Molecular and evolutionary analysis of dengue virus serotype 2 isolates from Korean travelers in 2015

Clinical, Virological, and Immunological Features in Cosmopolitan Genotype DENV-2-Infected Patients during a Large Dengue Outbreak in Sri Lanka in 2017

In 2017, Sri Lanka experienced its largest dengue epidemic and reported severe and unusual presentations of dengue with high morbidity. This outbreak was associated with the reemergence of dengue virus-2 (DENV-2), with the responsible strain identified as a variant of the previously circulating DENV-2 cosmopolitan genotype. In this study, we characterized the DENV-2 cosmopolitan genotype from patients during this epidemic. Also, we identified host factors that contributed to the severity of dengue infection in patients infected with this particular virus. Ninety-one acute serum samples from patients at the National Hospital in Kandy were randomly selected. Of these, 40.2% and 48.9% were positive for dengue IgM and IgG, respectively. NS1 antigen levels were significantly higher in primary infections. The severe dengue (SD) and dengue with warning signs (DWWS) groups exhibited significantly higher viral genome and infectivity titers than the dengue without warning signs (DWoWS) group. The highest viremia level was observed in SD patients. As for host cytokine response, interferon α (IFN-α) levels were significantly higher in the DWoWS group than in the DWWS and SD groups, whereas interleukin (IL)-12p40 and tumor necrosis factor α (TNF-α) levels in SD patients were significantly higher than in the other two groups. The TNF-α, IL-4, and monocyte chemoattractant protein-1 concentrations were positively correlated with NS1 antigen levels. From whole-genome analysis, NS4 had the highest frequency of amino acid variants, followed by the E gene. Our study suggests that viremia levels and immune responses contributed to SD outcomes, and these findings may help in identifying an effective therapeutic strategy against SD infection.

Dengue virus neutralizing antibody: a review of targets, cross-reactivity, and antibody-dependent enhancement

Dengue is the most common viral infection spread by mosquitoes, prevalent in tropical countries. The acute dengue virus (DENV) infection is a benign and primarily febrile illness. However, secondary infection with alternative serotypes can worsen the condition, leading to severe and potentially fatal dengue. The antibody raised by the vaccine or the primary infections are frequently cross-reactive; however, weakly neutralizing, and during subsequent infection, they may increase the odds of antibody-dependent enhancement (ADE). Despite that, many neutralizing antibodies have been identified against the DENV, which are thought to be useful in reducing dengue severity. Indeed, an antibody must be free from ADE for therapeutic application, as it is pretty common in dengue infection and escalates disease severity. Therefore, this review has described the critical characteristics of DENV and the potential immune targets in general. The primary emphasis is given to the envelope protein of DENV, where potential epitopes targeted for generating serotype-specific and cross-reactive antibodies have critically been described. In addition, a novel class of highly neutralizing antibodies targeted to the quaternary structure, similar to viral particles, has also been described. Lastly, we have discussed different aspects of the pathogenesis and ADE, which would provide significant insights into developing safe and effective antibody therapeutics and equivalent protein subunit vaccines.

Color Preference for Host-Seeking Activity of Aedes albopictus and Culex pipiens (Diptera: Culicidae)

A cue for long-range vision allows mosquitoes to identify hosts and differentiate the ecological niches (e.g., habitats). However, the visual factors involved in attracting mosquitoes to a host are complex and have not been fully understood. Therefore, we assessed color preference to Aedes albopictus (Skuse) and Culex pipiens (Conquillett) as diurnal and nocturnal species, respectively, using seven fundamental colors including black, white, red, yellow, green, blue, and purple with each trap at 100 lux in a laboratory. We used a binary behavioral assay using the Mosquito Preference Index (MPI) as a preference ratio with a range of 0-1. Our analyses showed that Ae. albopictus had a greater response to black (MPIs, 0.7), followed closely by red, blue, and purple (MPIs, 0.6). We also found that red, blue, and purple were significantly higher (P < 0.05) than those of green (MPI, 0.5), white (MPI, 0.3), and yellow (MPI, 0.2). Similarly, the MPIs for Cx. pipiens were significantly higher at black and red (MPIs, 0.7; P < 0.05) compare to those of white and yellow (MPIs, 0.3; P < 0.05). The color preference of Ae. albopictus showed significant correlation to luminous intensities (L-value) (r = -0.640; P = 0.000) and blue intensities (b-value) (r = -0.372; P = 0.000) for all seven colors. In addition, Cx. pipiens negatively correlated (r = -0.703; P = 0.000) between color preference and L-value. Our analyses provide a greater understanding of how color plays a role in visual sensory stimuli, and how that could potentially affect mosquito host-seeking behavior.

Molecular evolution of dengue virus types 1 and 4 in Korean travelers

Dengue virus (DV) is a mosquito-borne virus that is endemic to many tropical and subtropical areas. Recently, the annual incidence of DV infection has increased worldwide, including in Korea, due to global warming and increased global travel. We therefore sought to characterize the molecular and evolutionary features of DV-1 and DV-4 isolated from Korean overseas travelers. We used phylogenetic analysis based on the full coding region to classify isolates of DV-1 in Korea into genotype I (43251, KP406802), genotype IV (KP406803), and genotype V (KP406801). In addition, we found that strains of DV-4 belonged to genotype I (KP406806) and genotype II (43257). Evidence of positive selection in DV-1 strains was identified in the C, prM, NS2A, and NS5 proteins, whereas DV-4 showed positive selection only in the non-structural proteins NS2A, NS3, and NS5. The substitution rates per site per year were 5.58 × 10^-4 and 6.72 × 10^-4 for DV-1 and DV-4, respectively, and the time of the most recent common ancestor was determined using the Bayesian skyline coalescent method. In this study, the molecular, phylogenetic, and evolutionary characteristics of Korean DV-1 and DV-4 isolates were evaluated for the first time.

Oligonucleotide-Based Approaches to Inhibit Dengue Virus Replication

Dengue fever is one of the most common viral infections affecting humans. It is an expanding public health problem, particularly in tropical and subtropical regions. No effective vaccine or antiviral therapies against Dengue virus (DENV) infection are available. Therefore, there is a strong need to develop safe and effective therapeutic strategies that can reduce the burden and duration of hospitalizations due to this life-threatening disease. Oligonucleotide-based strategies are considered as an attractive means of inhibiting viral replication since oligonucleotides can be designed to interact with any viral RNA, provided its sequence is known. The resultant targeted destruction of viral RNA interferes with viral replication without inducing any adverse effects on cellular processes. In this review, we elaborate the ribozymes, RNA interference, CRISPR, aptamer and morpholino strategies for the inhibition of DENV replication and discuss the challenges involved in utilizing such approaches.