Researchers discover unique changes in bacteria’s sugar coat to aid in the creation of pneumococcal vaccines.

The capsular polysaccharide (CPS) is a sugar layer that covers many disease-causing bacteria like Streptococcus pneumoniae (S. pneumoniae). Infections frequently call for this layer.

Researchers from the Yong Loo Lin School of Medicine at the National University of Singapore (NUS Medicine) made a ground-breaking discovery in which they identified features of the CPS that aid the bacteria in colonizing the human respiratory tract. According to the findings, the CPS capsule’s structures, linkages, and combinations play a significant role in facilitating the bacteria’s ability to attach to and survive on the linings of the upper and lower respiratory tracts of humans.

The team from the Infectious Diseases Translational Research Programme at NUS Medicine, led by Assistant Professor Chris Lok-To Sham and graduate student Jade Chun Ye-Yu, created bacterial mutants displaying one of the 84 types of CPS found in S. pneumoniae in order to challenge the widely held belief that S. pneumoniae’s structurally diverse CPS capsules all promote bacterial colonization.

In order to investigate the mutants’ capacity to bind to respiratory cells, they were then introduced to respiratory cells. Utilizing a sub-atomic standardized tag to recognize the strains, the group analyzed whether fluctuating CPS in these freaks would influence restricting on the nasal and bronchial cells.

“In the past, scientists recognized that the proteins found in bacteria are not by chance, and they serve a purpose.” Bacteria have showed a preference for various types of sugars on their capsules, as well as a specific sugar linkage. Our research shows that some of these combinations benefit the bacteria by assisting in colonization of the human respiratory tract. This discovery will shed further insight on the types of CPS to be included in future vaccines, as present vaccinations against S. pneumoniae do not cover the different varieties of CPS produced by the bacteria.”

Jade Chun, who is also from the Department of Microbiology and Immunology at NUS Medicine.

The outcomes showed that the CPS with rhamnose sugar deposits bound ineffectively to the aviation route cells, while CPS with glycan themes bound unequivocally. The experiment demonstrated that the types of CPS and structural configurations have a significant impact on attachment strength and survival on the human airway.

“Before, researchers perceived that the proteins found in microbes are not by some coincidence, and they truly do fill a need. On their capsules, bacteria have demonstrated a preference for particular sugars and a particular sugar-to-sugar linkage. Our examination demonstrates that a portion of these mixes benefit the microscopic organisms since they help in colonizing the human respiratory plot. As current vaccines against S. pneumoniae do not cover the many types of CPS produced by the bacteria, this finding will shed more light on the range of CPS types that will be included in future vaccines,” Jade Chun, who is also from the Department of Microbiology and Immunology at NUS Medicine, added.

Pneumonia, septicaemia, and meningitis are all caused in large part by S. pneumoniae. When taken as a whole, these infections are among the most common causes of illness and death in young children and the elderly. Pneumococcal vaccines are given to combat these lethal infections to increase CPS-specific antibody production. However, the bacteria can evade these antibodies by manipulating their CPS structure. S. pneumoniae produces over one hundred different types of CPSs as a result of this biochemical conflict, making it harder to develop vaccines that work. Although the diversity of CPS is well-recognized, it is still unclear what makes it a deadly weapon for bacteria.

In The Proceedings of the National Academy of Sciences, the findings were made public.

More information: Ye-Yu Chun et al, Influence of glycan structure on the colonization of Streptococcus pneumoniae on human respiratory epithelial cells, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2213584120

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