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Baylor College of Medicine News

Vaccine development plays major role in National School of Tropical Medicine

Vaccine development is an important component of the National School of Tropical Medicine at Baylor College of Medicine. The Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development have several vaccines in different stages of development.

"Through the product development partnership of the Sabin Vaccine Institute, we are making vaccines for neglected tropical diseases in the nonprofit sector right here on the campus of Baylor College of Medicine and Texas Children's Hospital," said Dr. Peter Hotez, dean of the National School of Tropical Medicine at BCM.

The Process

Researchers are using recombinant protein-based vaccine platforms for the development of these vaccines. They first try to understand what are the pathogen's crucial pathways or mechanisms for survival and then identify molecules or proteins that, if you interfere with their function or expression, can eventually block some of these crucial pathways within the parasite, according to Dr. Maria Elena Bottazzi, associate dean of the National School of Tropical Medicine.

Once these molecules or proteins have been identified, through genetic engineering they are cloned and made recombinantly in the laboratory. Researchers clone the genetic sequences using various expression platform systems such as yeast or bacteria

The yeast/bacteria produce the pathogen's protein as a part of its own cellular machinery, which is a key part of the vaccine production process. This process is generally called "fermentation". Other components of the production processes through which the vaccine development progresses include purification and formulation. Quality control testing is also an integral part of the entire vaccine development process.

Preventive Vaccines

For hookworm, schistosomiasis and leishmaniasis, the group is developing preventive vaccines to thwart infection.

The hookworm vaccine is being developed as a bivalent vaccine. That means it contains two hookworm antigens, molecules that trigger the production of an antibody response by the immune system and prevents infection. The vaccine antigens will be administered in combination with adjuvants – chemicals that supercharge the immune system. One antigen, gluthatione-S-transferase, is a molecule expressed by the adult hookworm. This antigen is about to undergo testing in people to determine its safety. The second antigen, a modified and inactivated aspartic protease, is also expressed in the adult hookworm and is currently undergoing preclinical safety testing and should be ready for clinical testing early next year.

The schistosomiasis vaccine is being developed as a monovalent vaccine with one single parasite antigen and its adjuvant. The vaccine is currently nearing the stage where it can be manufactured under Good Manufacturing Practices.

Finally, a bivalent vaccine is in development for leishmaniasis, a parasitic disease transmitted by the sandfly. One molecule will be directed against the actual parasite and the other molecule will be directed towards disrupting the ability of the sandfly to transmit the disease. Scientists call this a transmission blocking vaccine.

Therapeutic Vaccines

A vaccine for Chagas disease is in development as a therapeutic vaccine used to treat someone who already has the disease. Researchers have identified the important target molecules and are developing the processes for making them, the production processes.

The therapeutic vaccine for Chagas ultimately may replace expensive and sometimes toxic medicines currently in use. The vaccine is being developed in partnership with Sabin Vaccine Institute and several academic and industrial organizations in Mexico, including the Autonomous University of Yucatan, the Center for Advanced Research and Birmex, Mexico's national vaccine manufacturer.

Future Vaccines

As new infectious diseases emerge, the need for vaccines to prevent and treat these diseases grows. Researchers have submitted several proposals to expand their vaccine development portfolio to include the development of vaccines against new threats as well as those that are almost as old as time itself.