Identification of disease associated EBV genotypes in Hong Kong

Abstract

INTRODUCTION: Epstein-Barr virus (EBV) is a type 1 carcinogen endemic in Hong Kong that can be readily detected in saliva from infected individuals. A comprehensive phylogenetic analysis of one or multiple genes may be used to characterize the lineage of EBV in patients. OBJECTIVE: To compare EBV genotype profiles of 120 human immunodeficiency virus (HIV) infected individuals, 120 nasopharyngeal cancer (NPC) patients and 72 healthy individuals. METHODS: Unstimulated whole saliva was collected. EBV DNA sequences were obtained by PCR amplification of the polymorphic carboxy terminal of EBV LMP1 gene (nt 168130-168389) followed by sequencing. Genotypes were characterized by aligning sequences with those of reference strains. Phylogentic trees were generated using neighbor-joining method. 190 novel DNA sequences were deposited in NCBI GenBank. RESULTS: Six genotypes were characterized as belonging to HK/EBV lineage; China1, China2, Med+/-, NorthC and B9–58. China1 was significantly more prevalent compared to other genotypes (P<0.001). HIV infected individuals shed multiple strains in saliva, including China1(79.12%), China2(9.89%), NorthC(1.1%), B95–8(2.2%) and Med+/-(7.69%). A higher prevalence of Med+/- genotypes associated with lymphoma formation was seen during HIV infection(87.5%). Only single strains, either China1 or China 2 were detected in NPC. Strikingly, 30bp deletion in LMP1 was significantly prevalent in NPC patients (69/71) compared to other groups (P<0.0001). CONCLUSION: For the first time we have demonstrated phylogenetically distinct EBV LMP1 genotypes in saliva during HIV and NPC disease as wells healthy individuals. 30bp LMP1 deletion genotypes indicate a possible down regulation of immunogenic viral epitopes during NPC formation.