Zika virus was first isolated in from nonhuman primate in 1947. It is in the genus Flavivirus, closely related to other flavivirus like Dengue, West Nile, Yellow fever and Japanese encephalitis virus. Since 2007 epidemic in Yap island, zika virus infections had spread to the countries in Micronesia and South Pacific. In 2015, Zika virus outbreak occurred in Brazil and now more than 40 countries in American continents reported autochthonous infection. The virus is transmitted mainly by Ae. aegypti mosquito with many other Aedes mosquito species known as vector. Recently, Zika virus infection is known to cause severe neurological complications and congenital malformation. In this paper, we will review current knowledge on Zika virus history, biology, clinical characteristics and preventive method.
Aedes ; Biology ; Brazil ; Culicidae ; Dengue ; Encephalitis Virus, Japanese ; Flavivirus ; Methods ; Microcephaly ; Micronesia ; Primates ; Yellow Fever ; Zika Virus Infection* ; Zika Virus*

Zika virus (ZIKV) is an arthropod-borne member of the genus Flavivirus, closely related to the dengue, West Nile, Japanese encephalitis, and yellow fever viruses and is transmitted by Aedes spp. mosquitoes. It has emerged explosively since 2007 to cause a series of epidemics in Micronesia, the South Pacific, and most recently the Americas. Following the first detection of ZIKV on the American continent, autochthonous ZIKV transmission has been confirmed throughout Central and South America. The unprecedented numbers of people infected during recent outbreaks in the South Pacific and the Americas may have resulted in enough ZIKV infections to notice patterns of the associated incidence of congenital microcephaly, Gillain-Barre symdrome, and acute diffuse encephalomyelitis. Here we review the history, emergence, biology, transmission, and control strategies for the ongoing outbreak through vector-centric approaches on ZIKV to date.
Aedes ; Americas ; Arboviruses ; Biology ; Culicidae ; Dengue ; Disease Outbreaks ; Encephalitis, Japanese ; Encephalomyelitis ; Flavivirus ; Incidence ; Microcephaly ; Micronesia ; South America ; Yellow fever virus ; Zika Virus*

Acute viral encephalitis caused by neurotrophic viruses, such as mosquito-borne flaviviruses, is an emerging and re-emerging disease that represents an immense global health problem. Considerable progression has been made in understanding the pathogenesis of acute viral encephalitis, but the immune-pathological processes occurring during the progression of encephalitis and the roles played by various molecules and cellular components of the innate and adaptive systems still remain undefined. Recent findings reveal the significant contribution of Toll-like receptors (TLRs) and regulatory CD4+ T cells in the outcomes of infectious diseases caused by neurotrophic viruses. In this review, we discuss the ample evidence focused on the roles of TLRs and CD4+ helper T cell subsets on the progression of acute viral encephalitis. Finally, we draw attention to the importance of these molecules and cellular components in defining the pathogenesis of acute viral encephalitis, thereby providing new therapeutic avenues for this disease.
Communicable Diseases ; Dengue Virus ; Encephalitis ; Encephalitis Virus, Japanese ; Encephalitis, Viral ; Flavivirus ; T-Lymphocyte Subsets ; T-Lymphocytes ; Toll-Like Receptors ; West Nile virus

BACKGROUND: The genus Flavivirus consists of many emerging arboviruses, including Dengue virus (DV), Japanese encephalitis virus (JEV) and West Nile virus (WNV). Effective preventive vaccines remain elusive for these diseases. Mice are being increasingly used as the animal model for vaccine studies. However, the pathogenic mechanisms of these viruses are not clearly understood. Here, we investigated the interaction of DV and JEV with murine bone marrow-derived dendritic cells (bmDC). METHODS: ELISA and FACS analysis were employed to investigate cytokine production and phenotypic changes of DCs obtained from bone marrow following flavivirus infection. RESULTS: We observed that these viruses altered the cytokine profile and phenotypic markers. Although both viruses belong to the same family, JEV-infected bmDC produced anti-inflammatory cytokine (IL-10) along with pro-inflammatory cytokines, whereas DV infection induced production of large amounts of pro-inflammatory cytokines (IL-6 and TNF-alpha) and no IL-10 from murine bmDCs. Both flaviviruses also up-regulated the expression of co-stimulatory molecules such as CD40, CD80 and CD86. JEV infection led to down-regulation of MHC II expression on infected bmDCs. We also found that cytokine production induced by JEV and DV is MyD88-dependent. This dependence was complete for DV, as cytokine production was completely abolished in the absence of MyD88. With regard to JEV, the absence of MyD88 led to a partial reduction in cytokine levels. CONCLUSION: Here, we demonstrate that MyD88 plays an important role in the pathogenesis of flaviviruses. Our study provides insight into the pathogenesis of JEV and DV in the murine model.
Animals ; Arboviruses ; Bone Marrow ; Cytokines* ; Dendritic Cells* ; Dengue Virus ; Down-Regulation ; Encephalitis Virus, Japanese ; Enzyme-Linked Immunosorbent Assay ; Flavivirus Infections ; Flavivirus* ; Humans ; Interleukin-10 ; Interleukin-6 ; Mice ; Models, Animal ; Tumor Necrosis Factor-alpha ; Vaccines ; West Nile virus

Aims: The presence of a C-terminally extended form of NS1 (NS1’ protein) has been previously reported in encephalitic flaviviruses, due to the presence of -1 programmed ribosomal frameshift at the N-terminal of NS2A protein. This present study is aimed to further confirm that the NS1’ protein production is independent of the authentic cleavage at NS1-2A junction. Methodology and results: Six different constructs (P1-Leu, P2-Asp, P3-Phe, P3-Leu, P3-Gly and P5-8 Ala) containing various mutations at conserved and variable amino acids at C-terminal of NS1 protein were generated by site-directed mutagenesis and analysed with transient polyprotein expression assay. While analysis on the NS1-2A cleavage of the mutants exhibited extremely poor to efficient cleavage ranging from 6-89%, significant amount of NS1’ being expressed in all mutants irrespective of their NS1-2A cleavage outcome. Conclusion, significance and impact study: In this analysis, we showed for the first time that the abolishment of the authentic NS1-2A cleavage in Murray Valley encephalitis virus (MVEV) did not impact on NS1’ production. This observation extend on previous studies to show that NS1 and NS2A proteins are the product of NS1-2A cleavage which is catalysed by an unknown host protease while NS1’ protein is a product of ribosomal frameshift, independent of the authentic cleavage at NS1-2A junction.
Flavivirus

Zika virus (ZIKV) was spread to both eastward and westward from Uganda where the virus was identified approximately in 1947 by a group of arbovirus researchers. In 2015, ZIKV reached Americas with major outbreaks in Brazil. Most countries with mosquito transmitted ZIKV infection are located in tropical and subtropical areas, where ZIKV is endemic with other flaviviruses, including JEV, dengue and yellow fever virus. Approximately 40 countries in Central and South Americas and territories in South Pacific Islands and South East Asia show autochthonous ZIKV endemics. American lineage of ZIKV is known significantly to be mutated in susceptibility to host and in pathogenicity from Asian and Asian lineages approximately since 2014. Early and specific identification of ZIKV infection is very important for the effective management of patients. First of all, optimal collection of specimens for the laboratory diagnosis is required for both nucleic acid testing (NAT) and serological tests. Specimens for NAT tests and serological tests should be determined by the available laboratory resources, work-flow in each laboratory and the geographic areas of specimen collected in addition to days after showing symptoms. Testing strategy for specific differentiation among flaviviruses will vary depending on the prevalence of viruses known to be circulating in the area where the patients were exposed. NAT will be employed for the patients presenting with onset of symptoms less than 7 days. Advanced diagnostic technologies should be continuously developed for the increase of specificity and sensitivity of ZIKV diagnosis.
Americas ; Arboviruses ; Asian Continental Ancestry Group ; Biology* ; Brazil ; Clinical Laboratory Techniques* ; Culicidae ; Dengue ; Diagnosis ; Disease Outbreaks ; Epidemiology* ; Far East ; Flavivirus ; Humans ; Pacific Islands ; Prevalence ; Sensitivity and Specificity ; Serologic Tests ; South America ; Uganda ; Virulence ; Yellow fever virus ; Zika Virus*

The Japanese encephalitis virus (JEV), a member of the Flaviviridae family and Flavivirus genus, is transmitted by mosquitoes. JEV, of which some 35,000 cases are recorded every year, is a positive RNA virus. Two types of JEV vaccines have been developed to prevent the onset of encephalitis in humans, namely formalin-inactivated and liveattenuated vaccines. JEV inactivated vaccines are usually made using the Nakayama-NIH or Beijing-1 strains of the JEV virus. In this study, the immunological response to the Nakayama-NIH and Beijing-1 strains was analyzed as part of the effort to compile basic data which could lead to the selection of a suitable vaccine strain. To this end, the virus titer of Beijing-1 was found to be two-fold higher than that of Nakayama-NIH by plaque assay. Moreover, Beijing-1-induced neutralizing antibodies showed a higher level of titers when confronted by Korean JEV isolates than Nakayama-NIH-induced neutralizing antibodies (1:320 vs. 1:160, respectively). However, as a minimum ratio of 1:10 neutralizing antibody titers are required to protect against JEV infection, both strains in effect exhibited a sufficient level of neutralizing antibody titers. What's more, Beijing-1 was found to induce a somewhat higher cytotoxic T lymphocyte (CTL) response than Nakayama-NIH. Taken together, this can be taken to mean that Beijing-1 may in fact be a more effective vaccine candidate strain when it comes to inducing a high level of protective immunity against JEV infection.
Antibodies, Neutralizing* ; Asian Continental Ancestry Group* ; Culicidae ; Encephalitis ; Encephalitis Virus, Japanese* ; Encephalitis, Japanese* ; Flaviviridae ; Flavivirus ; Humans ; Lymphocytes* ; RNA Viruses ; Vaccines ; Vaccines, Inactivated ; Viral Load

BACKGROUNDTo compare the biological characteristics of West Nile virus (WNV) and Japanese encephalitis virus (JEV), including cells sensitivity, pathogenicity, viral morphology, as well as the results of immunological and molecular biological detection.

METHODSCytopathic effect (CPE) and pathogenicity were observed in C6/36 cells and in suckling mice inoculated intracerebrally with the WNV or JEV, respectively. The sliced tissue samples for electron microscopic examination were prepared for the morphologic observation of the viruses. Serum antibody to WNV or JEV was detected using indirect immunofluorescence assay (IFA), and the viral RNA was analyzed by RT-PCR method.

RESULTSWNV or JEV-caused CPE was characterized by cell fusion and cell shedding, respectively. There was no significant difference in the pathogenicity to suckling mice between WNV and JEV. The morphologic observation showed that the shape and size of the two virions were similar. WNV and JEV were found to have antigenic cross-reactivity. The viral RNA could be detected from both WNV and JEV samples with universal primer set, but only nucleoside fragments of corresponding virus could be amplified when specific primers were used.

CONCLUSIONCPE in C6/36 cell and detection of the viral RNA should be useful in discrimination of WNV and JEV, and simultaneously examining the titers of serum antibodies against WNV and JEV may be helpful to diagnosis of infection with these agents.

Animals ; Brain ; virology ; Cell Line ; Diagnosis, Differential ; Encephalitis Virus, Japanese ; immunology ; isolation & purification ; Encephalitis, Japanese ; diagnosis ; virology ; Flavivirus Infections ; diagnosis ; virology ; Immunoglobulin G ; blood ; Mice ; Mice, Inbred BALB C ; West Nile virus ; immunology ; isolation & purification

We developed a Rapid Diagnostic Test (RDT) kit for detecting IgG/IgM antibodies against Zika virus (ZIKV) using monoclonal antibodies to the envelope (E) and non-structural protein 1 (NS1) of ZIKV. These proteins were produced using baculovirus expression vector with Sf9 cells. Monoclonal antibodies J2G7 to NS1 and J5E1 to E protein were selected and conjugated with colloidal gold to produce the Zika IgG/IgM RDT kit (Zika RDT). Comparisons with ELISA, plaque reduction neutralization test (PRNT), and PCR were done to investigate the analytical sensitivity of Zika RDT, which resulted in 100% identical results. Sensitivity and specificity of Zika RDT in a field test was determined using positive and negative samples from Brazil and Korea. The diagnostic accuracy of Zika RDT was fairly high; sensitivity and specificity for IgG was 99.0 and 99.3%, respectively, while for IgM it was 96.7 and 98.7%, respectively. Cross reaction with dengue virus was evaluated using anti-Dengue Mixed Titer Performance Panel (PVD201), in which the Zika RDT showed cross-reactions with DENV in 16.7% and 5.6% in IgG and IgM, respectively. Cross reactions were not observed with West Nile, yellow fever, and hepatitis C virus infected sera. Zika RDT kit is very simple to use, rapid to assay, and very sensitive, and highly specific. Therefore, it would serve as a choice of method for point-of-care diagnosis and large scale surveys of ZIKV infection under clinical or field conditions worldwide in endemic areas.
Antibodies ; Antibodies, Monoclonal ; Baculoviridae ; Brazil ; Cross Reactions ; Dengue Virus ; Diagnosis ; Diagnostic Tests, Routine ; Enzyme-Linked Immunosorbent Assay ; Flavivirus ; Gold Colloid ; Hepacivirus ; Immunoglobulin G ; Immunoglobulin M ; Korea ; Methods ; Neutralization Tests ; Point-of-Care Systems ; Polymerase Chain Reaction ; Reagent Kits, Diagnostic ; Sensitivity and Specificity ; Sf9 Cells ; Yellow Fever ; Zika Virus

This report describes a case of yellow fever vaccine-associated viscerotropic disease (YEL-AVD) that occurred after vaccination in a 23-year-old male. Seven days after vaccination, our patient presented with fever, myalgia, and nausea. The IgM enzyme-linked immunosorbent assay (ELISA) for yellow fever virus was positive. After a 24 day hospitalization, he recovered and was discharged. Yellow fever is a viral hemorrhagic febrile illness caused by a flavivirus and transmitted by mosquitoes. The clinical presentation ranges from a mild febrile illness to a serious infection, leading to hepatic and renal failure, myocardial injury, hemorrhage, and shock, with a case fatality rate of 20-30%. Because yellow fever is a potentially fatal disease, vaccination is encouraged for people traveling to high-risk areas. Although considered a safe vaccine, severe adverse reactions have been reported. In 2001, rare, but severe, acute viscerotropic disease following vaccination was first described. We report the case of a 23-year-old male with fever and hepatitis following vaccination with 17D yellow fever vaccine.
Culicidae ; Enzyme-Linked Immunosorbent Assay ; Fever ; Flavivirus ; Hemorrhage ; Hepatitis ; Hospitalization ; Humans ; Immunoglobulin M ; Male ; Nausea ; Renal Insufficiency ; Shock ; Vaccination ; Yellow Fever ; Yellow Fever Vaccine ; Yellow fever virus ; Young Adult