Eliane Chungue

Prospective study of the duration and magnitude of viraemia in children hospitalised during the 1996-1997 dengue-2 outbreak in French Polynesia.

The magnitude and duration of viraemia in children admitted to the hospital with dengue was studied during a dengue 2 outbreak in French Polynesia in 1996–1997. Forty‐nine patients from whom at least 3 plasma samples were available were included in the study. Based on analysis of IgG‐ELISA and haemagglutination inhibition assay, 21 of these were primary and 28 were secondary infections. According to World Health Organization criteria, 42 were dengue fever and 7 were dengue haemorrhagic fever. Virus was detectable by reverse transcription‐PCR in all patients for at least the first 3 days of the onset of fever, but was never detected after the 6th day (mean duration = 4.4 days). Plasma virus titers ranged from 1.7–5.6 Log10 TCID50/ml. A significant difference was not observed in the magnitude and duration of viraemia in patients with primary versus secondary infections. The severity of the illness, however, was correlated with both criteria. J. Med. Virol. 60:432–438, 2000.

Identification of dengue sequences by genomic amplification: rapid diagnosis of dengue virus serotypes in peripheral blood

Polymerase chain reaction (PCR) was developed for the in vitro amplification of dengue virus RNA via cDNA. A fraction of the N-terminus gene of the envelope protein in the four dengue serotypes was amplified using synthetic oligonucleotide primer pairs. Amplified products were cloned and used as dengue type-specific probes in gel electrophoresis and dot-blot hybridization. We detected and characterized dengue virus serotypes in blood samples by the three-step procedure DNA-PAH consisting in cDNA priming (P), DNA amplification (A) and hybridization (H) using specific non-radiolabelled probes. Our findings showed that DNA-PAH was more rapid and sensitive in the identification of the infecting serotype than the mosquito cell cultures. Moreover, the failure of cultures to detect virus particles in sera containing few copies of viral genome or anti-dengue antibodies justified the approach of DNA-PAH to the dengue identification in clinical specimens.

MOLECULAR EPIDEMIOLOGY OF DENGUE-1 AND DENGUE-4 VIRUSES

Genetic variation between geographically and temporally distinct isolates of dengue-1 (DEN-1) and dengue-4 (DEN-4) viruses was investigated. The nucleotide sequences of a fragment of the envelope protein gene encoding amino acids 28 to 87 of 35 DEN-1 isolates and 28 DEN-4 isolates were determined. Maximum nucleotide sequence variation was 6.9% and 4.9% for DEN-1 and DEN-4 viruses, respectively. Taking a divergence of 6% between the nucleotide sequences as the cut-off value, three genotype groups were defined for DEN-1 viruses, whereas only one was observed for DEN-4 viruses. Molecular analysis of isolates from the South Pacific permits the classification of the recent strains of DEN-1 (1988-1989 epidemics) into a genotype distinct from the genotype which comprises earlier strains. This observation suggests that the recent epidemics were due to the introduction of a new genotype rather than to the re-emergence of the earlier strain.

Dengue: an evaluation of dengue severity in French Polynesia based on an analysis of 403 laboratory-confirmed cases

Summary We conducted a retrospective study of 403 laboratory‐confirmed dengue cases hospitalized in Tahiti between August 1989 and March 1997. According to standard WHO criteria, 337 of these cases were dengue fever (DF) and 64 were dengue haemorrhagic fever (DHF). Of the 10 fatal cases, 6 were DF and 4 were DHF. As an alternative, we used a correspondence analysis procedure to define dengue severity based on basic clinical and biological criteria for which we assigned a severity score, and then selected the 50 most severe cases from this analysis. Of the latter, 17 patients had been classified as DF and 33 as DHF by the WHO criteria. From this analysis, haemorrhages and decreased platelets counts associated with hepatic disorders are the main criteria associated with the severe dengue cases. Thus in our study population, the WHO classification does not account for the overall severity of dengue; hepatic failure should be considered as a specific severe form of dengue since plasma leakage, which is the pathophysiological hallmark of DHF, is only one of the pathogenic mechanisms leading to severity.

Molecular epidemiology of dengue 3 viruses and genetic relatedness among dengue 3 strains isolated from patients with mild or severe form of dengue fever in French Polynesia

The nucleotide sequences of a short fragment of the envelope protein gene encoding amino acids 25 to 89 of 27 dengue 3 viruses were determined by direct sequencing of PCR-amplified products, and the viruses were compared regarding their time of isolation and geographic distribution. Four distinct genotypic groups were discerned at 6% divergence between nucleotide sequences. The first group contained isolates from the South Pacific (1988 to 1992), Singapore (1973) and Indonesia (1973 to 1991). The second group comprised viruses from Asia (1956 to 1989) including the reference strain H-87. The third was composed of one isolate from Thailand (1971), and the fourth included the early strains from French Polynesia (1964 to 1969) and from Puerto Rico (1963). Furthermore, the difference between early and recent strains from the South Pacific was as high as 12.3%. This observation suggests that the recent epidemics in the South Pacific were probably the consequence of the spread of a new variant that emerged from New Caledonia. However, relatedness between nucleotide sequence and disease severity, or between strains from epidemics with mild disease (New Caledonia) and strains from epidemics with severe disease (French Polynesia) could not be demonstrated.

Dengue Virus Inhibits Human Hematopoietic Progenitor Growth In Vitro

Dengue disease, whether it be classical dengue fever (DF), dengue hemorrhagic fever (DHF), or dengue shock syndrome (DSS), is frequently associated with hematologic disorders. The underlying cause of these abnormalities is unknown. To determine if an inhibitory effect on human hematopoietic progenitor growth can be observed, normal cord blood mononuclear cells were exposed to low-passaged clinical isolates from DF, DHF, and DSS patients and to the prototype strain of dengue-3 virus (H-87). In primary methylcellulose cultures, there was no inhibition of colony formation. After an initial 8-day liquid culture, inhibition was observed with the isolates, but strain H-87 had no effect. Furthermore, isolates from patients with DSS showed a more potent inhibitory effect. These data represent the first documented study of in vitro impaired progenitor cell growth by dengue virus and suggest that this inhibition could be dependent upon the isolate tested.

Changing clinical and biological manifestations of dengue during the dengue-2 epidemic in French Polynesia in 1996/97 - description and analysis in a prospective study

In August 1996 dengue‐2 virus was detected in French Polynesia for the first time since 1976. A prospective study was conducted from November 1996 to April 1997. Each time one of 7 physicians suspected dengue, the patient was enrolled and epidemiological, clinical and biological data were recorded. Dengue diagnosis was confirmed by virus isolation and IgM detection. The aims of this study were to find clinical and biological predictive factors constituting a specific profile of dengue (DF) and dengue haemorrhagic fever (DHF/DSS) and to assess the possibility of diagnosing dengue at primary health care level using clinical criteria and basic laboratory parameters. Of 298 clinically suspect cases, 196 (66%) were confirmed as dengue. The association of macular rash, pruritis, low platelet count and leukopenia was statistically predictive of dengue but not clinically, since these four signs occur in many other viral infections. As the prevalence of clinical and biological manifestations varied over time in our study, a specific profile useful for dengue diagnosis cannot be defined. With six cases of DHF, the morbidity of this dengue‐2 outbreak was very low despite the sequential infection scheme DEN‐3/DEN‐2. The clinical expression of dengue could depend on a specific virus strain circulating in a specific population in a particular place, with varying virulence over time.

Plasma levels of tumour necrosis factor a and transforming growth factor β-1 in children with dengue 2 virus infection in French Polynesia

Abstract The pathogenesis of dengue haemorrhagic fever (DHF) is not well understood. In the absence of predictive clinical or biological criteria, the management of DHF patients remains difficult. The role played by cytokines in the occurrence of DHF has been suggested by several authors. In this study, we determined the plasma levels of tumour necrosis factor α (TNFα) and transforming growth factor β-1 (TGFβ-1) in 52 children with laboratory-confirmed dengue virus infection admitted to hospital during the recent dengue 2 outbreak in French Polynesia. Thirty-three children were classified as having dengue fever (DF) and 19 as DHF. The plasma of both DF and DHF patients contained similar levels of TNFα. By contrast, plasma obtained from children with DHF had significantly higher levels of TGFβ-1 than plasma from children with DF, especially from days 1 to 3 after the onset of fever.

Human T Lymphotropic Virus Type 1 Subtype C Melanesian Genetic Variants of the Vanuatu Archipelago and Solomon Islands Share a Common Ancestor

BACKGROUNDnMelanesia is endemic for human T lymphotropic virus type 1 (HTLV-1) subtype C. In 2005, we identified 4 infected women from Ambae Island, Vanuatu. Subsequently, 4247 Ni-Vanuatu originating from 18 islands were enrolled to define HTLV-1 epidemiological determinants and to characterize the viral strains molecularly.nnnMETHODSnPlasma from 1074 males and 3173 females were screened for HTLV-1/2 antibodies by particle agglutination (PA) and an immunofluorescence assay (IFA). Positive and/or borderline samples were then tested by a Western blot (WB) confirmatory assay. DNAs were amplified to obtain a 522-bp env gene fragment. Phylogenetic and molecular-clock analyses were performed.nnnRESULTSnOf 4247 samples, 762 were positive and/or borderline by IFA/PA, and 26 of them were confirmed to be HTLV-1 positive by WB. The overall HTLV-1 seroprevalence was 0.62%. Viral transmission was found within families of infected index case patients. A geographic heterogeneity of HTLV-1 seroprevalence was observed among the islands. All 41 of the new env sequences belonged to HTLV-1 subtype C. Phylogenetic and molecular-clock analyses suggested that Ni-Vanuatu and Solomon Islander strains emerged from a common ancestor ~10,000 years ago.nnnCONCLUSIONnThe Vanuatu archipelago is endemic for HTLV-1 with a diversity of subtype C variants. These strains were probably introduced into Vanuatu during ancient migration of the original settlers a few thousand years ago.

Diversity in symbiotic dinoflagellates (Pyrrhophyta) from seven scleractinian coral species : Restriction enzyme analysis of small subunit ribosomal RNA genes

ABSTRACT The diversity of symbiotic dinoflagellates (SD) from seven coral species (Fungia scutaria, Fungia paumotensis, Lep‐tastrea transversa, Pavona cactus, Pocillopora verrucosa, Montastrea curia, and Acropora fonnosa) was studied in a restricted geographical area, the Lagoon of Arue on the island of Tahiti. Their diversity was explored by small subunit ribosomal RNA gene (SSU rDNA) restriction fragment length polymorphism (RFLP). After a nested amplification with SD specific primers, RFLP analyses were performed directly and after a cloning step. The diversity of these different SSU rDNA was estimated in respect to possible technical artifacts. In an axenic culture of SD from the coral Galaxea fascicularis, both heterogeneous SSU rDNAs and artifact molecules were observed as in our SD samples. According to the number of patterns observed, corals Fungia paumotensis, Leptastrea transversa. Pavona cactus, Montastrea curia, and Acropora fonnosa contained one class of SD SSU rDNAs. whereas Fungia scutaria and Pocillopora verrucosa contained three and two classes of SD SSU rDNAs respectively. In the limited geographic area studied. SD from different coral species shared the same pattern, except SD from Montastrea curta, which showed a unique pattern. In addition to the possibility of SD flux among different coral species, specific mechanisms could also be involved in the establishment of a symbiosis.