Zeroing in on an Effective Vaccine for Leishmaniasis
While the world has spent the past two years focused on combating COVID-19, Dr. Abhay Satoskar, Ph. D., at the Ohio State University and his team of research scientists have been developing a vaccine for another devastating, but far less known disease, leishmaniasis. Satoskar, a AAAS Member, works with researchers from McGill University, the U.S. Food and Drug Administration, the National Institute of Allergy and Infectious Diseases, Gennova Biopharmaceuticals and Nagasaki University.
Seldom seen in the developed world until recently, symptoms in different forms of leishmaniasis range from skin ulcers to fatal organ failures. It is spread when infected female sand flies inject parasites under the skin. Among parasitic diseases, it the second most widespread parasitic disease after malaria. The National Institutes of Health reports up to two million new cases per year, mostly in warm weather developing countries. There are an estimated 70,000 deaths annually.
“What is interesting is that many of the lesions [from leishmaniasis] are painless. Because there is no pain, a lot of times patients may delay care, and that can allow a parasite to replicate,” Satoskar says.
Satoskar saw his first case of leishmaniasis as a medical student. He was working in the emergency department at King Edward Memorial Hospital in Mumbai, the biggest public hospital in India. What first appeared to be a child injured in a fall turned out to be something tragically different.
“There were some wounds you could suture up, but the clinical presentation was much more severe. Before we could know anything, the kid went into cardiac arrest. We could not revive him, and he passed,” he says.
An autopsy revealed the child’s death was from visceral leishmaniasis, which caused the boy’s spleen to rupture, and he bled to death. Satoskar says the child was likely from a migrant family in northern India, where the disease was endemic. There had been no outward signs of the disease.
“That was something which really shook me up. That kind of started my interest in this,” he says.
Satoskar is now a professor of experimental pathology and microbiology at Ohio State. His research focuses on infectious disease and parasite immunology and his work over the past three decades has attracted millions of dollars in support from around the world.
After small, early grants from the National Institutes of Health and Department of Defense, additional support to create a leishmaniasis vaccine came from the Global Health Innovation Technology Fund in Japan, and the Wellcome Trust in the United Kingdom.
Satoskar says the global scramble to create a COVID-19 vaccine garnered attention and interest on all vaccine research, including his. Additionally, the impact of the global climate crisis on infectious diseases is putting leishmaniasis on the radar of both health care workers and the public.
Once found almost exclusively in Africa, the Middle East and South America, a warming planet has moved sand flies north, to Europe and in many parts of United States. Leishmaniasis is one of the top ten neglected tropical diseases in the world. While it’s frustrating that a few cases in southern Texas have gotten more attention than years of infections in Syrian refugee camps in Turkey, Satoskar welcomes the increased awareness.
“There are all these infectious diseases, which are creeping up, which were not thought to be the problem of developed countries such as the U.S. But now, given climate change, the sand fly vector is moving up, and this disease is creeping into the U.S.,” he says.
Satoskar credits modern techniques, such as CRISPR gene-editing technology, for being able to mutate the parasite that causes leishmaniasis in developing a successful vaccine. But he also gives generous credit to folk medicine healers in the Middle East, where a strategy called “leishmanization” has been a surprisingly effective tactic for generations, even though its safety is questionable.
“People used to deliberately infect themselves with these kinds of parasites just to protect [themselves]. I think even now in villages in Iran, when a child is born, they make this child basically sleep outside, where the sandflies are. They cover the child at night, except for the buttocks. If the sand fly bites the buttocks, of course, the child will get a small lesion which will resolve itself. That would then make their child immune to disease,” he says.
Getting FDA approval for a safe and efficacious vaccine is infinitely more complicated than a small inoculation of parasites on the backside, but it’s based on that same live vaccine principle, such as smallpox and polio—that a mild infection can bring long term immunity.
After animal tests proved extremely successful, Satoskar and his team now expect to begin the first phase of human trials of the leishmaniasis vaccine within a year. One trial will be conducted in the United States, a non-endemic country, and another in an endemic country, likely India. Doctors and researchers from seven different countries are part of the research team.
“The credit goes to my team. It is not me alone. I cannot do this without them.” He also credits AAAS for helping him connect with other scientists with the expertise and vision needed for such a complex project.
“I'm very happy to tell you that 60, 70% of my students are women and underrepresented minorities, from Sri Lanka, Pakistan, Bangladesh, India, Nepal, Mexico and Ethiopia,” he says.
Satoskar recently intervened to secure a visa for a young woman from Pakistan. That action could have a long-term impact on increasing the number of well-trained, compassionate doctors and scientists in developing countries.
“I had to write a letter to the visa officer in the Embassy of the United States in Islamabad, to say it is important for her to come here because not only is she going to learn, but most importantly, she's going to go back into her community and educate other women. And that is extremely important.”
The visa was secured, and after working with Satoskar’s team, this Ph.D. pharmacist is back in Pakistan, educating other women.
If we are to keep leishmaniasis at bay, Satoskar believes we need to support scientists like his colleague, no matter where they are located.
“I think it's important to provide resources to researchers so they can come up with solutions, so that this doesn't become a problem of great magnitude like COVID has become,” he says.
by Marsha Walton