| Background and objective: Epstein-Barr virus(EBV), also known as human herpesvirus 4(HHV4), infects more than 90% of the adult population worldwide. It’s associated with many kinds of human malignant tumors. The evasion mechanisms of EBV may compromise the elimination of EBV-transformed cells, and thus contribute to malignancies associated with EBV infection. BNLF2 a is an early lytic gene of EBV, it can inhibit the antigen transporting function of TAP, thereby perturbing the host immune response to EBV. It’s reported that EBV strains from different regions show different gene polymorphism in a variety of gene loci. Meanwhile, the incidence distribution of EBV-associated malignancies differs in geographic regions. Thus whether certain EBV subtypes are preferentially associated with particular malignancies remains controversial. In order to illuminate the polymorphism character of BNLF2 a and to explore whether the polymorphism of BNLF2 a gene has a role in different types of EBV associated tumors, we conducted complete sequencing of the gene BNLF2 a in lymphomas, gastric carcinomas, nasopharyngeal carcinomas and throat washings from healthy individuals in Guangdong(NPC endemic area) and Shandong(NPC non-endemic area) of China.Methods: Polymerase chain reaction(PCR) and DNA sequencing were chosen for the BNLF2 a gene polymorphism study in EBV positive lymphomas, gastric carcinomas, nasopharyngeal carcinomas and throat washings from healthy individuals. After sequencing, the sequences were compared with EBV prototype B95-8 by DNAStar. All sequences were aligned and categorized by their consensus changes. One sequence was chosen to represent the samples which have identical sequences. Alignments between representative sequences were performed using Meg Align in DNAStar software and the phylogenetic tree was drawn using Clastal W method. The distribution of virus genotypes were compared among the groups and compared with the previous data in other areas.Results:(1)The BNLF2 a gene was successfully amplified and sequenced in 408 samples, According to the common mutations and the phylogenetic tree, all isolates can be divided into 2 subtypes, named BNLF2a-A and BNLF2a-B.(2) BNLF2a-A was the predominant gene type, it was detected in 374 samples. The new common mutation 167415 nt gâ†'a was detected.(3)BNLF2a-B was the subordinate gene type which was detected in 34 samples, the two common mutations were A8 T and R40 K.(4)The TWs and tumors from the Guangdong had significantly higher rate of BNLF2a-A subtype than in the specimens from the Shandong(P<0.05), respectively. And the frequency of BNLF2a-A was higher in Guangdong NPC than Shandong NPC(P<0.05).(5)The distribution of BNLF2 a subtypes was significantly different in the groups of Shandong isolates with P value <0.001. The frequency of BNLF2a-B was significantly higher in Shandong TWs than in malignancies(P<0.05); however the variation type distribution was not significantly different between lymphoma, EBVa GCs, and NPCs in Shandong province(P>0.05).Conclusions:(1)BNLF2a gene is highly conserved, BNLF2a-A is the predominant gene type in china.(2)The BNLF2a-A frequency of Guangdong population is higher than Shandong, the distribution of BNLF2 a polymorphism is geographically restricted.(3)The frequency of BNLF2a-A is significantly higher in Shandong malignancies than in TWs, thus it was inferred that BNLF2 a type EBV may contributed to the genisis of EBV associated tumors. |
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