Deficient Generation of Spike-Specific Long-Lived Plasma Cells in the Bone Marrow After Severe Acute Respiratory Syndrome Coronavirus 2 Infection.

Generation of a stable long-lived plasma cell (LLPC) population is the sine qua non of durable antibody responses after vaccination or infection. We studied 20 individuals with a prior coronavirus disease 2019 infection and characterized the antibody response using bone marrow aspiration and plasma samples. We noted deficient generation of spike-specific LLPCs in the bone marrow after severe acute respiratory syndrome coronavirus 2 infection. Furthermore, while the regression model explained 98% of the observed variance in anti-tetanus immunoglobulin G levels based on LLPC enzyme-linked immunospot assay, we were unable to fit the same model with anti-spike antibodies, again pointing to the lack of LLPC contribution to circulating anti-spike antibodies.

Equine pegiviruses cause persistent infection of bone marrow and are not associated with hepatitis.

Pegiviruses frequently cause persistent infection (as defined by >6 months), but unlike most other Flaviviridae members, no apparent clinical disease. Human pegivirus (HPgV, previously GBV-C) is detectable in 1-4% of healthy individuals and another 5-13% are seropositive. Some evidence for infection of bone marrow and spleen exists. Equine pegivirus 1 (EPgV-1) is not linked to disease, whereas another pegivirus, Theiler's disease-associated virus (TDAV), was identified in an outbreak of acute serum hepatitis (Theiler's disease) in horses. Although no subsequent reports link TDAV to disease, any association with hepatitis has not been formally examined. Here, we characterized EPgV-1 and TDAV tropism, sequence diversity, persistence and association with liver disease in horses. Among more than 20 tissue types, we consistently detected high viral loads only in serum, bone marrow and spleen, and viral RNA replication was consistently identified in bone marrow. PBMCs and lymph nodes, but not liver, were sporadically positive. To exclude potential effects of co-infecting agents in experimental infections, we constructed full-length consensus cDNA clones; this was enabled by determination of the complete viral genomes, including a novel TDAV 3' terminus. Clone derived RNA transcripts were used for direct intrasplenic inoculation of healthy horses. This led to productive infection detectable from week 2-3 and persisting beyond the 28 weeks of study. We did not observe any clinical signs of illness or elevation of circulating liver enzymes. The polyprotein consensus sequences did not change, suggesting that both clones were fully functional. To our knowledge, this is the first successful extrahepatic viral RNA launch and the first robust reverse genetics system for a pegivirus. In conclusion, equine pegiviruses are bone marrow tropic, cause persistent infection in horses, and are not associated with hepatitis. Based on these findings, it may be appropriate to rename the group of TDAV and related viruses as EPgV-2.

Presence of Endogenous Viral Elements Negatively Correlates with Feline Leukemia Virus Susceptibility in Puma and Domestic Cat Cells.

While feline leukemia virus (FeLV) has been shown to infect felid species other than the endemic domestic cat host, differences in FeLV susceptibility among species has not been evaluated. Previous reports have noted a negative correlation between endogenous FeLV (enFeLV) copy number and exogenous FeLV (exFeLV) infection outcomes in domestic cats. Since felids outside the genus Felis do not harbor enFeLV genomes, we hypothesized absence of enFeLV results in more severe disease consequences in felid species lacking these genomic elements. We infected primary fibroblasts isolated from domestic cats (Felis catus) and pumas (Puma concolor) with FeLV and quantitated proviral and viral antigen loads. Domestic cat enFeLV env and long terminal repeat (LTR) copy numbers were determined for each individual and compared to FeLV viral outcomes. FeLV proviral and antigen levels were also measured in 6 naturally infected domestic cats and 11 naturally infected Florida panthers (P. concolor coryi). We demonstrated that puma fibroblasts are more permissive to FeLV than domestic cat cells, and domestic cat FeLV restriction was highly related to enFeLV-LTR copy number. Terminal tissues from FeLV-infected Florida panthers and domestic cats had similar exFeLV proviral copy numbers, but Florida panther tissues have higher FeLV antigen loads. Our work indicates that enFeLV-LTR elements negatively correlate with exogenous FeLV replication. Further, Puma concolor samples lacking enFeLV are more permissive to FeLV infection than domestic cat samples, suggesting that endogenization can play a beneficial role in mitigating exogenous retroviral infections. Conversely, presence of endogenous retroelements may relate to new host susceptibility during viral spillover events.IMPORTANCE Feline leukemia virus (FeLV) can infect a variety of felid species. Only the primary domestic cat host and related small cat species harbor a related endogenous virus in their genomes. Previous studies noted a negative association between the endogenous virus copy number and exogenous virus infection in domestic cats. This report shows that puma cells, which lack endogenous FeLV, produce more virus more rapidly than domestic cat fibroblasts following cell culture challenge. We document a strong association between domestic cat cell susceptibility and FeLV long terminal repeat (LTR) copy number, similar to observations in natural FeLV infections. Viral replication does not, however, correlate with FeLV env copy number, suggesting that this effect is specific to FeLV-LTR elements. This discovery indicates a protective capacity of the endogenous virus against the exogenous form, either via direct interference or indirectly via gene regulation, and may suggest evolutionary outcomes of retroviral endogenization.

Resistance to ectromelia virus infection requires cGAS in bone marrow-derived cells which can be bypassed with cGAMP therapy.

Cells sensing infection produce Type I interferons (IFN-I) to stimulate Interferon Stimulated Genes (ISGs) that confer resistance to viruses. During lympho-hematogenous spread of the mouse pathogen ectromelia virus (ECTV), the adaptor STING and the transcription factor IRF7 are required for IFN-I and ISG induction and resistance to ECTV. However, it is unknown which cells sense ECTV and which pathogen recognition receptor (PRR) upstream of STING is required for IFN-I and ISG induction. We found that cyclic-GMP-AMP (cGAMP) synthase (cGAS), a DNA-sensing PRR, is required in bone marrow-derived (BMD) but not in other cells for IFN-I and ISG induction and for resistance to lethal mousepox. Also, local administration of cGAMP, the product of cGAS that activates STING, rescues cGAS but not IRF7 or IFN-I receptor deficient mice from mousepox. Thus, sensing of infection by BMD cells via cGAS and IRF7 is critical for resistance to a lethal viral disease in a natural host.

Bone marrow haemophagocytosis indicates severe infection with severe acute respiratory syndrome coronavirus 2.

AIMS: Haemophagocytosis in the bone marrow of patients who have succumbed to coronavirus disease 19 (COVID-19) has not been widely studied. The aims of the present study were to perform morphological analyses and morphometry of haemophagocytosis in the bone marrow of patients with severe COVID-19, and to correlate the findings with the clinical course of the disease. METHODS AND RESULTS: In this single-centre study performed at the University Hospital Jena, bone marrow specimens of 15 deceased patients who had experienced a severe course of COVID-19 were sampled from the vertebral column during autopsy. Slides of the bone marrow were stained with routine stains or immunohistochemically, and further examined for haemophagocytosis by the use of light microscopy. To substantiate the morphological findings, additional slides were stained for CD163 and morphometry was performed. In all bone marrow samples, an increase in cellularity was found. Haemophagocytes with erythrophagocytosis were detected in 67% of the deceased patients. In tissues with low numbers of haemophagocytes or ill-defined haemophagocytes, an increase in iron deposits was frequently seen. Morphological findings were then correlated with several important clinical data, and the HScore (probability of having a reactive hemophagocytic syndrome) was calculated to posthumously confirm the diagnosis of secondary haemophagocytic lymphohistiocytosis. The median duration of disease and the hospitalisation time were lower in patients with haemophagocytosis (n = 10) than in patients without haemophagocytosis (n = 5). In addition, patients with haemophagocytes showed increased inflammatory parameters 2-5 days prior to death, in contrast to patients without haemophagocytes. CONCLUSIONS: Haemophagocytosis is a common finding in the bone marrow of deceased individuals with severe COVID-19, and may indicate fatal severe acute respiratory syndrome coronavirus 2 infections.

µ-Lat: A mouse model to evaluate human immunodeficiency virus eradication strategies.

A critical barrier to the development of a human immunodeficiency virus (HIV) cure is the lack of a scalable animal model that enables robust evaluation of eradication approaches prior to testing in humans. We established a humanized mouse model of latent HIV infection by transplanting "J-Lat" cells, Jurkat cells harboring a latent HIV provirus encoding an enhanced green fluorescent protein (GFP) reporter, into irradiated adult NOD.Cg-Prkdcscid Il2rgtm1Wjl /SzJ (NSG) mice. J-Lat cells exhibited successful engraftment in several tissues including spleen, bone barrow, peripheral blood, and lung, in line with the diverse natural tissue tropism of HIV. Administration of tumor necrosis factor (TNF)-α, an established HIV latency reversal agent, significantly induced GFP expression in engrafted cells across tissues, reflecting viral reactivation. These data suggest that our murine latency ("µ-Lat") model enables efficient determination of how effectively viral eradication agents, including latency reversal agents, penetrate, and function in diverse anatomical sites harboring HIV in vivo.

Hydroa Vacciniforme-like Lymphoproliferative disorder in an adult invades the liver and bone marrow with clear pathological evidence: a case report and literature review.

BACKGROUND: Hydroa Vacciniforme-like Lymphoproliferative Disorder (HV-LPD) is the name given to a group of Epstein-Barr virus (EBV)-associated diseases. It resembles hydroa vacciniforme (HV), the rarest form of photosensitivity, and is a T-cell disorder associated with an Epstein-Barr virus infection. The majority of diagnosed cases occur in East Asia and South America. It is rare in the United States and Europe. Multiple studies have revealed the clinical manifestation of an enlarged liver, but no gold standard such as pathology has yet supported this as a clinical sign of HV-LPD. CASE PRESENTATION: Here, we report a case of a 34-year-old Asian female with definite liver invasion. The patient had complained of a recurring facial rash for many years. The patient was admitted to the hospital because of an enlarged liver. After hospitalization, she was given an EB virus nucleic acid test. The EB virus nucleic acid test was positive, and pathological examination suggested that HV-LPD had invaded the skin, bone marrow, and liver. After being given antiviral treatment, the patient's symptoms were mitigated. CONCLUSIONS: Our case confirms the liver damage was caused by HV-LPD and the effectiveness of antiviral treatment.

Polyostotic osteosarcoma associated with avian leukosis virus infection in a captive bare-faced curassow (Crax fasciolata).

BACKGROUND: Osteosarcoma is a malignant mesenchymal bone tumor. Although it is a common tumor in the appendicular skeleton of dogs and cats, it is rarely reported in birds. Retroviruses are usually associated with solid tumor development in different avian species. CASE PRESENTATION: This report aims to describe a case of osteosarcoma associated with the avian leukosis virus in a captive bare-faced curassow (Crax fasciolata). A captive adult female bare-faced curassow presented with lameness, hyporexia, and a non-ulcerative and firm tumor in the right femur. The bird was euthanized due to the poor prognosis. Histopathology revealed an infiltrative mesenchymal neoplasm consisting of spindle cells with moderate cell pleomorphism, organized in bundles and interspersed by marked deposition of the osteoid matrix, which was compatible with osteosarcoma affecting both femur and tibiotarsus, with renal metastasis. Immunohistochemistry of the primary and metastatic tumor demonstrated vimentin expression by neoplastic cells. Samples of the neoplasm, bone marrow, and spleen were processed for PCR, which enabled the demonstration of proviral avian leukosis virus (ALV) DNA. CONCLUSIONS: To the best of our knowledge, this is the first report of an osteosarcoma in a bare-faced curassow with an unusual polyostotic manifestation and associated with ALV infection.

Mx1 in Hematopoietic Cells Protects against Thogoto Virus Infection.

Myxovirus resistance 1 (Mx1) is an interferon-induced gene that encodes a GTPase that plays an important role in the defense of mammalian cells against influenza A and other viruses. The Mx1 protein can restrict a number of viruses independently of the expression of other interferon-induced genes. Mx genes are therefore considered to be an important part of the innate antiviral immune response. However, the possible impact of Mx expression in the hematopoietic cellular compartment has not been investigated in detail in the course of a viral infection. To address this, we performed bone marrow chimera experiments using congenic B6.A2G Mx1+/+ and B6.A2G Mx1-/- mice to study the effect of Mx1 expression in cells of hematopoietic versus nonhematopoietic origin. Mx1+/+ mice were protected and Mx1-/- mice were susceptible to influenza A virus challenge infection, regardless of the type of bone marrow cells (Mx1+/+ or Mx1-/- ) the animals had received. Infection with Thogoto virus, however, revealed that Mx1-/- mice with a functional Mx1 gene in the bone marrow compartment showed reduced liver pathology compared with Mx1-/- mice that had been grafted with Mx1-/- bone marrow. The reduced pathology in these mice was associated with a reduction in Thogoto virus titers in the spleen, lung, and serum. Moreover, Mx1+/+ mice with Mx1-/- bone marrow failed to control Thogoto virus replication in the spleen. Mx1 in the hematopoietic cellular compartment thus contributes to protection against Thogoto virus infection.IMPORTANCE Mx proteins are evolutionarily conserved in vertebrates and can restrict a wide range of viruses in a cell-autonomous way. The contribution to antiviral defense of Mx1 expression in hematopoietic cells remains largely unknown. We show that protection against influenza virus infection requires Mx1 expression in the nonhematopoietic cellular compartment. In contrast, Mx1 in bone marrow-derived cells is sufficient to control disease and virus replication following infection with a Thogoto virus. This indicates that, in addition to its well-established antiviral activity in nonhematopoietic cells, Mx1 in hematopoietic cells can also play an important antiviral function. In addition, cells of hematopoietic origin that lack a functional Mx1 gene contribute to Thogoto virus dissemination and associated disease.

A proof of evidence supporting abnormal immunothrombosis in severe COVID-19: naked megakaryocyte nuclei increase in the bone marrow and lungs of critically ill patients.

Coronavirus disease 2019 (COVID-19) is a global public health emergency with many clinical facets, and new knowledge about its pathogenetic mechanisms is deemed necessary; among these, there are certainly coagulation disorders. In the history of medicine, autopsies and tissue sampling have played a fundamental role in order to understand the pathogenesis of emerging diseases, including infectious ones; compared to the past, histopathology can be now expanded by innovative techniques and modern technologies. For the first time in worldwide literature, we provide a detailed postmortem and biopsy report on the marked increase, up to 1 order of magnitude, of naked megakaryocyte nuclei in the bone marrow and lungs from serious COVID-19 patients. Most likely related to high interleukin-6 serum levels stimulating megakaryocytopoiesis, this phenomenon concurs to explain well the pulmonary abnormal immunothrombosis in these critically ill patients, all without molecular or electron microscopy signs of megakaryocyte infection.

Paradoxical myeloid-derived suppressor cell reduction in the bone marrow of SIV chronically infected macaques.

Myeloid derived suppressor cells (MDSCs), which suppress anti-tumor or anti-viral immune responses, are expanded in the peripheral blood and tissues of patients/animals with cancer or viral infectious diseases. We here show that in chronic SIV infection of Indian rhesus macaques, the frequency of MDSCs in the bone marrow (BM) was paradoxically and unexpectedly decreased, but increased in peripheral blood. Reduction of BM MDSCs was found in both CD14+MDSC and Lin-CD15+MDSC subsets. The reduction of MDSCs correlated with high plasma viral loads and low CD4+ T cell counts, suggesting that depletion of BM MDSCs was associated with SIV/AIDS disease progression. Of note, in SHIVSF162P4-infected macaques, which naturally control viral replication within a few months of infection, the frequency of MDSCs in the bone marrow was unchanged. To investigate the mechanisms by which BM MDSCs were reduced during chronic SIV infection, we tested several hypotheses: depletion due to viral infection, alterations in MDSC trafficking, and/or poor MDSC replenishment. We found that the possible mobilization of MDSCs from BM to peripheral tissues and the slow self-replenishment of MDSCs in the BM, along with the viral infection-induced depletion, all contribute to the observed BM MDSC reduction. We first demonstrate MDSC SIV infection in vivo. Correlation between BM CD14+MDSC reduction and CD8+ T cell activation in tissues is consistent with decreased immune suppression by MDSCs. Thus, depletion of BM MDSCs may contribute to the pathologic immune activation during chronic SIV infection and by extension HIV infection.

Aggressive large B-cell lymphoma triggered by a parvovirus B19 infection in a previously healthy child.

In absence of red blood cells disease or immune defect, parvovirus B19 (PVB-19) is usually considered as a benign condition. Here, we report the case of a 10-year-old boy, previously healthy, presenting with a PVB-19 infection revealed by a bicytopenia and a voluminous axillary adenopathy. Pathophysiology examination showed reactional lymphoid population. Nine months later and in the absence of remission, a new biopsy of the same adenopathy revealed a Hodgkin lymphoma with area of T-cell rich aggressive large B-cell lymphoma. This case suggests PVB-19 as potential trigger of this malignant childhood hemopathy. Although no definitive conclusion can be drawn, our clinical case questions the role of PVB-19 in lymphomagenesis.

Hodgkin lymphoma at Groote Schuur Hospital, South Africa: the effect of HIV and bone marrow infiltration.

Human immunodeficiency virus (HIV) is associated with an increased risk of developing Hodgkin lymphoma (HL). South Africa (SA) has the highest HIV prevalence rate in the world. There is currently no outcome-based data for HIV-associated HL from SA. A bone marrow database was compiled of all bone marrow biopsies (BMB) reported at National Health Laboratory Service (NHLS) Groote Schuur Hospital (GSH) between January 2005 and December 2012. Patients who had a BMB performed for staging of HL or where HL was diagnosed on the BMB were included for further analysis. Clinical and laboratory data was extracted from medical and laboratory records. Primary outcome measures included histological subtype, bone marrow infiltration (BMI) by HL, CD4 count, HIV-viral load (HIV-VL), tuberculosis (TB) data, treatment with chemotherapy and 5-year overall survival (OS). The database included 6569 BMB and 219 patients of these had HL and were included for analysis. The median age at presentation (32 years) was similar in the HIV+ and HIV- populations. While males predominated in the HIV- group, females predominated in the HIV+ group (male:female ratio of 1.5:1 vs 0.7:1, respectively). The majority of patients (71%) were HIV negative (HIV-) and 29% were HIV positive (HIV+). The diagnosis of HL was made on BMB in 17% of cases. BMI was seen in 37% (82/219) overall, and was found in more HIV+ patients (61%; 39/64) than HIV- patients (28%; 43/155; p = 0.03). The histological subtype varied according to HIV status with nodular sclerosis classical Hodgkin lymphoma (NSCHL) being most frequent in the HIV- group and classical Hodgkin lymphoma (CHL)-unclassifiable the most frequent in the HIV+ group. HIV+ patients had a median CD4 count of 149 × 106/L and 39% were anti-retroviral therapy (cART) naive at HL diagnosis. HIV+ patients had received anti-TB therapy more frequently than HIV- patients (72% vs 17%; p = 0.007). More HIV+ patients did not receive chemotherapy than HIV- patients (31% vs 3%; p = 0.001). The 5-year OS was 56%. HIV+ patients with BMI had a 5-year OS of 18%. BMI, HIV status, low CD4 count, histological subtype and TB therapy had a statistical significant impact on 5-year OS (p < 0.01). The 5-year OS was 56%, with both BMI and HIV+ status being associated with poor survival. BMB provided the diagnosis of HL in 17% of cases, confirming its diagnostic utility in our setting. Our cohort showed similar survival outcomes to other countries in Africa, Asia and Central America with comparable socio-economic constraints to SA.

Hemophagocytic syndrome in patients living with HIV: a retrospective study.

Various infectious diseases can hyper-stimulate the immune system, causing hemophagocytic syndrome (HPS). Little is known regarding the accuracy of diagnostic criteria and epidemiological triggering factors in the acquired immunodeficiency syndrome (AIDS) setting. We investigated the major infectious disease triggers of HPS in patients living with human immunodeficiency virus (HIV)/AIDS and determined the accuracy of bone marrow aspiration (BMA). The inclusion criteria were (i) confirmed HIV diagnosis, (ii) bone marrow aspiration, and (iii) a minimum of four HPS criteria. Patients were further classified into those with four presumed HPS criteria, or ≥ 5 confirmed criteria. The disease triggers, accuracy of bone marrow aspiration, and prognosis markers were examined. Presumed HPS was observed in 15/36 patients (41%), and confirmed HPS in 58% (n = 21). The major etiological triggers were infection with Mycobacterium (34%), Cytomegalovirus (14%), Cryptococcus neoformans (11%), and hematological or tumoral disease (11%). BMA demonstrated 93% specificity on screening diagnosis (odds ratio [OR] 12.7, 95% confidence interval [CI] 1.4-115.1, P = 0.01). Ferritin > 5000 ng/mL correlated with probability of death in univariate analysis (OR 6.00, 95% CI 1.33-27.05, P = 0.02). Ferritin performance as test of death probability presented area under the curve as 0.74 (95% CI 0.56-0.91, P = 0.016). However, neither cluster of differentiation for lymphocyte count nor HIV viral load correlated with patient deaths. Mycobacterium spp. and Cytomegalovirus were the main factors triggering HPS, followed by Cryptococcus neoformans, and hematological and tumoral diseases. High ferritin levels were associated with increased death probability. High specificity was noted with BMA.

Fatal parvovirus B19 infections: a report of two autopsy cases.

Parvovirus B19 (PVB19) commonly infects children and is usually asymptomatic. Lethal outcomes of PVB19 infection are unusual; nevertheless, the two cases reported here are rare examples of PVB19-induced hemophagocytic syndrome and myocarditis in infants and children. The two cases show the indisputable usefulness of immunohistochemistry and in situ hybridization in the detection of PVB19. In the death investigations, histopathological examinations provided stronger evidence than did serology or molecular biology. The cases also highlight the importance of forensic autopsy in vaccine-related death. As vaccine-related deaths are what people fear and may cause declines in vaccination rates, it is important to clarify deaths temporally or causally associated with vaccine administration.

Severe rhabdomyolysis associated with severe fever with thrombocytopenia syndrome in a married couple: a case report.

BACKGROUND: Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne infection that has recently emerged. This infectious disease is due to the transfer of SFTS virus (SFTSV) from the infected blood of animals to humans. Approximately 30% of patients who are infected with SFTS die from multiorgan failure associated with severe infection, systemic inflammatory response syndrome, or disseminated intravascular coagulation. We treated an elderly Japanese couple (husband and wife) who had genetically identical SFTSV infections and who both developed severe rhabdomyolysis. CASE PRESENTATION: An 80-year-old man presented to the clinic with a fever; his 74-year-old wife presented with a fever 9 days later. Their laboratory results at diagnosis showed severe rhabdomyolysis with significantly elevated creatinine kinase (detected levels: husband, 9546 U/L; wife, 15,933 U/L). The creatinine kinase isozyme was 100% MM type in both patients. In both the husband and wife, SFTSV was identified with real-time polymerase chain reaction analysis. The detected SFTSVs in both the husband and wife were identical according to the genome sequence analysis. The husband's bone marrow indicated macrophage activation syndrome, but he responded to supportive therapy. He was discharged after being hospitalized for 32 days. The wife was admitted to our hospital in critical condition 2 days after SFTS symptom onset. She died of multiorgan failure 8 days after onset, despite being cared for in an intensive care unit. Both of the patients presented with rhabdomyolysis following SFTS symptom onset. The patients' clinical outcomes were different from each other; i.e., the husband survived, and the wife died. CONCLUSIONS: SFTSV infection-associated rhabdomyolysis has been reported in one patient, and simultaneous onset in two related patients has not been described previously. Our findings suggest that similar biological responses occurred, but they resulted in different clinical outcomes in the patients infected by the identical SFTSV isolates. Notably, a patient's clinical outcome depends on their own immune response. We suggest that one component of viral rhabdomyolysis involves immune-mediated responses. Severe immunological responses may adversely affect the treatment outcome, as demonstrated by the wife's clinical course. Our findings demonstrate that a patient's immune response contributes to their prognosis following SFTSV infection.

Comparative measurement of FeLV load in hemolymphatic tissues of cats with hematologic cytopenias.

BACKGROUND: Feline leukemia virus (FeLV) is a serious viral infection in cats. FeLV is found in some tissues, such as spleen, lymph nodes and epithelial tissues. However, there is controversy about the organ in which the virus can be reliably detected in infected cats. The purpose of this study was to determine the level of viral infection in hemolymphatic tissues, including blood, bone marrow and spleen by reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR). RESULTS: A total of 31 cats with clinical signs of FeLV infection associated with at least a single lineage hematologic cytopenia were included in this study. Peripheral blood, bone marrow and spleen samples were obtained from each cat. Complete blood counts, biochemical tests, and a rapid test to detect FeLV p27 antigen in blood samples of cats were performed. Of 31 cats, 9 had anemia alone, 4 had thrombocytopenia alone, 2 had neutropenia alone, 9 had bicytopenia of anemia and thrombocytopenia, 3 had bicytopenia of anemia and neutropenia, and 4 had pancytopenia. FeLV RNA was then detected by RT-qPCR in the whole blood, bone marrow and spleen. Viral RNA copy numbers were detected in all cats by RT-qPCR whereas 24 out of 31 cats were positive for the serum FeLV antigen. We detected a significantly greater number of viral RNA in the spleen compared with the whole blood and bone marrow. CONCLUSION: Spleen is a site where FeLV is most frequently detected in cats with hematologic cytopenias.

EBV-encoded RNA1-positive cells in the bone marrow specimens of patients with EBV-negative lymphomas and sarcomas.

Epstein-Barr virus (EBV) infection is associated with pathogenesis of various cancers, including extranodal natural killer/T-cell lymphoma, nasal type (ENKL). ENKL tumor cells are positive for EBV-encoded RNA1 (EBER1), which is the most useful marker to identify ENKL tumor cells in histopathology. Currently, EBER1 in situ hybridization (ISH) is recommended to evaluate bone marrow (BM) involvement of ENKL. However, the actual burden of EBER1-positive cells in normal BM specimens remains unclear. In the present study, we performed EBER1 ISH on 111 BM specimens, which were obtained during an initial staging procedure in patients with EBV-negative cancers and were also negative for BM involvement. One or more EBER1-positive cells per whole specimen were observed in 38 specimens (34%). The number of EBER1-positive cells was distributed as follows: single positive cell, n = 17; two positive cells, n = 13; three positive cells, n = 3; and four positive cells, n = 5. These findings suggest that four or fewer EBER1-positive cells can be observed in BM specimens of patients with non-EBV-related cancers. The clinical implications of a small number of EBER1-positive cells in BM specimens of patients with ENKL should be evaluated in further studies.

Pathogenicity of Ebola and Marburg Viruses Is Associated With Differential Activation of the Myeloid Compartment in Humanized Triple Knockout-Bone Marrow, Liver, and Thymus Mice.

Ebola virus (EBOV) and Marburg virus (MARV) outbreaks are highly lethal, and infection results in a hemorrhagic fever with complex etiology. These zoonotic viruses dysregulate the immune system to cause disease, in part by replicating within myeloid cells that would normally innately control viral infection and shape the adaptive immune response. We used triple knockout (TKO)-bone marrow, liver, thymus (BLT) humanized mice to recapitulate the early in vivo human immune response to filovirus infection. Disease severity in TKO-BLT mice was dissimilar between EBOV and MARV with greater severity observed during EBOV infection. Disease severity was related to increased Kupffer cell infection in the liver, higher levels of myeloid dysfunction, and skewing of macrophage subtypes in EBOV compared with MARV-infected mice. Overall, the TKO-BLT model provided a practical in vivo platform to study the human immune response to filovirus infection and generated a better understanding of how these viruses modulate specific components of the immune system.

A patient with severe fever with thrombocytopenia syndrome and hemophagocytic lymphohistiocytosis-associated involvement of the central nervous system.

Severe fever with thrombocytopenia syndrome (SFTS), a severe infectious disease caused by novel bunyavirus, SFTS virus (SFTSV), is endemic to China, Korea, and Japan. Most SFTS patients show abnormalities in consciousness. Pathological findings in the central nervous system (CNS) of SFTS patients are not reported. A 53-year-old Japanese man was admitted to Uwajima City Hospital with an 8-day history of fever and diarrhea. Laboratory tests revealed leukopenia, thrombocytopenia, and liver enzyme elevation. He was diagnosed as having severe fever with thrombocytopenia syndrome (SFTS) following detection of the SFTSV genome in his blood. Bone marrow aspiration revealed hemophagocytic lymphohistiocytosis. He suffered progressive CNS disturbance and died on day 13 from onset of first symptoms. The SFTSV genome load in blood and levels of certain cytokines increased over the disease course. Necrotizing lymphadenitis with systemic lymphoid tissues positive for nucleocapsid protein (NP) of SFTSV was revealed by immunohistochemical (IHC) analysis. SFTSV-NP-positive immunoblasts were detected in all organs examined, including the CNS, and in the vascular lumina of each organ. Parenchymal cells of all organs examined were negative for SFTSV-NP on IHC analysis. Microscopic examination of the pons showed focal neuronal cell degeneration with hemosiderin-laden macrophages around extended microvessels with perivascular inflammatory cell infiltration and intravascular fibrin deposition. Autopsy confirmed this patient with SFTS was positive for systemic hemophagocytic lymphohistiocytosis including in the CNS. This patient's neurological abnormalities may have been caused by both functional and organic abnormalities. These novel findings provide important insights into the pathophysiology of SFTS.