Thermosensation: How a human-infective nematode finds its host

Abstract

The parasitic nematode Strongyloides stercoralis locates human hosts via thermal cues through unknown neural mechanisms. A new study finds that the heat-sensing neuron AFD mediates attraction to human body heat. Interestingly, this neuron also mediates thermotaxis in the nematode C. elegans.

Figure 1.. Heat-sensing mechanisms in C. elegans versus S. stercoralis.

Heat-sensing mechanisms in S. stercoralis show striking parallels to those found in C. elegans, but exhibit a biphasic calcium response, suggesting a more complex mechanism. In both panels, upper red trace represents neuronal calcium level, while lower black trace represents corresponding temperature change. Both traces plotted across time. A) Top: Warming ramps above cultivation temperature induce excitatory responses in Ce-AFD. Bottom: The Ce-AFD signal transduction cascade mediating thermotaxis in C. elegans. Upon warming above ambient temperatures, guanylate cyclases GCY-8, −18, −23 are activated to catalyze the production of cGMP from GTP. cGMP opens cyclic-nucleotide gated (CNG) channels to allow cation influx, resulting in neuronal excitation.(B) Top: Warming ramps above cultivation temperature induce a biphasic response in Ss-AFD, characterized by a transient inhibitory response followed by a linear relaxation upon approaching host body temperature. Bottom: Proposed Ss-AFD signal transduction cascade mediating neuronal inhibition. Decreases in both calcium and cGMP are observed upon warming above ambient temperatures. Phophodiesterase potentially mediates this initial transient inhibitory phase in Ss-AFD. Models made using Biorender.