T cell-stimulatory fragments of foot-and-mouth disease virus released by mild treatment with cathepsin D.
Cathepsin D and cathepsin B are endosomal/lysosomal proteases that are thought to play a role during in vivo antigen processing, releasing fragments for binding to major histocompatibility complex class II products and subsequent presentation to T cells. Here we treated purified foot-and-mouth disease virus (FMDV) strain A10Holland with both enzymes. Cathepsin D, but not cathepsin B, was shown to release fragments from reduced or non-reduced FMDV under mild conditions in vitro. Twenty-eight predominant cathepsin D-released fragments were purified by HPLC and identified by amino acid composition analysis and sequencing. The unseparated set of fragments produced (the digest) was able to stimulate T cells from eight vaccinated cattle. With respect to the response to intact virus the extent of the response to the digest differed between animals: four animals could be classified as good responders, three as intermediate responders and one as a low responder. Subsequently, we investigated the proliferative T cell response to a large set of synthetic peptides in detail for two animals, one belonging to the group of good responders, the other being the low responder. The peptides covered all 28 cathepsin D-released fragments analysed and also several sequences not recovered from the digest. In this way seven T cell sites could be identified, five of which coincided with cathepsin D-released fragments. The other two T cell sites were VP2[54-72], being a homologue of a T cell site identified for FMDV strain O1K and the N terminus of VP4. Whether the most dominantly recognized T cell site was recovered from the digest or not was shown to be related to the good or low response to the digest. These findings suggest a role for cathepsin D in the release of some but not all T cell-stimulatory fragments from FMDV.
van Lierop
M J
MJ
Department of Immunology, Faculty of Veterinary Medicine, University of Utrecht, The Netherlands.
van Noort
J M
JM
Wagenaar
J P
JP
Rutten
V P
VP
Langeveld
J
J
Meloen
R H
RH
Hensen
E J
EJ
D000595:Amino Acid Sequence; D000818:Animals; D000956:Antigens, Viral / Q000276:immunology*; D005537:Aphthovirus / Q000276:immunology*; D002213:Capsid / Q000737:chemistry / Q000276:immunology*; D036022:Capsid Proteins; D002401:Cathepsin B / Q000378:metabolism; D002402:Cathepsin D / Q000378:metabolism*; D002417:Cattle; D005260:Female; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology*; D010449:Peptide Mapping; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
D000956:Antigens, Viral; D036022:Capsid Proteins; D010446:Peptide Fragments; D010455:Peptides; C442501:VP1 protein, Foot-and-mouth disease virus; C442459:VP2 protein, Foot-and-mouth disease virus; C442460:VP3 protein, Foot-and-mouth disease virus; C060339:VP4 protein, Rotavirus; D002401:Cathepsin B; D002402:Cathepsin D