GB virus type C NS5A sequence polymorphisms: association with interferon susceptibility and inhibition of PKR-mediated eIF2alpha phosphorylation.
GB virus type C (GBV-C) causes persistent infection in humans, although the mechanism by which the virus avoids clearance by the host is unknown. To determine if amino acid polymorphisms in the GB virus type C (GBV-C) NS5A and E2 proteins alter response to interferon (IFN) therapy, we studied the sequence of GBVC NS5A and E2 obtained from people receiving IFN therapy. In addition, we expressed recombinant GBVC NS5A protein to determine if it interferes with RNA-activated protein kinase (PKR) function in vitro. GBVC NS5A amplified from a person whose virus was cleared by IFN therapy (IFN sensitive) demonstrated unique amino acid changes occurring in the region that aligns with the hepatitis C virus (HCV) IFN sensitivity-determining region (ISDR) compared with NS5A sequences from individuals who did not clear GBV-C (IFN resistant). There were no differences in the E2 sequences obtained from IFN-sensitive and IFN-resistant isolates. Using a yeast genetic system, IFN-resistant NS5A inhibited PKR-mediated phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha) in yeast, whereas IFN-sensitive NS5A did not inhibit PKR function. GBV-C NS5A amino acid polymorphisms appear to be involved in response to IFN therapy, and IFN-resistant GBV-C NS5A inhibited PKR-mediated eIF2alpha phosphorylation in a yeast genetic system, suggesting a mechanism by which GBV-C may evade clearance by naturally occurring host antiviral responses.
Xiang
Jinhua
J
Department of Internal Medicine and Research, Iowa City VA Medical Center and University of Iowa, Iowa City, IA 52242, USA.
Martinez-Smith
Christina
C
Gale
Michael
M
Chang
Qing
Q
Labrecque
Douglas R
DR
Schmidt
Warren N
WN
Stapleton
Jack T
JT
D000595:Amino Acid Sequence; D001483:Base Sequence; D004279:DNA, Viral / Q000235:genetics; D024882:Drug Resistance, Viral / Q000235:genetics; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D018178:Flaviviridae Infections / Q000150:complications / Q000188:drug therapy / Q000821:virology; D029407:GB virus C / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology*; D015870:Gene Expression; D019698:Hepatitis C, Chronic / Q000150:complications / Q000188:drug therapy / Q000821:virology; D006525:Hepatitis, Viral, Human / Q000150:complications / Q000188:drug therapy / Q000821:virology; D006801:Humans; D066298:In Vitro Techniques; D007370:Interferon Type I / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011110:Polymorphism, Genetic; D011994:Recombinant Proteins; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques; D017361:Viral Nonstructural Proteins / Q000235:genetics* / Q000502:physiology; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors*
D004279:DNA, Viral; D015852:Eukaryotic Initiation Factor-2; D007370:Interferon Type I; C096041:NS5 protein, flavivirus; D011994:Recombinant Proteins; D017361:Viral Nonstructural Proteins; D019892:eIF-2 Kinase