Results are representative of 3 independent experiments. Molecular composition of exosomes Exosomes have been shown to contain proteins, lipids and nucleic acids and their cargo may vary depending on the cell type and ambient conditions24C26. DCs. Our study provides insight into the role of exosomes in HIV pathogenesis and suggests they can be CDC42BPA a target in development of novel therapeutic strategies against viral contamination. Introduction While there have been notable advances in combatting the AIDS epidemic, HIV-1 contamination remains a global health problem due to lack of an effective vaccine and frequent treatment failure1,2. This highlights the need to better understand the mechanisms involved in host-pathogen interaction, particularly viral immune evasion and cell-to-cell transmission. Escape of computer virus from immune detection may occur by altering the host cellular trafficking machinery, specifically inducing formation of cytoskeletal structures such as nanotubes and infectious synapses3C8. Recently, another mechanism involving Trojan exosomes has been implicated in viral spread and immune activation9C13. Exosomes are extracellular nanovesicles (30C200?nm in diameter) formed by the inward budding of the endosomal compartments, resulting in multivesicular bodies (MVBs) that are released upon fusion with the plasma membrane14C17. Actively secreted by various cell types, exosomes have been successfully isolated from various body fluids such as urine, saliva, bile, breast milk or blood and from cell culture medium13,18C23. They can carry proteins, lipids and nucleic acids; however their cargo mainly depends on physiological conditions and their origin24C26. Exosomes may act as regulators of Carbimazole both innate and acquired immunity by stimulating cytokine production, inflammatory responses and antigen presentation18,27C29. In addition, exosomes have been shown to play functions in viral pathogenesis by altering host defense mechanisms and facilitating dissemination of the microbes11,13,28,30C32. Analysis of exosomes derived from HIV-1 infected cells has revealed the presence of various viral components, including the viral genome9. Those derived from HIV-1 infected macrophages and dendritic cells (DCs) can transfer contamination to uninfected cells and induce strong viral replication13,31. When derived from CCR5 or CXCR4 positive cells, exosomes appear to transfer these HIV-1 co-receptors to CCR5 or CXCR4 unfavorable cells Carbimazole and may make them susceptible to contamination33,34. Furthermore, exosome-mediated transfer of HIV-1 nef to host cells can alter the intracellular trafficking machinery, enhance HIV-1 replication and release, and increase formation of MVBs35C37. Further, exposure to exosomes made up of HIV-1 nef and ADAM17 transformed resting CD4+ T cells, making them permissive for HIV-1 contamination, and may trigger apoptosis38. Under some conditions, exosomes may prevent viral contamination by activating immune cells and inducing anti-viral adaptive immune responses11,18,39. In this context, exosomes can transfer intrinsic resistance factors such as APOBEC3G Carbimazole from cell to cell and enhance resistance to HIV-1 contamination40. Exosomes isolated from human semen and breast milk have shown to inhibit HIV-1 replication and cell-to-cell transmission of computer virus41,42. Here, we characterize exosomes derived from HIV-1 infected and uninfected T cells and DCs and demonstrate that those derived from DCs can transfer HIV-1 to T cells and facilitate strong replication through fibronectin and galectin-3 mediated cellular fusion. Further, we show that such exosomes can induce production of pro-inflammatory cytokines. These novel observations provide insights into how computer virus may modulate host immune responses via exosomes to the benefit of the pathogen. Results Comparison of exosomes derived from T cells and DCs We first analyzed exosomes isolated from uninfected or HIV-1 infected T cells and DCs by examining the exosome markers CD63, CD9, CD81 and HSP7028. Western blot analysis revealed increased expression of these markers in exosomes derived from DCs compared to those from T cells. However, we did not observe significant differences in the expression pattern of these markers between exosomes derived from HIV-1 infected DCs compared to those derived from uninfected cells except HSP70, with markedly increased expression in exosomes derived from computer virus infected DCs (Fig.?1A and C). Surprisingly, when we analyzed exosomes isolated from T cells, we did not observe expression of CD81 and CD9 markers, but found poor expression of CD63 and HSP70 (Fig.?1A). Analysis of molecules involved in multivesicular endosome biogenesis revealed the expression of TSG101 and Alix in exosomes derived from DCs; expression.