Vazeille Marie, Gaborit Pascal, Mousson Laurence, Girod Romain, Failloux Anna-Bella
Institut Pasteur, Department of Virology, Arboviruses and Insect Vectors, 25 rue du Dr Roux, 75724, Paris Cedex 15, France.
Medical Entomology Unit, Institut Pasteur of French Guiana, Cayenne, French Guiana.
BMC Infect Dis. 2016 Jul 8;16:318. doi: 10.1186/s12879-016-1666-0.
Dengue viruses (DENV) are comprised in four related serotypes (DENV-1 to 4) and are critically important arboviral pathogens affecting human populations in the tropics. South American countries have seen the reemergence of DENV since the 1970's associated with the progressive re-infestation by the mosquito vector, Aedes aegypti. In French Guiana, DENV is now endemic with the co-circulation of different serotypes resulting in viral epidemics. Between 2009 and 2010, a predominant serotype change occurred from DENV-1 to DENV-4 suggesting a competitive displacement. The aim of the present study was to evaluate the potential role of the mosquito in the selection of the new epidemic serotype.
To test this hypothesis of competitive displacement of one serotype by another in the mosquito vector, we performed mono- and co-infections of local Ae. aegypti collected during the inter-epidemic period with both viral autochthonous epidemic serotypes and compared infection, dissemination and transmission rates. We performed oral artificial infections of F1 populations in BSL-3 conditions and analyzed infection, dissemination and transmission rates.
When two populations of Ae. aegypti from French Guiana were infected with either serotype, no significant differences in dissemination and transmission were observed between DENV-1 and DENV-4. However, in co-infection experiments, a strong competitive advantage for DENV-4 was seen at the midgut level leading to a much higher dissemination of this serotype. Furthermore only DENV-4 was present in Ae. aegypti saliva and therefore able to be transmitted.
In an endemic context, mosquito vectors may be infected by several DENV serotypes. Our results suggest a possible competition between serotypes at the midgut level in co-infected mosquitoes leading to a drastically different transmission potential and, in this case, favoring the competitive displacement of DENV-1 by DENV-4. This phenomenon was observed despite a similar replicative fitness in mono-infections conditions.
登革病毒（DENV）由四种相关血清型（DENV-1至4）组成，是影响热带地区人群的极其重要的虫媒病毒病原体。自20世纪70年代以来，南美国家见证了DENV的重新出现，这与蚊媒埃及伊蚊的逐步再次侵扰有关。在法属圭亚那，DENV现已成为地方病，不同血清型共同传播导致病毒流行。在2009年至2010年间，主要血清型从DENV-1转变为DENV-4，提示存在竞争性替代。本研究的目的是评估蚊子在新流行血清型选择中的潜在作用。
为了检验在蚊媒中一种血清型被另一种血清型竞争性替代的这一假设，我们用当地流行的两种病毒血清型对流行间期采集的埃及伊蚊进行了单感染和共感染，并比较了感染、传播和传播率。我们在生物安全3级条件下对F1代群体进行了经口人工感染，并分析了感染、传播和传播率。
当法属圭亚那的两群埃及伊蚊分别感染任一血清型时，DENV-1和DENV-4在传播和传播方面未观察到显著差异。然而，在共感染实验中，在中肠水平上观察到DENV-4具有很强的竞争优势，导致该血清型的传播率高得多。此外，埃及伊蚊唾液中仅存在DENV-4，因此能够传播。
在地方病流行的情况下，蚊媒可能会被几种DENV血清型感染。我们的结果表明，在共感染的蚊子中，血清型在中肠水平可能存在竞争，导致传播潜力截然不同，在这种情况下，有利于DENV-4竞争性替代DENV-1。尽管在单感染条件下复制适应性相似，但仍观察到了这一现象。
