Polymorphisms On Latent Membrane Protein 1 Gene Of Epstein-barr Virus In Pediatric Patients With Lymphoma And Infectious Mononucleosis

Background and objective: Epstein-Barr Virus(EBV)-encoded latent membrane protein 1(LMP1)plays important roles in the tumorigenesis of EBV-related tumors.Different sequence variations have been found in LMP1 gene and much attention has been focused on the association of LMP1 variants with EBV-associated tumors.Among the studies about polymorphisms of LMP1 in lymphoma cases,most limited to the lymphomas in adults.Furthermore,whether the LMP1 variants preferentially associate with lymphomas or represent geographical polymorphism remains controversial.To characterize the variations of the LMP1 gene in pediatric lymphomas and to explore the association between LMP1 gene variations and lymphomas,the sequences of LMP1 gene in pediatric patients with lymphoma and infectious mononucleosis(IM)from Qingdao area were analyzed.Method: PCR and DNA sequencing were used to analyze the gene sequences of LMP1 in isolates from 66 EBV-positive pediareic lymphoma tissues(26 Hodgkin's lymphomas and 40 non-Hodgkin's lymphomas)and 53 EBV-positive blood samples of IM in Qingdao.The nucleotide and amino acid sequences of LMP1 were compared with the prototype B95-8 strain and classified according to the signature changes and the phylogenetic tree.The distribution of LMP1 variants was compared between lymphomas and IM cases,as well as between different lymphomas.Results:(1)Compared with the LMP1 sequence of B95-8 prototype,all sequences of LMP1 gene from 119 isolates demonstrated sequence variations,including point nucleotide mutations,insert,deletions and repetitive sequence changes.According to phylogenetic tree and the signature changes in exons of LMP1,three major subtypes(China 1,China 2 and Med-)and a few recombinant strains of different subtypes,were identified.Furthermore,three major variants also carried characteristic changes in introns and repetitive sequence region.Three LMP1 subtypes demonstrated various spectrum to Xho I(-)(loss of an Xho I site)in N-terminus of LMP1 and del-LMP1(30 bp deletion)in C-terminus of LMP1.(2)The frequencies of China 1,China 2 and Med-in lymphomas were 84.8%(56/66),7.6%(5/66)and 6.1%(4/66),respectively,and those in IM cases were 67.9%(46/53),5.7%(3/53)and 22.6%(12/53),respectively.Another 1(1.5%)lymphoma isolate and 2(3.8%)IM isolates were recombinant strains of different subtypes.The distribution of LMP1 subtypes between lymphoma and IM was significant different(P=0.036).The frequencies of Xho I(-)and del-LMP1 in lymphomas(93.9%,62/66 and 84.8%,56/66)were significantly higher than those in IM cases(75.5%,40/53 and 69.8%,37/53),and the differences were significant(P=0.004,0.049).(3)There was no significant difference of the distribution of LMP1 gene variants between 26 Hodgkin's lymphomas and 40 non-Hodgkin's lymphomas.Conclusions:(1)China 1,Xho I(-)and del-LMP1 are the major LMP1 subtypes in pediatric patients with lymphoma and IM in Qingdao area.(2)The higher frequencies of China 1,Xho I(-)and del-LMP1 in lymphomas than IM suggest their association with the susceptibility of lymphomas although no evidence for cell tropism of specific lymphomas is found.