Relation between viral fitness and immune escape within the hepatitis C virus protease. Export

@article{citeulike:484871, abstract = {BACKGROUND: The hepatitis C virus (HCV) mutates within human leucocyte antigen (HLA) class I restricted immunodominant epitopes of the non-structural (NS) 3/4A protease to escape cytotoxic T lymphocyte (CTL) recognition and promote viral persistence. However, variability is not unlimited, and sometimes almost absent, and factors that restrict viral variability have not been defined experimentally. AIMS: We wished to explore whether the variability of the immunodominant CTL epitope at residues 1073-1081 of the NS3 protease was limited by viral fitness. PATIENTS: Venous blood was obtained from six patients (four HLA-A2+) with chronic HCV infection and from one HLA-A2+ patient with acute HCV infection. METHODS: NS3/4A genes were amplified from serum, cloned in a eukaryotic expression plasmid, sequenced, and expressed. CTL recognition of naturally occurring and artificially introduced escape mutations in HLA-A2-restricted NS3 epitopes were determined using CTLs from human blood and genetically immunised HLA-A2-transgenic mice. HCV replicons were used to test the effect of escape mutations on HCV protease activity and RNA replication. RESULTS: Sequence analysis of NS3/4A confirmed low genetic variability. The major viral species had functional proteases with 1073-1081 epitopes that were generally recognised by cross reactive human and murine HLA-A2 restricted CTLs. Introduction of mutations at five positions of the 1073-1081 epitope prevented CTL recognition but three of these reduced protease activity and RNA replication. CONCLUSIONS: Viral fitness can indeed limit the variability of HCV within immunological epitopes. This helps to explain why certain immunological escape variants never appear as a major viral species in infected humans.}, address = {Division of Clinical Virology, Karolinska Institutet at Karolinska University Hospital, S-141 86 Stockholm, Sweden.}, author = {S\"{o}derholm, J. and Ahl\'{e}n, G. and Kaul, A. and Frelin, L. and Alheim, M. and Barnfield, C. and Liljestr\"{o}m, P. and Weiland, O. and Milich, D. R. and Bartenschlager, R. and S\"{a}llberg, M.}, citeulike-article-id = {484871}, citeulike-linkout-0 = {http://dx.doi.org/10.1136/gut.2005.072231}, citeulike-linkout-1 = {http://view.ncbi.nlm.nih.gov/pubmed/16105887}, citeulike-linkout-2 = {http://www.hubmed.org/display.cgi?uids=16105887}, doi = {10.1136/gut.2005.072231}, issn = {0017-5749}, journal = {Gut}, keywords = {cd8, epitopes, escape, fitness, hcv}, month = {February}, number = {2}, pages = {266--274}, posted-at = {2006-01-29 19:02:02}, priority = {2}, title = {Relation between viral fitness and immune escape within the hepatitis C virus protease.}, url = {http://dx.doi.org/10.1136/gut.2005.072231}, volume = {55}, year = {2006} }

TY - JOUR ID - citeulike:484871 L3 - citeulike-article-id:484871 N2 - BACKGROUND: The hepatitis C virus (HCV) mutates within human leucocyte antigen (HLA) class I restricted immunodominant epitopes of the non-structural (NS) 3/4A protease to escape cytotoxic T lymphocyte (CTL) recognition and promote viral persistence. However, variability is not unlimited, and sometimes almost absent, and factors that restrict viral variability have not been defined experimentally. AIMS: We wished to explore whether the variability of the immunodominant CTL epitope at residues 1073-1081 of the NS3 protease was limited by viral fitness. PATIENTS: Venous blood was obtained from six patients (four HLA-A2+) with chronic HCV infection and from one HLA-A2+ patient with acute HCV infection. METHODS: NS3/4A genes were amplified from serum, cloned in a eukaryotic expression plasmid, sequenced, and expressed. CTL recognition of naturally occurring and artificially introduced escape mutations in HLA-A2-restricted NS3 epitopes were determined using CTLs from human blood and genetically immunised HLA-A2-transgenic mice. HCV replicons were used to test the effect of escape mutations on HCV protease activity and RNA replication. RESULTS: Sequence analysis of NS3/4A confirmed low genetic variability. The major viral species had functional proteases with 1073-1081 epitopes that were generally recognised by cross reactive human and murine HLA-A2 restricted CTLs. Introduction of mutations at five positions of the 1073-1081 epitope prevented CTL recognition but three of these reduced protease activity and RNA replication. CONCLUSIONS: Viral fitness can indeed limit the variability of HCV within immunological epitopes. This helps to explain why certain immunological escape variants never appear as a major viral species in infected humans. IS - 2 JF - Gut SN - 0017-5749 AD - Division of Clinical Virology, Karolinska Institutet at Karolinska University Hospital, S-141 86 Stockholm, Sweden. EP - 274 TI - Relation between viral fitness and immune escape within the hepatitis C virus protease. VL - 55 SP - 266 KW - cd8 KW - epitopes KW - escape KW - fitness KW - hcv AU - Söderholm, J AU - Ahlén, G AU - Kaul, A AU - Frelin, L AU - Alheim, M AU - Barnfield, C AU - Liljeström, P AU - Weiland, O AU - Milich, DR AU - Bartenschlager, R AU - Sällberg, M PY - 2006/02// UR - http://dx.doi.org/10.1136/gut.2005.072231 ER -