In recent decades Dengue has become one of the most uncontrolled and neglected infectious diseases, especially in the tropical and sub-tropical regions of the world. It is believed that societal and ecological changes/movement during the World wars increased vector-borne diseases, and dengue hyperendemicity began in the Southeast Asian regions, thus triggering epidemics of dengue hemorrhagic fever (DHF). Dengue viruses can be asymptomatic, or may also cause a wide spectrum of symptoms that can range from classic fever to plasma leakage, haemorrhaging, shock and even death.
The slow progress in vaccination and drug discovery is mainly because (i) the vaccine needs to be able to protect against all 4 DENV serotypes; (ii) of the lack of protective immune correlates; (iii) there is an absence of reliable animal models to represent dengue and (iv) the controversial and limited understanding of dengue pathogenesis.
Dengue diagnosis is not only important for clinical management of patients, but also for epidemiological surveillance, outbreak intervention and vaccine development and monitoring. Due to the absence of pathognomonic clinical features that can distinguish dengue from other febrile illnesses, laboratory confirmation is an essential part of diagnosing dengue. Dengue diagnosis is divided into two main phases, the early phase and the late phase.
We have been actively involved in the development of diagnostic kits. An in house method for the detection of dengue IgM via IgM capture ELISA, and a multiplex dengue viral RNA detection assays were developed and evaluated. We have also been involved in the evaluation projects of these kits conducted by the WHO. These evaluations revealed that the NS1 detection rate is inversely proportional while the IgM detection rate is directly proportional to the presence of IgG antibodies. This information helps in balancing the use of NS1 kits which are not entirely solely dependable as a single assay for the detection of dengue infection. Combining this assay with an IgM and/or IgG assay will increase the sensitivity of detection, especially in areas with a higher prevalence of secondary dengue virus infections. Newer technologies are being applied to fine-tune available diagnostic assays and also to design new ones that fit the ideal test concept.
Although many tests and assays have been carried out, we are still striving to improve better diagnosis of dengue infection. Our laboratory thrives to develop and test for new avenues in streamlining dengue diagnosis.
These past few decades have seen a surge in dengue research – in trying to understand the disease, the cause and the trigger. Our lab has been part of the worldwide research embarking on finding the cause and correlates of severe dengue and the occurrence of asymptomatic dengue cases.
We investigated immune correlates in dengue severity which included HLA association with dengue susceptibility/protection, T cell responses of dengue infected patients, and cytokine profiling of dengue patients at different phases of illness.
With the understanding that the asymptomatic dengue cases should not be taken lightly, our lab has investigated the asymptomatic dengue cohort to search for predisposing markers that constitute protection, or lack of clinical manifestations in these individuals, using microarray and high throughput quantitative PCR to assess the molecular basis of the human genomics.
More recently, we have ventured into the field of endothelium dysfunction of infectious diseases. The hallmark of severe dengue is plasma leakage and haemorrhage. The ‘organ’ crucial for regulating electrolyte content of intra- and extravascular spaces is the endothelium layer. Many other viruses have been known to target the endothelium leading to enhanced permeability. This is why we are also investigating endothelium dysfunctions caused by other viruses including respiratory viruses, influenza virus, and noroviruses. By gaining an understanding of the mechanism of endothelium dysfunction in infectious disease, we hope to move on to finding therapeutic strategies to prevent, limit, and reverse the disruption of the endothelial layer and thus minimise the severity of the disease.
Antimicrobial/Antiviral Drug Development
Pneumococcal diseases represent a global threat mainly affecting the elderly and children under the age of two – caused by Streptococcus pneumonia or pneumococcus, a Gram-positive, alpha-hemolytic, aerotolerant anaerobic member of the genus Streptococcus. This pathogen was a major cause of pneumonia in the late 19th Century and represents one of the major etiological agents causing life-threatening diseases such as pneumonia, meningitis, and bacteremia. Although antimicrobial drugs such as penicillin have diminished the risk from pneumococcal disease, the proportion of strains that are resistant to antibiotics is steadily increasing. Antimicrobial peptides (AMPs) represent an important part of the innate immune system and the primary role is to kill off invading pathogenic organisms. Our main focus is to design novel synthetic antimicrobial peptides (AMPs) as potential antimicrobial candidates against Streptococcus pneumonia.
Currently, we have designed and tested a series of hybrid AMPs exhibiting strong anti-pneumococcal effects, of which DM3 possessed promising in vitro and in vivo anti – pneumococcal activities, this has now been patented. Based on this current experience, we have begun to investigate other hybrids generated based on Ranalexin and Indolicidin which showed potent antipneumo – coccal activity and the mechanisms of these AMPs are being evaluated alongside in vivo therapeutic efficacy.
University of Malaya (Postgraduate Research Fund, High Impact Research Grants), Ministry of Higher Learning (MOHE), Ministry of Science & Technology Malaysia (IRPA RM6, MOSTI RM9, Brain Gain Malaysia, ScienceFund, Scientific Advancement Grant Allocation (SAGA), Exploratory Research Grant Scheme (ERGS), Fundamental Research Grant Scheme (FRGS) and Malaysian Agricultural Research and Development Institute (MARDI) and TDR/WHO.
TDR/WHO, The John Hopkins University, Perdana University Graduate School of Medicine Malaysia, University of South Florida, Colorado State University, University of Tubingen, Institute for Medical Research Malaysia, Faculty of Biomedical Engineering University of Malaya, University Sains Malaysia and the University of Brunei.
Shamala Devi Sekaran
Dept of Medical Microbiology- Faculty of Medicine