Chemotactic responses of Brugia pahangi infective third-stage larvae to tris(hydroxymethyl)aminomethane-related compounds and amino acids

Abstract

Since the exogenous compound tris(hydroxymethyl)aminomethane (Tris) showed a potent chemoattractant activity for Brugia pahangi infective third-stage larvae (L3), it was assumed that, in natural infection to a host, filarial L3 can be expected to recognize an endogenous Tris-related compound. In addition, a few amino acids have been identified as water-soluble attractants for second-stage juveniles of Meloidogyne incognita, a plant parasitic nematode. Therefore, the present study assesses the in vitro chemotactic responses of B. pahangi L3 to Tris-related compounds and amino acids using an agar-plate assay. Among Tris-related compounds, 2-amino-1,3-propanediol (APD) and 2-amino-2-methyl-1,3-propanediol (AMPD) exhibited a potent chemoattractant activity for filarial L3 at a level similar to Tris. Furthermore, arginine (Arg) was identified as a potent attractant for filarial L3 among amino acids. In addition, filarial L3 were attracted to Arg, APD and AMPD in mild alkaline conditions rather than acidic conditions. The chemoattractant activity of the three compounds for filarial L3 was observed in concentrations between 6.3 and 200 mm. This is the first report to demonstrate that Arg, APD and AMPD are potent chemoattractants for B. pahangi L3. Endogenous Arg and APD, in particular, may be involved in the regulation of the chemotactic behaviour of filarial L3 in the infection to a host. The present results will help to elucidate the mechanism of filarial skin-penetrating invasion of a host.

A high-throughput nematode sensory assay reveals an inhibitory effect of ivermectin on parasite gustation

“…We and others have previously shown that the L3 stage of vector-borne filarial nematodes specifically respond to a variety of cues associated with mammalian skin and internal tissues (Fraser et al, 2018;Kusaba et al, 2008;Mitsui et al, 2012;Mitsui et al, 2018;Mitsui et al, 2021;Wheeler et al, 2020). These were performed in two-dimensions on agarose plates, upon which L3s show limited translational movement (parasite larvae are placed only a few millimeters away from the cue, in comparison to C. elegans being placed several centimeters away from a cue).…”

“…For these nematodes, it is likely that gustation is more prominent than olfaction, yet the assays used to probe sensation of vector-borne nematodes are almost identical to those first developed using C. elegans. These assays have reliably shown that filarial nematodes respond to a variety of host cues (Fraser et al, 2018;Kusaba et al, 2008;Mitsui et al, 2021;Wheeler et al, 2020), but the throughput is low and the quantitative output lacks sensitivity, relying on large effect sizes in order to statistically resolve behavioral differences.…”