You don't typically see stuffed animals in a science lab. But these aren't your average children's stuffed animals. The cuteness of these colorful soft purple and green squishable toys belie what they actually represent—two dangerous parasites, namely Plasmodium vivax, one of the parasites that cause malaria in humans, and Trichomonas vaginalis, the parasite that causes trichomoniasis, a common STD (sexually transmitted disease). These toys are on display on the desk of Jane Carlton, the eponymous head of the Carlton Lab at New York University. They are a gift from her staff, a whimsical nod to the serious task at hand.
Carlton, a AAAS fellow, is sequencing the genomes of the parasites to learn how they grow and thrive. Trichomonas vaginalis is a persistent parasite that is the cause of approximately 170 million cases of trichomoniasis, also known as "trich," each year.
"Trichomonas vaginalis is a fascinating parasite," says Carlton. "It is full of so-called 'jumping-genes' and evolutionarily-speaking, should be extinct like the dinosaurs." Instead, it is very much alive in the human population and is the cause of trichomoniasis, considered the most common and curable STD worldwide.
Trichomoniasis is often asymptomatic, but when symptoms do appear, they can range from irritation, itching, soreness and redness, to severe inflammation in the genitals. Because trichomoniasis can lead to inflammation, it can also increase one's risk of contracting or transmitting STDs such as HIV. For pregnant women who have trichomoniasis, the risks of having a baby prematurely or giving birth to a baby with a low birthweight also are increased. The infection can be treated with anti-parasitic drugs.
Plasmodium vivax, which causes malaria, is also a persistent parasite that is a master of adaptation. The disease can lead to a wide variety of symptoms ranging from mild fever or chills to kidney failure, respiratory distress, and even death. One species, Plasmodium falciparum, killed an estimated 660,000 people worldwide in 2010, according to the World Health Organization (WHO).
This parasite's adaptability is one of the reasons why it has been problematic to develop a vaccine against malaria, even though there are antimalarial drugs. "These parasites change quickly and can develop new combinations of genes," says Carlton.
Carlton is a native of Scotland. Her interest in disease-causing parasites began decades ago when she was an undergraduate at the University of Edinburgh. After receiving a book on genetics from her older brother, who was working toward a degree in the life sciences, Carlton realized that genetics could be used to study an important and life-threatening disease, rather than studying "model organisms" such as mice and fruit flies.
She then undertook a project in a laboratory studying malaria. "I was literally bitten by the bug to study the disease from then on" she said.
Her desire to fight a global disease, brought Carlton the United States and to The Institute for Genomic Research (TIGR), now known as the J. Craig Venter Institute. There, she used genomics to study a range of parasites that causes various diseases, including African sleeping sickness, East Coast fever a severe disease of cattle in Africa, and several different species of malaria parasite.
Today, Carlton spends as much as 30 percent of her time working in India as part of a project called the Center for the Study of Complex Malaria. After Africa, India is the second most affected malaria region of the world, with an estimated 24 million cases per year, according to WHO.
Funded by the National Institutes of Health, the project's overall goal is to develop knowledge, tools and strategies to support malaria control programs, and to build research capacity in India and help train the next generation of malaria and mosquito vector biologists. There, Carlton and colleagues are undertaking a study looking at the distribution of different species of malaria parasite, their genetic make-up, and also how the the mosquito vector transmits the parasite, as well as using genomic technology to identify emerging drug-resistant parasites.
When studying these parasites, Carlton and her team—which includes her husband and data manager, Steven Sullivan—are essentially hunting for their weak points. "We are looking for gaps in the parasites' defense," says Carlton. The goal: to develop better methods to control and cure the infections such as malaria and trich.
"Even sequencing a genome for the first time can tell you so much," she notes. For example the complete gene and protein repertoire can be uncovered, metabolic pathways identified, and candidate genes the parasite may use to evade the human immune system or antimalarial drugs can be deduced.
With the work of Carlton and those like her, humans may finally win the fight against this 4,000-year-old disease.