CD11b maintains West Nile virus replication through modulation of immune response in human neuroblastoma cells.

BACKGROUND: West Nile virus (WNV) is a rapidly spreading mosquito-borne virus accounted for neuroinvasive diseases. An insight into WNV-host factors interaction is necessary for development of therapeutic approaches against WNV infection. CD11b has key biological functions and been identified as a therapeutic target for several human diseases. The purpose of this study was to determine whether CD11b was implicated in WNV infection. METHODS: SH-SY5Y cells with and without MEK1/2 inhibitor U0126 or AKT inhibitor MK-2206 treatment were infected with WNV. CD11b mRNA levels were assessed by real-time PCR. WNV replication and expression of stress (ATF6 and CHOP), pro-inflammatory (TNF-α), and antiviral (IFN-α, IFN-ß, and IFN-γ) factors were evaluated in WNV-infected SH-SY5Y cells with CD11b siRNA transfection. Cell viability was determined by MTS assay. RESULTS: CD11b mRNA expression was remarkably up-regulated by WNV in a time-dependent manner. U0126 but not MK-2206 treatment reduced the CD11b induction by WNV. CD11b knockdown significantly decreased WNV replication and protected the infected cells. CD11b knockdown markedly increased TNF-α, IFN-α, IFN-ß, and IFN-γ mRNA expression induced by WNV. ATF6 mRNA expression was reduced upon CD11b knockdown following WNV infection. CONCLUSION: These results demonstrate that CD11b is involved in maintaining WNV replication and modulating inflammatory as well as antiviral immune response, highlighting the potential of CD11b as a target for therapeutics for WNV infection.

Inhibition of tick-borne encephalitis virus in cell cultures by ribavirin.

Tick-borne encephalitis virus (TBEV) belonging to arboviruses is a major member of zoonotic pathogens. TBEV infection causes severe human encephalitis without specific antiviral drugs. Due to its use of antiviral drug against a wide range of viruses, we investigated antiviral effect of ribavirin against TBEV in susceptible human cell lines A549 and SH-SY5Y. Ribavirin displayed minor cytotoxicity on multiple cell lines. Ribavirin obviously impaired TBEV replication and protected the infected cells from cytopathic effect. Importantly, ribavirin markedly inhibited TBEV propagation, as evidenced by impairment of TBEV production and viral RNA replication. Treatment with ribavirin (co-treatment and post-treatment) led to a dose-dependent reduction in TBEV titers as well as the viral RNA levels. Antiviral protein myxovirus resistance A mRNA expression was significantly up-regulated and signal transducer and activator of transcription 3 was activated in TBEV-infected A549 cells upon the ribavirin treatment. Induction of inflammatory cytokine tumor necrosis factor alpha by TBEV was decreased in A549 cells with the treatment of ribavirin, whereas interleukin 1 beta release appeared to be unaffected. These results suggest that ribavirin might represent a promising safe and effective antiviral drug against TBEV.

Establishment of qRT-PCR for absolute quantitative detection of Chikungunya virus / 中国热带医学

@#Abstract: Objective　To develop a real-time fluorescent quantitative RT-PCR (qRT-PCR) method for qualitative and quantitative Chikungunya virus (CHIKV) analysis. Methods Based on the systematic analysis of the genomic sequences of Chikungunya and its related arboviruses, the specific nucleic acid sequences for Chikungunya virus were screened and identified, and then the primers and TaqMan probe were designed. Meanwhile, the human GAPDH gene was used as an internal reference. The reaction system for qRT-PCR was systematically optimized by L9(34) orthogonal design, and a rapid detection method for Chikungunya by qRT-PCR based on TaqMan probe methods was established. The sensitivity, specificity, reproducibility, and coverage of the established method were analyzed in detail. The standard curve was made, and the absolute quantitative method was established using the cloned nucleic acid fragments as positive samples. Results　A real-time fluorescent quantitative RT-PCR assay was developed for the qualitative and quantitative analysis of Chikungunya virus. The reaction system included Chikungunya virus and reference internal gene specific primers and probe, RT/Taq enzyme mixture, reaction buffer, and negative and positive reference. The established method obtained positive results with the ROSS strain of ECSA subtype, LR2006 strain of IOL branch, 181/25 strain of Asian type and Dongguan 2010 epidemic strains of Chikungunya virus, but there was no cross-reaction with other 18 arboviruses belonging to Flaviviruses, Alphaviruses and Bunyavirus. The minimum detection limit of the established method was 5.80 copies/mL, and a linear relationship was observed between the amount of input plasmid DNA and fluorescence signal value over a range of 5.80×102 copies/mL to 5.80×1010 copies/mL, and the correlation coefficient was 0.999 5. The qRT-PCR amplification efficiency was 91%, and the intra-assay variations and inter-assay variations were 0.01-0.07 and 0.03-0.11, respectively. Conclusions　The TaqMan qRT-PCR method developed in this study can qualitatively and quantitatively detect Chikungunya virus rapidly with specificity and sensitivity, providing a technical method for the prevention and control of this viral disease.

Preparation and separation of pure spherical cellulose nanocrystals from microcrystalline cellulose by complex enzymatic hydrolysis.

Spherical cellulose nanocrystals (CNCs), as a new and high value cellulose derivative, shows excellent application potential in many fields due to its special structure. The accurate and effective separation of pure spherical CNCs lays foundation for its further application. In this work, spherical CNCs were prepared by enzymatic hydrolysis of microcrystalline cellulose (MCC) with complex enzymes. In order to determine the optimal separation conditions of pure spherical CNCs, turbidity and Zeta potential were used to analyze the influence of pH on system stability, and the size and morphology of samples were characterized by DLS, AFM and SEM. The results showed that spherical CNCs with particle size of 24-76 nm can be separated from large particles with the help of alkali (pH = 9) dispersion and centrifugation speed of 3000 rpm. After three acid (pH = 4) washes, pure spherical CNCs were extracted and reducing sugars and enzyme proteins were removed. Compared with MCC, spherical CNCs had lower crystallinity but stronger reactivity and higher heat transfer. DTG results showed that the maximum weight loss temperature of spherical CNCs prepared by enzymatic hydrolysis was 309 °C.

Laboratory and Molecular Characterization of Dengue Viruses in a 2014 Outbreak in Guangfo Region, Southern China.

Non-specific symptoms and low viremia levels make early diagnosis of dengue virus (DENV) infection challenging. This study aimed to i) identify laboratory markers that can be used to predict a DENV-positive diagnosis and ii) perform a molecular characterization of DENVs from the 2014 Guangdong epidemic. This retrospective study analyzed 1,044 patients from the Guangdong epidemic who were clinically suspected cases of dengue. Viral RNA was detected by real-time RT-PCR, and viral-specific NS1 antigen was detected using enzyme-linked immuno sorbent assay. A molecular phylogenetic analysis was performed for the with the DENV C-prM gene junction. Patients with dengue infection had leukopenia (2.8 × 109/L), thrombocytopenia (109.0 × 109/L), elevated aspartate aminotransferase (56.0 IU/L) and alanine aminotransferase (43.5 IU/L), and prolonged activated partial thromboplastin time (APTT, 33.5 s) (all P ＜ 0.001) compared to patients without dengue. The positive predictive value of leukopenia and thrombocytopenia for DENV infection were 96.9% and 93.0%, respectively. Leukopenia, thrombocytopenia, elevated aminotransferases, and prolonged APTT were useful predictive markers for an early diagnosis of DENV infection. Phylogenetic analysis indicated that the DENVs from the 2014 epidemic were closely related to a 2010 New Delhi strain and a 2013 Guangzhou strain. The 2014 epidemic consisted of co-circulating DENV-1 genotypes I and V from multiple origins. Efficient dengue surveillance can facilitate rapid response to future outbreaks.

[Research progress in the structure and function of dengue virus non-structural 1 protein].

Dengue virus (DENV) is a re-emerging disease transmitted by the Aedes mosquitoes and has become a major public health problem in southern China. Currently, no antiviral drug or effective vaccine exist to control this disease. The chimeric DENV structural protein vaccine cannot elicit balanced levels of protective immunity to each of the four viral serotypes; therefore, non-structural protein components may be required to construct an effective DENV vaccine. The Dengue virus non-structural 1 (DENV NS1) protein plays a critical role in viral pathogenesis and protective immunity. Therefore, immunity to Dengue 1-4 NS1 subtypes may be crucial for the prevention of severe disease. This review attempts to provide an overview about the structure and function of DENV NS1.

[Study on E protein epitopes and primary identification of main yellow virus].

OBJECTIVE: To analysis the E protein epitopes of dengue virus type 1-4, Japanese encephalitis virus and yellow fever virus and to distinguish the shared or specific epitopes among them. METHODS: Bioinformatic software DNAStar was used to analyze the hydrophilicity, flexibility, surface probability and antigenicity of dengue virus type 1-4, Japanese encephalitis virus and yellow fever virus E protein amino acid sequences. The influence of secondary structure was also considered. Based on the bio-informatic analysis of E protein epitopes, 6 specific epitopes were amplified and inserted into prokaryotic expression vector pMAL-c2x. The vectors was then transferred into E. coli BL21 (DE3) and Rosetta (DE3). Isopropyl-beta-D-thiogalactoside (IPTG) was used to induce the expression of gene segments and SDS-PAGE were used identify the expression proteins. The antigenicity was tested, using Western blot. RESULTS: 15 shared epitopes and 47 specific epitopes were forecasted by bioinformatic analysis, and 6 specific epitopes from dengue virus type 1-4, Japanese encephalitis virus and yellow fever virus E protein were expressed in E. coli successfully. Two specific antigenic determinant from dengue virus type 1 and dengue virus type 2 were confirmed using Western blot, while the others epitopes shown no antigenic reaction property. CONCLUSION: Two specific antigenic determinant were confirmed, under Western blot.

[Detection and typing of dengue virus using polymerase chain reaction and microwell plate hybridization].

OBJECTIVE: To establish a specific, sensitive and practicable method for detection and typing of dengue virus. METHODS: Based on the genomic sequence analysis of dengue virus types 1-4, 4 pairs of primers were designed. The specific capture probes of dengue virus types 1-4 were amplified using RT-PCR, cloned and sequenced before using them for precoating the microwell plate. The samples were amplified using biotin-labeled forward primer and reverse primer, and microwell plate hybridization was carried out for detection and typing of dengue virus types 1-4. RESULTS: The absorbance of the positive samples were higher than 0.5, while the average absorbance of the negative samples was lower than 0.1, with the S/N higher than 10. CONCLUSION: The method of PCR-ELISA we established for early detection and typing of all 4 dengue viruses seretypes.

[Development of multiplex reverse translation-polymerase chain reaction methods for detection of dengue virus type 1-4 and its application in clinical use].

OBJECTIVE: To develop multiplex reverse translation-polymerase chain reaction (RT-PCR) method for detection of dengue virus type 1-4. METHODS: Based on the genomes sequence analysis of dengue virus type 1-4, four-pair of primers were designed. The specificity of the primers was primarily tested by searching the GenBank DNA sequence database. The optimal reaction conditions of the multiplex RT-PCR were then established. The specificity of RT-PCR was tested using the homologous yellow fever virus and Japanese encephalitis virus. 30 serum samples of dengue virus from suspected sufferers in the prevalence of dengue virus in 2003 were detected using the methods we developed. RESULTS: Positive segments about 295, 237, 118, 347 bp could be seen in the multiplex RT-PCR production of dengue virus type 1-4, respectively. There were no positive segments in the RT-PCR productions of Japanese encephalitis virus and yellow fever virus. 25 of the 30 serum samples showed dengue virus type 1 positive results, while the sequencing results suggesting the amplification sequence having a high homology with dengue virus type 1 strain Cambodia, GD14/97 and GD05/99 (97%, 97%, 98%, respective). CONCLUSION: The method of multiplex RT-PCR we established could be used for early detection and identification of dengue virus type 1-4.

[Analysis of the E gene sequences of three dengue virus type 1 isolates in Guangdong province].

OBJECTIVE: To trace the infection sources of three dengue virus type 1 isolates found in Guangdong province, namely GD05/99, GD14/97 and GD23/95. METHODS: According to the genomes of dengue virus type 1 S275 strain, a pair of primers was designed for amplification of the structural protein E gene of the isolated dengue virus type 1 strains by reverse transcriptase-PCR. The amplified gene fragment was then cloned into pMD18-T vector and sequenced. RESULTS: GD14/97 and GD05/99 shared a high nucleotide homology with Cambodia (98% and 99% respectively) and may belong to the same genotype. GD23/95 had a 95% nucleotide homology with A88, higher than that with other strains. GD23\95 and A88 may belong to another genotype. CONCLUSION: The dengue fever outbreak in Guangdong during 1999, 1997, and 1995 may originate from the viruses from different countries.

[Isolation, identification and sequence analyses of dengue virus type 2 strain GD19/2001].

OBJECTIVE: To identify the virus isolated from Jiangmen, Guangdong province and to discuss the possible origin. METHODS: Using characteristics of indirect fluorescent antibody tests (IFA), reverse transcription-polymerase chain reaction (RT-PCR), mouse neurovirulence and cell culture to identify the isolated virus. According to the nature of dengue virus type 2 NGC strain, two pairs of primers were designed. The structural protein gene of isolated dengue virus type 2 strain was then amplified by RT-PCR, cloned into pMD18-T vector and sequenced. RESULTS: Twenty-two of 37 serum samples showed a positive reaction to dengue antibody IgG, and 36 of 37 with IgM with the highest antibody titer 1:640. Ten samples were resulted in a cytopathy on C6/36 cells and showed a neurovirulence in suckling mice when inoculated intracerebrally. The structural gene of new isolate GD19/2001 containing 2 325 nucleotides which encoded 774 amino acids. Data on nucleotide homology were 98%, 96%, 94%, 94%, 92%, 92%, 92% and 91% compared with TSV01, GD06/93, NGC and 44, ThNH81/93, 04 and GD08/98, and S1 respectively. CONCLUSION: The isolated virus from Jiangmen, Guangdong province belonged to dengue virus type 2, which might come from Australia.