The common cold virus can reproduce itself more efficiently in the cooler temperatures found inside the nose than at core body temperature, according to a new Yale-led study. This finding may confirm the popular yet contested notion that people are more likely to catch a cold in cool-weather conditions.

Researchers have long known that the most frequent cause of the common cold, the rhinovirus, replicates more readily in the slightly cooler environment of the nasal cavity than in the warmer lungs. However, the focus of prior studies has been on how body temperature influenced the virus as opposed to the immune system, said study senior author and Yale professor of immunobiology Akiko Iwasaki.

To investigate the relationship between temperature and immune response, Iwasaki and an interdisciplinary team of Yale researchers spearheaded by Ellen Foxman, a postdoctoral fellow in Iwasaki's lab, examined the cells taken from the airways of mice. They compared the immune response to rhinovirus when cells were incubated at 37 degrees Celsius, or core body temperature, and at the cooler 33 degrees Celsius. "We found that the innate immune response to the rhinovirus is impaired at the lower body temperature compared to the core body temperature," Iwasaki said.

The study also strongly suggested that the varying temperatures influenced the immune response rather than the virus itself. Researchers observed viral replication in airway cells from mice with genetic deficiencies in the immune system sensors that detect virus and in the antiviral response. They found that with these immune deficiencies, the virus was able to replicate at the higher temperature. "That proves it's not just virus intrinsic, but it's the host's response that's the major contributor," Iwasaki explained.

Although the research was conducted on mouse cells, it offers clues that may benefit people, including the roughly 20% of us who harbor rhinovirus in our noses at any given time. "In general, the lower the temperature, it seems the lower the innate immune response to viruses," noted Iwasaki. In other words, the research may give credence to the old wives' tale that people should keep warm, and even cover their noses, to avoid catching colds.

Yale researchers also hope to apply this insight into how temperature affects immune response to other conditions, such as childhood asthma. While the common cold is no more than a nuisance for many people, it can cause severe breathing problems for children with asthma, noted Foxman. Future research may probe the immune response to rhinovirus-induced asthma.

The study was published in the Proceedings of the National Academy of Sciences.

参考译文：

千百年来，人体收到寒凉侵袭容易导致感冒是一种常识，直到今天仍是绝大多数人的真理。

医学上，上世纪70年代发表在新英格兰医学杂志上的系列研究认为寒冷与感冒没有直接相关性，并逐渐成为主流医学界共识。

但是，这并没有说服所有人，包括医学业内人士。因为除了常识之外，寒冷作为一种事件性因素，可以激发人体应激反应，而应激反应下人体免疫反应通常受到抑制。

而且，先前的研究已经确认，引起感冒的最常见病毒，鼻病毒在比人体核心温度低的鼻腔环境更容易复制。但是，以前的研究的重点是温度对于病毒的影响，而不是免疫系统。

发表在1月5日美国国家科学院院刊 上一项来自耶鲁大学的研究中，研究人员测试了采集自小鼠呼吸道的上皮细胞在不同温度下针对鼻病毒做出的先天性免疫反应强度，发现细胞在33℃下对鼻病毒免疫反应强度明显低于人体核心体温37℃情况下。

研究人员还观察了免疫感应缺陷小鼠呼吸道上皮细胞抗病毒免疫反应，发现较高的温度下病毒也可以在这些免疫缺陷细胞内复制。证明，温度的影响主要不在病毒本身而是宿主的免疫反应。

虽然该实验室离体细胞研究的结果不一定完全试用于人体，但是毕竟给出这样一个提示，温度越低细胞对于病毒先天性免疫应答强度也就越低。

通常情况下，大致有20%的人鼻腔存在可以引发感冒的鼻病毒，这个实验结果提示，受凉或许可以通过影响人体的免疫反应而更加容易发生感冒的可能性。

耶鲁大学的研究人员还希望能够用这种研究方法深入研究温度对于其他疾病可能存在的影响，比如儿童哮喘的免疫反应等。

原始来源：http://www.sciencedaily.com/releases/2015/01/150105170014.htm