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Apichai Tuanyok, Ph.D.

Assistant Professor, Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, Florida


Phone:
Office: BSB 320F
Email: tuanyok [at] hawaii.edu

Research Keywords: Burkholderia pseudomallei


Research Overview

Burkholderia pseudomallei is the cause of melioidosis, a severe tropical disease that remains a public health problem in Southeast Asia and northern Australia. Because there is no vaccine for melioidosis, successful patient management is solely based on early diagnosis and subsequent treatment with antibiotics. B. pseudomallei exhibits very high recombination frequency in both its core and accessory genomes creating great strain-to-strain diversity. Gene differences that account for the virulence between B. pseudomallei and its close non-pathogenic relatives (e.g., B. thailandensis) are now being better understood, but the genetic and molecular basis for differential virulence, drug resistance, and physiology among B. pseudomallei strains remains unknown.

Central hypothesis: B. pseudomallei is known as one of the most genetically recombining bacterial species. Various phenotypic characteristics and clinical outcomes are believed to be associated with its genomic diversity.

Objectives:

  1. To determine genetic and molecular basis of differential phenotypes of B. pseudomallei.
  2. To identify antigens and fundamental protective immunity of B. pseudomallei.

Specific Aim 1: Identify and characterize drug-resistance mechanisms of B. pseudomallei. Antimicrobial therapy for melioidosis has been complicated due to the fact that B. pseudomallei is resistant to most antibiotics used in the empirical management of sepsis.

  • Hypothesis: Primary resistance to parental drugs e.g., ceftazidime and amoxicillin - clavulanic acid is relatively rare, while the resistance mostly occurs clinically. Mutations of the pathogen are not random, most of which are gene or site-specific that play important roles in resistance mechanisms.

  • Rationale: Identifying antibiotic resistance mechanisms in B. pseudomallei will provide proven and clinically relevant signatures for monitoring the development of antibiotic resistance in this deadly pathogen.

  • Experimental Plan: A large strain collection of drug resistant B. pseudomallei from around the world will be developed. Next generation sequencing e.g., Illumina and PacBio will be used to identify genetic markers such as SNPs of the mutations. The genetic markers (e.g., SNPs of Class A Beta-lactamase gene) will be characterized using allelic replacement. The mutants will be tested for pharmacokinetics against a series of antibiotics.

Specific Aim 2: Identify potential antigens for vaccine development against melioidosis.

  • Hypothesis: We believe that novel approaches to vaccine development that target non-polysaccharide antigens are needed for melioidosis. Proteins are generally more antigenic than polysaccharides and induce antibody subclasses with high complement-fixing capacity. Extracellular and cell surface proteins can be considered as viable vaccine antigens.

  • Rationale: Identification of the secreted surface antigens and understanding of fundamental protective immunity are important for vaccine development against B. pseudomallei.

  • Experimental Plan: Proteomic analyses such as 2-dimentional electrophoresis (2-DGE), immunoblotting, and mass spectrometry will be used to identify surface and/or secreted antigens of B. pseudomallei. Heterologous expression and liquid chromatography will be used to purify the antigens. These antigens will be tested for protection against melioidosis in mouse models. Luminex and flow cytometry-based assays will be used to study protective immunity of these antigens.

Selected Publications