Elissa A. Hallem
Mechanisms of Host-Parasite Interactions
The overall goal of our research is to understand the molecular and cellular basis of parasite-host interactions. A major focus is the behavioral responses of parasites to host olfactory cues. A second focus is the immune response to parasitic infection. We use insect-parasitic nematodes, mammalian-parasitic nematodes, and the free-living nematode C. elegans as model systems.
The neural basis of olfaction in parasitic nematodes
Host-seeking behavior by many parasites involves the integration of responses to the universal host cue carbon dioxide (CO2) with responses to host-specific olfactory cues. We previously showed that both free-living and parasitic nematodes respond to CO2, and that conserved neural circuitry mediates CO2 response across species regardless of whether CO2 is attractive or repulsive. We are now investigating the neural circuits and signaling pathways that mediate CO2 response in free-living and parasitic nematodes to gain insight into how parasites respond to hosts and how the nervous systems of parasites have evolved to support parasitic behaviors.
We are also investigating responses to host-specific olfactory cues. We are identifying host-derived odors by gas chromatography-mass spectrometry, and we are comparing the odor response profiles of insect-parasitic, mammalian-parasitic, and free-living nematodes in response to these and other ecologically relevant odors as well as live hosts. We are also mapping the neural circuits that mediate responses to host-derived odors and investigating the functional properties of these circuits. These experiments will provide insight into the evolution of olfactory behavior and olfactory neural circuitry in species with different lifestyles and ecological niches.
Immune response to parasitic nematode infection
We have shown that the insect-parasitic nematode Heterorhabditis bacteriophora is capable of infecting the fruit fly Drosophila melanogaster, and that infection results in a dynamic humoral immune response. We are now examining the humoral and cellular immune response of Drosophila to infection with H. bacteriophora and other insect-parasitic nematodes to better understand how animals respond to nematode infection.
Parasitic nematodes of humans, livestock, and plants cause extensive morbidity, mortality, and economic loss worldwide. A better understanding of how parasitic nematodes locate and infect hosts may lead to the development of new strategies for combating harmful nematode infections.