Volume 5 Supplement 1

Fourth Dominique International Conference. Maternal chronic viral infections transmitted to infants: from mechanisms to prevention and care

Open Access

HIV-1 internalization in polarized human trophoblasts occurs through a peculiar endocytic pathway

  • Michel J Tremblay1 and
  • Gaël Vidricaire
Retrovirology20085(Suppl 1):O5

DOI: 10.1186/1742-4690-5-S1-O5

Published: 9 April 2008

Background

In human trophoblastic cells, a correlation between early endosomal trafficking of HIV-1 and virus infection was previously documented. However, if HIV-1 is massively internalized in these cells, the endocytic pathway(s) responsible for viral uptake is still undefined.

Materials and methods

The process through which HIV-1 is endocytosed was studied using different reagents (e.g. chlorpromazine, cholera toxin B, water-soluble cholesterol, colchicine, cytochalasin B, filipin, jasplakinolide, methyl-beta-cyclodextrin, paclitaxel, and vinblastine) and experimental strategies (e.g. transfection of JAR cells with various expression vectors, virus internalization test, infection assay, confocal laser scanning, co-localization analysis and digital image preparation).

Results

Amongst all the putative endocytic pathways present in polarized trophoblastic cells, we demonstrate that HIV-1 infection of these cells is independent of clathrin-mediated endocytosis and macropinocytosis. Importantly, treatment with the cholesterol-sequestering drug filipin severely impairs virus internalization, whereas the cholesterol-depleting compound methyl-beta-cyclodextrin has no impact on this pathway. Moreover, viral internalization is unaffected by overexpression of a mutant dynamin 2 or treatment with a kinase or tyrosine phosphatase inhibitor. Thus, HIV-1 infection in polarized trophoblastic cells occurs primarily via a clathrin-, caveolae-, and dynamin-independent pathway requiring free cholesterol. Notably, even though HIV-1 did not initially co-localize with transferrin, some virions migrate at later time points to transferrin-enriched endosomes, suggesting an unusual transit from the non-classical pathway to early endosomes. Finally, virus internalization in these cells does not involve the participation of microtubules but relies partly on actin filaments.

Conclusions

We demonstrate that HIV-1 internalization in polarized human trophoblastic cells occurs primarily via a clathrin-, caveolea-, and dynamin-independent pathway which is sensitive to a cholesterol-sequestering drug.

Authors’ Affiliations

(1)
Centre de Recherche en Infectiologie, Centre Hospitalier de l'Université Laval, and Département de Biologie médicale, Université Laval

Copyright

© Tremblay and Vidricaire; licensee BioMed Central Ltd. 2008

This article is published under license to BioMed Central Ltd.

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