Snake Venom Research

    Snake venom is an interesting subject for biological study for at least two reasons. First, venoms poisoning can lead to high mobidity or motality; thus treatment modalities particularly for local tissue necrosis, need to be studied, and potent polyvalent antivenoms need to be prepared. Secondly, since venoms are rich sources of biological compounds, the study of these bioactive molecules can lead to the elucidation/characterization of natural pathways/components. Moreover, these molecules may be useful as lead compounds for drug development.

    In tropical countries where venomous snakes coinhabit with the rural people, venom poisoning is common and remains a medical problem. The most effective treatment for systemic poisoning is the administration of specific antivenoms. However, venom proteins from different families and genus may exhibit similar biochemical and pharmacological activities, but they are distinct immunochemically. The preparation of highly potent and polyvalent antivenoms is difficult to achieve, especially those against elapids (cobra, krait) whose toxins are of low molecular weight, highly toxic and poorly immunogenic.

    Snake venoms can produce local and/or systemic toxicity. While systemic effect of the venoms can be effectively treated with specific antivenom, the local toxicity which can lead to severe tissue necrosis is not affected by antivenom administration and may require skin graft or even amputation. No effective treatment modality is currently available to prevent or reduce the local tissue necrosis induced by venoms, and this remains a challenge in snake venom research.

    Snake venoms have evolved to serve two main functions: to immobilize prey and to digest the prey which are swollowed whole. The venom toxins/enzymes are usually highly potent and specific for some vital physiological pathways. Some of them act as agonists and activate certain steps while others act as antagonists. Elapid venoms, e.g., cobra venom, contain highly potent postsynaptic neurotoxins which act specifically and quasi-irreversibly on nicotinic acetylcholine receptor. These toxins are instrumental to the isolation and characterization of the receptor. In viper venoms, various enzymes like serine proteases, metalloproteases and phospholipases can affect the hematologic system e.g., hemolysis, hemorrhage and coagulation. Many of these proteins have been characterized and used as therapeutic agents or as lead compounds for drug development. For example; a thrombin-like enzyme (Ancrod) from the Malayan pit viper has been used to treat thrombosis. Venom proteins with RGD (Arg-gly-asp) sequence of disintegrins have been used in the design of molecules with antiplatelet activity. It is therefore likely that proteins with important and novel biological activities can be found in the diverse population of venomous snakes in Thailand.

Development of Diagnostic Tests

    Many immunoassays and immunodiagnostic kits have been developed for the detection of chemicals/biochemicals and microorganisms. These tests have been very useful in the early detection or diagnosis of various diseases, for example, tumor markers of various types of cancer, sexually-transmitted diseases including HIV, hepatitis antigen/antibody etc. Immunodiagnostic tests for hCG in pregnancy tests and for drugs of abuse have also been developed and extensively used. All these rapid and early detection methods have aided in the management of these health conditions.

    The Laboratory of Immunology has been involved in developing simple immunodiagnostic tests based on immunochromatography (IC) for infectious agents that affect Thais and other people of this region. In collaboration with scientists from Mahidol University , we have developed and patented two IC tests

1. IC test for diagnosis of human Pythiosis. This is an emerging infectious disease caused by Pythium insidiosum and affected mostly farmers in the region.Due to lack of early diagnosis, the infection causes tissue necrosis of limbs, often requiring amputation and sometimes resulting in death. The test kit enables early diagnosis and leads to successful treatment with antibiotics.

2. Development of an IC test for Fasciola gigantica which is a liver parasite in ruminants. This disease causes economic loss of about half a billion Baht annually. The simple IC test of blood specimen, in place of fecal egg count, leads to treatment with anthelmintics. This should result in higher product value and reduces the spread of the disease and increases the market value of the ruminants.

     We are currently interested in developing IC test for lipopolysaccharide (LPS) of gram negative bacteria. Almost all IC tests are not sensitive enough to detect the pathogens in human specimens, and often require the time-consuming step of prior enrichment culture to increase the pathogen number. We think that the specific LPS (ca. 5 x 10⁶ molecules/cell), if it can be manipulated into favorable forms (e.g. mixed micelles), should enable detection by IC at much higher sensitivity than the currently available ones. In addition, we have also studied the use of liposome entrapped with fluorescent/luminescent compounds as signal generators to enhance the detection of specific interactions e.g., antigen-antibody and nucleotide hybridization.

Immunotoxicology Research

    An increasing number of chemicals are manufactured every year and continue to be released into the environment. These chemicals are widely used in both industrial and agricultural sectors where a great part of the human population may be exposed to them. Accumulated evidence has shown that these chemical pollutants could lead to adverse health effects. In this context, many of them probably affect the immune system as suggested by a significant increase in incidence of allergy and asthma in the population.

    Primarily, the immune system has a function to recognize and destroy foreign materials e.g. toxins and pathogens. This activity is a finely regulated network of different immune components and regulatory mediators developed during evolution. As foreign substances (xenobiotics), environmental pollutants could impair host resistance against microbial pathogens and neoplasia, or lead to hypersensitivity and autoimmune reactions. Experimental animal studies have shown that pesticides, metals and industrial chemicals etc., have the potential to cause immunosuppression while other studies indicated the possibility of these chemicals to interfere with human immune function.

    Thailand is an agriculture country and the agricultural sector is an important contributor to the country's gross domestic product (GDP). With the promotion of agricultural exports, farmers have to boost their production and efficiency by using large amounts of agrochemicals including fertilizers and pesticides. From the OAE report , 122,337 tons of pesticides were imported in 2007 for use in Thailand . Among these imported pesticides, herbicides account for the highest amount, followed by insecticides and fungicides for use mainly in the agricultural sector. Thus, Thai farmers are at great risk of pesticide poisoning, but direct study on the health effects, particularly on the immune system, is rare.