Escherichia coli Vaccines
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Escherichia coli
Escherichia coli is a Gram-negative coryneform bacterium that is often found in the lower intestinal tract of endotherms. E. coli and related bacteria occupy 0.1% of the gut flora, most of which are not pathogenic, and these non-pathogenic bacteria are the normal flora of the intestine. They can not only be beneficial to the human body by producing vitamin K2 but also prevents the colonization of pathogenic bacteria in the intestines. E. coli is mainly transmitted through the fecal-oral route, which is also the main route of transmission for pathogenic bacteria. Pathogenic E. coli can cause different diseases in humans and livestock, including gastroenteritis, neonatal meningitis, and urinary tract infections. The pathogenic E. coli can be classified into different types according to the antigens of the bacteria that could elicit immune responses in the animal, and these antigens include the O antigen located in the lipopolysaccharide layer, the K antigen in the capsule, and the flagellar antigen H.
Pathogenicity of Escherichia coli
According to the different toxicity characteristics of pathogenic E. coli, the bacteria can be classified into the following pathogenic types. Enterotoxigenic E. coli (ETEC) is the main pathogen causing diarrhea in humans and pigs, sheep, cattle, and other livestock. Its causative agent is fimbrial adhesin, which can bind to intestinal epithelial cells. ETEC exerts virulence by producing two enterotoxins. LT enterotoxin is structurally and functionally similar to cholera toxin, while ST enterotoxin has a lower molecular weight and is capable of accumulating cGMP in target cells and causing fluids and electrolytes to flow into the intestinal lumen. ETEC settles in the intestine and is a non-invasive bacterium.
Enteropathogenic E. coli (EPEC) is a causative agent of diarrhea in humans, dogs, cats, and rabbits. Although it can cause diarrhea like ETEC, the pathogenesis of the two is not the same. EPEC does not produce LT and ST toxins, they use intimin (an adhesin) to bind to the host's intestinal cells. Adherence of EPEC to the intestinal mucosa causes rearrangement of host cell actin and leads to severe deformation. EPEC has a mild invasive ability to enter host cells and trigger an inflammatory response. After infection with EPEC, changes in the ultrastructure of intestinal cells may be the main cause of diarrhea.
Enteroinvasive E. coli (EIEC) is found only in humans, and its infection can cause profuse diarrhea and high fever, and the symptoms are the same as shigellosis. Enterohemorrhagic E. coli (EHEC) exists in human cattle and goats. One of its members, O157:H7, can cause bloody diarrhea without causing high fever. EHEC can also cause sudden kidney failure as well as hemolytic-uremic syndrome. Bacteria attach the cells through the fimbriae and can encode a Shiga toxin to produce a strong inflammatory response. In addition, the bacteria are also moderately invasive.
Enteroaggregative E. coli (EAEC) is only found in humans and causes watery diarrhea after infection with EAEC. EAEC is non-invasive and produces hemolysin and ST enterotoxin similar to that produced by ETEC. Adherent-Invasive E. coli (AIEC) found in humans can invade intestinal epithelial cells and is able to replicate in cells. In the innate immune-deficient human body, AIEC has a stronger proliferative capacity, and the bacterium is associated with Crohn's disease.
Development of the Escherichia coli Vaccines
The main strategy for the treatment of bacterial infections is the use of antibiotics, but the abuse of antibiotics has made bacteria resistance to antibiotics an increasingly prominent problem. Different strains of E. coli have different susceptibility to antibiotics, and the use of antibiotics depends on the sensitivity of the bacteria to antibiotics in specific areas. Vaccines are a safe and effective method for bacterial infections. In 2006, studies of E. coli O157:H7 O-specific polysaccharide vaccine conjugated to Pseudomonas aeruginosa recombinant exotoxin A showed that it was able to elicit an immune response against E. coli in children 2-5 years of age. Some previous data also show that the vaccine is safe for both children and adults. The vaccine is currently undergoing Phase III clinical trials to validate its effectiveness in large-scale applications. Another genetically modified live attenuated vaccine can control bacterial infections in chickens and provide protection against O78. Canada has also developed a vaccine for immunizing cattle that reduces the amount of O157:H7 in the manure by 1000 times and significantly reduces pathogens in manure. In 2009, scientists at Michigan State University also announced the development of a potent E. coli vaccine that is currently patented and ready for commercial production. In addition, the cholera vaccine rCTB-WC is able to provide E. coli with a short-term protection of approximately 85-100%. Vaccines containing recombinant cholera B subunit rCTB and formalin-inactivated E. coli cells have shown safety and immunogenicity in clinical trials and are effective in protecting American against diarrhea, but is invalid for the children in Egypt. Furthermore, the vaccine LCTBA is being tested in clinical trials. The vaccine is capable of overexpressing major CFs as well as LT-like hybrid toxins.
Bacterial infections seriously affect people's life and quality of life. Creative Biolabs is an expert in the field of vaccines. We have achieved a lot of fruits in the exploration and research of bacterial vaccines, and we have also produced a wealth of products and services. As a well-respected company, we will continue to provide quality and reliable products and services to vaccine developers around the world.
All of our products can only be used for research purposes. These vaccine ingredients CANNOT be used directly on humans or animals.
