On Wednesday, January 11, 2012, Peter J. Hotez, MD, PhD, gave the Maurice Hilleman Pediatric Grand Rounds lecture at The Children’s Hospital of Philadelphia/University of Pennsylvania. Hotez is an internationally recognized expert on tropical diseases and vaccine development and holds the following positions: Professor of Pediatrics and Molecular Virology & Microbiology and Chief of the Section of Pediatric Tropical Medicine at Baylor College of Medicine; Endowed Chair of Tropical Pediatrics at Texas Children’s Hospital; and President, Sabin Vaccine Institute.
Hotez focused on the topic that occupies so much of his research attention: the neglected tropical diseases that affect the world’s 1.4 billion people who live on less than US $1.25 a day. The “bottom billion” (a phrase popularized in Paul Collier’s 2007 book The Bottom Billion: Why the Poorest Countries Are Failing and What Can Be Done About It) suffer from not only the deadly effects of HIV/AIDS, tuberculosis, and malaria, but also from the less deadly, but more insidious, effects of mostly parasitic diseases such as
- soil-transmitted helminthic diseases (ascariasis, [roundworms], trichuriasis [whipworms], and hookworm infection)
- schistosomiasis (snail fever)
- lymphatic filariasis (elephantiasis)
- onchocerciasis (river blindness)
- Chagas disease
- trypanosomiasis (sleeping sickness)
These diseases, and others like them, do not often cause death but are frequently chronic and disabling. In children they may lead to stunted growth and can affect intellectual development as well. As a group, they contribute to significant losses in agricultural productivity and help to perpetuate generational poverty all over the world.
As an example, Hotez noted that in Paquila, a village in Guatemala, researchers found that virtually all the resident children suffered from ascariasis and many were co-infected with trichuriasis as well. That situation, Hotez said, is not unique to that village, country, or region. It’s not difficult to imagine the long-term health and economic effects on populations when disease prevalence is so high.
Other disease interactions are troubling, as well, such as the relationship between urogenital schistosomiasis, which affects tens of millions of girls and women, and HIV/AIDS. Urogenital schistosomiasis causes chronic irritation of urogenital tissues and certain immunological effects that may make girls and women with the infection more vulnerable to HIV infection than they would be otherwise.
Mass drug administration (giving medication to an entire population) is one possible solution to addressing some of the NTDs. The Global Network for Neglected Tropical Diseases advocates a combination of drugs that, for $.50 per person per year, can treat the seven most common NTDs in a four-drug combination. (This video describes the approach.) But this is not an elimination strategy since, for some of the diseases, re-infection can occur quickly. And the prospect that the disease agents may develop resistance to the medication is a troubling possibility.
Vaccines may offer the best hope of combating NTDs, but innovative solutions are necessary to develop and produce them. Hotez briefly described the challenges in devising effective vaccines for complex, multicellular organisms (current vaccines address only bacteria and viruses), and also noted that vaccines for NTDs would likely be a money-losing enterprise for pharmaceutical companies that have already devoted considerable funds to NTD drug treatments. Accordingly, nonprofits like the Sabin Vaccine Institute that Hotez heads are not only working on vaccine concepts for several NTDs, but are developing systems and relationships that should facilitate ramp up to industrial production once the vaccines have been tested and are ready for licensure. He specifically mentioned recombinant protein vaccines in development for hookworm, schistosomiasis, and Chagas disease.
Finally, Hotez closed with a nod to Albert Sabin, whose work in the USSR on oral poliovirus vaccine in the late 1950s and early 1960s was the first example of what Hotez called “vaccine diplomacy.” Several countries with which the United States currently has difficult relations, such as Iran, would benefit greatly from vaccines for NTDs. Perhaps a new era of vaccine diplomacy is imminent.