Recently, it has been suggested that HIV can exploit a preexisting exosome trans-dissemination pathway intrinsic to mDCs, thus allowing trans-infection of CD4 þ T cells. 60, 61 Exosomes are membrane vesicles of 30-100 nm in diameter and of endocytic origin, which are produced and secreted in vitro by living cells of diverse origin. They are involved in the stimulation of a specific immune response and they can transfer antigens from infected, tumoral, or antigen-presenting cells to mDCs, increasing the number of DCs bearing a particular antigen, thus amplifying the initiation of primary adaptive immune response. 62 Exosomes from DCs loaded with tumor-derived epitopes on MHC-I molecules are able to stimulate in vivo cytotoxic T lymphocyte-mediated anti-tumor responses, 63 and to indirectly activate in vivo naïve CD4 þ T cells through the exchange of functional peptide-MHC complexes between DCs through a trans-dissemination mechanism. 64 A recent study has shown that upon maturation, DCs are able to capture large amounts of HIV, HIV-gag-VLP, or exosomes, resulting in localization within a CD81 þ compartment, and efficient transmission of captured particles to target T cells in an envelope glycoprotein-independent manner. 65 This 'Trojan exosome pathway' 60 used by mDCs that allows HIV to move between cells in the absence of fusion events could have a prominent role in promoting viral dissemination.