PLoS Negl Trop Dis：低温可降低蚊子免疫力 使其对某些病毒更加易感

近日，刊登在国际杂志PLoS Neglected Tropical Diseases上的一篇研究报告中，来自弗吉尼亚理工学院的研究者通过研究表明，当蚊子处于低温条件下后，其机体免疫力会变弱，这就使得其对危险的病毒更加易感，而且有可能将这些易感病毒传染给人类。

研究者Myles表示，我们的研究数据提出了一种合理的假说，就是天气的变化如何影响疾病的传播。随着全球气候的变化，多样的天气随时都会发生。本文的研究者就重点研究了气候改变和疾病传播之间的关系。

研究者说道，蚊子一般在黑暗潮湿的环境中繁殖产卵，因为其产的卵会在水中生存很久，蚊子不会在太阳光下产卵，因为不利于卵的存活，尽管如此，研究者依然试图去研究环境对蚊子免疫系统的影响，研究者希望可以通过本项研究来建立更好的研究模型从而预测疾病的传播趋势。

当前的计算机疫情模型主要考虑到气象学的变化以及人口指数，但是并没有考虑到温度对于蚊子免疫力的影响效应，研究者就发现当蚊子处于较低温度下时，其RNA干扰途径就会被损伤，进而就会增加对某些病毒的易感性，从而就会间接地传染给人类。

疾病的传播以及爆发都会发生在意想不到的地方，比如1999年在纽约爆发的西尼罗河病毒、2007年和2010年在意大利和法国爆发的切昆贡亚病毒等，因此本项研究对于预测蚊子所携带疾病的传播非常重要。

Cooler Temperatures Destabilize RNA Interference and Increase Susceptibility of Disease Vector Mosquitoes to Viral Infection
Background
The impact of global climate change on the transmission dynamics of infectious diseases is the subject of extensive debate. The transmission of mosquito-borne viral diseases is particularly complex, with climatic variables directly affecting many parameters associated with the prevalence of disease vectors. While evidence shows that warmer temperatures often decrease the extrinsic incubation period of an arthropod-borne virus (arbovirus), exposure to cooler temperatures often predisposes disease vector mosquitoes to higher infection rates. RNA interference (RNAi) pathways are essential to antiviral immunity in the mosquito; however, few experiments have explored the effects of temperature on the RNAi machinery.
Methodology/Principal Findings
We utilized transgenic “sensor” strains of Aedes aegypti to examine the role of temperature on RNA silencing. These “sensor” strains express EGFP only when RNAi is inhibited; for example, after knockdown of the effector proteins Dicer-2 (DCR-2) or Argonaute-2 (AGO-2). We observed an increase in EGFP expression in transgenic sensor mosquitoes reared at 18°C as compared with 28°C. Changes in expression were dependent on the presence of an inverted repeat with homology to a portion of the EGFP sequence, as transgenic strains lacking this sequence, the double stranded RNA (dsRNA) trigger for RNAi, showed no change in EGFP expression when reared at 18°C. Sequencing small RNAs in sensor mosquitoes reared at low temperature revealed normal processing of dsRNA substrates, suggesting the observed deficiency in RNAi occurs downstream of DCR-2. Rearing at cooler temperatures also predisposed mosquitoes to higher levels of infection with both chikungunya and yellow fever viruses.
Conclusions/Significance
This data suggest that microclimates, such as those present in mosquito breeding sites, as well as more general climactic variables may influence the dynamics of mosquito-borne viral diseases by affecting the antiviral immunity of disease vectors.