Sequence analysis of E/NS1 gene junction of Dengue Type-1 viruses isolated in Klang Valley 2010 to 2012

Dengue is a mosquito-borne viral disease caused by four serotypes of dengue virus, affecting the human population for decades in many tropical and subtropical regions of the world. In Malaysia, all four dengue serotypes co-circulates in a dengue season even though any one of the serotypes can predominate. In this study, serum samples were collected from dengue fever and severe dengue fever patients within Klang Valley from 2010-2012 to determine the prevailing dengue serotypes. In addition, sequencing of the envelope/nonstructural 1 (E/NS1) gene junction of the virus isolated was performed to identify the presence of any mutations that are suggestive of increased virulence in the virus. The results showed that Dengue-1 (DEN-1) was the predominant circulating serotype. The E/NS1 gene sequences of the isolates were analysed to trace the evolutionary knowledge of the strains. All sequences of the isolates were compared with DEN-1 prototype Hawaii strain as the reference sequence. The E/NS1 sequences of other dengue strains from neighbouring regions as well as other parts of the world obtained from the GenBank database were also included in the phylogenetic tree analysis. Analyses showed that there was 97% to 100% similarity among the ten isolates at the nucleotide level. Similarly, the amino acid analogue also showed 98% to 100% homology. However, all five non-severe dengue isolates showed variation at position 780, resulting in an amino acid change from valine to alanine as compared to severe dengue isolates. A rooted phylogenetic tree was performed using neighbour-joining method with DEN-2 and DEN-3 as the outgroups. Results showed that all ten isolates were classified as genotype I. In addition, the five isolates from severe dengue patients were found to be clustered together with JN697057 and JN697058, Malaysian DEN-1 strains from the 2005 outbreak.

Acute flaccid paralysis surveillance: looking beyond the global poliomyelitis eradication initiative.

In 1992 surveillance of acute flaccid paralysis (AFP) cases was introduced in Malaysia along with the establishment of a national referral laboratory at the Institute for Medical Research. The objective of this study was to determine the incidence, viral etiology and clinical picture of AFP cases below 15 years of age, reported from 2002 to 2007. Six hundred seventy-eight of 688 reported cases were confirmed as AFP by expert review. The clinical presentation of acute flaccid paralysis in these cases was diverse, the most commonly reported being Guillian-Barre syndrome (32.3%). Sixty-nine viruses were isolated in this study. They were Sabin poliovirus (25), Echovirus (22), Cocksackie B (11), EV71 (5), Cocksackie A (1), and untypable (5). Malaysia has been confirmed as free from wild polio since the surveillance was established.

Comparison of sequences of E/NS1 gene junction of dengue type 3 virus following culture subpassage in C6/36 cells to study the possible occurrence of mutations.

The aim of this study was to determine whether mutations could occur in the dengue virus genome following three subpassages of the virus in a mosquito cell line. This was done because sources of virus isolates used for sequencing studies are usually maintained in cell lines rather than in patients' sera. Therefore it must be assured that no mutation occurred during the passaging. For this purpose, sequencing was carried out using the polymerase chain reaction (PCR) products of the envelope/non-structural protein 1 junction region (280 nucleotides) of dengue type 3 virus. Sequence data were compared between the virus from a patient's serum against the virus subpassaged three times in the C6/36 cell line. We found that the sequence data of the virus from serum was identical to the virus that was subpassaged three times in C6/36 cell line.

The use of polymerase chain reaction (PCR) as a diagnostic tool for dengue virus.

This study describes the use of polymerase chain reaction as a diagnostic tool for detecting and typing of dengue virus. PCR was compared against virus isolation. First RT-PCR was done using dengue consensus primers after which positive samples were subjected to RT-PCR using type-specific primers. This study shows that the local strains of the dengue virus could be detected using the chosen primers. Furthermore, RT-PCR was found to be more sensitive than virus isolation in identifying the dengue positive samples.