Laboratoire de recherche en virologie médicale, Institut Louis Malardé, Papeete, Tahiti, French Polynesia.
PLoS One. 2011;6(12):e29555. doi: 10.1371/journal.pone.0029555. Epub 2011 Dec 28.
Infection by dengue virus (DENV) is a major public health concern in hundreds of tropical and subtropical countries. French Polynesia (FP) regularly experiences epidemics that initiate, or are consecutive to, DENV circulation in other South Pacific Island Countries (SPICs). In January 2009, after a decade of serotype 1 (DENV-1) circulation, the first cases of DENV-4 infection were reported in FP. Two months later a new epidemic emerged, occurring about 20 years after the previous circulation of DENV-4 in FP. In this study, we investigated the epidemiological and molecular characteristics of the introduction, spread and genetic microevolution of DENV-4 in FP.
METHODOLOGY/PRINCIPAL FINDINGS: Epidemiological data suggested that recent transmission of DENV-4 in FP started in the Leeward Islands and this serotype quickly displaced DENV-1 throughout FP. Phylogenetic analyses of the nucleotide sequences of the envelope (E) gene of 64 DENV-4 strains collected in FP in the 1980s and in 2009-2010, and some additional strains from other SPICs showed that DENV-4 strains from the SPICs were distributed into genotypes IIa and IIb. Recent FP strains were distributed into two clusters, each comprising viruses from other but distinct SPICs, suggesting that emergence of DENV-4 in FP in 2009 resulted from multiple introductions. Otherwise, we observed that almost all strains collected in the SPICs in the 1980s exhibit an amino acid (aa) substitution V287I within domain I of the E protein, and all recent South Pacific strains exhibit a T365I substitution within domain III.
CONCLUSIONS/SIGNIFICANCE: This study confirmed the cyclic re-emergence and displacement of DENV serotypes in FP. Otherwise, our results showed that specific aa substitutions on the E protein were present on all DENV-4 strains circulating in SPICs. These substitutions probably acquired and subsequently conserved could reflect a founder effect to be associated with epidemiological, geographical, eco-biological and social specificities in SPICs.
登革热病毒（DENV）感染是数百个热带和亚热带国家的主要公共卫生关注点。法属波利尼西亚（FP）经常经历登革热疫情，这些疫情是由 DENV 在其他南太平洋岛国（SPICs）的传播引发或相继引发的。2009 年 1 月，在 DENV-1 传播十年后，FP 首次报告了 DENV-4 感染病例。两个月后，新的疫情爆发，这是 DENV-4 在 FP 上一次流行后约 20 年发生的。在这项研究中，我们调查了 DENV-4 在 FP 中的引入、传播和遗传微进化的流行病学和分子特征。
方法/主要发现：流行病学数据表明，FP 中 DENV-4 的近期传播始于背风群岛，该血清型迅速取代了 FP 中的 DENV-1。对 1980 年代和 2009-2010 年在 FP 采集的 64 株 DENV-4 株的 E 基因核苷酸序列和来自其他 SPICs 的一些额外株进行的系统进化分析表明，来自 SPICs 的 DENV-4 株分为基因型 IIa 和 IIb。近期 FP 株分为两个簇，每个簇均包含来自其他但不同 SPICs 的病毒，表明 2009 年 FP 中 DENV-4 的出现是由多次传入引起的。此外，我们观察到，1980 年代在 SPICs 采集的几乎所有菌株在 E 蛋白的 I 结构域中都表现出氨基酸（aa）取代 V287I，而最近的所有南太平洋菌株在 III 结构域中都表现出 T365I 取代。
结论/意义：本研究证实了 DENV 血清型在 FP 中的周期性再次出现和取代。此外，我们的研究结果表明，所有在 SPICs 循环的 DENV-4 株都存在 E 蛋白上的特定 aa 取代。这些取代可能获得并随后保守，可能反映了与 SPICs 的流行病学、地理、生态生物学和社会特殊性相关的创始效应。
