This page will give you an overview of our project. The whole process is shown below following the detailed description.
As is shown above, neoantigens have already shown the promising potential in individualized cancer treatment (See more details about neoantigens, visit the Background-Neoantigen). And as we find the efficient protein delivery tool of type III secretion system (T3SS) in P. aeruginosa (See more details about T3SS, visit the Background-T3SS), We establish a method which can deliver neoantigens into the immune system using the Type III secretion system of Pseudomonas aeruginosa. We select colorectal cancer as our target and use the bioinformatics method to filter our item antigens. Then we use the T3SS to deliver the item antigens into the immune system through oral intake of engineered attenuated bacteria.
1 We utilize the data resources from TCGA, which contain cancer cells’ SNVs (single nucleotide variations) from many kinds of cancers. We establish a program to filter the antigens we want from these data. What we need to do
2 Antigen sequences which have been filtered will be combined with the Type III secretion system in the attenuated P. aeruginosa. The engineered P. aeruginosa is made into enteric capsule after lyophilization.
3 Through orally intake the enteric capsule, the capsule goes into the intestine and releases the engineered P. aeruginosa. Because the intestine possesses its own immune system and there are many interstitial cells including APCs (antigen presenting cells). The engineered P. aeruginosa can attach the APCs which are our target cells.
4 The attachment of the engineered P. aeruginosa and the APCs will trigger the formation of the Type III secretion system injectisome which is colored as red and also triggers the expression of the fusion proteins. The fusion proteins contain the antigens we filtered above and a T3SS effector or secretion signal and they will go through the injectisome and enter the APCs cytosol. Through this process, the antigens will be successfully injected into the APCs to start the MHC-I antigen presenting pathway without being interrupted by the complicated intestine environment.
5 Through the MHC-I antigen presenting pathway, the antigens are presented on the APCs' membrane for the recognition of the T cells. The T cells recognize and are activated by the antigens through the TCR binding to the presented antigens.
6 As the T cells are activated by the antigens, they will have the ability to recognize and kill the tumor cells.
To describe our project fully and reasonably, there are also some questions that remain unsolved.
1 Why we choose Type III secretion system (T3SS) as our protein delivery tool?When comes to human disease treatment, transgenic techniques, such as transfection and viral infection, have some disadvantages. It may result in the overproduction of the target protein, the altering endogenous gene expression and the potential danger of insertion and recombination. As the T3SS can directly deliver the target protein directly into the cell cytosol, it can work without genome disruption and it is quite easy to operate. To know more information about the T3SS, go to visit our Background-T3SS.
2 Why we choose P. aeruginosa as our engineered bacteria?Type III secretion system (T3SS) is one of the features that belong to the Gram-negative bacteria. As it holds the promising potential of protein delivery, there are significant differences between every species and we need to decide which type bacteria we can choose to deliver the antigens of interest better. P. aeruginosa’s T3SS shows little differences associated with the change of pH value, which high pH value is a distinct feature showed in intestinal environment. And also, through some research literature, the P. aeruginasa is more likely to gather in the organs which are related to the immune cells, like liver and spleen. So we can infer that the P. aeruginosa prefers to attach to the immune cells.
In fact, there are many types of bacteria which are widely used in the research and applying of T3SS, such as Salmonella Typhimurium, Yersinia enterocolitica and so on. But when it comes to the pathogenicity of wild type bacteria, P. aeruginosa has the lowest pathogenicity among them, which we think it can maintain the safety better. And also, P. aeruginosa does not belong to the inherent germs in our intestine, which means that they cannot stay in the intestine for too much time. To know more about the reason we choose P. aeruginosa, you can visit the Background-P.A.
What’s more, we use the attenuated P. aeruginasa and a light-control system to prevent the gene releasing, to know more about our safety measures of P. aeruginosa, you can visit the Safety-P.A.
3 Why we choose the way of oral intake?According to Type III secretion system research literature, many researchers choose to directly inject the attenuated bacteria into the vein. The bacteria will go through the body and finally attach to the target cell. When injecting the P. aeruginosa into the vein, the P. aeruginosa will finally gather in the liver and spleen. Also the P. aeruginosa strain we use is auxotrophic strain, it is still quite unsafe. As the intestine also has its own immune system, we decide to use the oral intake method to deliver the antigens of interest.
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