L-SIGN is a receptor on liver sinusoidal endothelial cells for SARS-CoV-2 virus.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a pandemic. Severe disease is associated with dysfunction of multiple organs, but some infected cells do not express ACE2, the canonical entry receptor for SARS-CoV-2. Here, we report that the C-type lectin receptor L-SIGN interacted in a Ca2+-dependent manner with high-mannose-type N-glycans on the SARS-CoV-2 spike protein. We found that L-SIGN was highly expressed on human liver sinusoidal endothelial cells (LSECs) and lymph node lymphatic endothelial cells but not on blood endothelial cells. Using high-resolution confocal microscopy imaging, we detected SARS-CoV-2 viral proteins within the LSECs from liver autopsy samples from patients with COVID-19. We found that both pseudo-typed virus enveloped with SARS-CoV-2 spike protein and authentic SARS-CoV-2 virus infected L-SIGN-expressing cells relative to control cells. Moreover, blocking L-SIGN function reduced CoV-2-type infection. These results indicate that L-SIGN is a receptor for SARS-CoV-2 infection. LSECs are major sources of the clotting factors vWF and factor VIII (FVIII). LSECs from liver autopsy samples from patients with COVID-19 expressed substantially higher levels of vWF and FVIII than LSECs from uninfected liver samples. Our data demonstrate that L-SIGN is an endothelial cell receptor for SARS-CoV-2 that may contribute to COVID-19-associated coagulopathy.

Age influences susceptibility of brain capillary endothelial cells to La Crosse virus infection and cell death.

BACKGROUND: A key factor in the development of viral encephalitis is a virus crossing the blood-brain barrier (BBB). We have previously shown that age-related susceptibility of mice to the La Crosse virus (LACV), the leading cause of pediatric arbovirus encephalitis in the USA, was associated with the ability of the virus to cross the BBB. LACV infection in weanling mice (aged around 3 weeks) results in vascular leakage in the olfactory bulb/tract (OB/OT) region of the brain, which is not observed in adult mice aged > 6-8 weeks. Thus, we studied age-specific differences in the response of brain capillary endothelial cells (BCECs) to LACV infection. METHODS: To examine mechanisms of LACV-induced BBB breakdown and infection of the CNS, we analyzed BCECs directly isolated from weanling and adult mice as well as established a model where these cells were infected in vitro and cultured for a short period to determine susceptibility to virus infection and cell death. Additionally, we utilized correlative light electron microscopy (CLEM) to examine whether changes in cell morphology and function were also observed in BCECs in vivo. RESULTS: BCECs from weanling, but not adult mice, had detectable infection after several days in culture when taken ex vivo from infected mice suggesting that these cells could be infected in vitro. Further analysis of BCECs from uninfected mice, infected in vitro, showed that weanling BCECs were more susceptible to virus infection than adult BCECs, with higher levels of infected cells, released virus as well as cytopathic effects (CPE) and cell death. Although direct LACV infection is not detected in the weanling BCECs, CLEM analysis of brain tissue from weanling mice indicated that LACV infection induced significant cerebrovascular damage which allowed virus-sized particles to enter the brain parenchyma. CONCLUSIONS: These findings indicate that BCECs isolated from adult and weanling mice have differential viral load, infectivity, and susceptibility to LACV. These age-related differences in susceptibility may strongly influence LACV-induced BBB leakage and neurovascular damage allowing virus invasion of the CNS and the development of neurological disease.

Postmortem examination of COVID-19 patients reveals diffuse alveolar damage with severe capillary congestion and variegated findings in lungs and other organs suggesting vascular dysfunction.

AIMS: Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has rapidly evolved into a sweeping pandemic. Its major manifestation is in the respiratory tract, and the general extent of organ involvement and the microscopic changes in the lungs remain insufficiently characterised. Autopsies are essential to elucidate COVID-19-associated organ alterations. METHODS AND RESULTS: This article reports the autopsy findings of 21 COVID-19 patients hospitalised at the University Hospital Basel and at the Cantonal Hospital Baselland, Switzerland. An in-corpore technique was performed to ensure optimal staff safety. The primary cause of death was respiratory failure with exudative diffuse alveolar damage and massive capillary congestion, often accompanied by microthrombi despite anticoagulation. Ten cases showed superimposed bronchopneumonia. Further findings included pulmonary embolism (n = 4), alveolar haemorrhage (n = 3), and vasculitis (n = 1). Pathologies in other organ systems were predominantly attributable to shock; three patients showed signs of generalised and five of pulmonary thrombotic microangiopathy. Six patients were diagnosed with senile cardiac amyloidosis upon autopsy. Most patients suffered from one or more comorbidities (hypertension, obesity, cardiovascular diseases, and diabetes mellitus). Additionally, there was an overall predominance of males and individuals with blood group A (81% and 65%, respectively). All relevant histological slides are linked as open-source scans in supplementary files. CONCLUSIONS: This study provides an overview of postmortem findings in COVID-19 cases, implying that hypertensive, elderly, obese, male individuals with severe cardiovascular comorbidities as well as those with blood group A may have a lower threshold of tolerance for COVID-19. This provides a pathophysiological explanation for higher mortality rates among these patients.

Epstein-Barr virus noncoding RNAs from the extracellular vesicles of nasopharyngeal carcinoma (NPC) cells promote angiogenesis via TLR3/RIG-I-mediated VCAM-1 expression.

Viral noncoding RNAs (Epstein-Barr virus-encoded RNAs, EBERs) are believed to play a critical role in the progression of lymphoma and nasopharyngeal carcinoma (NPC). However, the accurate mechanisms accounting for their oncogenic function have not been elucidated, especially in terms of interaction between tumor cells and mesenchymal cells. Here, we report that, in addition to NPC cells, EBERs are also found in endothelial cells in Epstein-Barr virus (EBV)-infected NPC parenchymal tissues, which implicates NPC-derived extracellular vesicles (EVs) in transmitting EBERs to endothelial cells. In support of this hypothesis, we first ascertained if EBERs could be transferred to endothelial cells via EVs isolated from NPC culture supernatant. Then, we clarified that EVs-derived EBERs could promote angiogenesis through stimulation of VCAM-1 expression. Finally, we explored the involvement of EBER recognition by TLR3 and RIG-I in NPC angiogenesis. Our observations collectively illustrate the significance and mechanism of EVs-derived EBERs in angiogenesis and underlie the interaction mechanisms between EBV-infected NPC cells and the tumor microenvironment.

Perforin inhibition protects from lethal endothelial damage during fulminant viral hepatitis.

CD8 T cells protect the liver against viral infection, but can also cause severe liver damage that may even lead to organ failure. Given the lack of mechanistic insights and specific treatment options in patients with acute fulminant hepatitis, we develop a mouse model reflecting a severe acute virus-induced CD8 T cell-mediated hepatitis. Here we show that antigen-specific CD8 T cells induce liver damage in a perforin-dependent manner, yet liver failure is not caused by effector responses targeting virus-infected hepatocytes alone. Additionally, CD8 T cell mediated elimination of cross-presenting liver sinusoidal endothelial cells causes endothelial damage that leads to a dramatically impaired sinusoidal perfusion and indirectly to hepatocyte death. With the identification of perforin-mediated killing as a critical pathophysiologic mechanism of liver failure and the protective function of a new class of perforin inhibitor, our study opens new potential therapeutic angles for fulminant viral hepatitis.

Zika Virus Persistence and Higher Viral Loads in Cutaneous Capillaries Than in Venous Blood.

We collected venous and capillary serum samples from 21 Zika virus‒infected patients on multiple days after symptom onset and found RNA load was higher and median duration of virus detection significantly longer in capillary than in venous blood. These findings raise questions about the role of the capillary compartment in virus transmission dynamics.

Postinfectious glomerulonephritis secondary to Erythrovirus B19 (Parvovirus B19): case report and review of the literature.

A previously healthy 32-yearold woman developed arterial hypertension, proteinuria, and hematuria (nephritic syndrome) with normal renal function and was diagnosed with post-infectious glomerulonephritis secondary to parvovirus B19 infection. The renal biopsy showed endocapillary glomerulonephritis, with positive IgG, C3, and C1q immunoreactivity in the capillary walls and ultrastructural evidence of subendothelial deposits. The diagnosis of parvovirus B19 infection was confirmed by IgG/IgM serological positivity and parvovirus DNA demonstration in both peripheral blood and kidney tissue. Glomerular involvement improved spontaneously. To be noted are the atypical signs and symptoms of our patient who, unlike previously reported cases, failed to show fever, skin rash, or affected relatives.

Transferrin Receptor 1 Facilitates Poliovirus Permeation of Mouse Brain Capillary Endothelial Cells.

As a possible route for invasion of the CNS, circulating poliovirus (PV) in the blood is believed to traverse the blood-brain barrier (BBB), resulting in paralytic poliomyelitis. However, the underlying mechanism is poorly understood. In this study, we demonstrated that mouse transferrin receptor 1 (mTfR1) is responsible for PV attachment to the cell surface, allowing invasion into the CNS via the BBB. PV interacts with the apical domain of mTfR1 on mouse brain capillary endothelial cells (MBEC4) in a dose-dependent manner via its capsid protein (VP1). We found that F-G, G-H, and H-I loops in VP1 are important for this binding. However, C-D, D-E, and E-F loops in VP1-fused Venus proteins efficiently penetrate MBEC4 cells. These results imply that the VP1 functional domain responsible for cell attachment is different from that involved in viral permeation of the brain capillary endothelium. We observed that co-treatment of MBEC4 cells with excess PV particles but not dextran resulted in blockage of transferrin transport into cells. Using the Transwell in vitro BBB model, transferrin co-treatment inhibited permeation of PV into MBEC4 cells and delayed further viral permeation via mTfR1 knockdown. With mTfR1 as a positive mediator of PV-host cell attachment and PV permeation of MBEC4 cells, our results indicate a novel role of TfR1 as a cellular receptor for human PV receptor/CD155-independent PV invasion of the CNS.

Capillaries in the olfactory bulb but not the cortex are highly susceptible to virus-induced vascular leak and promote viral neuroinvasion.

Viral neuroinvasion is a critical step in the pathogenesis of viral encephalitis. Multiple mechanisms of neuroinvasion have been identified, but their relative contribution to central nervous system (CNS) infection remains unclear for many viruses. In this study, we examined neuroinvasion of the mosquito-borne bunyavirus La Crosse (LACV), the leading cause of pediatric viral encephalitis in the USA. We found that the olfactory bulb (OB) and tract were the initial areas of CNS virus infection in mice. Removal of the OB reduced the incidence of LACV-induced disease demonstrating the importance of this area to neuroinvasion. However, we determined that infection of the OB was not due to axonal transport of virus from olfactory sensory neurons as ablation of these cells did not affect viral pathogenesis. Instead, we found that OB capillaries were compromised allowing leakage of virus-sized particles into the brain. Analysis of OB capillaries demonstrated specific alterations in cytoskeletal and Rho GTPase protein expression not observed in capillaries from other brain areas such as the cortex where leakage did not occur. Collectively, these findings indicate that LACV neuroinvasion occurs through hematogenous spread in specific brain regions where capillaries are prone to virus-induced activation such as the OB. Capillaries in these areas may be "hot spots" that are more susceptible to neuroinvasion not only for LACV, but other neurovirulent viruses as well.

Hantavirus interferon regulation and virulence determinants.

Hantaviruses predominantly replicate in primary human endothelial cells and cause 2 diseases characterized by altered barrier functions of vascular endothelium. Most hantaviruses restrict the early induction of interferon-ß (IFNß) and interferon stimulated genes (ISGs) within human endothelial cells to permit their successful replication. PHV fails to regulate IFN induction within human endothelial cells which self-limits PHV replication and its potential as a human pathogen. These findings, and the altered regulation of endothelial cell barrier functions by pathogenic hantaviruses, suggest that virulence is determined by the ability of hantaviruses to alter key signaling pathways within human endothelial cells. Our findings indicate that the Gn protein from ANDV, but not PHV, inhibits TBK1 directed ISRE, kB and IFNß induction through virulence determinants in the Gn cytoplasmic tail (GnT) that inhibit TBK1 directed IRF3 phosphorylation. Further studies indicate that in response to hypoxia induced VEGF, ANDV infection enhances the permeability and adherens junction internalization of microvascular and lymphatic endothelial cells. These hypoxia/VEGF directed responses are rapamycin sensitive and directed by mTOR signaling pathways. These results demonstrate the presence of at least two hantavirus virulence determinants that act on endothelial cell signaling pathways: one that regulates antiviral IFN signaling responses, and a second that enhances normal hypoxia-VEGF-mTOR signaling pathways to facilitate endothelial cell permeability. These findings suggest signaling pathways as potential targets for therapeutic regulation of vascular deficits that contribute to hantavirus diseases and viral protein targets for attenuating pathogenic hantaviruses.

Old World hantaviruses: aspects of pathogenesis and clinical course of acute renal failure.

Hantavirus-associated diseases represent emerging infections that are ranked in the highest priority group of communicable diseases for surveillance and epidemiological research. In the last years, several novel hantavirus species were described and the number of host reservoir species harboring hantaviruses is also increasing. Reports of cases with severe or atypical clinical courses become also more frequent. These facts raise more and more questions concerning host reservoir specificity, pathogenicity and molecular mechanism of pathogenesis. Hantavirus disease is characterized by vascular leakage due to increased capillary permeability. The infection manifests often in the lung (hantaviral cardiopulmonary syndrome; HCPS) or in the kidney (hemorrhagic fever with renal syndrome, HFRS). The underlying mechanisms of both syndromes are probably similar despite the difference in organ tropism. Characterization of hantaviral replication cycle and of patient-specific determinants will help to identify factors responsible for the clinical symptoms and course.

Hemorrhagic Fever with Renal Syndrome in the New, and Hantavirus Pulmonary Syndrome in the Old World: paradi(se)gm lost or regained?

Since the first clinical description in 1994 of the so-called "Hantavirus Pulmonary Syndrome" (HPS) as a "newly recognized disease", hantavirus infections have always been characterized as presenting in two distinct syndromes, the so-called "Hemorrhagic Fever with Renal Syndrome" (HFRS) in the Old World, with the kidney as main target organ, in contrast to HPS in the New World, with the lung as main target organ. However, European literature mentions already since 1934 a mostly milder local HFRS form, aptly named "nephropathia epidemica" (NE), and caused by the prototype European hantavirus species Puumala virus (PUUV). Several NE reports dating from the 1980s and early 1990s described already non-cardiogenic HPS-like lung involvement, prior to any kidney involvement, and increasing evidence is now mounting that a considerable clinical overlap exists between HPS and HFRS. Moreover, growing immunologic insights point to common pathologic mechanisms, leading to capillary hyperpermeability, the cardinal feature of all hantavirus infections, both of the New and Old World. It is now perhaps time to reconsider the paradigm of two "different" syndromes caused by viruses of the same Hantavirus genus in the same Bunyaviridae family, and to agree on a common, more logical disease denomination, such as simply and briefly "Hantavirus fever".

Endothelial cell permeability during hantavirus infection involves factor XII-dependent increased activation of the kallikrein-kinin system.

Hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS) are diseases caused by hantavirus infections and are characterized by vascular leakage due to alterations of the endothelial barrier. Hantavirus-infected endothelial cells (EC) display no overt cytopathology; consequently, pathogenesis models have focused either on the influx of immune cells and release of cytokines or on increased degradation of the adherens junction protein, vascular endothelial (VE)-cadherin, due to hantavirus-mediated hypersensitization of EC to vascular endothelial growth factor (VEGF). To examine endothelial leakage in a relevant in vitro system, we co-cultured endothelial and vascular smooth muscle cells (vSMC) to generate capillary blood vessel-like structures. In contrast to results obtained in monolayers of cultured EC, we found that despite viral replication in both cell types as well as the presence of VEGF, infected in vitro vessels neither lost integrity nor displayed evidence of VE-cadherin degradation. Here, we present evidence for a novel mechanism of hantavirus-induced vascular leakage involving activation of the plasma kallikrein-kinin system (KKS). We show that incubation of factor XII (FXII), prekallikrein (PK), and high molecular weight kininogen (HK) plasma proteins with hantavirus-infected EC results in increased cleavage of HK, higher enzymatic activities of FXIIa/kallikrein (KAL) and increased liberation of bradykinin (BK). Measuring cell permeability in real-time using electric cell-substrate impedance sensing (ECIS), we identified dramatic increases in endothelial cell permeability after KKS activation and liberation of BK. Furthermore, the alterations in permeability could be prevented using inhibitors that directly block BK binding, the activity of FXIIa, or the activity of KAL. Lastly, FXII binding and autoactivation is increased on the surface of hantavirus-infected EC. These data are the first to demonstrate KKS activation during hantavirus infection and could have profound implications for treatment of hantavirus infections.

Cutting edge: intravascular staining redefines lung CD8 T cell responses.

Nonlymphoid T cell populations control local infections and contribute to inflammatory diseases, thus driving efforts to understand the regulation of their migration, differentiation, and maintenance. Numerous observations indicate that T cell trafficking and differentiation within the lung are starkly different from what has been described in most nonlymphoid tissues, including intestine and skin. After systemic infection, we found that >95% of memory CD8 T cells isolated from mouse lung via standard methods were actually confined to the pulmonary vasculature, despite perfusion. A respiratory route of challenge increased virus-specific T cell localization within lung tissue, although only transiently. Removing blood-borne cells from analysis by the simple technique of intravascular staining revealed distinct phenotypic signatures and chemokine-dependent trafficking restricted to Ag-experienced T cells. These results precipitate a revised model for pulmonary T cell trafficking and differentiation and a re-evaluation of studies examining the contributions of pulmonary T cells to protection and disease.

The significance of renal C4d staining in patients with BK viruria, viremia, and nephropathy.

Peritubular capillary C4d staining in allograft kidney is an important criterion for antibody-mediated rejection. Whether BK virus infection can result in complement activation is not known. We studied 113 renal allograft biopsies from 52 recipients with a history of BK virus activation. The samples were classified into four groups according to the concurrent detection of BK virus DNA in urine, plasma, and/or biopsy: BK-negative (n=37), viruria (n=53), viremia (n=7), and nephropathy (n=16) groups. The histological semiquantitative peritubular capillary C4d scores in the viremia (0.3+/-0.8) and BK nephropathy (0.6+/-0.9) groups were lower than those in the BK-negative group (1.2+/-1.1, P=0.05 and P=0.06, respectively) and the viruria group (1.2+/-1.1, P=0.04 and P=0.06, respectively). Diffuse or focal peritubular capillary C4d staining was present in 9/76 (12%) and 14/76 (19%) of all samples with concurrent BK virus reactivation (viruria, viremia, and nephropathy). The diagnosis of antibody-mediated rejection could be established in 7/9 (78%) and 5/14 (36%) of these samples, respectively. Diffuse tubular basement membrane C4d staining was restricted to BK nephropathy cases (4/16, 25%). Semiquantitative tubular basement membrane C4d scores were higher in BK nephropathy (1.2+/-1.3) compared with BK-negative (0.05+/-0.3, P=0.017) and viruria (0.0+/-0.0, P=0.008) groups. Bowman's capsule C4d staining was more frequent in BK nephropathy (5/16) compared with the aforementioned groups (2/36 (P=0.023) and 4/51 (P=0.03), respectively). Within the BK nephropathy group, samples with tubular basement membrane stain had more infected tubular epithelial cells (12.1+/-7.6% vs 4.4+/-5.0%, P=0.03) and a trend toward higher interstitial inflammation scores. In conclusion, peritubular capillary C4d staining remains a valid marker for the diagnosis of antibody-mediated rejection in the presence of concurrent BK virus infection. A subset of biopsies with BK nephropathy shows tubular basement membrane C4d staining, which correlates with marked viral cytopathic effect.

Hepatitis C virus RNA quantitation in venous and capillary small-volume whole-blood samples.

Quantitation of hepatitis C virus (HCV) RNA in plasma and serum samples is a costly procedure in both time and reagents. Additionally, cell-associated viral RNA may not be detected. This study evaluated the accuracy of HCV RNA quantitation in small-volume whole-blood (WB) samples, which would be appropriate for point-of-care diagnostic devices. HCV RNA was extracted from 222 clinical plasma and WB samples of 82 patients with chronic hepatitis C by a specific locked nucleic acid-mediated capture method and quantified by real-time reverse transcription-PCR. The results were compared to the reference plasma viral load determined with the COBAS AmpliPrep/TaqMan (CAP/CTM) HCV test. This assay had an analytical sensitivity of 9 IU per 10-microl sample (95% limit of detection [95% LOD]), a linearity range of 500 to 5 x 10(6) IU/ml, and was accurate in testing 10 HCV subtypes (<0.22 log10 unit) in plasma. The assay was matrix equivalent for plasma and WB samples (coefficient of determination [R2] of 0.943) and had a specificity of 100% (n = 20) in WB samples. The HCV RNA concentration in clinical WB samples exceeded the estimated hematocrit-corrected plasma viral loads by 0.22 log10 unit, but absolute quantitation results in plasma and WB samples were identical (95% confidence interval, -0.06 to 0.04 log10 unit). The sensitivity in WB samples was 100% (n = 141) for plasma concentrations above the 95% LOD. Quantitation results in 10-microl WB samples correlated linearly with the CAP/CTM HCV plasma test results (R2 = 0.919; n = 140) and did not differ between capillary and venous samples (R2 = 0.960; n = 40). This study shows that HCV RNA quantitation in 10-microl WB samples is appropriate for monitoring viral loads of >900 IU/ml, although the use of WB does not increase the diagnostic sensitivity.

Neurodegeneration induced by PVC-211 murine leukemia virus is associated with increased levels of vascular endothelial growth factor and macrophage inflammatory protein 1 alpha and is inhibited by blocking activation of microglia.

PVC-211 murine leukemia virus (MuLV) is a neuropathogenic retrovirus that has undergone genetic changes from its nonneuropathogenic parent, Friend MuLV, that allow it to efficiently infect rat brain capillary endothelial cells (BCEC). To clarify the mechanism by which PVC-211 MuLV expression in BCEC induces neurological disease, we examined virus-infected rats at various times during neurological disease progression for vascular and inflammatory changes. As early as 2 weeks after virus infection and before any marked appearance of spongiform neurodegeneration, we detected vessel leakage and an increase in size and number of vessels in the areas of the brain that eventually become diseased. Consistent with these findings, the amount of vascular endothelial growth factor (VEGF) increased in the brain as early as 1 to 2 weeks postinfection. Also detected at this early disease stage was an increased level of macrophage inflammatory protein 1 alpha (MIP-1 alpha), a cytokine involved in recruitment of microglia to the brain. This was followed at 3 weeks postinfection by a marked accumulation of activated microglia in the spongiform areas of the brain accompanied by an increase in tissue plasminogen activator, a product of microglia implicated in neurodegeneration. Pathological observations at the end stage of the disease included loss of neurons, decreased myelination, and mild muscle atrophy. Treatment of PVC-211 MuLV-infected rats with clodronate-containing liposomes, which specifically kill microglia, significantly blocked neurodegeneration. Together, these results suggest that PVC-211 MuLV infection of BCEC results in the production of VEGF and MIP-1 alpha, leading to the vascular changes and microglial activation necessary to cause neurodegeneration.

Use of capillary blood samples as a new approach for diagnosis of Dengue virus infection.

We evaluated the use of capillary blood samples stored on filter papers for diagnosis of dengue virus infection. Venous and capillary blood samples were collected from 130 patients suspected of having dengue fever. We compared the performances of standard reference methods using capillary blood samples absorbed onto filter papers versus venous blood samples. The resulting sensitivity, specificity, and positive predictive value of tests performed on filter paper compared to those performed on venous blood samples were 81.6% (62/76; 95% confidence interval [CI], 74.9% to 88.3%), 90.7% (49/54; 95% CI, 85.7% to 95.7%), and 92.5% (62/67; 95% CI, 86.2% to 98.8%), respectively. During the acute phase of dengue virus infection (day 1 to day 4), the tests performed on capillary blood samples had a sensitivity of 88.5% (95% CI, 82.0% to 95.0%) and a specificity of 93.8% (95% CI, 88.9% to 98.7%). During the convalescent phase of infection, this method allowed the viral serotype to be determined for 4 of 15 (27%) dengue virus-infected patients for whom virological diagnosis using venous samples was negative. Capillary blood samples could therefore be a good alternative for the diagnosis of dengue virus infection in tropical areas. Indeed, these samples are convenient for storage and transport without the need for a cold chain and simplify the collection of samples from children. Moreover, our results suggest that viral particles persist longer in capillary blood than in peripheral blood. Analysis of the viability of viral particles under these conditions may give new insights into the physiopathology of dengue virus infection and the transmission of dengue virus during outbreaks.

Cytomegalovirus-associated pulmonary septal capillary injury sine inclusion body change: a distinctive cause of occult or macroscopic pulmonary hemorrhage in the immunocompetent host.

The authors describe four patients with symptomatic lung disease morphologically representing a septal capillary injury syndrome temporally associated with serologic and culture evidence of active cytomegalovirus (CMV) infection but without classic cytopathic changes. The authors conducted a thorough review of clinical data, microscopic examination, and in situ hybridization to detect CMV mRNA encoding immediate early protein. The assay detects transcripts that encode early and immediate early proteins. In two cases additional tissue was available for direct immunofluorescent studies. The disease process in each of the patients was morphologically indistinguishable from the pattern of organ injury associated with autoimmune diseases including a small vessel microvascular injury syndrome involving skin and lung and immune complex- mediated glomerulonephritis. Cytopenias were seen in all cases, most commonly thrombocytopenia. All treated patients demonstrated improvement on combined ganciclovir and low-dose steroid therapy. CMV infection may be of pathogenetic importance in some cases of alveolar hemorrhage, especially when accompanied by peripheral blood cytopenia in otherwise healthy patients and if clinical worsening occurs in the setting of a traditional immunosuppressive regimen typically used to treat vasculitis.