Homogeneous bicomponent glycoconjugate vaccines

Since Edward Jenner discovered in the late 18th century that inoculation with cowpox can protect humans against infection by smallpox, the history of vaccination has been a story of success. Whole virus vaccines, which for instance consist of dead microorganisms, have eradicated smallpox and polio and reduced the mortality of many other pathogens. However, there are microorganisms that cannot be targeted with these vaccines or may cause severe infections in immune-compromised people. Glycoconjugate vaccines overcome some of these issues and are successfully used as vaccines for Haemophilus influenza B and Streptococcus pneumoniae. Since these vaccines show some disadvantages as well like insufficient immune responses or heterogeneity, this project aims to producing better vaccines by the application of a completely new strategy. Herein we present the concept of well-defined bicomponent glycoconjugats. The efficiency of this method will be demonstrated by the design of a vaccine against the bacterium Streptococcus pyogenes (GAS). This bacterium causes more than 700 million cases of throat inflammation worldwide and many infected patients develop immune cells that show abnormal immune response and can therefore develop an autoimmune disease. A protective vaccine is still not available and the bacterium is therefore the perfect target to apply the new strategy. To elicit optimal immunity for the targeted pathogen, we will base the vaccine on a protein of the bacterium itself that is known to trigger the human immune system. Attachment of a special sugar that is present in all GAS-types will enhance the immune response by targeting two different bacterial structures. To overcome the issue of heterogeneity of conventional glycoconjugates, that may cause issues in the approval of resulting vaccines, we will introduce the sugar in a site-specific way onto the carrier protein. By the incorporation of special markers the protein will be targeted selectively to introduce stimulators later on. We hypothesize that this program will lead to a new class of highly effective and homogenous glycoconjugate vaccines against GAS and will demonstrate effectiveness of this novel concept.

Since Edward Jenner discovered in the late 18th century that inoculation with cowpox can protect humans against infection by smallpox, the history of vaccination has been a story of success. Whole virus vaccines, which for instance consist of dead microorganisms, have eradicated smallpox and polio and reduced the mortality of many other pathogens. However, there are microorganisms that cannot be targeted with these vaccines or may cause severe infections in immune-compromised people. Glycoconjugate vaccines overcome some of these issues and are successfully used as vaccines for Haemophilus influenza B and Streptococcus pneumoniae. Since these vaccines show some disadvantages as well, like reduced immune responses or heterogeneity, this project aims to produce better glycoconjugate vaccines by the application of a new strategy. Herein, we present the concept of so-called microbial multi-component vaccines. It is based on the protein CRM197, a non-toxic version of the diphtheria toxin, which is part of already licensed vaccines, and ensures a broad immune response of the vaccine scaffold. To target a certain pathogen, specific carbohydrate structures, only naturally abundant in the microorganism of choice, were used. These carbohydrates were chemically synthesized and then fused with the protein carrier. The third component of the vaccine scaffold consisted of an immune stimulant. This functionality was attached to the protein carrier, to further increase vaccine efficiency. Additionally, we designed the protein carrier in a way that enabled a selective assembly of each of the vaccine components to yield well-defined products only. To test the applicability of this concept, we focused on the bacterium pseudomonas aeruginosa. It is a major threat in high-risk groups where it can cause acute pneumonia, meningitidis, wound infections, blood stream infections or sepsis. Additionally, it is strongly related to hospital acquired infections and in ventilator-associated pneumonia it is even one of the most prevalent bacteria found. Currently, there is no vaccine on the market that prevents infection and antibiotic treatment becomes steadily more challenging due to the rising occurrence of multidrug-resistant strains. For that purpose, we synthesized several carbohydrate structures that are related to this bacterium and used them for our multi-component vaccine assemblies. These constructs will be further biologically evaluated and could reveal the efficiency of our microbial multi-component vaccine.