocytes remain to be described in this compartment.

Methods

We analysed breast milk and blood lymphocytes from 12 HIV-1-infected lactating women. All women were treated by anti-retroviral therapy or have been recently exposed to anti-retroviral drugs for prophylaxis of mother-to-child transmission. Milk samples were collected 5 to 42 days post partum. Phenotype of breast milk cells were analyzed by flow cytometry and cells function by ELISpot assays.

Results

In contrast to their blood counterpart, naive B cells remained largely underrepresented in breast milk. Breast milk B cells mostly consisted of IgD- memory B cells. They displayed a phenotype of class-switched memory B cell, with few IgD+ memory and naive B cells. As compared with blood, higher percentages of activated B cells (CD38+), large size B cells, plasmablasts and plasma cells (CD19+, CD20low/-, CD27high, CD138+) were found. This indicates that a significant proportion of breast milk B cells underwent terminal plasma cell differentiation. We also observed a higher frequency of cells secreting spontaneously Ig in breast milk. Among these cells, IgG-secreting cells (SCs) predominated over IgA-SCs as measured by Ig-ELISpot assays. Specific Ab-SCs were investigated following polyclonal activation using the CD40L ligation. The detection of anti-HIV-1-SCs demonstrated the existence of B cells specific to HIV-1 Ag in breast milk from HIV-1-infected women. Finally, we observed that breast milk B lymphocytes bore a unique profile of adhesion molecules (CD44+, CD62L-, α4/β7+/-, α4/β1+) suggesting that these cells may originate from the gut-associated lymphoïd tissue (GALT).

Conclusion

Breast milk from lactating women infected by HIV-1 contains activated B cells including cells specific to HIV-1 antigens. These cells display a phenotype strikingly different from blood, with a mucosal homing profile related to B cells located in the GALT.

Author information

Correspondence to Edouard Tuaillon.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Tuaillon, E., Valea, D., Al Tabaa, Y. et al. Human Immunodeficiency Virus-specific B cells in human breast milk. Retrovirology 6, O8 (2009) doi:10.1186/1742-4690-6-S1-O8

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Keywords

  • Breast Milk
  • Milk Sample
  • ELISpot Assay
  • Lactate Woman
  • Post Partum