Related Experiment Video
Updated: May 28, 2026
Opsonophagocytic Killing Assay to Assess Immunological Responses Against Bacterial Pathogens
Published on: April 5, 2019
Biofilm and planktonic pneumococci demonstrate disparate immunoreactivity to human convalescent sera
Carlos J Sanchez1, Brady J Hurtgen, Anel Lizcano
1Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 78229, USA.
Background:
Streptococcus pneumoniae (the pneumococcus) is the leading cause of otitis media, community-acquired pneumonia (CAP), sepsis, and meningitis. It is now evident that S. pneumoniae forms biofilms during nasopharyngeal colonization; the former which facilitates persistence, the latter, a prerequisite for subsequent development of invasive disease. Proteomic evaluation of S. pneumoniae suggests the antigen profile available for host-recognition is altered as a consequence of biofilm growth. This has potentially meaningful implications in regards to adaptive immunity and protection from disseminated disease. We therefore examined the antigen profile of biofilm and planktonic pneumococcal cell lysates, tested their reactivity with human convalescent sera and that generated against biofilm pneumococci, and examined whether immunization with biofilm pneumococci protected mice against infectious challenge.
Results:
Biofilm pneumococci have dramatically altered protein profiles versus their planktonic counterparts. During invasive disease the humoral immune response is skewed towards the planktonic protein profile. Immunization with biofilm bacteria does not elicit a strong-cross-reactive humoral response against planktonic bacteria nor confer resistance against challenge with a virulent isolate from another serotype. We identified numerous proteins, including Pneumococcal serine-rich repeat protein (PsrP), which may serve as a protective antigens against both colonization and invasive disease.
Conclusion:
Differential protein production by planktonic and biofilm pneumococci provides a potential explanation for why individuals remain susceptible to invasive disease despite previous colonization events. These findings also strongly suggest that differential protein production during colonization and disease be considered during the selection of antigens for any future protein vaccine.
Insights
Streptococcus pneumoniae biofilms alter protein profiles, impacting immune responses. Vaccines targeting biofilm antigens may improve protection against pneumococcal infections.
Area of Science:
- Microbiology
- Immunology
- Vaccine Development
Background:
- Streptococcus pneumoniae causes major infectious diseases like pneumonia and meningitis.
- Pneumococcal biofilms facilitate persistent nasopharyngeal colonization, a precursor to invasive disease.
- Biofilm formation alters the bacterial antigen profile, potentially evading host immunity.
Purpose of the Study:
- To compare the antigen profiles of biofilm and planktonic pneumococci.
- To assess immune responses to these different forms.
- To evaluate the protective efficacy of biofilm-based immunization in a mouse model.
Main Methods:
- Proteomic analysis of biofilm and planktonic pneumococcal cell lysates.
- Testing reactivity with human convalescent and anti-biofilm sera.
- Immunizing mice with biofilm pneumococci and challenging them with virulent isolates.
Main Results:
- Biofilm pneumococci exhibit significantly different protein profiles compared to planktonic forms.
- Humoral immune responses during invasive disease favor planktonic antigens.
- Immunization with biofilm bacteria showed limited cross-protection against other serotypes.
Conclusions:
- Differential protein expression in biofilm vs. planktonic pneumococci explains susceptibility despite prior colonization.
- Antigen selection for future pneumococcal protein vaccines must consider these differential protein productions.
