Abstract
The immunological response against Clostridioides difficile (C. difficile) is crucial for an improved understanding of disease mechanisms and the development of novel therapeutic strategies. From April 2014 to February 2015, adult patients with C. difficile infection (CDI) were recruited, and the clinical course and treatment response were carefully monitored. On day 1, 3, and 6 after diagnosis, patient plasma samples were screened for anti-GDH (glutamate dehydrogenase), anti-TcdA, anti-TcdB, and anti-CWP84 (cell-wall protein 84) antibodies by ELISA. Additionally, neutralization assays of toxins from conditioned media of clinical isolates (RT010, RT014, and RT027) were performed. Most patients with CDI (n = 46) had antibodies against GDH (85%) and CWP84 (61%), but only few had antibodies against TcdA (11%) and TcdB (28%). We found patients with neutralizing antibodies against C. difficile toxins (conditioned media) produced by RT027 (26%). A subgroup of these samples could neutralize both toxins from RT027 and RT014 [11%, (5/46)]; however, no single sample neutralized only RT014. Overall, neutralizing antibody titers were low (≤1:16). In a one week follow-up of acute infection, we never observed an early booster effect with seroconversion or antibody increases, irrespective of disease severity. No correlation was found between the presence of antigen-specific (ELISA) or neutralizing antibodies and the clinical course of disease. Anti-TcdB but not anti-TcdA antibodies correlated with the occurrence of neutralizing antibodies. In conclusion, natural antibody titers against C. difficile toxins were absent or low and were not associated with disease severity. The correlation between the anti-TcdB with toxin neutralization confirms the importance of TcdB for virulence of CDI. Alternative sensitization strategies, e.g., through vaccine development, are required to overcome the regular low-titer antibody production following natural intestinal C. difficile exposure.
Highlights
MATERIALS AND METHODSClostridioides difficile is a Gram positive, anaerobic, sporeforming bacterium, and the major cause of infectious nosocomial diarrhea
The growth of the investigated C. difficile strain ribotype 027 (RT027) in liquid cultures resulted in higher toxin production as compared to the strain RT014
Enhanced toxin production of RT027 strain occurred despite delayed growth kinetics as compared to RT014 and RT010 strains (Figure 2)
Summary
Clostridioides difficile is a Gram positive, anaerobic, sporeforming bacterium, and the major cause of infectious nosocomial diarrhea. The aim of this prospective single-center study was to investigate the presence and dynamics of natural antibody response during the acute phase of CDI (anti-TcdA, anti-TcdB, anti-GDH, anti-CWP84, and neutralizing antibodies) and to assess the corresponding clinical course of disease. This prospective study was conducted at a Tertiary Care University Medical Center in Germany from April 2014 to February 2015 and included adult CDI patients (≥18 years). For toxin neutralization test (NT), natural toxins were produced in vitro by C. difficile strains RT014 and RT027 from clinical isolates verified by ribotyping (institutional strain collection) These two strains were selected due their epidemiologic importance in Germany. The software GraphPad Prism version 6.04 (GraphPad Software, San Diego, California, United States) was used
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