title: Differences in the immunogenicity of latent membrane protein 1 (LMP1) encoded by Epstein-Barr virus genomes derived from LMP1-positive and -negative nasopharyngeal carcinoma.
abstract: We have previously shown that an EBV-encoded latent membrane protein 1 (LMP1) gene derived from a nude mouse-propagated nasopharyngeal carcinoma (NPC) tumor and expressed in nonimmunogenic murine mammary carcinoma S6C cells failed to convey immunogenicity (rejectability) in syngeneic mice, whereas the corresponding B-cell derived LMP1 gene made the mice highly immunogenic. This raised the question of whether LMPL-expressing NPCs have been selected for low immunogenicity at the viral gene expression level. If so, LMP1-negative tumors that carry highly methylated LMP1 regulatory sequences may not have been exposed to a similar immunoselection. In the present study, we have compared LMP1 genes derived from two LMP1-positive NPCs and two LMP1-negative NPCs. All four genes were expressed in S6C cells in parallel with the previously tested isolates from a B-cell (B95-8)-derived and a nude mouse-propagated NPC (Cao)-derived gene. As in the previous study, we have found that the B-cell-derived LMP1 isolate was highly immunogenic. LMP1-positive tumor-derived isolates were poorly immunogenic, whereas the isolates from the LMP1-negative NPC tumor had intermediate immunogenicity. Sequence data revealed that LMP1 genes from LMP1-expressing NPC had 16 amino acid substitutions, whereas LMP1 from non-LMP1-expressing NPC had only 9 amino acid changes in the coding region. Three of the changes were at shared sites, but with different modifications. The fact that the gene from non-LMP1-expressing NPC mutated at a low frequency but was more immunogenic than the LMP1 gene derived from LMP1-expressing NPC, which was highly mutated but less immunogenic, favors the idea that LMP1-positive tumors escape immunosurveillance in immunocompetent hosts by either a selective down-regulation of LMP1 expression, methylation in the LMP1 promoter sequence, or mutation of LMP1 in LMP1-expressing samples.
authors.affiliation: Microbiology and Tumour Biology Centre, Karolinska Institute, Stockholm, Sweden. lifu.hu@mtc.ki.se
authors.forename: L
authors.initials: L
authors.lastname: Hu
authors.forename: B
authors.initials: B
authors.lastname: Troyanovsky
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: P
authors.initials: P
authors.lastname: Trivedi
authors.forename: I
authors.initials: I
authors.lastname: Ernberg
authors.forename: G
authors.initials: G
authors.lastname: Klein
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D016679:Genome, Viral; D004854:Herpesvirus 4, Human / Q000235:genetics*; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D009154:Mutation; D009303:Nasopharyngeal Neoplasms / Q000235:genetics / Q000276:immunology* / Q000821:virology; D014763:Viral Matrix Proteins / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*
chemical_list: C037662:EBV-associated membrane antigen, Epstein-Barr virus; D014763:Viral Matrix Proteins