Clostridium difficile Research and Development Community June – July 2014


Here’s the latest from the Clostridium difficile research community:

Two of the leading symptoms associated with Clostridium difficile infection in the intestine are colitis and pseudomembranous colitis. In this paper, the authors study the role of GM-CSF, an inflammatory cytokine, using a neutralizing monoclonal antibody. It was found that treating mice with an anti-GM-CSF mAb did not affect C. difficile colonization levels but did reduce the expression of the neutrophil chemokines CXCL1 and CXCL2. In addition, there were reduced numbers of neutrophils in histology sections and reduced expression of SLPIs, secretory leukocyte protease inhibitors. The authors conclude that GM-CSF is involved in the signaling network associated with neutrophil recruitment but does not have an effect on the elimination of infection.

In this paper, the serum levels of antibodies of patients with a single episode of CDI are compared to the levels of patients who have had a recurrence of CDI to determine if lower serum concentrations of anti-TcdA and anti-TcdB antibodies correlate with a higher risk of recurrence. The authors examined the IgA and IgG antibody levels against the two major toxins and against non-toxin cell surface antigens in serum. They found that advanced age and low serum concentrations of anti-toxin antibodies are associated with recurrence but anti-cell surface antigen antibodies were not. The authors also note that serum TcdB neutralizing capacity was not significantly associated with recurrence of Clostridium difficile infection.;jsessionid=D532390E50ED61A88A1E011B8EE768A6.f04t02

Disturbance of a host’s natural intestinal microbiota by means of antibiotic intake, most commonly after hospitalization, makes a patient susceptible to colonization of Clostridium difficile and prone to CDI. In this paper, the authors use the lethal enterocolitis model in Syrain golden hamsters to evaluate changes in intestinal microbiota following a dose of Clindamycin. Using 16S ribosomal RNA analysis and sequencing, it was found that there were drastic changes in fecal microbiota, particularly involving the phyla of Bacteriodetes and Proteobacteria. The authors mention that the host’s gut microbiota produces certain soluble factors that may be involved in the interruption of the growth of C. difficile.

Although toxin-neutralizing epitopes have been found on the receptor-binding domains (RBD) of Toxin A and Toxin B, which have gained attention since they are viable vaccine targets, the authors of this paper evaluate the potential of DNA vaccination against CDI. Highly optimized plasmids that encode this receptor-binding domain were created and introduced to mice and non-human primates intramuscularly. It was found that this immunization significantly increased the levels of both anti-RBD antibodies and RBD antibody secreting cells. In addition, the immunized mice were protected from a lethal challenge of purified toxins and from a challenge with C. difficile spores from UK1 and VPI 10463 strains.

Cwp84, a surface-located cysteine protease, is responsible for the post-translational cleavage of SlpA, a surface protein, into subunits during S-layer biogenesis. In this paper, the first crystal structure of Cwp84 is illustrated at a 1.4 Å resolution. The authors identify the important structural components of the enzyme and give insight to the role of Cwp84 in C. difficile S-layer maturation.

Alanine racemase (Alr) is a PLP-dependent enzyme that catalyzes the reversible racemization of L- and D-alanine, an important part of the peptidoglycan cell wall of bacteria. Being that there are no known alanine racemase homologue in humans, the authors of this paper decided to test it as an antibiotic target. In this paper, the catalytic properties and crystal structures of alanine racemase from Clostridium difficile 630 are evaluated, the first steps towards Alr structure-based therapeutics for CDI.


Chandrabali Ghose-Paul,MS,PhD, Chairperson of Research and Development