Dengue Hemorrhagic Fever And Dengue Shock Syndrome Research Articles

Mosquito Trails: Ecology, Health, and the Politics of Entanglement by Alex M. Nading (review)

Reviewed by: Mosquito Trails: Ecology, Health, and the Politics of Entanglement by Alex M. Nading José G. Rigau Pérez Alex M. Nading. Mosquito Trails: Ecology, Health, and the Politics of Entanglement. Berkeley: University of California Press, 2014. xvi + 269 pp. Ill. $29.95 (978-0-520-28262-9). This ethnographic, anthropologic examination of dengue control activities in Ciudad Sandino (Managua metropolitan area, Nicaragua, 2006–9) seeks to demonstrate the importance of local specifics of how “people, pathogens, vectors, and their shared surroundings are always in the process of becoming, together” because “environments do not just cause health problems; rather humans and non-humans incorporate one another’s actions” (p. 202). Nading’s informants included community health workers (brigadistas, who worked as dengue case investigators and vector control officials), garbage collectors, scavengers, scrap metal buyers, Ciudad Sandino residents, physicians, entomologists, and epidemiologists. The analysis is first concerned with the layout and culture of the place, its relation to garbage as a source of both mosquitoes and income (recycling), and the parasitic relationships between large brokers and scavengers, mosquitoes and people, and humans and the environment. Then Nading stresses the appeals of [End Page 629] a well-ordered house and knowledge of the mosquito life cycle; the similarity of public health work with evangelical house-to-house visits and the mosquito’s life (brief visits to the homes’ most intimate spaces); and the gendered condition of dengue control work (women held responsible for prevention activities in the home, and the paradoxical self-identification of single-mother brigadistas with female mosquitoes, which become dangerous, biting humans and laying eggs, only after the males impregnate them and fly away). Finally, the author examines the intricacies of disease surveillance for global and local health, the disappearance of human stories into data points, and the repetitiveness and confluence of viral epidemics and clinical diagnoses. Nading defines “entanglement” as an analytical framework to examine “the unfolding, often incidental attachments and affinities, antagonisms and animosities that bring people, nonhuman animals, and things into each other’s worlds” (p. 11). Even in strictly biological terms, dengue is quite “entangled.” It is produced by any of four closely related viruses (dengue serotypes 1–4) transmitted by Aedes mosquitoes (mostly Ae. aegypti, also the vector of yellow fever). They breed in containers of relatively clean water associated with human environments, such as flower vases, old tires, cans, and bottles. Dengue is characterized by sudden onset, fever, headache, muscle and joint pains, loss of appetite, and other symptoms or signs of variable frequency. Each viral serotype provokes immunity only to itself, so residents of endemic areas with multiple serotypes face the lifetime probability of as many episodes of dengue. Repeat infections increase the risk of shock (sudden drop in blood pressure), which overwhelms the body’s control of coagulation and produces difficult-totreat hemorrhages and a fatal outcome. The nonspecific initial symptoms, variable nature of disease progression, and lack of inexpensive, rapid diagnostic tests or specific curative drugs produce a complicated situation for medical management. The explanations for the behavior of the disease further complicate the story. Dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) were characterized in Southeast Asia in the late 1950s and early 1960s. A prolonged controversy about the relative power of two factors for severity—viral characteristics versus immune response—was resolved in a consensus that both are important, but immune response is the common underlying trigger. This imposed the goal of a vaccine effective against all serotypes simultaneously, to avoid the chance of repeated infection and severe disease. At the end of the 1990s, new laboratory techniques raised hopes for a vaccine, so study sites were established to examine dengue in populations that might benefit from immunization (e.g., in Managua, pp. 148–49, 176, 186). In the meantime, control has focused on mosquito abatement through the elimination of breeding sites. The methods developed for individuals and communities to assume responsibility for vector control have shown limited success, and Nading shows many of the obstacles (pp. 64, 90, 98–99, 112, 126, 129–30, 140, 145, 147, 154–59). Dengue control efforts, as the author makes clear, must consider not only the universal interaction among...

Dengue Hemorrhagic Fever at 60 Years: Early Evolution of Concepts of Causation and Treatment.

During the decade of the 1960s, the epidemiology of a new dengue disease, dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS), was described by collaborative research performed by Thai scientists from many institutions and by workers at the U.S. Army's SEATO Medical Research Laboratory in Bangkok, Thailand. Careful clinical and physiological studies provided the initial description of DSS. DSS cases were caused by each of the four dengue viruses (DENV) and not chikungunya (CHIK) virus or DENV 5 and 6, were associated with a secondary-type dengue antibody response in children over the age of 1 year, were associated with a primary antibody response in infants less than 1 year old whose mothers had neutralizing antibodies to all four DENV, were associated more frequently with secondary DENV 2 infections than those due to DENV 1 and 3, and were more common in females than males over the age of 3 years. Robust laboratory methods for growth and recovery of DENV in tissue cultures were introduced. In addition, life-saving principles of fluid and plasma protein resuscitation of hypovolemia were described. Most epidemiological observations made during the decade of the 1960s have been confirmed in the succeeding 45 years. Much contemporary research on pathogenesis fails to address the two distinct immunological antecedents of DHF/DSS.

Subversion of early innate antiviral responses during antibody-dependent enhancement of Dengue virus infection induces severe disease in immunocompetent mice.

Dengue is a mosquito-borne disease caused by one of four serotypes of Dengue virus (DENV-1-4). Epidemiologic and observational studies demonstrate that the majority of severe dengue cases, dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS), occurs predominantly in either individuals with cross-reactive immunity following a secondary heterologous infection or in infants with primary DENV infections born from dengue-immune mothers, suggesting that B-cell-mediated and antibody responses impact on disease evolution. We demonstrate here that B cells play a pivotal role in host responses against primary DENV infection in mice. After infection, μMT(-/-) mice showed increased viral loads followed by severe disease manifestation characterized by intense thrombocytopenia, hemoconcentration, cytokine production and massive liver damage that culminated in death. In addition, we show that poly and monoclonal anti-DENV-specific antibodies can sufficiently increase viral replication through a suppression of early innate antiviral responses and enhance disease manifestation, so that a mostly non-lethal illness becomes a fatal disease resembling human DHF/DSS. Finally, treatment with intravenous immunoglobulin containing anti-DENV antibodies confirmed the potential enhancing capacity of subneutralizing antibodies to mediate virus infection and replication and induce severe disease manifestation of DENV-infected mice. Thus, our results show that humoral responses unleashed during DENV infections can exert protective or pathological outcomes and provide insight into the pathogenesis of this important human pathogen.

Dengue virus localization in human tissues (case study)

Dengue is an arboviral disease which is present in tropical and subtropical regions of the world. Dengue virus (DENV) can cause benign dengue fever (DF) to the most severe forms, dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS). Many studies have been confirmed the dengue viral antigens in various types of naturally infected human tissues but little work has been done and is not certain the localization of viral RNA in human tissues. We studied tissue specimens of two patients who died from clinically diagnosed DHF to confirm serologically or virologically. DENV was detected by dengue specific Reverse transcription polymerase chain reaction (RT-PCR) for the detection of dengue viral RNA. From the RT-PCR, dengue viral RNA was detected in liver, kidney and lungs tissues while the DENV RNA absence in brain, heart, spleen and pancreas tissues. DENV can infect a number of different tissue types.

Therapeutic Efficacy of Antibodies Lacking FcγR against Lethal Dengue Virus Infection Is Due to Neutralizing Potency and Blocking of Enhancing Antibodies

Dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) are life-threatening complications following infection with one of the four serotypes of dengue virus (DENV). At present, no vaccine or antiviral therapies are available against dengue. Here, we characterized a panel of eight human or mouse-human chimeric monoclonal antibodies (MAbs) and their modified variants lacking effector function and dissected the mechanism by which some protect against antibody-enhanced lethal DENV infection. We found that neutralizing modified MAbs that recognize the fusion loop or the A strand epitopes on domains II and III of the envelope protein, respectively, act therapeutically by competing with and/or displacing enhancing antibodies. By analyzing these relationships, we developed a novel in vitro suppression-of-enhancement assay that predicts the ability of modified MAbs to act therapeutically against antibody-enhanced disease in vivo. These studies provide new insight into the biology of DENV pathogenesis and the requirements for antibodies to treat lethal DENV disease.

HLA-A*0201-restricted CD8+T-cell epitopes identified in dengue viruses

BackgroundAll four dengue virus (DV) serotypes (D1V, D2V, D3V and D4V) can cause a series of disorders, ranging from mild dengue fever (DF) to severe dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS). Previous studies have revealed that DV serotype-specific CD8+ T cells are involved in controlling DV infection. Serotype cross-reactive CD8+ T-cells may contribute to the immunopathogenesis of DHF/DSS. The aim of the study was to identify HLA-A*0201-binding peptides from four DV serotypes. We then examined their immunogenicity in vivo and cross-reactivity within heterologous peptides.MethodsD1V-derived candidate CD8+ T-cell epitopes were synthesized and evaluated for their affinity to the HLA-A*0201 molecule. Variant peptides representing heterologous D2V, D3V, D4V serotypes were synthesized. The immunogenicity of the high-affinity peptides were evaluated in HLA-A*0201 transgenic mice.ResultsOf the seven D1V-derived candidate epitopes [D1V-NS4a56–64(MLLALIAVL), D1V-C46–54(LVMAFMAFL), D1V-NS4b562–570(LLATSIFKL), D1V-NS2a169–177(AMVLSIVSL), D1V-NS4a140–148(GLLFMILTV), D1V-NS2a144–152(QLWAALLSL) and D1V-NS4b183–191(LLMRTTWAL)], three peptides [D1V-NS4a140–148, D1V-NS2a144–152 and D1V-NS4b183–191] had a high affinity for HLA-A*0201 molecules. Moreover, their variant peptides for D2V, D3V and D4V [D2V-NS4a140–148(AILTVVAAT), D3V-NS4a140-148(GILTLAAIV), D4V-NS4a140-148(TILTIIGLI), D2V-NS2a144–152(QLAVTIMAI), D3V-NS2a144–152(QLWTALVSL), D4V-NS2a143–151(QVGTLALSL), D2V-NS4b182–190(LMMRTTWAL), D3V-NS4b182–190 (LLMRTSWAL) and D4V-NS4b179–187(LLMRTTWAF)] also had a high affinity for HLA-A*0201 molecules. Furthermore, CD8+ T cells directed to these twelve peptides were induced in HLA-A*0201 transgenic mice following immunization with these peptides. Additionally, cross-reactivity within four peptides (D1V-NS4b183–191, D2V-NS4b182–190, D3V-NS4b182–190 and D4V-NS4b179–187) was observed.ConclusionsTwo novel serotype-specific HLA-A*0201-restricted CD8+ T-cell epitopes (NS4a140-148 and NS2a144–152) and one cross-reactive HLA-A*0201-restricted CD8+ T-cell epitopes which is similar to a previously identified epitope were identified in D1V-D4V. Combining prediction algorithms and HLA transgenic mice is an effective strategy to identify HLA-restricted epitopes. Serotype-specific epitopes would be used to determine the protective role of serotype-specific CD8+ T cells, while cross-reactive epitopes may provide assistance in exploring the role of serotype cross-reactive CD8+ T cells in the immunopathogenesis of DHF/DSS.

DENGUE HEMORRHAGIC FEVER / DENGUE SHOCK SYNDROME

Objective: To study the clinical spectrum of Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome (DSS) in childrenadmitted in a tertiary care center during 2011 dengue epidemic in Lahore. Setting: This study was conducted in department of PediatricsLahore General Hospital (LGH) / Postgraduate Medical Institute (PGMI) Lahore, Pakistan. Design: Retrospective descriptive study. Period: 1stAugust to 31st October 2011. Method: All the children (<18 years) with clinical features of Dengue Hemorrhagic Fever and Dengue shockSyndrome (DHF/DSS) admitted to the Pediatric ward Lahore General Hospital, Lahore during the period of 1st August to 31st October 2011were enrolled in the study. The clinical manifestation were recorded on a standard questionnaire form. Clinically DHF/DSS cases wereconfirmed in the laboratory by different investigations. All the patient were diagnosed, managed and discharged according to WHO protocol.Results: A total of 254 patients were admitted in the ward labeled as dengue fever (DF) clinically. Out of these 142(55.9 %) were confirmed byserology. Of 254 DF cases 37(14.57%) were labeled as DHF and 02(0.79%) as DSS on their clinical manifestations and fulfilling the WHOcriteria. 55% were male and 45%females. Common symptoms were fever seen in 100%, headache 71.79% and vomiting seen in 58.97% of thecases. The most common bleeding manifestations were epistaxis seen in 69.23% of the cases. Positive IgM was noted in 53.9% and IgG in36.6% cases. A decrease in platelet count and increase in Heamatocrit ( Hct) during stay in ward was noted. Out of 39 patients only one patientexpired (2.56%).

Molecular Mimicry of Human Endothelial Cell Antigen by Autoantibodies to Nonstructural Protein 1 of Dengue Virus

The pathogenesis of dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS), both serious complications of dengue virus (DV) infection, remains unclear. In this study, we found that anti-DV NS1 (nonstructural protein 1) polyclonal antibodies cross-reacted with human umbilical vein endothelial cells (HUVECs). We further identified a complex-specific mAb, DB16-1, which could recognize DV NS1 and cross-react with HUVECs and human blood vessels. The target protein of DB16-1 was further purified by immunoaffinity chromatography. LC-MS/MS analysis and co-immunoprecipitation revealed that the target protein of DB16-1 was human LYRIC (lysine-rich CEACAM1 co-isolated). Our newly generated anti-LYRIC mAbs bound to HUVECs in a pattern similar to that of DB16-1. The B-cell epitope of DB16-1 displayed a consensus motif, Lys-X-Trp-Gly (KXWG), which corresponded to amino acid residues 116-119 of DV NS1 and mimicked amino acid residues 334-337 in LYRIC. Moreover, the binding activity of DB16-1 in NS1 of DV-2 and in LYRIC disappeared after the KXWG epitope was deleted in each. In conclusion, DB16-1 targeted the same epitope in DV NS1 and LYRIC protein on human endothelial cells, suggesting that it might play a role in the pathogenesis of DHF/DSS. Future studies on the role of the anti-NS1 antibody in causing vascular permeability will undoubtedly be performed on sera collected from individuals before, during, and after the endothelial cell malfunction phase of a dengue illness.

Enhanced Infection of Liver Sinusoidal Endothelial Cells in a Mouse Model of Antibody-Induced Severe Dengue Disease

Dengue virus (DENV) causes disease ranging from dengue fever (DF), a self-limited febrile illness, to the potentially lethal dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS). DHF/DSS usually occurs in patients who have acquired DENV-reactive antibodies prior to infection, either from a previous infection with a heterologous DENV serotype or from an immune mother. Hence, it has been hypothesized that subneutralizing levels of antibodies exacerbate disease, a phenomenon termed antibody-dependent enhancement (ADE). However, given the lack of suitable animal models for DENV infection, the mechanism of ADE and its contribution to pathology remain elusive. Here we demonstrate in mice that DENV-specific antibodies can sufficiently increase severity of disease so that a mostly nonlethal illness becomes a fatal disease resembling human DHF/DSS. Antibodies promote massive infection of liver sinusoidal endothelial cells (LSECs), resulting in increased systemic levels of virus. Thus, a subprotective humoral response may, under some circumstances, have pathological consequences.

Cellular and Molecular Basis of Antibody-Dependent Enhancement in Human Dengue Pathogenesis

Dengue fever is gaining increased attention as a major global health problem. It occurs annually in 50–100 million people in more than 100 countries, and places half a million people at risk of life-threatening diseases: dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS). The pathogenic mechanisms causing DHF/DSS are not clearly understood. This article reviews cellular and molecular mechanisms that might be responsible for the initiation of the pathogenic processes, including hypotheses for DHF/DSS, dengue-permissive target cells, putative dengue receptors, neutralizing and enhancing antibodies to dengue virus, mechanisms of vascular plasma leakage, innate immune response in dengue infection and antibody-dependent enhancement of dengue infection. While reviewing the literature, the article also gives the author’s opinion on perceived areas of importance for future research in human dengue pathogenesis.

Dengue virus infection induces passive release of high mobility group box 1 protein by epithelial cells

Dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) are severe complications of secondary dengue virus (DV) infection. In the current study, we provide the first evidence of induction of cellular necrosis by DV type 2 (DV-2). The epithelial cell line A549 can support replication of dengue virus as demonstrated by expression of viral NS1 antigen and virus plaque assay. DV-2 infection of cells induced cell death in approximately half of the cells that were actively infected. Using sodium 3'-[1-(phenylaminocarbonyl)-3, 4-tetrazolium]-bis(4-methoxy-6-nitro) benzene sulfonic acid hydrate [XTT]-based cell viability assays, we found that DV-2 infection at a multiplicity of infection (MOI) of 10 resulted in significant death of cells as well as high extracellular lactate dehydrogenase (LDH) activity and leakage of the high mobility group 1 (HMGB1) protein into the extracellular space. These results suggest that HMGB1 may be a signal of tissue or cellular injury by DV-2, which in turn is likely to induce and/or enhance an immune reaction.

Epitope Mapping of Dengue-Virus-Enhancing Monoclonal-Antibody Using Phage Display Peptide Library

The Antibody-Dependent Enhancement (ADE) hypothesis has been proposed to explain why more severe manifestations of Dengue Hemorrhagic Fever and Dengue Shock Syndrome (DHF/DSS) occur predominantly during secondary infections of Dengue Virus (DV) with different serotypes. However, the epitopes recognized by these enhancing antibodies are unclear. Recently, antipre-M monoclonal antibody (mAb 70-21), which recognized all DV serotypes without neutralizing activity, were generated and demonstrated as an enhancing antibody for DV infection. In the present study, the epitope recognized by mAb 70-21 was identified using a phage-displayed random-peptide library. After three rounds of biopanning, ELISA showed that immunopositive phage clones specifically bound to mAb 70-21 but not to serum or purified IgG from naive mice. DNA sequencing of these phage clones showed a consensus sequence, QNNLGPR. Like mAb70-21, these phageinduced antisera also enhanced the DV infection of cells. In addition, indirect fluorescent assays showed phage-induced antisera bound to human rhabdomyosarcoma or Vero cells. Western blotting and immunoprecipitation analysis showed that phage-induced antisera recognized hsp 60 in BHK cell lysate. Moreover, the sera levels of antibodies against the synthetic peptide QNNLGPR correlated with the disease severity of dengue patients. Taken together, these results suggest that antibodies which recognized epitopes shared by pre-M of DV and hsp 60 of host cells may enhance DV infection and be involved in the development of DHF or DSS.

Autoimmune Pathogenesis in Dengue Virus Infection

The pathogenic mechanisms of dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) caused by dengue virus (DV) infection remain unresolved. Patients with DHF/DSS are characterized by several manifestations, including severe thrombocytopenia, vascular leakage, and hepatomegaly. In addition to the effect of virus load and virus variation, abnormal immune responses of the host after DV infection may also account for the progression of DHF/DSS. Actually, viral autoimmunity is involved in the pathogenesis of numerous viral infections, such as human immunodeficiency virus, human hepatitis C virus, human cytomegalovirus, herpes simplex virus, Epstein- Barr virus, and DV. In this review, we discuss the implications of autoimmunity in dengue pathogenesis. Antibodies directed against DV nonstructural protein 1 (NS1) showed cross-reactivity with human platelets and endothelial cells, which lead to platelet and endothelial cell damage and inflammatory activation. Based on these findings, we hypothesize that anti-DV NS1 is involved in the pathogenesis of DF and DHF/DSS, and this may provide important information in dengue vaccine development.

Tissue plasminogen activator induced by dengue virus infection of human endothelial cells.

Dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) are severe complications of dengue virus (DV) infection. However, the pathogenesis of hemorrhage induced by dengue virus infection is poorly understood. Since endothelial cells play a pivotal role in the regulation of hemostasis, we studied the effect of DV infection on the production of tissue plasminogen activator (tPA) and plasminogen activator inhibitor 1 (PAI-1) in vitro using both primary isolated endothelial cells, human umbilical cord veins cells, and a human microvascular endothelial cell line. DV infection significantly induced the secretion of tPA but not PAI-1 of human endothelial cells. In addition, tPA mRNA of endothelial cells was induced by DV as demonstrated by RT-PCR. Antibody against IL-6 but not control antibody inhibited DV-induced tPA production of endothelial cells. Furthermore, a good correlation between sera levels of IL-6 and tPA was found in DHF but not DF patients. These results suggest that IL-6 can regulate DV-induced tPA production of endothelial cells, which may play important roles in the pathogenic development of DHF/DSS.

Dengue hemorrhagic fever in infants: research opportunities ignored.

The age distribution of cases of dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) in infants under the age of 1 year are reported from Bangkok, Thailand, and for the first time for Ho Chi Minh City, Vietnam; Yangon, Myanmar; and Surabaya, Indonesia. The four dengue viruses were isolated from Thai infants, all of whom were having a primary dengue infection. Progress studying the immunologically distinct infant DHF/DSS has been limited; most contemporary research has centered on DHF/DSS accompanying secondary dengue infections. In designing research results obtained in studies on a congruent animal model, feline infectious peritonitis virus (FIPV) infections of kittens born to FIPV-immune queens should be considered. Research challenges presented by infant DHF/DSS are discussed.

Generation of IgM anti‐platelet autoantibody in dengue patients

Dengue virus infection causes a wide range of diseases from dengue fever to life-threatening dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS). The mechanisms involved in DHF/DSS pathogenesis remain unclear. Patient sera collected from an outbreak in southern Taiwan from November 1998 to January 1999 were studied. The presence of antibodies which cross-reacted with platelets could be detected in patient sera, and the isotype of these autoantibodies was IgM. The anti-platelet IgM levels were higher in DHF/DSS than in dengue fever patient sera in disease acute phase. These autoantibodies were still detectable in convalescent stage (1–3 weeks after acute phase) and even eight to nine months after illness. The platelet binding activity was not observed in other virus-infected patient sera tested. Further investigation showed that dengue patient sera caused platelet lysis in the presence of complement. The platelet cytotoxicity induced by DHF/DSS patient sera was higher than that by dengue fever sera. Dengue patient sera also inhibited platelet aggregation which, however, appeared to be not related to DHF/DSS development. J. Med. Virol. 63:143–149, 2001. © 2001 Wiley-Liss, Inc.

Generation of IgM anti-platelet autoantibody in dengue patients

Dengue virus infection causes a wide range of diseases from dengue fever to life-threatening dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS). The mechanisms involved in DHF/DSS pathogenesis remain unclear. Patient sera collected from an outbreak in southern Taiwan from November 1998 to January 1999 were studied. The presence of antibodies which cross-reacted with platelets could be detected in patient sera, and the isotype of these autoantibodies was IgM. The anti-platelet IgM levels were higher in DHF/DSS than in dengue fever patient sera in disease acute phase. These autoantibodies were still detectable in convalescent stage (1-3 weeks after acute phase) and even eight to nine months after illness. The platelet binding activity was not observed in other virus-infected patient sera tested. Further investigation showed that dengue patient sera caused platelet lysis in the presence of complement. The platelet cytotoxicity induced by DHF/DSS patient sera was higher than that by dengue fever sera. Dengue patient sera also inhibited platelet aggregation which, however, appeared to be not related to DHF/DSS development.

Activation of coagulation and fibrinolysis during dengue virus infection.

Dengue virus infection can induce mild dengue fever (DF) or severe dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS) in human. The pathogenesis of hemorrhage in dengue virus infection is not fully understood. Since hemostasis depends on the balance between coagulation and fibrinolysis, alternation of some coagulation parameters (platelet count and activated partial thromoboplastin time, APTT) as well as fibrinolytic parameters (tissue plasminogen activator, tPA and plasminogen activator inhibitor-1, PAI-1) were compared in 8 DHF/DSS and 17 DF patients. Patients showed thrombocytopenia, APTT prolongation, and tPA increase in the acute stage of disease, indicating activation of coagulation and fibrinolysis. The activation of coagulation and fibrinolysis in DHF/DSS patients was much more severe than DF patients. In the convalescent stage, a rise of PAI-1 level and platelet count with concomitant decline of tPA level and APTT returned to normal in both DHF/DSS and DF patients. Therefore, the activation of coagulation and fibrinolysis during the acute stage of dengue virus infection is offset by the increase of platelet and PAI-1 during convalescent stage. Taken together, these results suggest that the degree of coagulation and fibrinolysis activation induced by dengue virus infection is associated with the disease severity.