Clostridium difficile is a gastrointestinal infection transmitted as an endospore cause antibiotic-associated colitis in patients which leads to 20

Clostridium difficile is a gastrointestinal infection transmitted as an endospore cause antibiotic-associated colitis in patients which leads to 20,000 deaths in the world (32, 33). With the emergence of the different hyper virulent strain, more cytotoxicity and resistance to conventional drugs have been reported lead to severity and mortality. Clostridium difficile toxicity derives from two exotoxins: toxin A (TcdA) and toxin B, (TcdB), responsible of epithelial barrier disruption and colon pseudo-membrane formation, diarrhea, inflammation severity and recurrent relapse in treated patients (34, 35). So at first, there is an urgent demand for rapid and certain detection method to control and decrease rate of infection in patient. Second of all, new effective non-antibiotic treatment is required. Traditionally, toxin detection methods based on enzyme-linked immunosorbent assays (ELISA) suffer from adequate sensitivity and specificity (36, 37). Additionally, another initial screening, Glutamate dehydrogenase (GDH) enzyme testing, lacking of discriminating between toxigenic and non-toxigenic strains and subsequent confirmative ELISA assay is inevitable (38, 39). With the aim to reduce some limitation of antibody based detection method such as cost, stability and cross reactivity with other bacteria, new effective bio-recognition tools was developed.
Ochsner et al (2013) produced SOMAmer (slow off-rate modifiable aptamers) by using the SELEX method in an in vitro assay. Their results indicated that SOMAmer has a high affinity and specificity for binding to A, B toxins (37). Therefore, SOMAmer could be used for A, B toxins discrimination from C toxins that are expressed by most of the C. Difficile strains. Because of higher sensitivity and specificity of aptamers, many studies have suggested that they may be more useful than Abs in toxins tracking procedures.
In several studies the potential of those therapeutic approaches which are based on mAb Abs has been analyzed. It has been suggested that intraperitoneal (i.p) administration of anti-TcdA and anti-TcdB mAbs decrease the hamster’s mortality. Moreover, these two mAbs were beneficiary in case of clinical trials (40, 41).
VHH fragments were successful in neutralization of cytotoxic effect of TcdB expression in an in vitro cell-based assay (42). Additionally, lactobacilli expressing anti-TcdB successfully protected hamster challenged with spores TcdA TcdB strain of C. difficile and delayed mortality rate using oral administration. It could be exploited as a prophylactic effective treatment and promising inhibitor in patient (43). Considering the potential of VHH in toxin neutralization, tetra-valent platform –ABA- showed increased toxin inactivation of Clostridium difficile infection in an in vitro and in vivo assay (44).


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