Dr. Theerapong Krajaejun

Theerapong Krajaejun, MD, PhD, is a young researcher in the Faculty of Medicine Ramathibodi Hospital at Mahidol University, Thailand. His research surrounds the oomycete pathogen Pythium insidiosum, which causes a life-threatening infectious disease called pythiosis in humans and animals in tropic and subtropic countries. Thailand is an endemic area of human pythiosis. Thalassemia, a major genetic disorder of Thai population, is a prominent predisposing factor for human pythiosis. As a medical doctor, Dr. Krajaejun has witnessed patient suffering and poor prognosis from this disease. Diagnosis of pythiosis is difficult. Conventional antifungal drugs are ineffective for treatment. Surgical removal of infected organs (such as eyes and legs, leading to life-long disabilities), and death from progressive infection are common outcomes. Although new cases have been increasingly reported, basic information about P. insidiosum’s natural history is still very limited.

In the long term, Dr. Krajaejun's P. insidiosum research will emphasize the biology, pathogenesis and host-pathogen interaction at the cellular and molecular levels. Dr. Krajaejun received a Fellowship from the International Nutrition Foundation/Ellison Medical Foundation (INF/EMF) Fellowship Program to support his post-doctoral research experience in the laboratory of Professor Bruce Klein at the University of Wisconsin-Madison, USA, for 3 years (2003-6). In the Klein lab, he conducted microbiological research aimed at understanding molecular pathogenesis and host-pathogen interaction, using the pathogenic-fungus Blastomyces dermatitidis as a model organism. Through this research, Dr. Krajaejun learned techniques in molecular biology, molecular genetics, cell biology, and immunology, including: DNA cloning and analyses, RNA interference, targeted gene disruption, cell transformation, transgenic gene expression and detection, cytokine detection, cell isolation, use of experimental animal models, and flow cytometry. These techniques are useful in meeting my goals in P. insidiosum research.

After finishing the training at the University of Wisconsin, Dr. Krajaejun returned to Thailand and started a pythiosis study group at the Research Center, Ramathibodi Hospital, Mahidol University. His current research projects are focusing on both clinical and basic biology studies of P. insidiosum. For clinical study, Dr. Krajaejun and his lab have developed some serological tests for facilitating diagnosis of pythiosis, they have tested some anti-fungal agents for their effect against the pathogen in vitro, and they have generated a recombinant protein for development of vaccine against P. insidiosum infection. For basic biology study, their attempt is to elucidate basic biology of P. insidiosum and pathogenesis of pythiosis, such as, why thalassemic patients are susceptible to pythiosis? It is known that thalassemic patients have tissue iron overload. It is also known that acquiring iron from host is an essential process for successful pathogens. Therefore, searching for P. insidiosum genes that involve in iron metabolism would be a beginning step to explore the association between thalassemia and pythiosis. Dr. Krajaejun and his lab have identified hundreds of P. insidiosum genes by using Expressed Sequence Tags strategy. Many P. insidiosum genes were predicted to involve in biological processes. For examples, there are genes that may involve or interact with some essential nutrients, such as, iron, calcium, and lipid. Molecular genetic tools for P. insidiosum, such as, DNA transformation and RNA interference, are now being developed for functional analysis of these genes.

It is apparent that more needs to be done in the way of basic research to provide insights into P. insidiosum’s biology, and thereby lead to the discovery of novel strategies for infection control, such as, new antimicrobial agents and vaccines.

Dr. Krajaejun and members of his lab group

Dr. Krajaejun's Publications:

1. Jindayok T, Piromsontikorn S, Srimuang S, Khupulsup K, Krajaejun T.  Hemagglutination Test for Rapid Serodiagnosis of Human Pythiosis. Clin Vaccine Immunol 2009; 16: 1047-51.
2. Krajaejun T, Imkhieo S, Intaramat A, Ratanabanangkoon K. Development of an Immunochromatographic Test for Rapid Serodiagnosis of Human Pythiosis. Clin Vaccine Immunol 2009; 16: 506-9.
3. Krajaejun T, Sathapatayavongs B, Chaiprasert A, Srimuang S. Do You Know Human Pythiosis? J Infect Dis Antimicrob Agents 2008; 25: 45-51.
4. Krajaejun T, Gauthier GM, Rappleye CA, Sullivan TD, and Klein BS. Development and Application of a Green Fluorescent Protein Sentinel System for Identification of RNA Interference in Blastomyces dermatitidis Illuminates the Role of Septin in Morphogenesis and Sporulation. Eukaryo Cell 2007; 6:1299-309. 
5. Pannanusorn S, Chaiprasert A, Prariyachatigul C, Krajaejun T, Vanittanakom N, Chindamporn A, Wanachiwanawin W, Satapatayavong B. Random Amplified Polymorphic DNA Typing and Phylogeny of Pythium insidiosum Clinical Isolates in Thailand. Southeast Asian J Trop Med Public Health 2007; 38:383-91.
6. Krajaejun T, Sathapatayavongs B, Pracharktam R,  Nitiyanant P, Leelachaikul P, Wanachiwanawin W, Chaiprasert A, Assanasen P, Saipetch M, Mootsikapun P, Chetchotisakd P, Lekhakula A, Mitarnun W, Kalnauwakul S, Supparatpinyo K, Chaiwarith R, Chiewchanvit S, Tananuvat N, Srisiri S, Suankratay C, Kulwichit W, Wongsaisuwan M, and Somkaew S. Clinical and Epidemiological Analyses of Human Pythiosis in Thailand. Clin Infect Dis 2006; 43:569-76.
7. Krajaejun T, Kunakorn M, Pracharktam R, Chongtrakool P, Sathapatayavongs B, Chaiprasert A, Vanittanakom N , Chindamporn A, and Mootsikapun P. Identification of a Novel 74-kDa Immunodominant Antigen of Pythium insidiosum Recognized by Sera from Human Patients with Pythiosis. J Clin Microbiol 2006; 44:1674-1680.
8. Krajaejun T, Pracharktam R, Wongwaisayawan S, Rochanawutinon M, Kunakorn M, and Kunavisarut S. Ocular Pythiosis: Is It Under-Diagnosed? Am J Ophthalmol 2004; 137:370-2.
9. Krajaejun T, Kunakorn M, Niemhom S, Chongtrakool P and Pracharktam R. Development and Evaluation of an In-House Enzyme-Linked Immunosorbent Assay for Early Diagnosis and Monitoring of Human Pythiosis. Clin Diagn Lab Immunol 2002; 9:378-382.