Downloaded from www.microbiologyresearch.org by IP: 23.22.24.125 On: Fri, 26 Feb 2016 22:21:18 Journal of General Virology (1997), 78, 2279–2286. Printed in Great Britain ............................................................................................................................................................................................................... SHORT COMMUNICATION Molecular evolution and phylogeny of dengue-4 viruses Robert S. Lanciotti, Duane J. Gubler and Dennis W. Trent Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Public Health Service, US Department of Health and Human Services, PO Box 2087, Fort Collins, CO 80522, USA Nucleotide sequences of the envelope protein genes of 19 geographically and temporally distinct dengue (DEN)-4 viruses were determined. Nucleic acid sequence comparison revealed that the ident- ity among the DEN-4 viruses was greater than 92 %. Similarity among deduced amino acids was between 96 and 100 % ; in most cases identical amino acid substitutions occurred among viruses from similar geographical regions. Alignment of nucleic acid sequences followed by parsimony analysis generated phylogenetic trees, which indicated that geographically independent evol- ution of DEN-4 viruses had occurred. DEN-4 viruses were separated into two genetically distinct sub- types (genotypes). Genotype-1 contains viruses from the Philippines, Thailand and Sri Lanka ; genotype-2 consists of viruses from Indonesia, Tahiti, the Caribbean Islands (Puerto Rico, Dominica) and Central and South America. Dengue viruses (family Flaviviridae, genus Flavivirus) are single-stranded plus-sense RNA viruses that are the aetio- logical agents of dengue fever (DF) and dengue haemorrhagic feverdengue shock syndrome (DHFDSS) in humans. These viruses are transmitted between humans primarily by Aedes aegypti mosquitoes and are currently endemic throughout most tropical areas of the world (Gubler, 1991). Epidemics of DF occurred irregularly during the first half of the 20th century. However, after World War II epidemic DHF emerged in Southeast Asia and has subsequently spread to the Pacific Islands and the Americas (Gubler, 1988 ; Henchal & Putnak, 1990). Dengue viruses are serologically classified into four antigenically distinct serotypes (DEN-1, DEN-2, DEN-3 and DEN-4). In most cases, infection results in a mild, self-limiting febrile illness (DF). However, some dengue virus infections result in vascular and haemostatic abnormalities, which may Author for correspondence : Robert S. Lanciotti. Fax  1 303 221 6476. e-mail rs12CIDVBI1.EM.CDC.GOV The GenBank accession numbers of the sequences reported in this paper are U18425–U18442. progress to haemorrhage and shock (DHFDSS). The precise mechanism(s) by which dengue viruses cause severe haem- orrhagic disease is not well understood. One theory suggests that severe disease results from secondary infection with a heterologous dengue serotype virus (Halstead, 1988). This model postulates that circulating antibodies to the primary infecting virus can bind to the heterologous secondary infecting virus and enhance virus infection of mononuclear cells. An alternative explanation postulates that the increase in worldwide transmission of dengue virus in the past 50 years has elevated the rate of virus evolution, resulting in the generation of more virulent or epidemic strains (Rosen, 1977 ; Zanotto, 1996). Laboratory data support both hypotheses, and it is likely that both mechanisms are involved in producing epidemics of severe disease (Gubler & Trent, 1994). Previous studies of dengue virus evolution have described the extent of molecular evolution within DEN-1, DEN-2, DEN-3 and DEN-4 serotypes (Blok et al., 1989, 1991 ; Rico- Hesse, 1990 ; Lewis et al., 1993 ; Lanciotti et al., 1994 ; Chungue Table 1. Description of DEN-4 viruses compared by sequence analysis Geographical GenBank origin Year Strain accession no. Brazil 1982 1385 U18425 Dominica 1981 814669 – El Salvador 1983 1411 U18426 El Salvador 1994 BC6494 U18427 Indonesia 1973 30153 U18428 Indonesia 1976 1036 U18429 Indonesia 1977 1132 U18430 Mexico 1984 1492 U18431 New Caledonia 1981 5489 U18432 Philippines 1956 H-241 U18433 Philippines 1964 16589-64 U18434 Philippines 1984 12123 U18435 Puerto Rico 1986 1650 U18436 Sri Lanka 1978 S-44750 U18437 Tahiti 1979 S-44754 U18438 Tahiti 1985 114-094-85 U18439 Thailand 1963 TC2443-63 U18440 Thailand 1978 D78-017 U18441 Thailand 1984 D84-024 U18442 0001-4402 CCHJ