With each issue, Trib+Health brings you an interview with experts on issues related to health care. Here is this week's subject:
Afzal A. Siddiqui is a professor of Immunology and Molecular Microbiology, Internal Medicine and Pathology at the Texas Tech University School of Medicine. He also serves as the Director of the Center for Tropical Medicine and Infectious Diseases. He is working to develop a vaccine to schistosomiasis, a parasitic disease.
Editor's note: This interview has been edited for length and clarity.
Trib+Health: Can you tell me a little bit about schistosomiasis and whom it primarily affects?
Afzal A. Siddiqui: OK, so schistosomiasis is a parasitic disease. It's a neglected tropical disease, and it infects somewhere between 200-600 million people, the estimates vary, in 74 different countries. The estimates are that an additional 800 million people are at risk of getting the infection. Roughly speaking, 1 billion people could potentially be impacted by this disease.
So what happens is that people get infected when they play, and it's usually children ... between, say, three years to 12 years because they have more contact with water. They go to these lakes and ponds where you have these snails, and the snails carry the disease. The larvae come out from the snail, and they go through the skin, and that's how one gets infected.
Trib+Health: Why did you decide to start researching a vaccine for this particular disease?
Siddiqui: Because this is one of the diseases for which we only have one drug, and that drug was developed 40 years ago. And we're starting to see drug resistance, and the instances of this disease are spreading rapidly.
So there's no backup plan. We are really worried that if drug resistance emergences, it'd be a major problem. That's why we have developed other strategies that if we combined them all together, including a vaccine, that may be helpful in reducing the burden of this disease.
Trib+Health: How is the infection spread?
Siddiqui: It's not a contagious disease. So you don't get infected by touching somebody who's already (infected). In fact, the only way one can get infected is if you are in contact with a snail, which is the vector of this parasite. ... What happens in this disease is that these eggs, which the parasite produces, they get trapped within the body of the host.
Then you get a response, and you get enlargement of the liver and the spleen. You may have seen pictures of children, mostly from African countries, with bulging bellies, and that is because of the parasitic infections that they have enlargement of their spleen and liver.
Trib+Health: So how did you approach finding a vaccine?
Siddiqui: So this all started about 23 years ago ... The first thing we did was that we were looking for some Achilles heel in the parasite. What we found was that the parasite lives in the human host for 20 years or so. So it devised this sort of strategy, a way to evade the host's immune system. And the way it does it is by changing its surface membranes.
There's a protein involved in the changing of that membrane. So that is the protein we are targeting, and that is called Sm-p80. You eliminate that protein, and the parasite cannot change its surface. If it cannot change its surface, it cannot invade the host's immune system, and it gets killed.
So that is the approach we took. That took a long time to first find a protein, which is functionally important for the parasite. Once we found it, then we developed a strategy to be tested in animal models. And once we were sure that it works in animals, now we're getting ready for human clinical trials.
Trib+Health: So what research needs to be done before the vaccine can be put out in the market and used on humans?
Siddiqui: It takes about 15 to 20 years to have a vaccine from the discovery into clinical trials. So we have finished all of the preclinical work, and we just got the NIH grant to make the vaccine in a way that it can be used in humans ... We're hoping that by next year we should be able to have the safety trials of this vaccine in humans.
Trib+Health: Why did you decide to patent this vaccine?
Siddiqui: It's a different kind of reasoning for us. If you have, say, a vaccine against flu or something else, you patent it so that a company can take over that patent and can sell it and make a profit off it. Their investors will get something in return.
The reason we did it was that we wanted to make sure that we made the vaccine in a way that it's available to people who really do not have that much financial resources. We wanted to keep it cheaper so that it's affordable for those 74 countries where we have this disease. That's why we want to get the patent.
We can make it cheap, and so that other people can't make profit off it. That was the whole reason, and that's why we have these collaborations with nonprofit organizations like the Gates Foundation, who have invested in this vaccine.
Trib+Health: Why do you think it's important to study diseases like this one that aren't prevalent domestically?
Siddiqui: First of all, diseases do not recognize borders. It's a misconception that we don't have parasitic diseases in North America. So it is not totally correct that we don't use these technologies in the United States. Also, when you have a vaccine against these kinds of parasitic diseases, this can be used in the armed forces and in travelers.
Another thing is that if you make a vaccine against a disease that affects the poor in those countries, it's also a diplomatic strategy.
So it works in many different ways. And if you cure the disease, you cure the disease. It doesn't matter where the disease is because diseases, they spread. Schistosomiasis was very common in Puerto Rico 25 years ago. ... And also we do have the snail, which can get infected. If heaven forbid it spreads.
One human life is the same human life, as you see it here, or you see it somewhere else. If you can heal those people, we can save lives.
Trib+Health: What's your ultimate goal for this vaccine, when it is on the market?
Siddiqui: I think the best scenario would be that you have a vaccine, which we can make for under $1 and it prevents infection in young children. That way you have less numbers of eggs going in the environment. You can cut down the transmission and, with other control strategies like public hygiene, we hope to see that disease, if not totally eliminated, at least curtailed to a point where there's not that much clinical manifestation in the next 20 years.
It doesn't take much to get rid of a parasitic disease. If you look at what the Carter Foundation did for the guinea worm, which was an ancient parasite infection ... The only thing (the foundation) did was that it provided cheesecloth, so that people can pour the water through, so that the larval stage … is eliminated before people drank it.
That disease has been eliminated from all of the word except one place, South Sudan, where we have 250 or so infections left. So all of that is possible. You just need to have the right tool to be put in the mix to control the disease.