Genotype of dengue virus serotype 1 in relation to severe dengue in Guangzhou, China.

Guangzhou has been the city most affected by the dengue virus (DENV) in China, with a predominance of DENV serotype 1 (DENV-1). Viral factors such as dengue serotype and genotype are associated with severe dengue (SD). However, none of the studies have investigated the relationship between DENV-1 genotypes and SD. To understand the association between DENV-1 genotypes and SD, the clinical manifestations of patients infected with different genotypes were investigated. A total of 122 patients with confirmed DENV-1 genotype infection were recruited for this study. The clinical manifestations, laboratory tests, and levels of inflammatory mediator factors were statistically analyzed to investigate the characteristics of clinical manifestations and immune response on the DENV-1 genotype. In the case of DENV-1 infection, the incidence of SD with genotype V infection was significantly higher than that with genotype I infection. Meanwhile, patients infected with genotype V were more common in ostealgia and bleeding significantly. In addition, levels of inflammatory mediator factors including IFN-γ, TNF-α, IL-10, and soluble vascular cell adhesion molecule 1 were higher in patients with SD infected with genotype V. Meanwhile, the concentrations of regulated upon activation normal T-cell expressed and secreted and growth-related gene alpha were lower in patients with SD infected with genotype V. The higher incidence of SD in patients infected with DENV-1 genotype V may be attributed to elevated cytokines and adhesion molecules, along with decreased chemokines.

Two different dengue virus strains in the Japanese epidemics of 2014.

In late August 2014, dengue cases were reported in Japan, and a total of 162 cases were confirmed. In the present study, the envelope (E) gene sequences of 12 specimens from the dengue patients were determined. A dengue virus serotype 1 (DENV1) strain (D1/Hu/Shizuoka/NIID181/2014), which was clearly different from the first reported strain (D1/Hu/Saitama/NIID100/2014), was identified, although the other 11 specimens showed the same nucleotide sequences as D1/Hu/Saitama/NIID100/2014. The E gene sequences of two different strains were compared with those of nine DENV1 strains of imported cases in Japan in 2014. Phylogenetic analysis based on the E gene sequences showed that the D1/Hu/Saitama/NIID100/2014 strain was closely related to a strain isolated from an imported case from Singapore. Although no strain closely related to D1/Hu/Shizuoka/NIID181/2014 was found in these imported strains, the strain was closely related to isolates in Thailand and Taiwan in 2009. These data indicate that the dengue cases in Japan were caused by two different dengue virus strains that entered Japan through different means.

A unified global genotyping framework of dengue virus serotype-1 for a stratified coordinated surveillance strategy of dengue epidemics.

BACKGROUND: Dengue is the fastest spreading arboviral disease, posing great challenges on global public health. A reproduceable and comparable global genotyping framework for contextualizing spatiotemporal epidemiological data of dengue virus (DENV) is essential for research studies and collaborative surveillance. METHODS: Targeting DENV-1 spreading prominently in recent decades, by reconciling all qualified complete E gene sequences of 5003 DENV-1 strains with epidemiological information from 78 epidemic countries/areas ranging from 1944 to 2018, we established and characterized a unified global high-resolution genotyping framework using phylogenetics, population genetics, phylogeography, and phylodynamics. RESULTS: The defined framework was discriminated with three hierarchical layers of genotype, subgenotype and clade with respective mean pairwise distances 2-6%, 0.8-2%, and ≤ 0.8%. The global epidemic patterns of DENV-1 showed strong geographic constraints representing stratified spatial-genetic epidemic pairs of Continent-Genotype, Region-Subgenotype and Nation-Clade, thereby identifying 12 epidemic regions which prospectively facilitates the region-based coordination. The increasing cross-transmission trends were also demonstrated. The traditional endemic countries such as Thailand, Vietnam and Indonesia displayed as persisting dominant source centers, while the emerging epidemic countries such as China, Australia, and the USA, where dengue outbreaks were frequently triggered by importation, showed a growing trend of DENV-1 diffusion. The probably hidden epidemics were found especially in Africa and India. Then, our framework can be utilized in an accurate stratified coordinated surveillance based on the defined viral population compositions. Thereby it is prospectively valuable for further hampering the ongoing transition process of epidemic to endemic, addressing the issue of inadequate monitoring, and warning us to be concerned about the cross-national, cross-regional, and cross-continental diffusions of dengue, which can potentially trigger large epidemics. CONCLUSIONS: The framework and its utilization in quantitatively assessing DENV-1 epidemics has laid a foundation and re-unveiled the urgency for establishing a stratified coordinated surveillance platform for blocking global spreading of dengue. This framework is also expected to bridge classical DENV-1 genotyping with genomic epidemiology and risk modeling. We will promote it to the public and update it periodically.

Profile of the 2016 dengue outbreak in Nepal.

OBJECTIVE: The objective of this study was to obtain clinical, virological and demographic data detailing the 2016 dengue outbreak in Nepal. RESULTS: Dengue disease was first reported in Nepal in 2004 and several major outbreaks have occurred since then, with a significant impact on public health. An outbreak of dengue fever occurred in Nepal during June to November 2016, with a peak number of cases reported in September. 1473 patients with laboratory confirmed DENV infections visited or were admitted to hospitals during this period. The most common clinical symptoms included fever, headache, joint pain and thrombocytopenia. Serotyping of 75 serum samples from patients having fever for less than 4 days was carried out with a dengue virus (DENV) serotype-specific RT-PCR strategy. Our results indicate that the dengue outbreak in Nepal during 2016 was caused predominantly, if not exclusively, by DENV-1, representing a shift in the prevailing serotype from DENV-2, the dominant serotype characterizing the 2013 dengue epidemic in Nepal. Hopefully, this report will assist Nepalese public health agencies in developing improved dengue-related programs including mosquito-vector control, DENV surveillance, and diagnosis and treatment of dengue fever patients, in order to reduce the impact of future dengue epidemics.

Molecular characterisation and phylogenetic analysis of dengue outbreak in Pasighat, Arunachal Pradesh, Northeast India.

BACKGROUND AND OBJECTIVES: Dengue is one of the most prevalent arboviral diseases in the world with 390 million dengue infections per year. In this study, we report the molecular characterisation of dengue outbreak in Pasighat, Arunachal Pradesh, Northeast India during 2015. SUBJECTS AND METHODS: : A total of 613 dengue-suspected cases were screened for dengue virus by dengue NS1 Ag and anti-dengue IgM antibody depending on the duration of sample collection and onset of symptom. Further, molecular characterisation was done by amplifying the C-PrM region by real-time polymerase chain reaction followed by phylogenetic analysis. RESULTS: Molecular characterisation revealed that the dengue outbreak was predominantly due to dengue virus serotype-1 (DENV-1) (90.9%) while DENV-2 was detected in 7.5% of samples. Co-infection of DENV-1 and DENV-2 was detected in one case. Phylogenetic analysis of the DENV-1 strains with the prototype revealed that the DENV-1 strains were grouped within genotype III. Similarly, DENV-2 strains were clustered within genotype IV. The study revealed a change in the predominant serotype in recent years with DENV-3 in 2012 to DENV-1, 2, 3 and 4 in 2014 to DENV-1 in 2015 in the study region. A unique L24M mutation was observed in the DENV-1 strains of Arunachal Pradesh which was absent in all the circulating strains in India except one strain from the state of Kerala in South India. Marked variation within the DENV-2 strains was observed at A102V and I163V in one strain similar to earlier circulating isolates in India. CONCLUSIONS: The present study reveals a shift in the serotype dominance in the study region. As serotype shifts and secondary infection with a heterologous DENV serotype are frequently associated with disease severity, there is an urgent need for sustained monitoring of the circulating serotypes and enhanced surveillance operations, especially in the monsoon and post-monsoon periods to prevent large-scale, severe dengue outbreaks in this region.

Potent Neutralization Ability of a Human Monoclonal Antibody Against Serotype 1 Dengue Virus.

The incidence of dengue virus (DENV) infections has been escalating in tropical and subtropical countries, but there are still no effective therapeutic options. In the present study, a DENV-1-specific human monoclonal antibody (HMAb), 1G5, isolated from single plasma cells obtained from the peripheral blood mononuclear cells of dengue patients was found to have potent neutralization activity against serotype 1 DENV (DENV-1). Its neutralization activity against DENV-2 was not as strong, and it was almost absent for DENV-3 and DENV-4. The results showed that HMAb 1G5 only binds to the envelop protein of intact DENV-1 or the envelop protein under unheated and non-reducing conditions, and that it does not bind to recombinant envelope protein. This could mean that the antibody recognizes a conformational epitope of the envelope protein. Further, the findings showed that HMAb 1G5 potently neutralizes DENV-1 in both the pre- and post-attachment phases of the virus at low concentrations. In vivo studies showed that HMAb 1G5 provides protection from DENV-1 infection in a murine model. In addition, antibody-dependent enhancement that occurs at lower doses of the antibody was completely abrogated by the introduction of Leu-to-Ala mutations (1G5-LALA) or deletion of nine amino acids (1G5-9del) in the Fc region. Therefore, HMAb 1G5 shows promise as a safe and effective agent for prophylactic and therapeutic treatment of DENV-1 infection.