Bat trypanosome models for Trypanosoma cruzi

Abstract

Amongst the Trypanosomatidae, the sub- genus Schlzotrypanum is relatively homogeneous. It comprises about 6 species of Trypanosoma, which are stenoxenous (or monoxenous) parasites of bats (Chiroptera), with only Trypanosoma cruzi having escaped this host restriction to become euryxenous, able to infect a wide range of mammals in- cluding man. Comparative biochemical and genetic studies on T. cruzi and its stenoxenous relatives could help to ex- plain the important and widespread phenomenon of host specificity, and re- cent work supports the earlier suggestion that bat trypanosomes such as T. d~on~sfi could serve as useful laboratory models for the more dangerous T. cruzi i . Two members of the subgenus Schizo- trypanum, T. (S.) dionl~;ii and T. (S.) vesper- tihonls 2 parasitize bats (Chiroptera) in Eng- land (Fig. I). The prevalence of infection is probably over 50%, and three bat species have been found infected: pipistrelles (Piplstrellus plpistrellus) (with both trypanosome species), noctules (Nyctalus noctula) and Leisler's bat (N. letslen) (both with T. vespertihonis only). The trypano- somes are transmitted in the faeces of the bat bedbug Cimex pipistrelli 3, but there is no evidence that the trypanosomes harm their host. T. dionisii will also develop and multiply in Rhodnius proh~<us, although it fails to establish permanent infections4; this could be useful as a simple teaching model for T. cruzi transmission. The trypanosomes grow readily Jh vitro (Fig. I) in a variety of simple culture media such as Grace's insect tissue culture medium supplemented with 30% (v/v)in- activated foetal bovine serum s . Both species also infect several lines of tissue cul- ture cells in vitro. Susceptible cells include mouse L cells 6, HeLa cells 6, unstimulated mouse peritoneal macrophages61 and 'buf- falo' (= bison)lung (BL) cells 7 (Fig. 2). Both species of trypanosome have been biochemically characterized by DNA bouyant density 8, isoenzyme elec- trophoresis 8, and polypeptide profiles 9. T. dionisii, at least, seems to be strictly re- stricted to chiropteran hosts ~h vivo m, and there is no evidence that either species can infect man, although this has not, of course, been investigated experimentally. It there- fore seems a reasonable assumption that T. dion~siiis a safe organism to handle in the laboratory without the need to take special precautions I L ELISA investigation has revealed considerable cross-reactivity between T. dionis#, T. vespe~lionls and T. cruzi 12. T. dionisii and 7-. vespertilionis them- selves share at least two ¢omrnon anti-