Dengue Virus Antigen Research Articles

Monocytes, but not T or B cells, are the principal target cells for dengue virus (DV) infection among human peripheral blood mononuclear cells

A better understanding of the pathogenesis of dengue hemorrhagic fever and dengue shock syndrome requires the precise identification of dengue virus (DV) permissive target cells. To examine the relative DV permissiveness among cell subsets, we inoculated unfractionated human peripheral blood mononuclear cells with DV2-16681 in the presence or absence of pooled DV-immune human sera (PHS), and assessed infection with fluorescent dye labeled DV-specific monoclonal antibody and cell surface markers using flow cytometry. We found significantly higher levels of DV antigen staining on DV-infected than mock-infected primary monocytes (3.54 +/- 3.42% vs. 0.50 +/- 0.38%; P = 0.001). The magnitude of infection was markedly enhanced in the presence of highly diluted PHS (10.04 +/- 6.10% vs. 3.54 +/- 3.42%; P = 0.015). Under identical experimental conditions, primary T or B cells were not infected either with or without the addition of PHS (0.06 +/- 0.04% and 0.44 +/- 0.22% for T and B cells, respectively). Furthermore, depletion of CD14+ monocytes prior to DV inoculation abrogated the detection of infected cells, and the addition of monoclonal antibodies to either FcgammaRI (CD64) or FcgammaRII (CD32) led to a 50-70% reduction in antibody-dependent enhancement (ADE) of DV infection. Collectively, these results provide further support to the notion that primary monocytes and FcgammaRs expressed on these cells may be important in the initial steps of immune enhancement observed in some patients with natural DV infection. They also demonstrate that using modern experimental technology, DV infection, and neutralization and enhancement of DV infection can be easily assessed simultaneously in multiple cell types.

Primary Human Splenic Macrophages, but Not T or B Cells, Are the Principal Target Cells for Dengue Virus Infection In Vitro

Understanding the pathogenesis of dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) requires the precise identification of dengue virus (DV)-permissive target cells. In a previous study using unfractionated human peripheral blood mononuclear cells, we found that monocytes, but not B or T cells, were the principal DV-permissive cells in the absence of DV-immune pooled human sera (PHS) and the major mediators of antibody-dependent enhancement in the presence of PHS. To further identify DV-permissive target cells in other tissues and organs, we isolated human splenic mononuclear cells (MNCs), inoculated them with DV type 2 (strain 16681) in the presence or absence of PHS, and assessed their infection either directly using flow cytometry and reverse transcription-PCR (RT-PCR) assays or indirectly by plaque assay. We found that in the absence of PHS, a small proportion of splenic macrophages appeared to be positive for DV antigens in comparison to staining controls by the flow cytometric assay (0.77% +/- 1.00% versus 0.18% +/- 0.12%; P = 0.07) and that viral RNA was detectable by the RT-PCR assay in MNCs exposed to DV. Additionally, supernatants from cultures of DV-exposed MNCs contained infectious virions that were readily detectable by plaque assay. The magnitude of infection was significantly enhanced in splenic macrophages in the presence of highly diluted PHS (5.41% +/- 3.53% versus 0.77% +/- 1.00%; P = 0.001). In contrast, primary T and B cells were not infected in either the presence or absence of PHS. These results provide evidence, for the first time, that human primary splenic macrophages, rather than B or T cells, are the principal DV-permissive cells in the spleen and that they may be uniquely important in the initial steps of immune enhancement that leads to DHF/DSS in some DV-infected individuals.

Apoptosis in tissues from fatal dengue shock syndrome

Background Apoptosis, or programmed cell death, has been implicated in dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) pathogenesis. Objectives To determine the in vivo apoptosis contribution to the pathogenesis of fatal DHF/DSS during a Cuban dengue epidemic. Study design We detected apoptosis by the TdT-mediated dUTP Nick-End Labeling (TUNEL) technique and dengue virus (DENV) antigens by an immunohistochemical assay in different tissues from six individuals who died of DHF/DSS during the Santiago de Cuba DENV-2 epidemic in 1997. Results DENV antigens were immunolocalized mainly in hepatocytes. Apoptotic cells were found in five of the six cases studied. Apoptosis was demonstrated in liver, brain, intestinal and lung tissues. Severe brain hypoxia and ischemia in the studied subjects during DHF/DSS probably might induce apoptosis in cerebral cells. Apoptotic microvascular endothelial cells (ECs) in pulmonary and intestinal tissues, a finding only previously reported in vitro, are likely related to vascular plasma leakage manifested by the individuals. Conclusions Apoptosis was demonstrated in cerebral cells, white blood cells, intestinal and pulmonary microvascular ECs from Cuban fatal cases of DHF/DSS. As far as we know, these findings have not been previously reported in DHF/DSS. Our results indicate there is very likely an in vivo contribution of apoptosis to the pathophysiological mechanisms of DHF/DSS.

Production of dengue 2 envelope domain III in plant using TMV-based vector system

The envelope protein of dengue virus is the major protein involved in host cell receptor binding for viral entry and induction of immunity. A gene fragment encoding domain III of the dengue 2 envelope protein (D2EIII, amino acids 298-400) was successfully expressed in Nicotinana benthamiana plant using a tobacco mosaic virus (TMV)-based transient expression system. The N-terminal 5' untranslated region-omega sequence located upstream of D2EIII increased protein production in infected plant tissues. The recombinant protein was reactive with anti-D2EIII polyclonal and anti-His tag antibodies. The intramuscular immunization of mice with D2EIII induced the production of the anti-dengue virus antibody. The induced antibody demonstrated neutralizing activity against dengue type 2 virus. The result indicates that the TMV expression system produces the dengue virus antigen in plant, which possesses appropriate antigenicity and immunogenicity.

Detektion antigen virus den on monocyts by streptavidin biotin test as early diagnostic for dengue fever haemorhagic

Dengue virus infection is the main cause of morbidity and mortality in the tropical and sub-tropical countries of the world. Clinically it may manifest as asymtomastic, undifferentiated fever,dengue fever,dengue haemorrhagic fever and dengue shock syndrome cases.. The mechanism underlying the disease with severe complication is not clear yet,however it has been previosus reported that primary andsecondary infections of dengue virus play an important role in the patogenesis of this diseases. Early diagnosis of dengue virus infection has a great contribution for appropriate management of the disease, especialy for the prognosis of the patient. Laboratory investigations for such cases will be methods on serological investigation as well as virus isolation and identification.of dengue virus infection could be madeby detection of specific virus ,viral antigen,genomic sequence and or detection of antibodies. These methods are sensitive and precise for detecting dengue virus infection,but there need special equipment,costly and detection of IgM and IgG often positive or negative false the dengue virus in the blood stream There for, this study was performed in order to develop a method to detect dengue virus antigen on the monocytes using Streptavidin biotin technique. The result of Streptavidin biotin study demonstrated that 32 sera from patient suspectedwith DHF 78,1% were positive DHF,and 21,9% were negative DHF. These results are consistent with the result from WHO criteria as standard .The Chi Square analysis showed that the presentage of sensitivity and specificity of Streptavidin biotin methode were 88% and 87,7% respectively. In conclusions ,immunocytochemistry method using streptavidin biotin technique could be used as a method to detect antigen dengue virus on monocytes in the serum patient suspected with DHF. This technique has high sensitivity and specivicity andconsistent with the clinical WHO criteria for DHF,© 2007 Jurusan Biologi FMIPA UNS SurakartaKey words: Dengue Haemorrhagic ,Monocyte , Steptavidin biotin

Cross-Reactive T-Cell Responses to the Nonstructural Regions of Dengue Viruses among Dengue Fever and Dengue Hemorrhagic Fever Patients in Malaysia

Dengue virus infections are a major cause of morbidity and mortality in tropical and subtropical areas in the world. Attempts to develop effective vaccines have been hampered by the lack of understanding of the pathogenesis of the disease and the absence of suitable experimental models for dengue viral infection. The magnitude of T-cell responses has been reported to correlate with dengue disease severity. Sixty Malaysian adults with dengue viral infections were investigated for their dengue virus-specific T-cell responses to 32 peptides antigens from the structural and nonstructural regions from a dengue virus isolate. Seventeen different peptides from the C, E, NS2B, NS3, NS4A, NS4B, and NS5 regions were found to evoke significant responses in a gamma interferon enzyme-linked immunospot (ELISPOT) assay of samples from 13 selected patients with dengue fever (DF) and dengue hemorrhagic fever (DHF). NS3 and predominantly NS3(422-431) were found to be important T-cell targets. The highest peaks of T-cell responses observed were in responses to NS3(422-431) and NS5(563-571) in DHF patients. We also found almost a sevenfold increase in T-cell response in three DHF patients compared to three DF patient responses to peptide NS3(422-431). A large number of patients' T cells also responded to the NS2B(97-106) region. The ELISPOT analyses also revealed high frequencies of T cells that recognize both serotype-specific and cross-reactive dengue virus antigens in patients with DHF.

Endothelial cell apoptosis induced by Dengue virus (B133)

Abstract Vascular leakage and hemorrhagic diathesis are life-threatening complications that occur to dengue hemorrhagic patients. However, the pathogenic mechanism of hemorrhage is not well understood. It has been shown that endothelial cells are permissive to dengue virus (DV) infection in vitro and DV antigen is found in endothelial cells of autopsy specimens collected from patients who died of DHF. Therefore, the study of interaction between DV and endothelial cells will shed light on the mechanism of dengue hemorrhage. We established a dengue hemorrhage mouse model in immunocompetent C57BL/6 mice by injecting DV serotype 2 strain 16681 intradermally. While high dose DV inoculation induced hemorrhage in all of the mice, 1/3 of those injected with 4–8 x 107 PFU developed hemorrhage in the subcutaneous tissues by day 3 of infection. Importantly, hemorrhage was accompanied by severe thrombocytopenia and vascular leakage. Double immunofluorescence staining revealed that DV targeted both macrophages and endothelial cells in the subcutaneous tissues. In vitro studies showed that human umbilical cord vein endothelial cells (HUVEC) and microvascular endothelial cell line (HMEC) were susceptible to DV and TNF-α enhanced DV-induced apoptosis. In addition, DV infection induced endothelial cell NOS and ROS production and endothelial cell apoptosis, which were also enhanced by TNF-α. These findings demonstrate that dengue virus and TNF-α-induced endothelial cell apoptosis is mediated by ROS and NO.

Up-regulated expression of β3 integrin induced by dengue virus serotype 2 infection associated with virus entry into human dermal microvascular endothelial cells

Permeability alteration of microvascular endothelia is a factor in the plasma leakage produced by dengue virus (DV) infection, and β3 integrin plays central roles in maintaining capillary integrity and regulating vascular permeability. In this study, interaction between β3 integrin and DV serotype 2 (DV2) was investigated using human dermal microvascular endothelial cell line-1 (HMEC-1). We reported that DV2 infection could induce high expression level of β3 integrin, and the high fluorescence intensity of β3 integrin antigen observed in HMEC-1 after infection showed high co-localization with DV antigen. Pre-incubation of the virus with soluble ανβ3 integrin could strongly inhibit DV2 entry. And about 90% of virus entry was inhibited when β3 integrin expression level was down-regulated by RNA interference. Our data indicated that DV2 infection could induce up-regulating expression of β3 integrin, and β3 integrin was required for DV2 entry into HMEC-1.

Two Complex, Adenovirus-Based Vaccines That Together Induce Immune Responses to All Four Dengue Virus Serotypes

Dengue virus infections can cause hemorrhagic fever, shock, encephalitis, and even death. Worldwide, approximately 2.5 billion people live in dengue-infested regions with about 100 million new cases each year, although many of these infections are believed to be silent. There are four antigenically distinct serotypes of dengue virus; thus, immunity from one serotype will not cross-protect from infection with the other three. The difficulties that hamper vaccine development include requirements of the natural conformation of the envelope glycoprotein to induce neutralizing immune responses and the necessity of presenting antigens of all four serotypes. Currently, the only way to meet these requirements is to use a mixture of four serotypes of live attenuated dengue viruses, but safety remains a major problem. In this study, we have developed the basis for a tetravalent dengue vaccine using a novel complex adenovirus platform that is capable of expressing multiple antigens de novo. This dengue vaccine is constructed as a pair of vectors that each expresses the premembrane and envelope genes of two different dengue virus serotypes. Upon vaccination, the vaccine expressed high levels of the dengue virus antigens in cells to mimic a natural infection and induced both humoral and cellular immune responses against multiple serotypes of dengue virus in an animal model. Further analyses show the humoral responses were indeed neutralizing against all four serotypes. Our studies demonstrate the concept of mimicking infections to induce immune responses by synthesizing dengue virus membrane antigens de novo and the feasibility of developing an effective tetravalent dengue vaccine by vector-mediated expression of glycoproteins of the four serotypes.

Morphological studies in a model for dengue-2 virus infection in mice

One of the main difficulties in studying dengue virus infection in humans and in developing a vaccine is the absence of a suitable animal model which develops the full spectrum of dengue fever, dengue haemorrhagic fever, and dengue shock syndrome. It is our proposal to present morphological aspects of an animal model which shows many similarities with the dengue infection in humans. BALB/c mice were intraperitoneally infected with non-neuroadapted dengue virus serotype 2 (DENV-2). Histopathological and morphometrical analyses of liver tissue revealed focal alterations along the infection, reaching wide-ranging portal and centrolobular veins congestion and sinusoidal cell death. Additional ultrastructural observations demonstrated multifocal endothelial injury, platelet recruitment, and alterated hepatocytes. Dengue virus antigen was detected in hepatocytes and in the capillar endothelium of the central lobular vein area. Liver function tests showed high levels of aspartate transaminase and alanine transaminase enzyme activity. Lung tissue showed interstitial pneumonia and mononuclear cells, interseptal oedema, hyperplasia, and hypertrophy of the bronchiolar epithelial cells. DENV-2 led to a transient inflammatory process, but caused focal alterations of the blood-exchange barrier. Viremia was observed from 2nd to 11th day p.i. by isolation of DENV-2 in C6/36 mosquito cell line inoculated with the supernatant of macerated liver, lung, kidney, and cerebellum tissues of the infected mice.

A synthetic dengue virus antigen elicits enhanced antibody titers when linked to, but not mixed with, Mycobacterium tuberculosis HSP70 domain II

Domain II of Mycobacterium tuberculosis (Mtb) heat shock protein 70 (HSP70), spanning amino acid residues 161–370, was covalently linked to a recently described synthetic dengue virus antigen to study the influence of the former on the immunogenicity of the latter. Using an enzyme-linked immunosorbent assay, dengue antigen-specific antibody titers elicited by the fusion protein in Balb/c mice were an order of magnitude higher than those elicited by either the synthetic dengue antigen alone or a physical mixture of the dengue antigen plus Mtb HSP70 domain II protein. Our data demonstrate that (i) Mtb HSP70 domain II is capable of potentiating B-cell response and (ii) it should be covalently linked to the target antigen to do so.

Inducible nitric oxide synthase (iNOS) expression in monocytes during acute Dengue Fever in patients and during in vitro infection

Mononuclear phagocytes are considered to be main targets for Dengue Virus (DENV) replication. These cells are activated after infection, producing proinflammatory mediators, including tumour-necrosis factor-α, which has also been detected in vivo. Nitric oxide (NO), usually produced by activated mononuclear phagocytes, has antimicrobial and antiviral activities.MethodsThe expression of DENV antigens and inducible nitric oxide synthase (iNOS) in human blood isolated monocytes were analysed by flow cytometry using cells either from patients with acute Dengue Fever or after DENV-1 in vitro infection. DENV-1 susceptibility to iNOS inhibition and NO production was investigated using NG-methyl L-Arginine (NGMLA) as an iNOS inhibitor, which was added to DENV-1 infected human monocytes, and sodium nitroprussiate (SNP), a NO donor, added to infected C6/36 mosquito cell clone. Viral antigens after treatments were detected by flow cytometry analysis.ResultsINOS expression in activated monocytes was observed in 10 out of 21 patients with Dengue Fever and was absent in cells from ten healthy individuals. DENV antigens detected in 25 out of 35 patients, were observed early during in vitro infection (3 days), significantly diminished with time, indicating that virus replicated, however monocytes controlled the infection. On the other hand, the iNOS expression was detected at increasing frequency in in vitro infected monocytes from three to six days, exhibiting an inverse relationship to DENV antigen expression. We demonstrated that the detection of the DENV-1 antigen was enhanced during monocyte treatment with NGMLA. In the mosquito cell line C6/36, virus detection was significantly reduced in the presence of SNP, when compared to that of untreated cells.ConclusionThis study is the first to reveal the activation of DENV infected monocytes based on induction of iNOS both in vivo and in vitro, as well as the susceptibility of DENV-1 to a NO production.

Pathologic study of a fatal case of dengue-3 virus infection in Rio de Janeiro, Brazil

Dengue hemorrhagic fever (DHF) is a severe febrile disease, characterized by abnormalities in hemostasis and increased vascular permeability, which in some cases results in hypovolemic shock syndrome and in dengue shock syndrome. The clinical features of DHF include plasma leakage, bleeding tendency and liver involvement. We studied the histopathological features of a fatal case of dengue-3 virus infection. The patient, a 63-year old male, presented with an acute onset of severe headache, myalgia and maculopapular rash. Tissue fragments (liver, spleen, lung, heart, kidney and lymph nodes) were collected for light microscopy studies and stained by standard methods. Histopathology revealed severe tissue damage, caused by intense hemorrhage, interstitial edema and inflammation. Some tissue sections were also processed with the immunoperoxidase reaction, which revealed the dengue viral antigen. Dengue-3 virus was isolated and identified with electron microscopy in a C6/36 cell culture inoculated with the patient's serum. Viral particles were detected in the infected cell culture.

Dendritic Cell-specific Intercellular Adhesion Molecule 3-grabbing Non-integrin (DC-SIGN)-mediated Enhancement of Dengue Virus Infection Is Independent of DC-SIGN Internalization Signals

Dengue virus (DV) is a mosquito-borne flavivirus that causes hemorrhagic fever in humans. In the natural infection, DV is introduced into human skin by an infected mosquito vector where it is believed to target immature dendritic cells (DCs) and Langerhans cells (LCs). We found that DV productively infects DCs but not LCs. We show here that the interactions between DV E protein, the sole mannosylated glycoprotein present on DV particles, and the C-type lectin dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) are essential for DV infection of DCs. Binding of mannosylated N-glycans on DV E protein to DC-SIGN triggers a rapid and efficient internalization of the viral glycoprotein. However, we observed that endocytosis-defective DC-SIGN molecules allow efficient DV replication, indicating that DC-SIGN endocytosis is dispensable for the internalization step in DV entry. Together, these results argue in favor of a mechanism by which DC-SIGN enhances DV entry and infection in cis. We propose that DC-SIGN concentrates mosquito-derived DV particles at the cell surface to allow efficient interaction with an as yet unidentified entry factor that is ultimately responsible for DV internalization and pH-dependent fusion into DCs.

Piezoelectric immunochip for the detection of dengue fever in viremia phase

The global prevalence of dengue fever has grown so dramatically in recent years that it is endemic in more than 100 countries and has become a major international public health concern. Moreover, since the flu-like symptoms that accompany dengue fever are atypical and varied, the detection procedures currently used to identify it are cumbersome and time-consuming, making early stage epidemiological control and effective medical treatment of this epidemic almost impossible. In this study, a QCM-based detection system was developed in which two monoclonal antibodies against dengue E and NS-1 protein, respectively, were control orientated immobilized on QCM via protein A to produce an immunochip. Various sample pretreatment procedures were evaluated to ascertain the most suitable combination, and both the simulating samples and the clinical specimen were examined by the immunochip. The results revealed that the cibacron blue 3GA gel-heat denature (CB-HD) method was the most effective sample pretreatment technique. Due to the complex composition of the serum, the immunochip could only effectively quantify dengue viral antigens in a 1/1000 untreated simulated sample. With the help of the CB-HD method, the dilution folds were found to capable of being reduced from 1000 to 100, and the detection limit lowered to 1.727 microg/ml (E protein) and 0.740 microg/ml (NS-1 protein) in the original sample. While the cocktail immunochip could not quantify both antigens separately, the higher signal level rendered it a more effective qualification tool for suspect screening. Moreover, the results of the analysis of clinical specimens also proved the ability and future potential of cocktail immunochip in discriminating dengue-positive cases from negative serum specimens in the viremia phase.

Short Communication: Detection of dengue virus antigens in desiccated mosquitoes: an improved tool for surveillance

We developed a surveillance tool to monitor dengue virus (DENV) infection in vector mosquitoes using a dengue antigen-capture enzyme immunoassay (EIA) on desiccated specimens stored at room temperature (RT). We tested the effect of storage on the stability of DEN1, DEN2, DEN3 and DEN4 antigens. Although desiccated infected Aedes aegypti mosquitoes stored between 31 and 34 degrees C (RT) showed greater reactivity in the EIA than those stored at -80 degrees C, a significant difference between the two was observed only with DEN2. Storage between 31 and 34 degrees C for up to 4 weeks (the longest period tested) did not affect the reactivity in the EIA, indicating the stability of DENV antigens.

540. Retroviral Mediated Gene Transfer of Hexb in Sandhoff Disease

Top of pageAbstract Vaccines that stimulate broadly neutralizing antibodies to HIV-1 will have a major impact on reducing transmission. However this remains an elusive goal because the antibodies induced by the envelope glycoprotein (Env) do not effectively neutralize primary isolates or viral strains that are important in transmission. Using DNA shuffling and screening technologies, we had identified novel gp120 variants with preferential reactivity to the neutralizing human mAb b12 and significantly weakened binding to non-neutralizing CD4BS-binding mAbs b3 and b6. This phenotype mimics that of the native trimeric envelope complex. Biacore studies of mAb-gp120 interaction demonstrated that the enhanced affinity of b12 in the shuffled variants resulted largely from a decrease in the dissociation rate. DNA shuffling of the 'core' form of gp120, which lacks V1/V2, V3 and parts of C1 and C5, also generated gp120 variants that possessed these antigenic properties. We immunized rabbits with >100 independent gp120 variants using electroporation-mediated DNA vaccination, followed by boosting with a heterologous or homologous recombinant protein antigen. A single-cycle pseudovirus-based assay was used to evaluate the HIV-1 neutralization activities of purified immunoglobulins. About 60% of the full-length gp120 variants induced neutralizing antibodies to the TCLA strain SF162, indicating that the DNA shuffling and screening approach provides novel variants that have gp120-like immunogenicity. Several of the shuffled variants induced antibodies to primary viral isolates and five clones were able to neutralize eight primary isolates in addition to TCLA strains. These shuffled variants are candidates for additional shuffling to screen for further improvements in immunogenicity and for testing using additional vaccine formats, including optimized immunization protocols. DNA shuffling extensively recombines mixtures of parental genes such as the Env coding sequences to create highly functional libraries of shuffled chimeras. We have successfully applied this technology to evolve novel viral phenotypes, to improve the antigenicity of the Hepatitis B virus envelope protein and to generate tetravalent Dengue virus antigens. The application of DNA shuffling to HIV vaccine development provides a new approach for generating novel Env structures as vaccine candidates.

Localization of dengue virus in naturally infected human tissues, by immunohistochemistry and in situ hybridization.

Dengue viral antigens have been demonstrated in several types of naturally infected human tissues, but little is known of whether these same tissues have detectable viral RNA. We studied tissue specimens from patients with serologically or virologically confirmed dengue infections by immunohistochemistry (IHC) and in situ hybridization (ISH), to localize viral antigen and RNA, respectively. IHC was performed on specimens obtained from 5 autopsies and 24 biopsies and on 20 blood-clot samples. For ISH, antisense riboprobes to the dengue E gene were applied to tissue specimens in which IHC was positive. Viral antigens were demonstrated in Kupffer and sinusoidal endothelial cells of the liver; macrophages, multinucleated cells, and reactive lymphoid cells in the spleen; macrophages and vascular endothelium in the lung; kidney tubules; and monocytes and lymphocytes in blood-clot samples. Positive-strand viral RNA was detected in the same IHC-positive cells found in the spleen and blood-clot samples. The strong, positive ISH signal in these cells indicated a high copy number of viral RNA, suggesting replication.

Development of immunochips for the detection of dengue viral antigens

Recently, dengue virus has become a new emerging disease in the world. However, the procedures currently used for the detection of dengue virus are cumbersome and time-consuming. This is unfavorable for early stage epidemiological control and effective medical treatment. A new detection system was developed based on the quartz crystal microbalance (QCM) coating using two monoclonal antibodies that act specifically against the dengue virus envelope protein (E-protein) and non-structural 1 protein (NS-1 protein), respectively. Three different immobilizing methods, the glutaraldehyde (GA) method, protein A method and carbodiimide method (1-ethyl-3-(3-dimethyl- aminopropyl) carbodiimide, EDC) were used to prepare the immunochips. The “cocktail” immunochip, which has both antibodies attached, was also fabricated and used in comparison. The results showed that the protein A method was the best among the three. The sensitivity of the immunochip was 100-fold greater than the conventional sandwich ELISA method. The cocktail immunochip had a higher signal level than the normal immunochip. The time required for detection was shorter (about 1 h) and a blood specimen could be used to detect the virus in the viremia phase.

Mycophenolic acid inhibits dengue virus infection by preventing replication of viral RNA.

Dengue fever is a mosquito-borne viral disease of global importance with no available antiviral therapy. We assessed the ability of mycophenolic acid (MPA), a drug currently used as an immunosuppressive agent, to inhibit dengue virus (DV) antigen expression, RNA replication, and virus production. Pharmacological concentrations of MPA effectively blocked DV infection, decreasing the percentage of infected cells by 99% and the levels of secreted virus by up to a millionfold. Results were reproduced with four hepatoma cell lines and different flaviviruses, including a recent West Nile virus isolate. Experiments were performed to define the stage in the viral lifecycle at which MPA abrogates infection. Early steps in viral infection, such as viral entry and nucleocapsid uncoating, were not the primary targets of MPA action since its inhibitory effect was retained when naked DV RNA was transfected directly into cells. Biosynthetic labeling experiments showed that MPA did not block the initial phase of viral translation but did interfere with viral protein synthesis in the amplification phase. Quantitative RT-PCR demonstrated that MPA prevented the accumulation of viral positive- and negative-strand RNA as the infection proceeded. We conclude that MPA inhibits flavivirus infection by preventing synthesis and accumulation of viral RNA.