Development of an Effective Treatment of Cryptosporidiosis in Bangladeshi Children

Background: Reports from longitudinal birth cohort study at Bangladesh show that 77% of children experience at least one incidence of cryptosporidiosis in the first two years of life. Cryptosporidiosis is also associated with the development of malnutrition leading to an estimate of an additional 4.2 million disability adjusted life years lost. A number of studies on cryptosporidiosis conducted at icddr,b showed that Cryptosporidium sp. was one of the most important causative agents of diarrhea associated with morbidity and mortality. Previous studies at icddr,b also made a number of other intriguing elucidations, which include:

1. Cryptosporidium sp. infected most children in the 1st year of life in a cohort at Mirpur, Dhaka. Investigators observed that up to 64% of infants were diagnosed with cryptosporidiosis in the 1st year of life while 26% of these cases had accompanying co-infections.
2. Cryptosporidium sp. was established as a top 10 diarrheal pathogen, with infections occurring with multiple other enteropathogens. Investigators discovered that infection and diarrhea with multiple entero-pathogens in infants in an LMIC setting was the norm, without any exception. On average each infant in Mirpur, Bangladesh had 3-5 enteric pathogens present in their stool at any a single time point.The importance of Cryptosporidium as a leading cause of infant diarrhea was validated by the MAL-ED study conducted across 8 different low to middle income sites.
3. Diarrhea due to Cryptosporidium in the first year of life was independently associated with the future development of malnutrition.
4. Impaired neurocognitive development at two years of age for infants with history of cryptosporidiosis as measure using the Bayley's scales of infant development.

Currently, there is no effective vaccine for cryptosporidiosis and the only approved drug for the treatment of diarrhea caused by Cryptosporidium infection is nitazoxanide (NTZ)(U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 2003). NTZ is the only treatment but its efficacy in controlled clinical trials has varied widely. While this drug has been generally shown to have an efficacy of >80%, in previous studies involving malnourished Zambian children it was shown to have an efficacy of only 56%. An effective therapy would be appealing for cryptosporidiosis in children in the developing world where the burden of infection is high and where persistence of the enteropathogen in the absence of diarrhea is associated with malnutrition.

Although the exact reason for NTZ exhibiting a higher failure rate in malnourished children is unclear, this drug has been shown to inhibit the pyruvate-ferredoxin oxidoreductase of parasites and anaerobic bacteria but its effectiveness in combating cryptosporidiosis is dependent on the host immune competence. The gut micro-environment is a key component of the host response to environmental challenge, with the gut microbiota being postulated to mediate integral roles in promoting and calibrating all aspects of the immune system. Fermented products (such as yogurt) have long been thought to promote health. However, in most commercial food products the levels of the beneficial microorganisms or probiotics are not consistent and at lower levels than required for the desired biological effect. Lactobacillus reuteri DSM 17938 has been one of the most extensively studied probiotic in children and adults with functional gastrointestinal disorders. Lactobacillus reuteri DSM 17938 in particular would be effective against cryptosporidiosis due to the presence of both microorganisms at duodenum of human. A recent study at icddr, b has shown this commonly used probiotic appeared safe and well-accepted by Bangladeshi families. Lactobacillus reuteri has been tested in clinical trials and has attained the "GRAS (generally regarded as safe)" status for use in both children and adults and has additionally demonstrated immunomodulatory activities. This probiotic is thus hypothesized to act as a beneficial supplement to the NTZ treatment in cryptosporidiosis through a potential reduction in the gut inflammation resulting from Cryptosporidium infection. Additionally, if the microbiota treatment promotes parasite clearance and decrease the burden, it will be associated with faster disease resolution and better clinical outcomes. Lactobacillus reuteri DSM 17938 has been reported to inhibit the RORa/y activity to suppress Th17 cells, thus promoting an appropriate immune response in improving the efficacy of the drug treatment. The Probiotic VSL#3 which contains Lactobacillus reuteri DSM 17938 as well as other bacteria with anti-inflammatory activities has been shown to reduce the severity of inflammatory diarrhea in animal models and has been included as one of the treatment options for pouchitis by the British Society of Gastroenterology. Investigator's goal in this study is to undertake an iterative approach to improve and optimize the currently used most effective treatment regime against cryptosporidiosis.

Experimental Design and Methodology: