ABSTRACT
Measles virus has been reported to enter host cells via either of two cellular receptors, CD46 and CD150 (SLAM). CD46 is found on most cells of higher primates, while SLAM is expressed on activated B, T, and dendritic cells and is an important regulatory molecule of the immune system. Previous reports have shown that measles virus can down regulate expression of its two cellular receptors on the host cell surface during infection. In this study, the process of down regulation of SLAM by measles virus was investigated. We demonstrated that expression of the hemagglutinin (H) protein of measles virus was sufficient for down regulation. Our studies provided evidence that interactions between H and SLAM in the endoplasmic reticulum (ER) can promote the down regulation of SLAM but not CD46. In addition, we demonstrated that interactions between H and SLAM at the host cell surface can also contribute to SLAM down regulation. These results indicate that two mechanisms involving either intracellular interactions between H and SLAM in the ER or receptor-mediated binding to H at the surfaces of host cells can lead to the down regulation of SLAM during measles virus infection.
Subject(s)
Glycoproteins/metabolism , Hemagglutinins, Viral/physiology , Immunoglobulins/metabolism , Measles virus/physiology , Animals , Antigens, CD/chemistry , Antigens, CD/genetics , Antigens, CD/metabolism , Cell Line , Cell Membrane/immunology , Cell Membrane/virology , Down-Regulation , Endoplasmic Reticulum/immunology , Endoplasmic Reticulum/virology , Genetic Variation , Glycoproteins/chemistry , Glycoproteins/genetics , Glycosylation , Hemagglutinins, Viral/genetics , Humans , Immunoglobulins/chemistry , Immunoglobulins/genetics , Measles virus/genetics , Measles virus/pathogenicity , Membrane Cofactor Protein , Membrane Glycoproteins/chemistry , Membrane Glycoproteins/genetics , Membrane Glycoproteins/metabolism , Mutation , Receptors, Cell Surface , Receptors, Virus/physiology , Signaling Lymphocytic Activation Molecule Family Member 1ABSTRACT
Hepatitis C virus (HCV) encodes a polyprotein consisting of core, envelope (E1, E2, p7), and nonstructural polypeptides (NS2, NS3, NS4A, NS4B, NS5A, NS5B). The serine protease (NS3/NS4A), helicase (NS3), and polymerase (NS5B) constitute valid targets for antiviral therapy. We engineered BH3 interacting domain death agonist (BID), an apoptosis-inducing molecule, to contain a specific cleavage site recognized by the NS3/NS4A protease. Cleavage of the BID precursor molecule by the viral protease activated downstream apoptotic molecules of the mitochondrial pathway and triggered cell death. We extended this concept to cells transfected with an infectious HCV genome, hepatocytes containing HCV replicons, a Sindbis virus model for HCV, and finally HCV-infected mice with chimeric human livers. Infected mice injected with an adenovirus vector expressing modified BID exhibited HCV-dependent apoptosis in the human liver xenograft and considerable declines in serum HCV titers.
