Abstract
BackgroundWe report the isolation and characterization of dengue virus (DENV) serotype 4 from a resident of Santa Fé, state of Paraná, South Brazil, in March 2013. This patient presented with hemorrhagic manifestations, high viral load and, interestingly, a mixed Th1/Th17 cytokine profile.Case presentationThe patient presented with classical dengue symptoms, such as fever, rash, myalgia, arthralgia, and hemorrhagic manifestations including petechiae, gum bleeding and a positive tourniquet test result. A serum sample obtained 1 day after the initial appearance of clinical symptoms was positive for NS1 viral antigen, but this sample was negative for both IgM and IgG against DENV. Dengue virus infection was confirmed by isolation of the virus from C6/36 cells, and dengue virus serotyping was performed via one-step RT-PCR. The infection was confirmed to be caused by a serotype 4 dengue virus. Additionally, based on multiple alignment and phylogeny analyses of its complete genome sequence, the viral strain was classified as genotype II (termed LRV13/422). Moreover, a mixed Th1/Th17 cytokine profile was detected in the patient’s serum, and this result demonstrated significant inflammation. Biological characterization of the virus via in vitro assays comparing LRV13/422 with a laboratory-adapted reference strain of dengue virus serotype 4 (TVP/360) showed that LRV13/422 infects both vertebrate and invertebrate cell lines more efficiently than TVP/360. However, LRV13/422 was unable to inhibit type I interferon responses, as suggested by the results obtained for other dengue virus strains. Furthermore, LRV13/422 is the first completely sequenced serotype 4 dengue virus isolated in South Brazil.ConclusionThe high viral load and mixed Th1/Th17 cytokine profile observed in the patient’s serum could have implications for the development of the hemorrhagic signs observed, and these potential relationships can now be further studied using suitable animal models and/or in vitro systems.Electronic supplementary materialThe online version of this article (doi:10.1186/s12985-016-0548-9) contains supplementary material, which is available to authorized users.
Highlights
We report the isolation and characterization of dengue virus (DENV) serotype 4 from a resident of Santa Fé, state of Paraná, South Brazil, in March 2013
Dengue virus serotype 4 (DENV-4) genotype II first circulated in Brazil in 1981 and 1982 in limited outbreaks in Boa Vista (Roraima), North Brazil [1], though no other case related to this serotype was reported in the 25 years
The resurgence of DENV-4 was reported in Manaus in 2008, when the virus was isolated from serum samples of three patients with no recent travel history [2]
Summary
Since the reemergence of DENV-4 in 2010 in Brazil, cocirculation of four dengue virus serotypes has occurred. The authors thank Itamar Crispim for producing Additional file 1: Figure S1. Authors’ contributions DK Manuscript writing, virus detection isolation and RT-PCR. LB Manuscript writing, figures, in vitro assays, and statistical analysis. Abbreviations °C, celsius; μL, microliter; DENV, dengue virus; DF, dengue fever; dpi, days post-infection; E, envelope; ELISA, enzyme-linked immunosorbent assay; FACS, fluorescence-activated cell sorting; FBS, fetal bovine serum; FFU, focusforming units; h, hour(s); hpi, hours post-infection; IFA, immunofluorescence assay; IFN, interferon; IgG, immunoglobulin G; IgM, immunoglobulin M; IL, interleukin; IU, international unit; MOI, multiplicity of infection; NS1, non-structural protein 1; PBS, phosphate-buffered saline; RT-PCR, reverse-transcription polymerase chain reaction; S, South; Th, T helper; TNF, tumor necrosis factor; v/v, volume/volume; W, West
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