%0 Journal Article %A Muratori, Claudia %A Ruggiero, Eliana %A Sistigu, Antonella %A Bona, Roberta %A Federico, Maurizio %T Human immunodeficiency virus type 1 (HIV-1) protease inhibitors block cell-to-cell HIV-1 endocytosis in dendritic cells %D 2009 %J Journal of General Virology, %V 90 %N 11 %P 2777-2787 %@ 1465-2099 %R https://doi.org/10.1099/vir.0.012609-0 %I Microbiology Society, %X Sexual transmission is now the most frequent means of diffusion of human immunodeficiency virus type 1 (HIV-1). Even if the underlying mechanism is still largely unknown, there is a consensus regarding the key role played by mucosal dendritic cells (DCs) in capturing HIV through contact with infected subepithelial lymphocytes, and their capacity to spread HIV by trans-infection. We found that HIV protease inhibitors (PIs) reduced virion endocytosis strongly in monocyte-derived immature (i) DCs contacting HIV-1-infected cells, and that this phenomenon led to dramatically impaired trans-infection activity. This inhibitory effect was not mediated by the block of viral protease activity, as it was also operative when donor cells were infected with a PI-resistant HIV-1 strain. The block of virus maturation imposed by PIs did not correlate with significant variations in the levels of virus expression in donor cells or of Gag/Env virion incorporation. Also, PIs did not affect the endocytosis activity of DCs. In contrast, we noticed that PI treatment inhibited the formation of cell–cell conjugates whilst reducing the expression of ICAM-1 in target iDCs. Our results contribute to a better delineation of the mechanisms underlying HIV-1 trans-infection activity in DCs, whilst having implications for the development of new anti-HIV microbicide strategies. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/vir.0.012609-0