Physiological age versus chronological age: defining how temperature impacts the aging of the mosquito immune system

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Insects fight infection by mounting immune responses. The effectiveness of these immune responses is dependent on multiple factors. One of these is the temperature of the environment, with different types of immune responses being stronger at different temperatures. Another factor that affects the strength of an insect’s immune response is age. As an insect becomes older, its immune system weakens. Although this is accepted, an important question that remains unanswered is whether the effect that temperature has on the immune system changes – for better or worse – as an insect becomes older. Therefore, the goal of this project is to understand how the immune systems ages, and the role that temperature plays in the aging process. This research is important because ongoing changes in the environment are shifting the temperature in which insects live. Overall, this project’s findings will allow researchers to predict how changes in environmental temperature alter the ability of an insect to fight an infection throughout its entire life, which is significant because some insects are essential for our food supply, and others are agricultural pests and transmitters of disease. Conducting this project will also advance the education of undergraduate students, graduate students and school-aged children, with the goal of motivating them to pursue experiences and careers in science. Outreach with high school students will be accomplished in partnership with the School for Science and Math at Vanderbilt, and outreach with elementary school students will be accomplished in partnership with Metro Nashville Public Schools.The ability of an insect to fight infection is modified by both the external environment and its life history. Two modifiers of immune processes are temperature and age. That is, immune proficiency changes as a function of the environmental temperature, and also declines as a function of age, a phenomenon known as senescence. Although both temperature and age impact immune proficiency, these two factors have always been studied in isolation. That is, studies testing the effect of temperature on immune function have been carried out at a predetermined age, and studies testing the effect of aging on immune proficiency have been carried out at a predetermined temperature. Therefore, the overarching goal of this project is to define how environmental temperature modifies immune senescence. Focusing on the societally important mosquito, Anopheles gambiae, this project will (i) define the infection-induced effects of temperature on the aging process, (ii) determine how temperature and infection interact to shape age-dependent humoral and cellular immunity, and (iii) define how blood feeding impacts the effect of temperature on aging. When completed, this project will uncover whether differences in environmental temperature alter the rate in which the insect immune system ages, resulting in a decoupling of chronological age and physiological age. The findings will provide a more holistic understanding of how insects fight infection in a changing landscape and should augment the robustness of models used to predict the effectiveness of insects as pollinators, agricultural pests, and disease vectors.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.