Serial propagation of the microsporidian Enterocytozoon bieneusi of human origin in immunocompromised rodents

Enterocytozoon bieneusi, a microsporidian, is clinically one of the most significant opportunistic causes of diarrhea and wasting associated with profound human immunodeficiencies. The lack of an animal model for E. bieneusi hinders serious investigations and limits the availability of spores to individuals with severe human immunodeficiency virus/AIDS disease who are infected with E. bieneusi. The development of procedures for purification and concentration of spores from stools of infected humans has led to the production of immune reagents and provided a source of spores to conduct research, including attempts to develop and serially propagate E. bieneusi in rodent models. We have evaluated and successfully infected six different immunodeficient and/or immunosuppressed rodent models and have demonstrated persistent infections lasting at least 18 weeks in SCID mice and in nude rats. To enhance the intensity and duration of infection in these two models, animals were given anti-gamma interferon monoclonal antibody injections at regular intervals. Of the six models evaluated, nude rats and gerbils immunosuppressed with dexamethasone excreted the highest number of spores and for longer time periods. Four different E. bieneusi isolates were equally infectious, and one of them was serially propagated in nude rats six times over a period of 10 months. Typically, rats challenged orally with 10(4) spores yielded 2 x 10(7) to 6.3 x 10(7) spores per single fecal sample when the level of spores was measured 2 weeks later. Rodent models and a nonhuman source of fresh spores will considerably enhance future investigations on this important opportunistic pathogen, including the screening and evaluation of urgently needed chemotherapeutic agents.

Monoclonal antibodies against Enterocytozoon bieneusi of human origin

Enterocytozoon bieneusi is clinically the most significant among the microsporidia infecting humans, causing chronic diarrhea, wasting, and cholangitis in individuals with human immunodeficiency virus/AIDS. The lack of immune reagents is largely due to the absence of methods for laboratory propagation of E. bieneusi. We recently described a procedure for the concentration and purification of spores from diarrheic stool of infected humans. Purified spores were used to immunize mice for production and screening of monoclonal antibodies (MAbs) against E. bieneusi. The eight immunoglobulin M MAbs generated and fully characterized did not cross-react with other human microsporidia or with other microorganisms normally present in stool. One of the MAbs, 2G4, reacted with E. bieneusi spores in stools from monkeys and humans, without background fluorescence, which makes it an ideal diagnostic reagent. It also recognizes intracellular stages of the parasite and will be suitable for determining tissue distribution of E. bieneusi in infected hosts. At least two immunodominant antigens of E. bieneusi of 33,000 and 35,000 Da exist, which were recognized by rabbit and mouse antisera. The availability of MAbs against E. bieneusi will simplify considerably the diagnosis of this infection in humans and will provide tools for epidemiologic investigations regarding the true prevalence of the infection in various human and mammalian populations and the environmental sources of infection.

In vitro cultivation of microsporidia of clinical importance

Although attempts to develop methods for the in vitro cultivation of microsporidia began as early as 1937, the interest in the culture of these organisms was confined mostly to microsporidia that infect insects. The successful cultivation in 1969 of Encephalitozoon cuniculi, a microsporidium of mammalian origin, and the subsequent identification of these organisms as agents of human disease heightened interest in the cultivation of microsporidia. I describe the methodology as well as the cell lines, the culture media, and culture conditions used in the in vitro culture of microsporidia such as Brachiola (Nosema) algerae, Encephalitozoon cuniculi, E. hellem, E. intestinalis, Enterocytozoon bieneusi, Trachipleistophora hominis, and Vittaforma corneae that cause human disease.

Using pig biliary system, in vivo propagation of Enterocytozoon bieneusi, an AIDS-related zoonotic pathogen

A microsporidian parasite Enterocytozoon bieneusi is the most common microorganism recognized in AIDS patients, and slow scientific progress is attributed to our inability to propagate the parasite. We report upon the development of a system of propagation using the pig biliary system. The parasite spores were continuously detected in the bile samples post onset of spore shedding in the gall bladder, which suggests that this organism maintain persistent infection in the biliary system and that the hepatobiliary tree may represent a reservoir of infection. In conclusion the biliary tree is an adequate niche for the propagation of E. bieneusi. This work has also resulted in the development of a procedure of ultrasound-guided cholecystocentesis for aspirating biles. This is a simple and non-surgical procedure, and creates no signs of clinical complications in the livers and the gall bladders after dozens of separate attempts. Thus, this is a very useful and safe technique for the aspiration of bile from live animals.