Oropouche orthobunyavirus infection is mediated by the cellular host factor Lrp1

Oropouche orthobunyavirus (OROV; Peribunyaviridae) is a mosquito-transmitted virus that causes widespread human febrile illness in South America, with occasional progression to neurologic effects. Host factors mediating the cellular entry of OROV are undefined. Here, we show that OROV uses the host protein low-density lipoprotein–related protein 1 (Lrp1) for efficient cellular infection. Cells from evolutionarily distinct species lacking Lrp1 were less permissive to OROV infection than cells with Lrp1. Treatment of cells with either the high-affinity Lrp1 ligand receptor-associated protein (RAP) or recombinant ectodomain truncations of Lrp1 significantly reduced OROV infection. In addition, chimeric vesicular stomatitis virus (VSV) expressing OROV glycoproteins (VSV-OROV) bound to the Lrp1 ectodomain in vitro. Furthermore, we demonstrate the biological relevance of the OROV-Lrp1 interaction in a proof-of-concept mouse study in which treatment of mice with RAP at the time of infection reduced tissue viral load and promoted survival from an otherwise lethal infection. These results with OROV, along with the recent finding of Lrp1 as an entry factor for Rift Valley fever virus, highlight the broader significance of Lrp1 in cellular infection by diverse bunyaviruses. Shared strategies for entry, such as the critical function of Lrp1 defined here, provide a foundation for the development of pan-bunyaviral therapeutics.

Bunyaviruses are a large group of related viruses with single-stranded, segmented, negative, or ambisense RNA genomes (1, 2). Within the order Bunyavirales, the Peribunyaviridae family contains viruses that infect humans and animals with confirmed or potential zoonotic transmission (2, 3). Oropouche virus (OROV; Orthobunyavirus genus; Simbu serogroup) is found primarily in the South American regions of Brazil, Trinidad, Peru, Panama, and Tobago (4). OROV has caused more than 30 epidemics, resulting in excess of 500,000 total cases of human febrile illness, making it the second most common arboviral disease in Brazil, behind Dengue fever (4–6). The true case number is likely higher as clinical testing for OROV is lacking and patients are often misdiagnosed as having Chikungunya or Dengue fevers (4). The arthropod vectors for OROV include Culicoides midges and Culex mosquitoes. In humans, OROV causes a febrile illness that manifests as fever, intense headache, myalgia, joint pain, retro-orbital pain, and photophobia, which can further develop into encephalitis or meningitis (5–7). Systemic infection manifests as rash, nausea, vomiting, and diarrhea. Viremia and leukopenia are common features (6), and virus can be detected in the cerebrospinal fluid (8, 9). In mice, the virus replicates in the liver and spleen after either subcutaneous or intracerebral infection (10).Due to the broad cellular tropism and ability to infect a variety of species, bunyaviruses are thought to use multiple receptors or attachment factors for entry and/or a protein that is widely expressed across different tissues and conserved across species. Recently, using a CRISPR-Cas9 screen, the conserved host protein low-density lipoprotein receptor (LDLR)-related protein-1 (Lrp1) was reported to mediate cellular infection with Rift Valley fever virus (RVFV), a phlebovirus within the Bunyavirales order (11). Lrp1 (also known as alpha-2-macroglobulin receptor or CD91) is a highly conserved multifunctional member of the LDLR family of transmembrane surface proteins. Lrp1 is important for ligand endocytosis, cell signaling, lipoprotein metabolism, blood–brain barrier maintenance, and angiogenesis (12–15). Homozygous deletion of Lrp1 is embryonically lethal in mice (16), further supporting the critical nature of Lrp1 in homeostatic functions.The M segment of Bunyavirales encodes the surface glycoproteins Gn and Gc, which form heterodimers and multimerize on the surface of the virion. Few studies have been conducted on the binding and entry mechanisms facilitated by OROV Gn/Gc. Given the conserved nature of Lrp1 across taxonomically distinct species and its expression in different tissues, we investigated whether OROV, a bunyavirus distantly related to RVFV, also requires Lrp1 for efficient infection of host cells. Despite having a similar genome organization among members of the Bunyavirales, many of the virally encoded sequences show little sequence homology. Therefore, studies to define similar host protein usage by these two distantly related viruses would have significant implications for pan-bunyavirus therapeutic and diagnostic development.Here, we used Lrp1 knockout (KO) cell lines to show that OROV infection is decreased compared to parental cells expressing Lrp1. Pretreatment of cells with varying concentrations of the high-affinity Lrp1-binding protein receptor-associated protein (RAP) significantly reduced OROV infection. Zika virus (ZIKV), an arbovirus outside the Bunyavirales order, was unaffected by the loss of Lrp1 or by treatment with Lrp1-binding RAP. Chimeric virions expressing OROV glycoproteins bound to the Lrp1 ectodomain. Finally, the role of Lrp1 in OROV infection was validated in vivo, whereby RAP treatment was able to reduce viral tissue titers and rescue mice from lethal intracerebral infection with OROV. Based on our findings, Lrp1 is a host factor for multiple bunyaviruses, presenting a potential therapeutic approach to address this important group of emerging arboviruses. This work also paves the way for future studies to understand the mechanism of OROV binding to Lrp1.     

Central Nervous System Involvement in Hepatitis C Virus Infection

Hepatic encephalopathy is the most obvious neurological consequence of chronic hepatitis C virus (HCV) infection. There are also case reports of HCV-associated cerebral vasculitis. This review is concerned with the possibility of an effect of HCV on cerebral dysfunction, occurring at an early stage of chronic infection, prior to the development of cirrhosis and unrelated to vasculitis. There is emerging evidence of mild, but significant neurocognitive impairment in HCV infection, which cannot be attributed to substance abuse, coexistent depression, or hepatic encephalopathy. In vivo magnetic resonance spectroscopy and neurophysiological studies have suggested that a biological mechanism may underlie these cognitive findings. The recent detection of HCV genetic sequences in postmortem brain tissue raises the intriguing possibility that HCV infection of the central nervous system may be related to the reported neuropsychological symptoms and cognitive impairment.     

The Pathogenesis of Saffold Virus in AG129 Mice and the Effects of Its Truncated L Protein in the Central Nervous System

Saffold Virus (SAFV) is a human cardiovirus that has been suggested to cause severe infection of the central nervous system (CNS). Compared to a similar virus, Theiler’s murine encephalomyelitis virus (TMEV), SAFV has a truncated Leader (L) protein, a protein essential in the establishment of persistent CNS infections. In this study, we generated a chimeric SAFV by replacing the L protein of SAFV with that of TMEV. We then compared the replication in cell cultures and pathogenesis in a mouse model. We showed that both SAFV and chimeric SAFV are able to infect Vero and Neuro2a cells well, but only chimeric SAFV was able to infect RAW264.7. We then showed that mice lacking IFN-α/β and IFN-γ receptors provide a good animal model for SAFV infection, and further identified the locality of the infection to the ventral horn of the spine and several locations in the brain. Lastly, we showed that neither SAFV nor chimeric SAFV causes persistence in this model. Overall, our results provide a strong basis on which the mechanisms underlying Saffold virus induced neuropathogenesis can be further studied and, hence, facilitating new information about its pathogenesis.     

Immune Responses to West Nile Virus Infection in the Central Nervous System

West Nile virus (WNV) continues to cause outbreaks of severe neuroinvasive disease in humans and other vertebrate animals in the United States, Europe, and other regions of the world. This review discusses our understanding of the interactions between virus and host that occur in the central nervous system (CNS), the outcome of which can be protection, viral pathogenesis, or immunopathogenesis. We will focus on defining the current state of knowledge of WNV entry, tropism, and host immune response in the CNS, all of which affect the balance between injury and successful clearance.     

Rabies Virus Populations in Humans and Mice Show Minor Inter-Host Variability within Various Central Nervous System Regions and Peripheral Tissues

Rabies virus (RABV) has a broad host range and infects multiple cell types throughout the infection cycle. Next-generation sequencing (NGS) and minor variant analysis are powerful tools for studying virus populations within specific hosts and tissues, leading to novel insights into the mechanisms of host-switching and key factors for infecting specific cell types. In this study we investigated RABV populations and minor variants in both original (non-passaged) samples and in vitro-passaged isolates of various CNS regions (hippocampus, medulla oblongata and spinal cord) of a fatal human rabies case, and of multiple CNS and non-CNS tissues of experimentally infected mice. No differences in virus populations were detected between the human CNS regions, and only one non-synonymous single nucleotide polymorphism (SNP) was detected in the fifth in vitro passage of virus isolated from the spinal cord. However, the appearance of this SNP shows the importance of sequencing newly passaged virus stocks before further use. Similarly, we did not detect apparent differences in virus populations isolated from different CNS and non-CNS tissues of experimentally infected mice. Sequencing of viruses obtained from pharyngeal swab and salivary gland proved difficult, and we propose methods for improving sampling.     

Leukemia in the Central Nervous System

ABSTRACT The frequency of central nervous system (CNS) leukemia was studied in patients aged 15–59 with acute leukemia, who had received induction treatment in the years 1971–1986. Twelve out of 103 patients with acute lymphoblastic leukemia (ALL) developed CNS leukemia in spite of prophylaxis consisting of intrathecal methotrexate. Ten out of 217 patients with acute myelogenous leukemia (AML) developed CNS leukemia. None had been given preventive treatment. Leukemic blasts with either M4 or M5 morphology appeared to increase the risk of CNS relapse. Treatment was adjusted to the clinical problem of each patient, but always included intrathecal methotrexate. Median survival after a diagnosis of CNS leukemia was 8 and 6 months in ALL and AML respectively, with bone marrow failure due to hematologic relapse as the leading cause of death. CNS leukemia, if properly treated, does probably not shorten survival. An active approach to diagnosis and treatment is therefore mandatory.     

Orthobunyaviruses: From Virus Binding to Penetration into Mammalian Host Cells

With over 80 members worldwide, Orthobunyavirus is the largest genus in the Peribunyaviridae family. Orthobunyaviruses (OBVs) are arthropod-borne viruses that are structurally simple, with a trisegmented, negative-sense RNA genome and only four structural proteins. OBVs are potential agents of emerging and re-emerging diseases and overall represent a global threat to both public and veterinary health. The focus of this review is on the very first steps of OBV infection in mammalian hosts, from virus binding to penetration and release of the viral genome into the cytosol. Here, we address the most current knowledge and advances regarding OBV receptors, endocytosis, and fusion.     

Molecular Mechanism and Role of Japanese Encephalitis Virus Infection in Central Nervous System-Mediated Diseases

The Japanese encephalitis virus (JEV) is the most common cause of neurodegenerative disease in Southeast Asia and the Western Pacific region; approximately 1.15 billion people are at risk, and thousands suffer from permanent neurological disorders across Asian countries, with 10–15 thousand people dying each year. JEV crosses the blood-brain barrier (BBB) and forms a complex with receptors on the surface of neurons. GRP78, Src, TLR7, caveolin-1, and dopamine receptor D2 are involved in JEV binding and entry into the neurons, and these receptors also play a role in carcinogenic activity in cells. JEV binds to GRP78, a member of the HSP70 overexpressed on malignant cells to enter neurons, indicating a higher chance of JEV infection in cancer patients. However, JEV enters human brain microvascular endothelial cells via an endocytic pathway mediated by caveolae and the ezrin protein and also targets dopamine-rich areas for infection of the midbrain via altering dopamine levels. In addition, JEV complexed with CLEC5A receptor of macrophage cells is involved in the breakdown of the BBB and central nervous system (CNS) inflammation. CLEC5A-mediated infection is also responsible for the influx of cytokines into the CNS. In this review, we discuss the neuronal and macrophage surface receptors involved in neuronal death.     

Kallikrein-Kinins in the Central Nervous System

We studied whether the components of the kallikrein-kinin system are present in the central nervous system. We found that human cerebrospinal fluid (CSF) contains free kinins: 53 ± 15 pg/ml; kininogen: 10.9 ± 2.1 ng kinin equivalent/ml, and kininogenase activity: 5.0 ± 2.1 ng kinins/ml/minute. Kininogenase activity was 2–3 fold augmented by preincubation with trypsin. Soybean trypsin inhibitor completely inhibited untreated CSF and partially inhibited trypsin activated kininogenase. Kininogenase activity and immunoreactive glandular kallikrein were present in rat brain, and their concentrations in hypothalamus is several-fold higher than in cortex, pons-medulla, basal ganglia and cerebellum. In the hypophysis, activity in pars-intermedia was between 6- and 20-fold higher than in posterior and anterior hypophysis, respectively. High activity was also found in the pineal gland. The kallikrein-kinin system is present in the central nervous system where it may participate in modulation of nervous and neuroendocrine functions.     

Human Brain Organoids as Models for Central Nervous System Viral Infection

Pathogenesis of viral infections of the central nervous system (CNS) is poorly understood, and this is partly due to the limitations of currently used preclinical models. Brain organoid models can overcome some of these limitations, as they are generated from human derived stem cells, differentiated in three dimensions (3D), and can mimic human neurodevelopmental characteristics. Therefore, brain organoids have been increasingly used as brain models in research on various viruses, such as Zika virus, severe acute respiratory syndrome coronavirus 2, human cytomegalovirus, and herpes simplex virus. Brain organoids allow for the study of viral tropism, the effect of infection on organoid function, size, and cytoarchitecture, as well as innate immune response; therefore, they provide valuable insight into the pathogenesis of neurotropic viral infections and testing of antivirals in a physiological model. In this review, we summarize the results of studies on viral CNS infection in brain organoids, and we demonstrate the broad application and benefits of using a human 3D model in virology research. At the same time, we describe the limitations of the studies in brain organoids, such as the heterogeneity in organoid generation protocols and age at infection, which result in differences in results between studies, as well as the lack of microglia and a blood brain barrier.     

Using CSF Proteomics to Investigate Herpesvirus Infections of the Central Nervous System

Herpesviruses have complex mechanisms enabling infection of the human CNS and evasion of the immune system, allowing for indefinite latency in the host. Herpesvirus infections can cause severe complications of the central nervous system (CNS). Here, we provide a novel characterization of cerebrospinal fluid (CSF) proteomes from patients with meningitis or encephalitis caused by human herpes simplex virus 1 (HSV-1), which is the most prevalent human herpesvirus associated with the most severe morbidity. The CSF proteome was compared with those from patients with meningitis or encephalitis due to human herpes simplex virus 2 (HSV-2) or varicella-zoster virus (VZV, also known as human herpesvirus 3) infections. Virus-specific differences in CSF proteomes, most notably elevated 14-3-3 family proteins and calprotectin (i.e., S100-A8 and S100-A9), were observed in HSV-1 compared to HSV-2 and VZV samples, while metabolic pathways related to cellular and small molecule metabolism were downregulated in HSV-1 infection. Our analyses show the feasibility of developing CNS proteomic signatures of the host response in alpha herpes infections, which is paramount for targeted studies investigating the pathophysiology driving virus-associated neurological disorders, developing biomarkers of morbidity, and generating personalized therapeutic strategies.     

Regulation of Angiotensinogen in the Central Nervous System

Several interventions known to alter plasma renin substrate in rats such as nephrectomy (NX), adrenalectomy (ADX) and glucocorticoid treatment changed the angiotensinogen content in the cerebrospinal fluid (CSF) in the same direction. However, peripheral and central angiotensinogen could be dissociated from each other by ADX and NX in combination, as well as by chronic converting enzyme blockade.

The regulation of brain angiotensinogen was further investigated in stroke-prone spontaneously hypertensive rats (SHR-sp) in comparison with normotensive Wistar Kyoto (WKY) rats. The angiotensinogen levels of the anterior hypothalamus and of the septal area showed strain and age-related differences. Chronic converting enzyme blockade, which kept SHR-sp normotensive, stimulated angiotensinogen in the anterior hypothalamus of both SHR-sp and WKY rats, but suppressed plasma renin substrate. A specific radioimmunoassay (RIA) for renin substrate of rat     

肾上腺髓质素在中枢神经系统内的分布

目的研究肾上腺髓质素（ＡｄＭ）在中枢神经系统内的分布。方法应用免疫组织化学（ＡＢＣ法）和反转录－聚合酶链式反应（ＲＴ－ＰＣＲ）方法，观察免疫活性的ＡｄＭ及其ＡｄＭｍＲＮＡ在大鼠和人脑内的分布。结果在所检查的大鼠每一个脑区，包括大脑皮层、室旁组织、下丘脑、中脑、延髓和小脑均发现有免疫活性的ＡｄＭ及ＡｄＭｍＲＮＡ存在，应用半定量ＲＴ－ＰＣＲ分析方法发现，在大鼠的室旁组织和延髓中，ＡｄＭｍＲＮＡ表达水平较高。在人脑也发现有ＡｄＭｍＲＮＡ表达。结论在大鼠和人的中枢神经系统中存在肾上腺髓质素，它可能作为一种神经递质、神经调质或神经激素发挥生物学作用。     

Replication and Spread of Oncolytic Herpes Simplex Virus in Solid Tumors

Oncolytic herpes simplex virus (oHSV) is a highly promising treatment for solid tumors. Intense research and development efforts have led to first-in-class approval for an oHSV for melanoma, but barriers to this promising therapy still exist that limit efficacy. The process of infection, replication and transmission of oHSV in solid tumors is key to obtaining a good lytic destruction of infected cancer cells to kill tumor cells and release tumor antigens that can prime anti-tumor efficacy. Intracellular tumor cell signaling and tumor stromal cells present multiple barriers that resist oHSV activity. Here, we provide a review focused on oncolytic HSV and the essential viral genes that allow for virus replication and spread in order to gain insight into how manipulation of these pathways can be exploited to potentiate oHSV infection and replication among tumor cells.     

柯萨奇B组病毒所致神经系统病变临床探讨

目的柯萨奇B组病毒（CoxsackieBvirusesCBV）所致神经系统病变目前报道较少，其实并非少见。主要因其感染后多系统损害症状复杂，很难使人们确诊为神经系统病变，如不早期确诊及时治疗，个别病人可导致失明或致残。方法所有可疑本病患者均经CBV抗体IgM、IgGI－Ⅳ型测定，采用酶联免疫吸附试验（ELISA），用（CBVI－Ⅳ）抗原分别检查患者血清中的抗体（包括IgM和IgG）IgMI：100·IgG1；800或1：1600视为阳性。结果9例病人IgM1：100、IgG1：1600阳性，5例IgM（－）、IgG1：1600阳性确诊为柯萨奇B组病毒感染。结论以上病人均给抗病毒和脑细胞活化剂治疗一个月，临床体征消失，头颅CT扫描转正常。临床实践证明病原学血清诊断是唯一先决条件，病毒特异性抗体检测已是公认的一种可靠快速可取的诊断方法。     

Fungal Infections of the Central Nervous System

Fungal infections of the central nervous system have manifold presentations and courses that depend largely on both host and organism characteristics. Although subjects with impaired immunity are generally at higher risk for severe disease, several fungal organisms are considered primary pathogens and can also cause disease in otherwise immunocompetent individuals. Herein, we describe the epidemiology, presentation, diagnosis, and management of central nervous system complications of several fungal pathogens.     

Secondary Central Nervous System Lymphoma

This review summarizes current knowledge of secondary central nervous system lymphoma (SCNSL) in adults. We define SCNSL as CNS involvement not obvious at the initiation of treatment for systemic lymphoma. Recently, polymerase chain reaction and flow cytometry assays of cerebrospinal fluid have become available for the correct diagnosis of SCNSL. We reviewed reports of patients treated without CNS prophylaxis to evaluate the incidence of SCNSL. Elevated serum lactate dehydrogenase levels, the involvement of more than one extranodal site, an advanced stage, a high age-adjusted International Prognostic Index score at presentation, and special anatomic sites of involvement such as the testis are important risk factors for SCNSL. Histologic evidence of aggressiveness is generally an indicator of risk for SCNSL. In addition to conventional treatment, stem cell transplantation, intrathecal administration of rituximab, and liposomal cytarabine have come into clinical use for the treatment of established SCNSL. Prevention of isolated CNS recurrence is thought to be the main target of CNS prophylaxis. The value of CNS prophylaxis according to histologic subtype, status of systemic lymphoma, and other risk factors is summarized. Although prophylaxis is fundamental for treating highly aggressive non-Hodgkin's lymphoma (NHL), it is beginning to be appreciated for the treatment of aggressive NHL. CNS involvement is almost always fatal; however, a CNS-active strategy could complement other approaches that have led to recent improvements in the prognosis for lymphoma.