Sequencing and structural analysis of structural gene of three dengue virus type 2 isolated from Guangdong province
Objective To study the interrelation, variation and origin of three strains of dengue virus prevailed in Guangdong province since 1990 by sequencing and structural analysis of their structural genes. Methods According to the genome of dengue virus type 2 NGC strain, two pairs of primers were designed. The structural protein genes (C, PrM, E) of three strains of dengue virus type 2 isolated from different years were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR), then cloned into pMD18-T vector and sequenced, respectively. Results The structural gene of each of three strains of dengue virus was constituted by 2325 nucleotides encoding 775 amino acids. The nucleotide (amino acid) homologies were 96% (97%), 94% (97%) and 92% (94%) between GD06/93 and GD19/2001, GD06/93 and GD08/98, and GD08/98 and GD19/2001, respectively. In three strains of dengue virus, the amino acids at the virulence related site E383-385 were all GLU-PRO-GLY, and at E126 were all GLU. GD06/93 and GD19/2001 showed a high homology with international standard strain TSV01 (Australia), the nucleotide (amino acid) homology was 98% (98%). Meanwhile strain GD08/98 showed a highest homology with international standard strain ThNH-P28/93 (Thailand), the nucleotide (amino acid) homology was 98%(98%). Compared with the non-neurovirulence of strain 04 of dengue virus type 2, the variance of amino acid second structure mainly situated at 393-400 and 337-343 sites, 3 isolates in this laboratory were EEEEHHHH and HH-------HHHHH,while strain 04 was EEEE----and --------HHHHE. Conclusion GD06/93, GD19/2001 and TSV01 may belong to the same genotype; GD08/98 and ThNH-P28/93 may belong to another genotype. Compared with the strain 04 of dengue virus type 2, the second structures of 3 strains of dengue virus isolated from Guangdong province in the Ⅲ domain of E protein show a notable variance, these variances may be related with the virulence of different strains of dengue virus. [