Genetic and biological differentiation of dengue 3 isolates obtained from clinical cases in Java, Indonesia, 1976–1978

Summary

Previous epidemiological, virological and clinical studies have documented a series of outbreaks of dengue fever and dengue haemorrhagic fever/dengue shock syndrome which occured in Java, Indonesia in 1976–1978. In the current study we compare growth characteristics in cell culture, and nucleotide sequence data for the viral prM and E genes, of five low passage DEN-3 isolates obtained during these epidemics from clinically defined cases. All isolates had the same passage history: human sera were passed twice in mosquitoes and three times in a mosquito cell line (Aedes albopictus, C6/36 cells). Growth differences were observed between individual isolates in Vero cells; growth differences were not observed in C 6/36 cells. Nucleotide sequencing of the prM and E gene region indicated that no two isolates were identical (sequence divergence ranged from 0.4 to 1.6% in pairwise comparisons) but that they were closely enough related to present a single genetic type. There were one or two differences in deduced amino acid sequence in E between isolates. Differences were at residues 65, 187, 298 or 443. One isolate differed from all others at residue 16 in the M protein. No relationship was apparent between the amino acid sequence of M or E and the nature of the disease profile, the year of isolation or the geographic region of isolation. The isolates showed 3.5 to 4.4% nucleotide sequence divergence from the highly-adapted H 87 prototype, isolated in the Philippines in 1956. The isolates showed a total of twelve common amino acid differences in prM and E proteins from H 87. Ten of these twelve residues were at positions which differed between the four dengue serotypes. Two differences (at residues 37 in M and 293 in E) were at positions which are conserved in sequence between the four dengue serotypes. The data are discussed in relation to the dengue outbreaks in Java in the period 1976–1978.