The effect of normal human serum on the mouse trypanosome Trypanosoma musculi in vitro and in vivo

Abstract

Trypanosoma musculi, a common blood flagellate found in mice, is similar in morphology and life cycle to the rat trypanosome T. lewisi. Both species belong to the subgenus Herpetosoma, and as T. lewisi has recently been shown to be a zoonotic pathogen, there is concern that T. musculi could also be potentially infective to humans. To test this hypothesis, a well-established method, the normal human serum (NHS) incubation test, was carried out which distinguishes human and non-human infective trypanosomes. We found that T. musculi could grow in 0.31% NHS in vitro, and even kept their infectivity to mice after incubation with 10% NHS for 24 h. In in vivo experiments, T. musculi were only slightly affected by NHS injection, confirming that it was less sensitive to the NHS than T. b. brucei, but more sensitive than T. lewisi. This resistance probably does not rely on a restricted uptake of ApoL-1. Due to this partial resistance, we cannot definitively confirm that T. musculi has the potential for infection to humans. As resistance is less than that of T. lewisi, our data suggest that it is unlikely to be a zoonotic pathogen although we would advise caution in the case of immunocompromised people such as AIDS and cancer patients.

Novel insertions in the mitochondrial maxicircle of Trypanosoma musculi, a mouse trypanosome

“…However, they do significantly differ in many aspects. In particular, T. lewisi infects only rats and sometimes humans (Sarataphan et al ., 2007; Verma et al ., 2011), while T. musculi infects only mice and is unlikely to be pathogenic to humans (Zhang et al ., 2018). A few research studies have indicated that both T. musculi and T. lewisi can modulate the host immune response in coinfections with various other infectious agents, to potentially cause more harm to the hosts, by altering the infection kinetics and increasing the duration of colonization in the host (Lowry et al ., 2014; Vaux et al ., 2016; Nzoumbou-Boko et al ., 2017; Gao et al ., 2021).…”