MECHANISTIC VIEWS ON THE ROLE OF DIOXIN IN EMERGING EPIDEMIC OF AVIAN INFLUENZA

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1 MECHANISTIC VIEWS ON THE ROLE OF DIOXIN IN EMERGING EPIDEMIC OF AVIAN INFLUENZA Ilya B. Tsyrlov, MD, Ph.D XENOTOX, Inc., Scarsdale, New York, USA. Vladimir S. Roumak, MD, Ph.D. Russian-Vietnamese Tropical Center, Hanoi, Vietnam. he global threat that most preoccupies the national and international health organizations is the H5N1 bird flu virus, which has ravaged poultry stocks in Asia since 2003 and recently spread to Europe through migratory birds. World health authorities fear the disease could mutate into a form that spreads easily from person-to-person, sparking a flu pandemic. Here, we discuss mechanistic viewpoints on how an elevated level of 2,3,7,8- tetrachlorodibezo-p-dioxin (TCDD) in Asian nesting birds, primarily ducks and chicken might contribute to lessening avian antiviral defense (Part 1), and also on how body burden TCDD in the people might become a molecular enhancer for influenza virus NS1 protein (Part 2). Both TCDD roles emerge into the factors of emerging global pandemic of influenza virus type A. Our general concept is based on science-proven data that at very low doses TCDD is fully potent of binding in mammalian or avian cells to a transcriptional factor, so-called Ah receptor, and activate the battery of target genes (Whitlock, 1996). As the proper targets of TCDD-caused transcriptional activation, these genes contain dioxin response elements (DRE) in their promoter region (Denison et al., 1989). Part 1. Concerning a triggering role of ducks in pandemic bird flu outbreak, scientists have good reason to say that animals play key role in flu pandemics. According to a Species DRE Summary, there are 19 DREs in the genome of the duck, which might shed a light on the ability of bioaccumulated TCDD to decrease duck s antiviral resistance, and augment persisting strains of bird virus. The above amount of DREs in duck genome suggest this species possible high susceptibility to TCDD, as this figure (19 DREs) prevail 144

2 over the amount of DREs in the genes known as sensitive targets to low-dose TCDD in mammals. Thus gene of CYP1A1 in the mouse contains 6 DREs, in the rat - 3 DREs, and in humans - 2 DREs. Following literature data add to the above information on multiple DRE in the duck genome, all demonstrating that this species is susceptible to (immuno) toxic effects of bioaccumulated from the environmental TCDD: A marked elevation of TCDD in residents of Southern Vietnam was found resulted from some of the food products, primarily ducks with 276 ppt and 331 ppt wet weight (A. Schecter et al., 2003); Very high levels of TCDD in soil, fish fat, duck fat, pooled human blood and breast milk were determined in samples collected between 1996 and 1999 in southern Vietnam (L. Dwernychuk et al., 2002); Specific biomagnification of TCDD and TFDD was measured in tufted ducks (Aythya fuligula) (Kang et al., 2002); The tissues of fish-eating bird and duck (Anas platyrhynchos) were very highly contaminated by TCDD/F due to ingestion of fish and other aquatic organisms from sediment. (Wu et al, 2001); Nesting wood ducks (Aix sponsa) were shown more sensitive to TCDD and PCDF contamination than some other aquatic birds and could serve as an indicator species for monitoring biological impacts from these contaminants (White & D. Hoffman, 1995); The thymus cells of both chicken and ducks embryos were very sensitive to toxic effects of TCDD, however for duck embryos, about a 100-fold higher concentration of TCDD was needed (Nikolaidis et al., 1988); TCDD levels in food of Agent Orange-sprayed and non-sprayed areas of Laos, and found that duck eggs from sprayed areas had several-fold higher TCDD levels than similar food samples from non-sprayed areas (Schecter et al., 2003); Environmental contaminants, if ingested, could affect the immunological status of wild birds, and in particular, ducks resistance to infectious disease. Immunosuppression caused 145

3 by environmental contaminants, could have a major impact on waterfowl populations, resulting in increased susceptibility to contagious disease agents, such as duck plague virus (Goldberg et al., 1990); A strong immunotoxicity of TCDD was demonstrated in birds. The Ah receptor-mediated toxic effects of TCDD on avian B-lymphocytes were shown (Puebla-Osorio et al., 2004); A systematic study might be designed to evaluate in TCDD-exposed and non-exposed areas in Vietnam what correlations (if any) exist among environmental TCDD level, bioaccumulated level of TCDD in ducks (and chicken), inducibility of avian P450s (a marker on Ah receptor involvement), the state of avian immunological status, and the titer and/or virulence activity of avian influenza virus type A (H5N1 and/or non-deadly strain of type A virus). Part 2. Researchers at St. Jude Hospital in Memphis, USA discovered the gene after a large analysis of samples of about 11,000 influenza viruses that Dr. Robert Webster has gathered from around the world since The samples include about 7,000 bird flu viruses, from poultry, ducks, gulls and other flocks. Initial results from the genetic analysis at all the bird flu viruses studied had the unique gene and none of the human flu viruses did. They also said people infected with H5N1 flu virus in Vietnam and Thailand had the "avian" version of the flu virus, and so was the case with the 1918 flu pandemic, which killed tens of millions of people globally. The researchers have completed the first large genetic analysis of more than 300 bird flu viruses from the virus collection. They identified 2,196 bird flu genes and 160 complete genomes. The study suggests that two nonstructural proteins, NS1 and NS2, may be key in helping avian virus latch onto and disrupt certain important cellular processes. The H5N1 bird flu virus was first found to have spread to people in It resurfaced in 2003 and has since infected at least 152 people and killed 83, according to the World Health Organization. Scientists fear the virus would soon mutate to become easily transmissible among people and cause a global pandemic similar to the 1918 outbreak How the problem of Agent Orange and later food-driven contamination with TCDD relates to one of the above non-structural proteins of influenza virus, namely NS1 protein, to low- 146

4 dose TCDD proven activation of the Ah receptor-mediated transcriptional pathway, and generally to pandemic Influenza viruses? To answer this complex question, the data corresponding to TCDD-influenza virus issue may be presented at the gene, cellular, and population levels. On the key level of gene structure, while searching through Dioxin Responsive Gene Database, we found that, similar to DREs within mammalian genes and genes of cancer-associated viruses, the gene encoding influenza virus NS1 protein does possess totally 13 DREs (i.e., 3 A-CGCAC 5 sequence), of those 2 are located in its 5 -flanking region. Three separate probes of NS1 gene were analyzed, and the following DRE positions were revealed in 5 -flanking region: (- 7900, - 645), (-7942, -687), and (-7942, -687). Therefore, in case if future direct experiments show that TCDD at very low concentrations causes upregulation effect on NS1 expression, all reverse genetics techniques to manipulate virus genome could be applied. Because exact DRE positions in promoter region are determined, a site-specific mutational analysis might also be designed. On a cellular level, it was postulated that some changes in infected cell expression might be beneficial for viral replication. So, a proposed ability of body burden (intracellular) TCDD to directly trans-activate expression of NS1 gene might represent not just a laboratory-set but rather very real set of events between cellular proven transcriptional factor, i.e., TCDD, and its newly target NS1 gene, which might determine the severity and outcome of viral infection. As regards TCDD effective concentration, because NS1 gene contains two DREs in promoter region, it is twice as much than a DRE in HIV-1 gene, but 5 times less than in cytomegalovirus gene promoter (10 DREs). Therefore, a proposed effective intracellular concentration of TCDD upregulating NS1 protein is a one lower than 1 nm but higher than 0.3 pm, i.e. about or slightly above than dioxin current human body burden. This proposition, again, might make TCDD-NS1 relationship the real problem related to emerging influenza pandemic. It is important that, if proven, all the above might lead to the development of a new tool for inhibition (complete or partial) of TCDD-caused upregulation of NS1 protein in infected cells. Specifically, some already known antagonists of TCDD binding at the Ah-receptor might be utilized, as well as inhibitors blocking binding of ligand-activated Ah-receptor- Arnt complex at the DRE. These candidates antagonists/inhibitors can also include 147

5 pharmaceutically used medicines like salycilamide, as well as some natural compounds like coplanar bioflavonoids. Finally, about a population level characterizing the TCDD-NS1 problem. I seems it is not a coincidence that the regions with most frequent ducks and poultry dying caused by H5N1 strain of the bird flu virus in China, Taiwan, Hong Kong, and geographically adjacent areas in Laos and Vietnam are often the same regions known as the most heavily contaminated with TCDD and other dioxin-like compounds. For instance, in contaminated (resulted mainly from Agent Orange usage during the Vietnam War) areas of Laos and Vietnam, the TCDD level determined in duck eggs is 29 ng/kg and 11 ng/kg, respectively, which might be pretty enough for effective upregulation of NS1 gene in H5N1 virus. With prioritizing the TCDD-H5N1 subject, XENOTOX Inc. is currently preparing a mutual epidemiological project with the Russian-Vietnamese Tropical Canter. It is XENOTOX s principal scientific and humane position that all efforts possible have to be made, in close collaboration with Russian and Vietnamese molecular toxicologists, virologists, and environmental epidemiologists, in order to lessen or defeat an awful virus strain that could become a pandemic with a horrendous outcome," as the WHO's representative in Vietnam Hans Troedsson said on February 3,

Avian Influenza (Bird Flu) Fact Sheet

Avian Influenza (Bird Flu) Fact Sheet What is an avian influenza A (H5N1) virus? Influenza A (H5N1) virus also called H5N1 virus is an influenza A virus subtype that occurs mainly in birds. It was first isolated from birds (terns) in South