GENETIC AND BIOLOGICAL DIFFERENTIATION OF DENGUE-3 ISOLATES OBTAINED FROM CLINICAL CASES IN JAVA, INDONESIA, 1976-1978

Previous epidemiological, virological and clinical studies have docume nted a series of outbreaks of dengue fever and dengue haemorrhagic fev er/dengue shock syndrome which occured in Java, Indonesia in 1976-1978 . In the current study we compare growth characteristics in cell cultu re, and nucleotide sequence data for the viral prM and E genes, of fiv e low passage DEN-3 isolates obtained during these epidemics from clin ically defined cases. All isolates had the same passage history: human sera were passed twice in mosquitoes and three times in a mosquito ce ll line (Aedes albopictus, C 6/36 cells). Growth differences were obse rved between individual isolates in Vero cells; growth differences wer e not observed in C 6/36 cells. Nucleotide sequencing of the prM and E gene region indicated that no two isolates were identical (sequence d ivergence ranged from 0.4 to 1.6% in pairwise comparisons) but that th ey were closely enough related to present a single genetic type. There were one or two differences in deduced amino acid sequence in E betwe en isolates. Differences were at residues 65, 187, 298 or 443. One iso late differed from all others at residue 16 in the M protein. No relat ionship was apparent between the amino acid sequence of M or E and the nature of the disease profile, the year of isolation or the geographi c region of isolation. The isolates showed 3.5 to 4.4% nucleotide sequ ence divergence from the highly-adapted H 87 prototype, isolated in th e Philippines in 1956. The isolates showed a total of twelve common am ino acid differences in prM and E proteins from H 87. Ten of these twe lve 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 sero types. The data are discussed in relation to the dengue outbreaks in J ava in the period 1976-1978.