Posts Tagged ‘Zika’
By: Sarah L Hawes, PhD
Diseases transmitted through contact with an animal carrier, or “vector,” cause over one million deaths annually, many of these in children under the age of five. More numerous, non-fatal cases incur a variety of symptoms ranging from fevers to lesions to lasting organ damage. Vector-borne disease is most commonly contracted from the bite of an infected arthropod, such as a tick or mosquito. Mosquito-borne Zika made recent, regular headlines following a 2015-2016 surge in birth defects among infants born to women bitten during pregnancy. Other big names in vector-borne disease include Malaria, Dengue, Chagas disease, Leishmaniasis, Rocky Mountain spotted fever and Lyme.
Vaccines do not exist for many of these diseases, and the Centers for Disease Control (CDC) Division of Vector-Borne Diseases focuses on “prevention and control strategies that can reach the targeted disease or vector at multiple levels while being mindful of cost-effective delivery that is acceptable to the public, and cognizant of the world’s ecology.” Prevention through reducing human contact with vectors is classically achieved through a combination of physical barriers (i.e. bed nets and clothing), controlling vector habitat near humans (i.e. dumping standing water or mowing tall grass), and reducing vector populations with poisons. For instance, the Presidential Malaria Initiative (PMI), initiated under President Bush in 2005, and expanded under President Obama, reduces vector contact through a complement of educating the public, distributing and encouraging the use of bed nets, and spraying insecticide. Now a 600 million dollar a year program, PMI has been instrumental in preventing several million Malaria-related deaths in the last decade.
But what if a potentially safer, cheaper and more effective solution to reduce human-vector contact exists in the release of Genetically Modified (GM) vector species? Imagine a mosquito engineered to include a new or altered gene to confer disease resistance, sterility, or to otherwise impede disease transmission to humans. Release of GM mosquitos could drastically reduce the need for pesticides, which may be harmful to humans, toxic to off-target species, and have led to pesticide-resistance in heavily-sprayed areas. Health and efficacy aside, it is impossible to overturn or poison every leaf cupping rainwater where mosquitos breed. GM mosquitos could reach and “treat” the same pockets of water as their non-GM counterparts. However, an insect designed to pass on disease resistance to future generations would mean persistence of genetic modifications in the wild, which is worrisome given the possibility of unintended direct effects or further mutation. An elegant alternative is the release of GM vector animals producing non-viable offspring – and this is exactly what biotech company Oxitec has done with mosquitos.
Oxitec’s OX513A mosquitos express a gene that interferes with critical cellular functions in the mosquitos, but this gene is suppressed in captivity by administering the antibiotic tetracycline in the mosquitos’ diet. Release of thousands of non-biting OX513A males into the wild results in a local generation of larvae which, in the absence of tetracycline, die before reaching adulthood. Release of OX513A has proven successful at controlling mosquito populations in several countries since 2009, rapidly reducing local numbers by roughly 90%. Oxitec’s OX513A line may indeed be a safe and effective tool. But who is charged with making this call for OX513A and, moreover for future variations in GM vector release?
Policy governing use of genetically modified organisms must keep pace with globally available biotechnology. Regulatory procedures for the use of GM vector release are determined by country, and there is a high degree of international policy alignment. The Cartagena Protocol on Biosafety is a treaty involving 170 nations currently (the US not included) that governs transport of “living modified organisms resulting from modern biotechnology” with potential to impact environmental or human health. The World Health Organization (WHO) and the Foundation for the National Institutes of Health (FNIH) published the 2014 guidelines for evaluating safety and efficacy of GM mosquitos.
Within the US, the 2017 Update to the Coordinated Framework for the Regulation of Biotechnology was published this January in response to a solicitation by the Executive Office of the President for a cohesive report from the Food and Drug Administration (FDA), Environmental Protection Agency (EPA), and US Department of Agriculture (USDA). Separately, biotech industry has been given fresh guidance on whether to seek FDA or EPA approval (in brief): if your GM product is designed to reduce disease load or spread, including vector population reduction, it requires New Animal Drug approval by FDA; if it is designed to reduce pest population but is un-related to disease, it requires Pesticide Product approval by EPA under the Federal Insecticide, Fungicide, and Rodenticide Act.
Thus, for a biotech company to release GM mosquitos in the US with the intent of curbing the spread of mosquito-borne disease, they must first gain FDA approval. Oxitec gained federal approval to release OX513A in a Florida suburb in August 2015 because of FDA’s “final environmental assessment (EA) and finding of no significant impact (FONSI).” These FDA assessments determined that the Florida ecosystem would not be harmed by eliminating the targeted, invasive Aedes aegypti mosquito. In addition, they affirmed that no method exists for the modified gene carried by OX513A to impact humans or other species. Risks were determined to be negligible, and include the accidental release of a few, disease-free OX513A females. For a human bitten by a rare GM female, there is zero risk of transgene transfer. There is no difference in saliva allergens, and therefore the response to a bite, from GM and non-GM mosquitos. In addition, as many as 3% of OX513A offspring manage to survive to adulthood, presumably by spawning in tetracycline-treated water for livestock. These few surviving offspring will not become a long-term problem because their survival is not a heritable loop-hole; it is instead analogous to a lucky few mosquitos avoiding contact with poison.
Solid scientific understanding of the nature of genetic modifications is key to the creation of good policy surrounding the creation and use of GMOs. In an updated draft of Guidelines For Industry 187 (GFI 187), the FDA advises industry seeking New Animal Drug Approval to include a molecular description of the intentional genetic alteration in animals, method for alteration, description of introduction to the animal, and whether the alteration is stable over time/across generations if heritable, and environmental and food safety assessments. Newer genomic DNA editing techniques such as CRISPR offer improved control over the location, and thus, the effect of genetic revisions. In light of this, the FDA is soliciting feedback from the public on the GFI 187 draft until April 19th, 2017, in part to determine whether certain types of genetic alteration in animals might represent no risk to humans or animals, and thus merit reduced federal regulation.
Following federal clearance, the decision on whether to release GM vectors rests with local government. Currently, lack of agreement among Florida voters has delayed the release of OX315A mosquitos. Similar to when GM mosquito release was first proposed in Florida following a 2009-2010 Dengue outbreak, voter concern today hinges on the perception that GM technology is “unproven and unnatural.” This illustrates both a healthy sense of skepticism in our voters, and the critical need to improve scientific education and outreach in stride with biotechnology and policy. Until we achieve better public understanding of GM organisms, including how they are created, controlled, and vetted, we may miss out on real opportunities to safely and rapidly advance public health.
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By: Arielle Glatman Zaretsky, PhD
Throughout history, humans have sought to understand the human body and remedy ailments. Since the realization that disease can be caused by infection and the establishment of Koch’s postulates, designed to demonstrate that a specific microbe causes a disease, humans have sought to identify and “cure” diseases. However, while we have been successful as a species at developing treatments for numerous microbes, viruses, and even parasites, pure cures that prevent future reinfection have remained elusive. Indeed, the only human disease that has been eradicated in the modern era (smallpox) was eliminated through the successful development and application of preventative vaccines, not the implementation of any treatment strategy. Furthermore, the two next most likely candidates for eradication, dracunculiasis (guinea worm disease) and poliomyelitis (polio), are approaching this status through the use of preventative measures, via water filtration and vaccination, respectively. In fact, despite the recent pushback from a scientifically unfounded anti-vaxxers movement, the use of a standardized vaccination regimen has led to clear reductions in disease incidence of numerous childhood ailments in the Americas, including measles, mumps, rubella, and many others. Thus, although the development of antibiotics and other medical interventions have dramatically improved human health, vaccines remain the gold standard of preventative treatment for the potential of disease elimination. By Centers for Disease Control and Prevention [Public domain], via Wikimedia Commons
Recently, there have been numerous outbreaks of emerging or reemerging infectious diseases. From SARS to Ebola to Zika virus, these epidemics have led to significant morbidity and mortality, and have incited global panic. In the modern era of air travel and a global economy, disease can spread quickly across continents, making containment difficult. Additionally, the low incidence of these diseases means that few efforts are exerted to the development of treatments and interventions for them, and when these are attempted, the low incidence further complicates the implementation of clinical trials. For example, though Ebola has been a public health concern since the first outbreak in 1976, no successful Ebola treatment or vaccine existed until the most recent outbreak of 2014-2016. This outbreak resulted in the deaths of more than 11,000 people, spread across more than 4 countries, and motivated the development of several treatments and 2 vaccine candidates, which have now reached human trials. However, these treatments currently remain unlicensed and are still undergoing testing, and were not available at the start or even the height of the outbreak when they were most needed. Instead, diseases that occur primarily in low income populations in developing countries are understudied, for lack of financial incentive. Thus, these pathogens can persist at low levels in populations, particularly in developing countries, creating a high likelihood of eventual outbreak and potential for future epidemics.
This stream of newly emerging diseases and the re-emergence of previously untreatable diseases brings the question of how to address these outbreaks and prevent global pandemics to the forefront for public health policy makers and agencies tasked with controlling infectious disease spread. Indeed, many regulatory bodies have integrated accelerated approval policies that can be implemented in an outbreak to hasten the bench to bedside process. Although the tools to identify new pathogens rapidly during an outbreak have advanced tremendously, the pathway from identification to treatment or prevention remains complicated. Regulatory and bureaucratic delays compound the slow and complicated research processes, and the ability to conduct clinical trials can be hindered by rare exposures to these pathogens. Thus, the World Health Organization (WHO) has compiled a blueprint for the prevention of future epidemics, meant to inspire partnerships in the development of tools, techniques, medications and approaches to reduce the frequency and severity of these disease outbreaks. Through the documentation and public declaration of disease priorities and approaches to promote research and development in these disease areas, WHO has set up a new phase of epidemic prevention through proactive research and strategy.
Recently, this inspired the establishment of the Coalition for Epidemic Preparedness Innovations (CEPI) by a mixed group of public and private funding organizations, including the Bill and Melinda Gates Foundation, inspired by the suggestion that an Ebola vaccine could have prevented the recent outbreak if not for the lack of funding slowing research and development, to begin to create a pipeline for developing solutions to control and contain outbreaks, thereby preventing epidemics. Instead of focusing on developing treatments to ongoing outbreaks, the mission at CEPI is to identify likely candidates for future outbreaks based on known epidemic threats and to lower the barriers for effective vaccine development through assisting with initial dose and safety trials, and providing support through both the research and clinical trials, and the regulatory and industry aspects. If successful, this approach could lead to a stockpile of ready-made vaccines, which could easily be deployed to sites of an outbreak and administered to aid workers to reduce their morality and improve containment. What makes this coalition both unique and exciting is the commitment to orphan vaccines, so called for their lack of financial appeal to the pharmaceutical industry that normally determines the research and development priorities, and the prioritization of vaccine development over treatment or other prophylactic approaches. The advantage of a vaccination strategy is that it prevents disease through one simple treatment, with numerous precedents for adaptation of the vaccine to a form that is permissive of the potential temperature fluctuations and shipping difficulties likely to arise in developing regions. Furthermore, it aids in containment, by preventing infection, and can be quickly administered to large at risk populations.
Thus, while the recent outbreaks have incited fear, there is reason for hope. Indeed, the realization of these vaccination approaches and improved fast tracking of planning and regulatory processes could have long reaching advantages for endemic countries, as well as global health and epidemic prevention.
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