Glucosidase inhibition enhances presentation of de-N-glycosylated hepatitis B virus epitopes by major histocompatibility complex class I in vitro and in woodchucks.
In this report, the possibility of pharmacologically altering the hepatitis B virus (HBV) epitopes presented by major histocompatibility complex class I on infected cells is demonstrated. The HBV middle envelope glycoprotein (MHBs) maturation appears to require calnexin-mediated folding. This interaction is dependent on glucosidases in the endoplasmic reticulum. Prevention of HBV envelope protein maturation in cultured cells through use of glucosidase inhibitors, such as 6-O-butanoyl castanospermine and N-nonyl deoxynorjirimycin, resulted in MHBs degradation by proteasomes. The de-N-glycosylation associated with polypeptide degradation was predicted to result in conversion of asparagine residues into aspartic acid residues. This prediction was confirmed by showing that peptides corresponding to the N-glycosylation sequons of MHBs, but with aspartic acid replacing asparagine, (1) can prime human cytotoxic T lymphocytes that recognize HBV-producing cells and (2) that the presentation of these envelope motifs by major histocompatibility complex class I is enhanced by incubation with glucosidase inhibitors. Moreover, although peripheral blood mononuclear cells isolated from woodchucks chronically infected with woodchuck hepatitis virus and vaccinated with woodchuck hepatitis virus surface antigen could be induced to recognize the natural MHBs asparagine-containing peptides, only cells isolated from animals treated with glucosidase inhibitor recognized the aspartic acid-containing peptides.


CONCLUSIONS
These data suggest that pharmacological intervention with glucosidase inhibitors can alter the MHBs epitopes presented. This editing of the amino acid sequence of the polypeptide results in a new epitope, or "editope", with possible medical significance.
Norton
Pamela A
PA
Drexel Institute for Biotechnology and Virology Research and Department of Microbiology and Immunology, Drexel University College of Medicine, Doylestown, PA, USA. pamela.norton@drexelmed.edu
Menne
Stephan
S
Sinnathamby
Gomathinayagam
G
Betesh
Lucy
L
Cote
Paul J
PJ
Philip
Ramila
R
Mehta
Anand S
AS
Tennant
Bud C
BC
Block
Timothy M
TM
D017485:1-Deoxynojirimycin / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D000939:Epitopes / Q000235:genetics; D005805:Genes, MHC Class I / Q000502:physiology*; D005959:Glucosidases / Q000037:antagonists & inhibitors*; D017919:Hepatitis B Virus, Woodchuck / Q000235:genetics / Q000276:immunology; D006515:Hepatitis B virus / Q000235:genetics*; D006801:Humans; D007212:Indolizines / Q000494:pharmacology*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008392:Marmota; D014759:Viral Envelope Proteins / Q000378:metabolism*; D054836:Indolizidines
D017485:1-Deoxynojirimycin; D004791:Enzyme Inhibitors; D000939:Epitopes; D005959:Glucosidases; D007212:Indolizines; D014759:Viral Envelope Proteins; C112150:N-nonyl-1-deoxynojirimycin; C114312:middle envelope protein, Hepatitis B virus; C070715:celgosivir; D054836:Indolizidines