Adamo Shelley A, Kovalko Ilya, Easy Russell H, Stoltz Don
Department of Psychology and Neuroscience, Dalhousie University, Halifax, NS, Canada B3H 4R2.
Department of Microbiology and Immunology, Dalhousie University, Halifax, NS, Canada B3H 4R2.
J Exp Biol. 2014 Jun 1;217(Pt 11):1970-6. doi: 10.1242/jeb.103408. Epub 2014 Mar 13.
We identified the insect iridovirus IIV-6/CrIV as a pathogen of the cricket Gryllus texensis using electron microscopy (EM) and polymerase chain reaction (PCR) analysis. EM showed that the virus attacks the fat body, an organ important for protein production, immune function and lipid storage. During infection the fat body hypertrophied, but egg production withered, leaving the lateral oviducts empty of eggs; the females were effectively sterile. EM of the testis of infected males suggests that the testis was not invaded by the virus, although sperm taken from the spermatophores of infected males showed little or no motility. Nevertheless, males and females continued to mate when infected. In fact, infected males were quicker to court females than uninfected controls. The virus benefits from the continued sexual behaviour of its host; transmission studies show that the virus can be spread through sexual contact. Sickness behaviour, the adaptive reduction of feeding and sexual behaviour that is induced by an activated immune system, was absent in infected crickets. Total haemolymph protein was reduced, as was phenoloxidase activity, suggesting a reduction in immune protein production by the fat body. The evidence suggests that during IIV-6/CrIV infection, the immune signal(s) that induces sickness behaviour is absent. Curtailment of a host's sickness behaviour may be necessary for any pathogen that is spread by host sexual behaviour.
我们通过电子显微镜（EM）和聚合酶链反应（PCR）分析，确定昆虫虹彩病毒IIV-6/CrIV是德州蟋螽的病原体。电子显微镜显示，该病毒攻击脂肪体，脂肪体是一个对蛋白质产生、免疫功能和脂质储存很重要的器官。在感染过程中，脂肪体肥大，但产卵量减少，侧输卵管内无卵；雌性实际上不育。对受感染雄性睾丸的电子显微镜观察表明，睾丸未被病毒侵袭，尽管从受感染雄性精荚中取出的精子活力很小或没有活力。然而，受感染的雄性和雌性在感染后仍继续交配。事实上，受感染的雄性比未受感染的对照组更快地向雌性求爱。病毒从其宿主持续的性行为中受益；传播研究表明，该病毒可通过性接触传播。受感染的蟋蟀没有出现疾病行为，即由激活的免疫系统诱导的适应性进食和性行为减少。血淋巴总蛋白减少，酚氧化酶活性也降低，这表明脂肪体产生的免疫蛋白减少。证据表明，在IIV-6/CrIV感染期间，诱导疾病行为的免疫信号不存在。对于任何通过宿主性行为传播的病原体来说，抑制宿主的疾病行为可能是必要的。
