Projects / Programmes
Virulence factors as potential targets of vaccines
| Code |
Science |
Field |
Subfield |
| 3.01.00 |
Medical sciences |
Microbiology and immunology |
|
| Code |
Science |
Field |
| B230 |
Biomedical sciences |
Microbiology, bacteriology, virology, mycology |
| Code |
Science |
Field |
| 3.05 |
Medical and Health Sciences |
Other medical sciences |
bacteraemia, sepsis, Escherichia coli, viruence factors, vaccine
Researchers (13)
Organisations (1)
Abstract
Bacterial resistance to antibiotics represents on a global scale one of the greatest threats to human health. Ever more frequent are reports of bacteria resistant to numerous clinically significant antimicrobial agents. In addition, some clinically significant antibiotics induce the evolution and dissemination of antibiotic resistances as well increase synthesis and dissemination of virulence factors of bacterial pathogens. On the other hand, escalating/ on the rise is also the prevalence of complicated infectious diseases such as community and hospital acquired bacteraemia as well as sepsis, the number of patients requiring invasive therapy and increasing numbers of immunocompromised patients.
Urgently needed are new approaches for treatment of infectious diseases or even better, for prevention with vaccines against virulence factors of pathogens. Vaccination has drastically reduced morbidity and mortality due to diphtheriae, tetanus and whooping cough, instigated by Corynebacterium diphtheriae, Clostridium tetani and Bordetella pertussis, respectively. Nevertheless, efficient vaccines are not available for a number of pathogens.
Virulence factors produced by bacteria enable colonization, invasion and damage of the host. In the case of pathogens which are also a part of the normal microbial flora, targets for vaccines should be virulence factors that (i) play a crucial role in pathogenesis (ii) are produced by all or the large majority of pathogens and none or only a very small portion of nonpathogenic strains. Pathogenic strains of Escherichia coli are the most frequent causative agents of complicated infections of the urinary tract, community acquired bacteraemia and among the most common hospital acquired bacteraemia and sepsis.
Protein USP is a crucial virulence factor of pathogenic E. coli strains isolated from patients with complicated urinary tract infections, bacteraemia and sepsis. Gene usp encoding the synthesis of USP is harbored by a 4.2 kbp long pathogenicity island. Downstream of usp are three additional open reading frames (orf) which are not involved in virulence. The characteristics of USP, its role and mechanism of action are as of yet completely unknown. The recently described protein TcpC of an uropathogenic E. coli strain, represents a new class of virulence factors, as binding of the TcpC TIR domain to TLR (Toll-like receptor) inhibits TLR signaling, suppressing innate immunity and increasing bacterial virulence.
The goal of the proposed research project is to employ protein USP and the TIR domain of protein TcpC for vaccine development to protect against E. coli strains causing the most severe infections. For this purpose we will investigate the prevalence of both proteins among commensal and pathogenic E. coli strains. The role of the USP gene cluster will be elucidated by cloning the cluster as well as the individual genes. The purified USP protein will be isolated, its biochemical characteristics determined and its activity against selected cell cultures investigated. In addition, we will determine which domain of the USP protein exhibits the pathogenic effect and subsequently, investigate induction of the immune response with the purified domain and the TIR domain of protein TcpC.
Significance for science
Even though the prevalence of bacteriemia and sepsis is increasing only a small number of investigations have characterized bacterial strains that provoke such infections. Increasing is also the prevalence of bacteria resistant against clinically significant antibiotics. Further, recent studies have shown that bacterial infections can provoke tumorigenesis due to inflammation or due to production of genotoxins that damage the host genome. In light of the similarity of the C terminal domain of Usp and colicin E7, it was previously presumed that it acts as a bacteriocin involved in bacterial competition. We were first to prepare a protocol for the successful isolation of protein Usp. Our study was also the irst to show that Usp is a bona fide virulence factor that in human cells provokes genome damage, rearrangement of the cytoskeleton, apoptosis and that it is secreted from the bacterial cell. DNA damage is the first step that provokes uncontrolled growth and tumorigenesis. All investigated E. coli strains encoding usp, were assigned to the phylogenetic group B2 and were statistically significantly associated with genes cnf1, hlyA, papGIII, tcpC and sfaDE. Even though usp was statistically significantly more frequently associated with pathogenic strains, we also detected usp among comensal strains from healthy individuals. Since Usp damages the genome it could be involved in tumorigenesis. Due to the high pervalence of antibiotic resistant bacteria, new approaches are urgently needed to successfuly battle infectious diseases. Vaccination prevents infection to avoid the use of antibiotics. A key aspect of vaccine development is induction of an immune response. We demonstrated that the catalytic domain of Usp induces an immune response and would therefore be appropriate for vaccine development that would protect against severe urinary tract infection, bacteriemia provoked by E. coli and possibly some cancers. We also demonstrated a new mechanism of bacterial protection agaisnt their own toxins – nonspecific genome masking by protein Imu3.
Significance for the country
Due to the rapid evolution and spread of antibiotic resistances consecutive treatment with different antibiotics or with combinations of antibiotics is often required, increasing medical costs. Treatment in hospitals will be required more frequently, additionally increasing health care expenses and influencing the quality of life. Simple surgical procedures and invasive medical treatments which rely upon concomitant antimicrobial therapy will, in the near future, pose high risks. Further, recent publications indicate that certain bacterial infections are associated with cancer. Urgently needed are new approaches, such as the isolation of virulence factors of pathogenic bacteria for the development of vaccines. E. coli strains are widespread and are the causative agents of numerous infections including sepsis. The latter is, in developed countries the tenth and in units of intensive medical care the second most frequent cause of death. The prevalence of sepsis is increasing also due to a higher prevalence of immune-compromised individuals (elderly population, patients with diabetes and wounds, transplant patients, patients requiring surgery, oncology patients) as well as due to bacterial resistance against antibiotics. An appropriate vaccine could protect vulnerable individuals and others, against the most severe infections drastically reducing health care costs. The role of bacteria in tumorigenesis is the subject of intense research performed by top research groups on a global scale. The discovery that Usp acts as a genotoxin and that it is produced by pathogenic and, to a lesser degree by commensal E. coli strains, places Slovenia among nations with the highest scientific impact. The discovery that immunity protein Imu3, protects the producer against Usp activity by nonspecifically DNA binding has great biotechnological potential – for example, DNA isolation from highly dilute environmental samples.
Most important scientific results
Annual report
2010,
2011,
2012,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2010,
2011,
2012,
final report,
complete report on dLib.si
