Yersinia Pestis Adhesins
Study on Structural-Functional Properties of Proteins Providing Specific Adhesion of Yersinia Pestis with the Host Cells and Development of Approaches to their Use to Prevent Plague
Tech Area / Field
- BIO-SFS/Biosafety and BioSecurity/Biotechnology
3 Approved without Funding
Institute of Immunological Engineering, Russia, Moscow reg., Lyubuchany
- Institute of Bioorganic Chemistry, Russia, Moscow
- University of California / Department of Chemistry and Biochemistry, USA, CA, Santa Cruz\nLondon School of Hygiene&Tropical Medicine, UK, London
Project summaryThe aim of the researches under the Project is the study on structural-functional properties of Y.pestis proteins with predicted adhesion function, evaluation of their immunogenic characteristics and development of approaches to the construction of a safe and effective anti-plague recombinant vaccine.
Epidemiological spreads of plague have been known to humankind from Bible times. The reasons for the rise and fall of plague epidemics are not clear. It has been suggested that a severe epidemic may be preceded by a subtle genetic change(s) in Y.pestis, which create highly virulent strains. Now plague is still represents a substantial threat for residents of various parts of Africa and Asia. Recent plague outbreak in India brought to the forefront economical consequences and potential global threat endangered by this pathogen. Every plague case is registered and is of importance for the health services as the patients with secondary pneumonic form of the disease could form a channel for dissemination of the primary pneumonic plague – fatal and highly contagious disease. Unfortunately, there is no commercial plague vaccine able to provide solid immunity against this devastating infection. Today bioterrorism as an accomplished fact has added another dimension to the importance of constructing of an effective anti-plague vaccine.
Public health officers are well aware of the fact that plague manifests an impressive capability to overcome the defense of the mammalian host organism. Realization of Y.pestis pathogenic properties in an infected organism is provided via regulatory system of coordinated expression of a set of the factors for virulence and pathogenicity of different functional trends. Development of infectious process in plague is determined mainly by the localization of input gates for Y.pestis bacteria in respect of which skin and mucous surfaces have weak barrier functions. Studies on pneumonic plague in laboratory animals as well as recent researches concerning invasiveness of epithelial cells demonstrate that Y.pestis bacteria are being a specific invasins and able to damage epithelial layer of lymphoid tissue. This is another evidence of the fact that upon entering of Y.pestis bacteria into the organism via digestive tract or by aerogenic pathway, surface colonization takes place with following highly effective invasion of the host cells and development of fatal systemic disease. It should be noted, that there is a wide gap in the studies on the initial infection with Y.pestis bacteria not giving a precise understanding using which antigens (virulence factors) these bacteria perform adhesion and penetration into the host cells. Identification and studies of these adhesins, on the one hand, will substantially widen our apprehension of plague pathogenesis and, on the other hand, will help to find another key for construction of a new optimal anti-plague vaccine including, despite capsular protein F1(Caf1) and V antigen, still unknown immunogen, the presence of which is essential for protection against F- Y.pestis strains appearing whether in nature or following the disease in human immunized with single F1.
Main adhesins (Inv, YadA, Ail) characteristic to Y.pseudotuberculosis and Y.enterоcolitica are not found in Y.pestis agent. The participants of the Project discovered ability of low molecular forms of 125I-labelled Caf1 to bind specifically to interleukin-1 (IL-1R) receptors on the target cells. Caf1 ability to interact with IL-1R testify, firstly, the participation of this antigen in the very first stages of disease development, secondly, indicate adhesive function of the capsule subunits, responsible for the bacterial contact with target cells, and, as the consequence: i) signal formation for initiation of expression and secretion of Y. pestis Yop-virulon proteins, ii) effective invasiveness. However, these findings do not explain how Y.pestis F- strains adhere the target cells. pPCP1plasmid intrinsic only to Y.pestis and encoding surface protease Pla, is clearly needed for highly effective invasion, but Y.pestis, lacking this plasmid all the same adheres to HeLa cells. Besides, to perform delivery of effector Yop proteins into the host cell, Y.pestis should have special factors with adhesive functions. Recently performed full decoding of Y.pestis genome indicates possible presence of 12 proteins with putative adhesion function [Parkhill J et al., Nature. 2001 Oct 4; 413(6855): 467, 469-70]. The fact that Y.pestis could have a trigger mechanism for expression activation of one or some of the putative adhesins able to complement, or duplicate or fully substitute Caf1 adhesive function cannot be excluded. Three proteins of the putative Y.pestis proteins with adhesive function (YPO1707, YPO2945 and YPO4044) have a high level homology with subunits of fimbrial proteins of E.Coli, Bordetella pertussis, Proteus mirabillis and other gram-negative bacteria. Underlining exceptional importance of the adhesion structures in virulence manifestation by pathogenic bacteria, we intend, in frames of the Project, to analyze gene expression of Y.pestis proteins with putative adhesion properties in various conditions of culturing for bacterial cells; to do a selection and cloning of the most perspective adhesive proteins, to obtain them in pure, and then to study a number of their structural-functional properties and perform a search for specific receptors on the target cell surface. After, we are going to study immunogenic properties of the adhesive proteins and, basing on the obtained clear landmarks for use of V and Caf1 proteins in the composition of molecular anti-plague vaccinees under development, to study immunity formation upon the application of a vaccine composed of the basic immunogenes (Caf1 + V antigen of Y.pestis) and the adhesive proteins under study.
It is supposed that the including of these adhesive proteins in the composition of an anti-plague vaccine would be an important contribution into construction of a new pure, safe and effective recombinant vaccine which would be designed by the scientific community and epidemiologists connected with plague control.