Klebsiella pneumoniae is a bacterium that normally inhabits the nasal mucosa and the gut of healthy individuals. However, it is also an opportunistic pathogen and a significant cause of hospital-acquired infections. In looking to thwart infections, a research team discovers a useful feat of the human immune system—it produces antibodies that not only neutralize Klebsiella but also other pathogens. The work is led by the German Cancer Research Center in Heidelberg and published in Nature Immunology.
From human peripheral blood memory B cells and plasmablasts, the team collected monoclonal antibodies that were directed against the against the lipopolysaccharide (LPS) O-antigen of K. pneumoniae. The team found that these antibodies successfully protected against different clinically relevant serotypes (sub-species that express different LPS antigens). More interestingly, the cross-specificity also appeared to extend to LPS antigens outside of K. pneumoniae.
"The antibodies protected against various subgroups of Klebsiella pneumoniae. But they were not restricted to this particular pathogen and also recognized other bacteria and even certain yeasts and viruses," said study senior co-author Hedda Wardemann.
In their paper, the team concludes that the production of cross-specific antibodies and their ability to recognize minimal glycan epitopes abundantly expressed on diverse microbial cells may serve “as an efficient humoral immunological mechanism to control invading pathogens.”
"In mice, the antibodies were capable of neutralizing various subgroups of Klebsiella, thus protecting the animals," said Wardemann. "In a next step, we will have to do further tests with the antibodies to show their clinical value in humans."
Image: Klebsiella bacteria. Image courtesy of NIAID / NIH.