Association of hepatitis C virus envelope proteins with exosomes.
As the human tetraspanin CD81 binds hepatitis C virus (HCV) envelope glycoprotein E2, we addressed the role CD81 may play in cellular trafficking of HCV envelope proteins. Studies on HCV life cycle are complicated by the lack of a robust cell culture system; we therefore transfected mammalian cells with HCV E1-E2 cDNA, with or without human CD81 (huCD81) cDNA. In the absence of huCD81, HCV envelope proteins are almost completely retained in the endoplasmic reticulum. Instead, when huCD81 is present, a fraction of HCV envelope proteins passes through the Golgi apparatus, matures acquiring complex sugars and is found extracellularly associated with exosomes. These are 60-100-nm membrane vesicles enriched in tetraspanins, released into the extracellular milieu by many cell types and having fusogenic activity. We also report that human plasma contains exosomes and that in HCV patients, viral RNA is associated with these circulating vesicles. We propose that the HCV-CD81 complex leaves cells in the form of exosomes, circulates in this form and exploits the fusogenic capabilities of these vesicles to infect cells even in the presence of neutralizing antibodies.
Masciopinto
Francesca
F
IRIS Research Center, Chiron Vaccines, Siena, Italy.
Giovani
Cinzia
C
Campagnoli
Susanna
S
Galli-Stampino
Luisa
L
Colombatto
Piero
P
Brunetto
Maurizia
M
Yen
T S Benedict
TS
Houghton
Michael
M
Pileri
Piero
P
Abrignani
Sergio
S
D000818:Animals; D015703:Antigens, CD / Q000276:immunology / Q000378:metabolism*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D005434:Flow Cytometry; D016174:Hepacivirus / Q000472:pathogenicity; D006526:Hepatitis C / Q000097:blood / Q000276:immunology / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D021381:Protein Transport / Q000502:physiology*; D012367:RNA, Viral / Q000097:blood / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D022142:Secretory Vesicles / Q000378:metabolism*; D060225:Tetraspanin 28; D014162:Transfection; D014759:Viral Envelope Proteins / Q000276:immunology / Q000378:metabolism*
D015703:Antigens, CD; C554798:CD81 protein, human; D012367:RNA, Viral; D060225:Tetraspanin 28; D014759:Viral Envelope Proteins; C091015:glycoprotein E2, Hepatitis C virus