Fever with thrombocytopenia associated with a novel bunyavirus in China

BACKGROUND

Heightened surveillance of acute febrile illness in China since 2009 has led to the identification of a severe fever with thrombocytopenia syndrome (SFTS) with an unknown cause. Infection with Anaplasma phagocytophilum has been suggested as a cause, but the pathogen has not been detected in most patients on laboratory testing.

METHODS

We obtained blood samples from patients with the case definition of SFTS in six provinces in China. The blood samples were used to isolate the causal pathogen by inoculation of cell culture and for detection of viral RNA on polymerase-chain-reaction assay. The pathogen was characterized on electron microscopy and nucleic acid sequencing. We used enzyme-linked immunosorbent assay, indirect immunofluorescence assay, and neutralization testing to analyze the level of virus-specific antibody in patients' serum samples.

RESULTS

We isolated a novel virus, designated SFTS bunyavirus, from patients who presented with fever, thrombocytopenia, leukocytopenia, and multiorgan dysfunction. RNA sequence analysis revealed that the virus was a newly identified member of the genus phlebovirus in the Bunyaviridae family. Electron-microscopical examination revealed virions with the morphologic characteristics of a bunyavirus. The presence of the virus was confirmed in 171 patients with SFTS from six provinces by detection of viral RNA, specific antibodies to the virus in blood, or both. Serologic assays showed a virus-specific immune response in all 35 pairs of serum samples collected from patients during the acute and convalescent phases of the illness.

CONCLUSIONS

A novel phlebovirus was identified in patients with a life-threatening illness associated with fever and thrombocytopenia in China. (Funded by the China Mega-Project for Infectious Diseases and others.).

Unique epidemiological and clinical features of the emerging 2019 novel coronavirus pneumonia (COVID-19) implicate special control measures

By 27 February 2020, the outbreak of coronavirus disease 2019 (COVID-19) caused 82 623 confirmed cases and 2858 deaths globally, more than severe acute respiratory syndrome (SARS) (8273 cases, 775 deaths) and Middle East respiratory syndrome (MERS) (1139 cases, 431 deaths) caused in 2003 and 2013, respectively. COVID-19 has spread to 46 countries internationally. Total fatality rate of COVID-19 is estimated at 3.46% by far based on published data from the Chinese Center for Disease Control and Prevention (China CDC). Average incubation period of COVID-19 is around 6.4 days, ranges from 0 to 24 days. The basic reproductive number (R0 ) of COVID-19 ranges from 2 to 3.5 at the early phase regardless of different prediction models, which is higher than SARS and MERS. A study from China CDC showed majority of patients (80.9%) were considered asymptomatic or mild pneumonia but released large amounts of viruses at the early phase of infection, which posed enormous challenges for containing the spread of COVID-19. Nosocomial transmission was another severe problem. A total of 3019 health workers were infected by 12 February 2020, which accounted for 3.83% of total number of infections, and extremely burdened the health system, especially in Wuhan. Limited epidemiological and clinical data suggest that the disease spectrum of COVID-19 may differ from SARS or MERS. We summarize latest literatures on genetic, epidemiological, and clinical features of COVID-19 in comparison to SARS and MERS and emphasize special measures on diagnosis and potential interventions. This review will improve our understanding of the unique features of COVID-19 and enhance our control measures in the future.

Coagulation disorders in coronavirus infected patients: COVID-19, SARS-CoV-1, MERS-CoV and lessons from the past

Coronavirus disease 2019 (COVID-19) or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel coronavirus strain disease, has recently emerged in China and rapidly spread worldwide. This novel strain is highly transmittable and severe disease has been reported in up to 16% of hospitalized cases. More than 600,000 cases have been confirmed and the number of deaths is constantly increasing. COVID-19 hospitalized patients, especially those suffering from severe respiratory or systemic manifestations, fall under the spectrum of the acutely ill medical population, which is at increased venous thromboembolism risk. Thrombotic complications seem to emerge as an important issue in patients infected with COVID-19. Preliminary reports on COVID-19 patients' clinical and laboratory findings include thrombocytopenia, elevated D-dimer, prolonged prothrombin time, and disseminated intravascular coagulation. As the pandemic is spreading and the whole picture is yet unknown, we highlight the importance of coagulation disorders in COVID-19 infected patients and review relevant data of previous coronavirus epidemics caused by the severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) and the Middle East Respiratory Syndrome coronavirus (MERS-CoV).

Severe fever with thrombocytopenia syndrome, South Korea, 2012

We report a retrospectively identified fatal case of severe fever with thrombocytopenia syndrome (SFTS) in South Korea from 2012. SFTS virus was isolated from the stored blood of the patient. Phylogenetic analysis revealed this isolate was closely related to SFTS virus strains from China and Japan.

Haematological manifestations in patients with severe acute respiratory syndrome: retrospective analysis

OBJECTIVES

To evaluate the haematological findings of patients with severe acute respiratory syndrome (SARS).

DESIGN

Analysis of the demographic, clinical, and laboratory characteristics of patients with SARS.

SETTING

Prince of Wales Hospital, Hong Kong. Subjects All patients with a diagnosis of SARS between 11 March and 29 March 2003 who had no pre-existing haematological disorders.

MAIN OUTCOME MEASURES

Clinical end points included the need for intensive care and death. Univariate and multivariate analyses were performed to examine factors associated with adverse outcome.

RESULTS

64 male and 93 female patients were included in this study. The most common findings included lymphopenia in 153 (98%) of the 157 patients, neutrophilia in 129 (82%), thrombocytopenia in 87 patients (55%), followed by thrombocytosis in 77 (49%), and isolated prolonged activated partial thromboplastin time in 96 patients (63%). The haemoglobin count dropped by more than 20 g/l from baseline in 95 (61%) patients. Four patients (2.5%) developed disseminated intravascular coagulation. Lymphopenia was shown in haemato-lymphoid organs at postmortem examination. Multivariate analysis showed that advanced age and a high concentration of lactate dehydrogenase at presentation were independent predictors of an adverse outcome. Subsets of peripheral blood lymphocytes were analysed in 31 patients. The counts of CD4 positive and CD8 positive T cells fell early in the course of illness. Low counts of CD4 and CD8 cells at presentation were associated with adverse outcomes.

CONCLUSIONS

Abnormal haematological variables were common among patients with SARS. Lymphopenia and the depletion of T lymphocyte subsets may be associated with disease activity.

Thrombocytopenia and its association with mortality in patients with COVID-19

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes novel coronavirus disease 2019 (COVID-19), is spreading rapidly around the world. Thrombocytopenia in patients with COVID-19 has not been fully studied.

OBJECTIVE

To describe thrombocytopenia in patients with COVID-19.

METHODS

For each of 1476 consecutive patients with COVID-19 from Jinyintan Hospital, Wuhan, China, nadir platelet count during hospitalization was retrospectively collected and categorized into (0, 50], (50, 100], (100-150], or (150-) groups after taking the unit (×109 /L) away from the report of nadir platelet count. Nadir platelet counts and in-hospital mortality were analyzed.

RESULTS

Among all patients, 238 (16.1%) patients were deceased and 306 (20.7%) had thrombocytopenia. Compared with survivors, non-survivors were older, were more likely to have thrombocytopenia, and had lower nadir platelet counts. The in-hospital mortality was 92.1%, 61.2%, 17.5%, and 4.7% for (0, 50], (50, 100], (100-150], and (150-) groups, respectively. With (150-) as the reference, nadir platelet counts of (100-150], (50, 100], and (0, 50] groups had a relative risk of 3.42 (95% confidence interval [CI] 2.36-4.96), 9.99 (95% CI 7.16-13.94), and 13.68 (95% CI 9.89-18.92), respectively.

CONCLUSIONS

Thrombocytopenia is common in patients with COVID-19, and it is associated with increased risk of in-hospital mortality. The lower the platelet count, the higher the mortality becomes.

Neutrophils recruited to sites of infection protect from virus challenge by releasing neutrophil extracellular traps

Neutrophils mediate bacterial clearance through various mechanisms, including the release of mesh-like DNA structures or neutrophil extracellular traps (NETs) that capture bacteria. Although neutrophils are also recruited to sites of viral infection, their role in antiviral innate immunity is less clear. We show that systemic administration of virus analogs or poxvirus infection induces neutrophil recruitment to the liver microvasculature and the release of NETs that protect host cells from virus infection. After systemic intravenous poxvirus challenge, mice exhibit thrombocytopenia and the recruitment of both neutrophils and platelets to the liver vasculature. Circulating platelets interact with, roll along, and adhere to the surface of adherent neutrophils, forming large, dynamic aggregates. These interactions facilitate the release of NETs within the liver vasculature that are able to protect host cells from poxvirus infection. These findings highlight the role of NETs and early tissue-wide responses in preventing viral infection.

Endemic Severe Fever with Thrombocytopenia Syndrome, Vietnam

Severe fever with thrombocytopenia syndrome (SFTS), a tickborne viral disease, has been identified in China, South Korea, and Japan since 2009. We found retrospective evidence of SFTS virus (SFTSV) infection in Vietnam, which suggests that SFTSV infections also occur in Vietnam, where the virus has not been known to be endemic.

Clinical course and outcome of 107 patients infected with the novel coronavirus, SARS-CoV-2, discharged from two hospitals in Wuhan, China

BACKGROUND

In December 2019, coronavirus disease 2019 (COVID-19) outbreak was reported from Wuhan, China. Information on the clinical course and prognosis of COVID-19 was not thoroughly described. We described the clinical courses and prognosis in COVID-19 patients.

METHODS

Retrospective case series of COVID-19 patients from Zhongnan Hospital of Wuhan University in Wuhan and Xishui Hospital, Hubei Province, China, up to February 10, 2020. Epidemiological, demographic, and clinical data were collected. The clinical course of survivors and non-survivors were compared. Risk factors for death were analyzed.

RESULTS

A total of 107 discharged patients with COVID-19 were enrolled. The clinical course of COVID-19 presented as a tri-phasic pattern. Week 1 after illness onset was characterized by fever, cough, dyspnea, lymphopenia, and radiological multi-lobar pulmonary infiltrates. In severe cases, thrombocytopenia, acute kidney injury, acute myocardial injury, and adult respiratory distress syndrome were observed. During week 2, in mild cases, fever, cough, and systemic symptoms began to resolve and platelet count rose to normal range, but lymphopenia persisted. In severe cases, leukocytosis, neutrophilia, and deteriorating multi-organ dysfunction were dominant. By week 3, mild cases had clinically resolved except for lymphopenia. However, severe cases showed persistent lymphopenia, severe acute respiratory dyspnea syndrome, refractory shock, anuric acute kidney injury, coagulopathy, thrombocytopenia, and death. Older age and male sex were independent risk factors for poor outcome of the illness.

CONCLUSIONS

A period of 7-13 days after illness onset is the critical stage in the COVID-19 course. Age and male gender were independent risk factors for death of COVID-19.

Person-to-person transmission of severe fever with thrombocytopenia syndrome bunyavirus through blood contact

Severe fever with thrombocytopenia syndrome bunyavirus is a newly discovered bunyavirus with high pathogenicity to human. The transmission model has been largely uncharacterized. Investigation on a cluster of severe fever with thrombocytopenia syndrome cases provided evidence of person-to-person transmission through blood contact to the index patient with high serum virus load.

Antiplatelet autoantibodies elicited by dengue virus non-structural protein 1 cause thrombocytopenia and mortality in mice

BACKGROUND

The mechanisms responsible for thrombocytopenia associated with dengue fever (DF) and dengue hemorrhage fever (DHF) remain unclear.

OBJECTIVE

In this study, we investigated the pathogenic effects of dengue virus (DENV) non-structural protein 1 (NS1) on the elicitation of platelet cross-reactive antibodies.

RESULTS

The results showed that anti-DENV NS1 immunoglobulins (Igs) derived from both patients with DF/DHF and recombinant NS1-immunized rabbits could opsonize normal human platelets and enhance platelet-macrophage engagements in vitro. In addition, treatments with anti-NS1 Igs abnormally activated human platelets and induced thrombocytopenia in mice. These prothrombotic characteristics of anti-NS1 Ig might increase the disease burden of coagulant-aberrant DHF patients. To test this hypothesis, we injected anti-NS1 Igs into C57BL/6J mice that were preconditioned into a hypercoagulable state by warfarin treatments. When given before but not after platelet-lysate pre-adsorption, the anti-NS1 Igs injection treatments significantly increased mortality, fibrin deposition in lung, and plasma D-dimer levels, but significantly decreased anticoagulant proteins C, protein S and antithrombin III.

CONCLUSIONS

These results suggest that the platelet-bound antibody fractions of anti-NS1 Ig are prothrombotic, which might exacerbate the severity of disease in hosts with an imbalanced coagulant system.

Hematological findings in coronavirus disease 2019: indications of progression of disease

Coronavirus disease 2019 (COVID-19) is a new human infectious disease. The etiology for this outbreak is a novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Thus far, related research on COVID-19 is still in preliminary stage. This paper summarized the latest outcomes of corresponding study from Chinese centers and clarified the hematopoietic abnormality caused by SARS-CoV-2 and potential mechanism. Lymphopenia was common in the early stage after the onset of COVID-19. A significant decrease was observed in peripheral CD4+ and CD8+ T lymphocytes. As the illness progressed, neutrophilia emerged in several cases, and patients with severe critical pulmonary conditions showed higher neutrophils than common type. Thrombocytopenia was resulting from the consumption and/or the reduced production of platelets in damaged lungs. Anemia was not observed notably, but the decrease in hemoglobin was frequent. The activation of monocyte-macrophage system aggravates the immune damage of lung and other tissues, which leads to the increase of D-dimer, prothrombin time, and platelet consumption.

HIV-related thrombocytopenia

Chronic thrombocytopenia is a common hematologic disorder in patients infected with the human immunodeficiency virus (HIV). Although often asymptomatic, the thrombocytopenia may be associated with a variety of bleeding abnormalities. The underlying pathophysiology includes accelerated peripheral platelet destruction and decreased ('ineffective') production of platelets from the infected megakaryocytes. HIV-related thrombocytopenia (HIV-TP) responds to antiretroviral therapy. Most studies have evaluated the use of AZT (zidovudine) and have shown increased platelet production. Combination therapy (HAART) also resulted in sustained platelet increases. When antiretroviral agents fail to improve the platelet count or cannot be used, other therapies, similar to those used in 'classic' immune thrombocytopenia (ITP), can be employed, including steroids, intravenous immunoglobulin (i.v.intravenous anti-D or splenectomy. Anti-D treatment offers advantages for HIV-TP because the duration of effect appears to be significantly longer than the response duration after i.v. therapy (initial results of our open-arm study were confirmed by our randomized trial). Of note, follow-up of heavily treated patients showed no acceleration of CD4 decline and no change in plasma viral load measurements. Splenectomy has been used to treat HIV-positive patients with refractory thrombocytopenia. Although it is effective therapy, there are concerns about infections and selection of appropriate candidates. Other treatment modalities, such as interferon, vincristine, danazol, low-dose splenic irradiation and staphylococcal protein A immunoadsorption have shown limited success in HIV-TP. Alternatively, thrombocytopenia in HIV-infected patients may be treated with pharmacological hyperstimulation of megakaryocytopoiesis (administration of PEG-rHuMGDF or TPO). Latest evidence indicates that the chemokine receptor CXCR4 (coreceptor for the cellular entry of lymphotropic HIV strains) is expressed on megakaryocytes; as a result, the development of chemokine receptor antagonists may modify the course of the disease.

Mechanisms of dengue virus-induced bone marrow suppression

Infection with many flaviviruses is associated with transient suppression of haematopoiesis. Of the flaviviruses of man, none are more accessible to clinical and laboratory study than dengue. Consequently, the clinical syndrome of dengue-associated bone marrow suppression has been well documented. A review of experimental dengue infections of volunteers and histopathological studies of bone marrow from patients with severe dengue virus infection suggests that marrow suppression evolves rapidly through several phases: (1) onset of marrow suppression within 3-4 days of infection; (2) onset of host inflammatory responses in the marrow and of fever shortly thereafter; (3) occurrence of a neutrophil nadir on the fourth to fifth day after onset of fever; (4) almost simultaneously, immune activation sufficient to neutralize viraemia and accelerate elimination of infected cells; (5) remission of symptoms; and (6) resolution of cytopenias. Clinical observations and experimental data bear on possible mechanisms of dengue virus-mediated marrow suppression. Work from the authors' laboratory in which long-term bone marrow cultures were used to investigate interactions between dengue virus and bone marrow cells (stromal elements and haematopoietic progenitors) is also reviewed. Long-term marrow culture (LTMC) was a useful experimental system. In vitro, early blast cells as well as the more differentiated haematopoietic elements were abortively infected, killed and eliminated by phagocytosis by specialized marrow macrophages called dendritic cells. Moreover, the ARC from stroma rather than haematopoietic precursors were productively infected. When ARC were infected, stroma failed to support haematopoiesis. Cytokine production by virus-infected stromal cells was altered. A hypothesis is proposed to account for dengue virus-induced marrow suppression. Down-regulation of haematopoiesis is probably a protective mechanism of the microenvironment that limits injury to the marrow stem/progenitor cell compartment during the subsequent process of elimination of infected cells.

Platelets and viruses: an ambivalent relationship

Thrombocytopenia is a frequent complication of viral infections providing evidence that interaction of platelets with viruses is an important pathophysiological phenomenon. Multiple mechanisms are involved depending on the nature of the viruses involved. These include immunological platelet destruction, inappropriate platelet activation and consumption, and impaired megakaryopoiesis. Viruses bind platelets through specific receptors and identified ligands, which lead to mutual alterations of both the platelet host and the viral aggressor. We have shown that HIV-1 viruses are internalized specifically in platelets and megakaryocytes, where they can be either sheltered, unaltered (with potential transfer of the viruses into target organs), or come in contact with platelet secretory products leading to virus destruction and facilitated platelet clearance. In this issue, we have reviewed the various pathways that platelets use in order to interact with viruses, HIV and others. This review also shows that more work is still needed to precisely identify platelet roles in viral infections, and to answer the challenge of viral safety in platelet transfusion.

Manifestation of thrombocytopenia in dengue-2-virus-infected mice

Dengue virus infection causes dengue fever, dengue haemorrhagic fever and dengue shock syndrome. No animal model is available that mimics these clinical manifestations. In this study, the establishment is reported of a murine model for dengue virus infection that resembles the thrombocytopenia manifestation. Dengue-2 virus (dengue virus type 2) can infect murine cells either in vitro (primary cell culture) or in vivo. Viraemia detected by RT-PCR was found transiently at 2 days after intravenous injection of dengue-2 virus. Transient thrombocytopenia developed at 10-13 days after primary or secondary infection. Anti-platelet antibody was generated after dengue-2 virus infection. There was strain variation in dengue-2 virus infection; the A/J strain was more sensitive than BALB/c or B6 mice. This dengue-2-virus-infected mouse system accompanied by thrombocytopenia and anti-platelet antibody will be a valuable model to study the pathogenicity of dengue virus infection.

Characteristics and Factors Associated with Death among Patients Hospitalized for Severe Fever with Thrombocytopenia Syndrome, South Korea, 2013

Surveillance for this emerging disease should be expanded to the outpatient setting.

In South Korea, nationwide surveillance for severe fever with thrombocytopenia syndrome (SFTS) began during 2013. Among 301 surveillance cases, 35 hospitalized case-patients in 25 areas were confirmed by using virologic testing, and 16 (46%) case-patients subsequently died. The SFTS cases occurred during May–November and peaked during June (9 cases, 26%). The incidence of SFTS was higher in the southern regions of South Korea. Age and neurologic symptoms, including decreased level of consciousness and slurred speech, were heavily associated with death; neurologic symptoms during the first week after disease onset were also associated with death. Although melena was common among patients who died, no other hemorrhagic manifestations were substantively more common among those who died. No effective treatments, including ribavirin, were identified. Expansion of SFTS surveillance to include the outpatient sector and development of an antibody test would enhance completeness of SFTS detection in South Korea.

Hepatitis C virus-related thrombocytopenia: clinical and laboratory characteristics compared with chronic immune thrombocytopenic purpura

Thrombocytopenia can be a complication of hepatitis C viral (HCV) infection. However, there is little published data regarding the clinical and laboratory manifestations of HCV-related thrombocytopenia (HCV-TP) compared with adult chronic immune thrombocytopenic purpura (CITP). We reviewed the medical records for all patients evaluated for chronic thrombocytopenia by the Haematology Service between January 1996 and June 2000. All patients were screened for HCV infection at the time of initial diagnosis. Of 250 patients who fulfilled American Society of Hematology criteria for CITP, 76 (30%) were HCV seropositive. HCV-TP patients were older [mean age (+/-SD) 54.9 +/- 8 years vs. 40.3 +/- 8 years, P </= 0.001] and equally distributed between both sexes. HCV-TP patients had less severe thrombocytopenia, defined as platelet count </=10 x 10(9)/l (4% vs. 46% for CITP, P </= 0.001). However, 56 (74%) had a platelet count </=50 x 10(9)/l. Symptoms and signs of thrombocytopenia were less frequent in HCV-TP, but major bleeding was more frequent (25% vs. 10%, P = 0.0059). Serum cryoglobulins and anticardiolipin antibodies were more frequent in HCV-TP (90% and 62% respectively), but rare in CITP (7% and 15%, P </= 0.001 compared with HCV-TP). HCV infection can be associated with significant thrombocytopenia and appears to be a distinct clinical entity.

Morbilliviruses and human disease

Morbilliviruses are a group of viruses that belong to the family Paramyxoviridae. The most instantly recognizable member is measles virus (MV) and individuals acutely infected with the virus exhibit a wide range of clinical symptoms ranging from a characteristic mild self-limiting infection to death. Canine distemper virus (CDV) and rinderpest virus (RPV) cause a similar but distinctive pathology in dogs and cattle, respectively, and these, alongside experimental MV infection of primates, have been useful models for MV pathogenesis. Traditionally, viruses were identified because a distinctive disease was observed in man or animals; an infectious agent was subsequently isolated, cultured, and this could be used to recapitulate the disease in an experimentally infected host. Thus, satisfying Koch's postulates has been the norm. More recently, particularly due to the advent of exceedingly sensitive molecular biological assays, many researchers have looked for infectious agents in disease conditions for which a viral aetiology has not been previously established. For these cases, the modified Koch's postulates of Bradford Hill have been developed as criteria to link a virus to a specific disease. Only in a few cases have these conditions been fulfilled. Therefore, many viruses have over the years been definitely and tentatively linked to human diseases and in this respect the morbilliviruses are no different. In this review, human diseases associated with morbillivirus infection have been grouped into three broad categories: (1) those which are definitely caused by the infection; (2) those which may be exacerbated or facilitated by an infection; and (3) those which currently have limited, weak, unsubstantiated or no credible scientific evidence to support any link to a morbillivirus. Thus, an attempt has been made to clarify the published data and separate human diseases actually linked to morbilliviruses from those that are merely anecdotally associated.

Platelets Endocytose Viral Particles and Are Activated via TLR (Toll-Like Receptor) Signaling

OBJECTIVE

Thrombocytopenia is associated with many viral infections suggesting virions interact with and affect platelets. Consistently, viral particles are seen inside platelets, and platelet activation markers are detected in viremic patients. In this article, we sought mechanistic insights into these virion/platelet interactions by examining how platelets endocytose, traffic, and are activated by a model virion. Approach and Results: Using fluorescently tagged HIV-1 pseudovirions, 3-dimensional structured illumination microscopy, and transgenic mouse models, we probed the interactions between platelets and virions. Mouse platelets used known endocytic machinery, that is, dynamin, VAMP (vesicle-associated membrane protein)-3, and Arf6 (ADP-ribosylation factor 6), to take up and traffic HIV-1 pseudovirions. Endocytosed HIV-1 pseudovirions trafficked through early (Rab4+) and late endosomes (Rab7+), and then to an LC3+ (microtubule-associated protein 1A/1B-light chain 3) compartment. Incubation with virions induced IRAK4 (interleukin 1 receptor-associated kinase 4), Akt (protein kinase B), and IKK (IκB kinase) activation, granule secretion, and platelet-leukocyte aggregate formation. This activation required TLRs (Toll-like receptors) and MyD88 (myeloid differentiation primary response protein 88) but was less extensive and slower than activation with thrombin. In vivo, HIV-1 pseudovirions injection led to virion uptake and platelet activation, as measured by IKK activation, platelet-leukocyte aggregate formation, and mild thrombocytopenia. All were decreased in VAMP-3-/- and, megakaryocyte/platelet-specific, Arf6-/- mice. Similar platelet activation profiles (increased platelet-leukocyte aggregates, plasma platelet factor 4, and phospho-IκBα) were detected in newly diagnosed and antiretroviral therapy-controlled HIV-1+ patients.

CONCLUSIONS

Collectively, our data provide mechanistic insights into the cell biology of how platelets endocytose and process virions. We propose a mechanism by which platelets sample the circulation and respond to potential pathogens that they take up.

Immunomodulation treatment for childhood virus-associated haemophagocytic lymphohistiocytosis

The Epstein-Barr virus (EBV), or human herpesvirus-6 (HHV-6) associated haemophagocytic lymphohistiocytosis, has been found prevalent in Taiwan; it affects previously healthy children and is always fatal when treated only supportively. Recognition of the underlying pathogenesis for this disease prompted adoption of an immunomodulatory regimen of intravenous immunoglobulin (IVIG) and/or etoposide on 17 such patients treated between 1990 and 1993. Remarkable improvement in patients' prognoses was demonstrated. Eight patients are still alive with a median follow-up of 1 year and 2 months post-treatment. Both IVIG and etoposide had positive immunomodulation effects such as alleviation of fever and normalization of haematological and hepatic parameters. Sustained complete response was obtained in two of nine cases of EBV-associated diseases treated with IVIG only. EBV transcripts became undetectable after etoposide and/or IVIG treatment without antiviral agents. Etoposide given by split-doses schedule appeared to be superior to conventional three-consecutive-days schedule for both remission induction and disease-free survival. Our preliminary trial apparently provides a promising improvement in the treatment of this previously fatal disease. IVIG or etoposide is effective in reversing the process of lymphohistiocytic dysregulation resulting from virus infection of immune cells in this syndrome and probably helps hosts to control active virus replication in certain cases, through immunomodulation.

HCV-associated thrombocytopenia: clinical characteristics and platelet response after recombinant alpha2b-interferon therapy

Hepatitis C virus (HCV) has been proposed as a possible causative agent of chronic thrombocytopenia. We investigated HCV infection in a series of 51 unselected Spanish patients with chronic acquired thrombocytopenia. Anti-HCV and HCV viraemia were detected in 13/51 (22.5%) of cases; this prevalence was particularly significant when compared with HCV seropositivity in age-matched controls (0.4%). Anti-HCV-positive patients, four men and nine women with a median age of 59.3 years (range 36-72), had a mean platelet count of 55.8 x 109/l (range 12-96). Only one of our HCV-positive thrombocytopenic patients had hypersplenism. Platelet-associated IgG (PAIgG) was negative, as measured by immunofluorescent flow cytometric analysis in 11/13 HCV-positive thrombocytopenic patients. Thus, thrombocytopenia in our HCV-positive patients appeared to be non-autoimmune mediated. In six patients, a trial of recombinant alpha2b-interferon (IFN-alpha) given at a dose of 3 MU three times per week for 6-24 months gave a durable (> 1 year) and significant increase in platelet count in all six patients. The maximum increase occurred after 6 months of IFN-alpha therapy. In conclusion, the ability of IFN-alpha to increase platelet counts in HCV-positive thrombocytopenic patients supports mechanisms involving a direct role for HCV inhibiting platelet production.

Mechanisms of thrombosis and cardiovascular complications in COVID-19

BACKGROUND

The novel coronavirus SARS-CoV-2, responsible for the 2019-2020 global (COVID-19) pandemic, is a respiratory virus associated with the development of thromboembolic complications and respiratory failure in severe cases. Increased risk of pulmonary embolism and thrombosis has been identified in COVID-19 patients, alongside accompanying elevations in potential prognostic biomarkers, including D-dimer, IL-6 and cardiac specific troponins. Our aim was to provide a scoping review of the available literature regarding thrombosis risk, other cardiovascular implications, and their biomarkers in COVID-19 to highlight potential disease mechanisms.

METHODS

Authors conducted a literature search in PubMed using MeSH headings "disseminated intravascular coagulation", "pulmonary embolism", "thromb*", "stroke", "myocardial infarction" and "acute lung injury", as well as terms "COVID-19", "SARS-CoV-2", "2019 novel coronavirus" and "2019-nCoV".

RESULTS AND CONCLUSIONS

COVID-19 disease is characterised by the interactions between hyperactive coagulation and complement systems - induced by hyper-inflammatory conditions, resulting in a pro-thrombotic state and diffuse tissue injury. There are several promising prognostic markers of disease severity, with D-dimer the most significant. The presence of thrombocytopenia appears to be a key indicator of patient deterioration. Further research is required to understand the underlying pathophysiology in COVID-19 and its implications in disease progression and patient management. Randomised trials are urgently needed to determine the safety of proposed therapeutic anticoagulation with heparin and the role for anti-platelet agents, such as Ticagrelor, in patient management.

Severe Fever with Thrombocytopenia Syndrome Virus Infection, South Korea, 2010

Severe fever with thrombocytopenia syndrome (SFTS) was reported in China in 2009 and in South Korea in 2012. We found retrospective evidence of SFTS virus infection in South Korea in 2010, suggesting that infections in South Korea occurred before previously reported and were more concurrent with those in China.