Creating the Building Blocks for a Malaria Vaccine

Creating the Building Blocks for a Malaria Vaccine

According to the World Health Organisation, there are over 200 million cases of malaria each year and nearly one million people a year die from the disease. Malaria is caused by plasmodium genus parasite, which is transmitted via the bites of infected mosquitoes. In the human body, the parasites multiply in the liver and then attach themselves to and infect red blood cells.

There is currently no effective vaccine for malaria, with the disease only preventable by either avoiding mosquito bites or taking preventative medication. However the latter is both expensive and not 100% effective as mosquitoes have become resistant to some of the common medications used in many regions. Therefore there is a need for a cost effective vaccine that can be produced en masse.

Generally, a vaccine is something that improves the body’s immunity to a particular disease or bacteria. In many cases, a vaccine is produced using a weakened version of the parasite, that when introduced to the body by the vaccine it stimulates the body’s immune system to create antibodies that recognise the parasite as foreign, destroy it and then remember it for when the parasite next tries to enter the body. This memory helps the immune system recognise the parasite more quickly and destroy the parasite earlier. Vaccines produced using a weakened version of the parasite are called attenuated vaccines.

Since the malaria parasite attaches to the body’s red blood cells, an attenuated vaccine is not possible as it may result in the immune system responding against the red blood cells and not just the parasite, thereby possibly damaging the circulatory system. An alternative to using a weakened version of the parasite to create a vaccine is to use only part of the parasite, such as a protein molecule, that can be recognised by the immune system. In order to ensure that the immune system remembers this molecule and reacts quickly, another molecule is then fused to the protein molecule and this is then used in the vaccine. This ensures that the immune system recognises the parasite, and then remembers to react quickly to fight it.

In order to develop such a vaccine, it is first necessary to identify and isolate an appropriate protein molecule of the parasite and then determine how to copy this in a scalable way. Once that is possible, it is then necessary to identify an appropriate molecule recognised by the immune system, and fuse this with the parasite’s protein molecule. This is where the work of Gottimukkala Chitti Babu, a research scholar at IITB-Monash Research Academy comes in.

Chitti Babu’s research focuses on developing a way to efficiently recreate protein molecules from the malaria parasite by developing a bacterial expression system. An expression system is the process by which the DNA of one being is recreated by another being, it is in effect a form of genetic engineering. In this instance, Chitti Babu’s research is utilising a bacteria to recreate specific protein molecules from the malaria parasite. An expression system is required in this instance because the malaria parasite attaches to red blood cells in the body, so in order to reproduce large quantities of the parasite’s molecules in its natural way, large volumes of red blood cells would be required, which is not viable. It is also not possible to recreate this protein by chemical processes. Therefore the expression system provides an alternative way to recreate and produce large quantities of the parasite’s protein molecules. The protein molecules that are produced are called recombinant proteins.

This research looks at how to develop an efficient bacterial expression system using the bacteria Bacillus subtilis (B. subtilis) as a host. The bacteria Escherichia coli has been used in research to date, but it is not ideal to use in the development of human vaccines as it is a human pathogen. A human pathogen is one that causes disease in the human body. However, B. subtilis is not a human pathogen and, therefore, can be recreated and used without affecting humans. The use of B. subtilis for this purpose has not been systematically attempted before.

Furthermore, B. subtilis is able to grow quickly, which means it also recreates more of the protein efficiently. It has previously been used in the production of industrial enzymes, so there are already standardised techniques to cultivate B. subtilis on a large scale, which also makes it cost-effective.

Chitti Babu’s research is looking at three particular types of protein that are most prevalent in helping malarial parasites attach to red blood cells, and thereby spread infection. These three proteins are Merozoite Surface Protein (MSP) 4, MSP 5 and MSP 1-19. His research then seeks to recreate these proteins using B. subtilis, which will then allow them to be produced at a larger scale which is required for the purpose of creating a vaccine.

As part of the research trials, these recreated proteins have been injected into mice to see if they help create effective antibodies. The initial trials indicate that they are effective in preventing the spread of malaria in mice which is very positive.

The next stage of the research looks at whether there are any suitable proteins that can be fused with the recombinant protein to help the immune system to recognise the parasite quicker, effectively improving the body’s immune response. This protein is called an adjuvant protein.

Since, the recombinant proteins have been recreated using the bacteria expression system, they are not original proteins, and there is a chance that the immune system may not recognise them quickly. For this reason the adjuvant protein is required to be fused to it in the vaccine.

There are several adjuvant proteins that are available in the market. For the purpose of this research, Chitti Babu has chosen to use Flagellin, which is a protein from the Salmonella parasite. Salmonella is recognised by the human immune system, and therefore the hypothesis was that its protein (Flagellin) would also be recognised by the immune system

To make the process cost effective, Chitti Babu fused the three MSP proteins, that had been recreated using the bacterial expression system, with Flagellin. By fusing these proteins to create one molecule, the production and purification costs will be reduced further downstream in the process of creating a vaccine.

This hypothesis was once again tested with mice, and was found to be successful. .This fused protein showed a better immune response in mice compared to MSP proteins that had been formulated individually. Thereby proving that this fusion protein may hold the key to a responsive malarial vaccine.

Overseen by Preofessor Santosh B Noronha from IIT Bombay and Professor Ross Coppel of Monash University, this research makes significant in-roads into the field of chemical engineering and micro-biology. It will form the foundation in which an effective vaccinne for malaria may be produced, potentially saving millions of lives in the future.

Graduate research scholars of IITB-Monash Research Academy study for a dually-badged PhD from both IIT Bombay and Monash University, spending time at both institutions to enrich their research experience. IITB-Monash Research Academy is a collaboration between India and Australia that endeavours to strengthen scientific relationships between the two countries.

Chitti Babu said “My research will make great inroads into the development of efficacious and cost effective malaria vaccine candidates and adjuvants that may help nearly 3 billion people (in over 100 countries) who live in danger of contracting malaria every day. My research work will also help in the development and deployment of these therapeutics at an affordable cost. The expression platform developed here may also be utilised for production of a variety of proteins intended for clinical use.”

Whilst there is still further testing and clinical trials to be undertaken, Chitti Babu’s research shows great potential in taking us a lot closer towards creating a vaccine for malaria. The potential impact of which will be gratefully experienced by millions in the futuer.

Research scholar: Gottimukkala Chitti Babu, IITB-Monash Research Academy

Project title: Production of recombitant proteins in Bacillus Subtilis

Supervisors: : Professor Santosh B Noronha and Professor Ross Coppel

Contact details: 08402402@iitb.ac.in

The above story was written by Ms Rakhee Ghelani based on inputs from the research student and IITB-Monash Research Academy. Copyright IITB-Monash Research Academy.