异嗜性小鼠白血病病毒相关病毒研究现状及展望

异嗜性小鼠白血病病毒相关病毒(XMRV)是第一个能够感染人类的γ逆转录病毒,该病毒最早在前列腺癌患者体内被发现。越来越多的研究提示,XMRV可能与前列腺癌和慢性疲劳综合征密切相关。我们就已知的XMRV的生物学特征、流行病学特征及研究展望做简要综述。     

新型人类逆转录病毒XMRV研究进展

异嗜性鼠白血病病毒相关病毒(xenotropic murine leukemia virus-related virus,XMRV)是迄今发现的第一种可以感染人类的r逆转录病毒。XMRV最初于2006年在RNase L基因缺陷型的前列腺癌组织中首次被鉴定,其序列与鼠科白血病病毒(murine leukemia virus,MLV)十分相似。目前,北美、欧洲和亚洲的多个研究机构在人类前列腺癌和慢性疲劳综合征(chronic fatigue syndrome,CFS)患者中检测到XMRV。但不同研究间结果差异很大,XMRV感染与人类疾病之间的相关性尚不明确。该文综述了目前XMRV的相关研究进展,包括与人类疾病的关系、XMRV的基本特征、病理生理学可能的机制等方面,并就今后研究趋势和注意问题进行了讨论。     

宿主因子莫罗尼白血病病毒10蛋白抑制异嗜性鼠白血病病毒相关病毒的复制

本研究探讨宿主因子莫罗尼白血病病毒10(Moloney leukemia virus 10MOV 10)蛋白对异嗜性鼠白血病病毒相关病毒(Xenotropic murine leukemia virus-related virusis,XMRV)复制的抑制作用,以及MOV 10抑制XMRV复制的初步机制和关键结构域。通过转染、感染、免疫印迹(Western blotting)及实时定量PCR(Real-time PCR)方法检测MOV10对XMRV的抑制作用及机制,结果显示MOV 10可明显抑制XMRV,并且这种抑制作用具有特异性。经进一步证实,MOV 10包裹进XMRV病毒中,随之在病毒感染细胞时发挥抑制作用;MOV 10可以抑制XMRV的DNA产生;MOV 10发挥抑制作用的关键结构域是MOV 10本身RNA解旋酶的7个保守结构域。以上的研究结果表明MOV 10对XMRV具有明显的抑制作用,初步阐明了MOV 10抑制XMRV复制的机制,明确了MOV 10发挥抑制作用的关键结构域。本研究进一步证实了MOV 10具有广谱的抗逆转录病毒的活性,在宿主对抗逆转录病毒感染时发挥重要作用。     

病毒突触的分子机制

人类嗜T细胞病毒I型(HTLV-1)和人类免疫缺陷病毒(HIV)感染CD4 T细胞后,已感染细胞通过病毒突触(virologicalsynapse)的方式与其他未感染的T细胞接触,将病毒颗粒直接传递到未感染细胞体内。这一新近发现的逆转录病毒感染方式涉及连续发生的一系列分子识别事件。目前对于病毒突触形成过程的分子识别机制尚无定论,但可以肯定的是,对其分子细节的深入研究必定会为人类攻克病毒性疾病提供新的思路。     

慢病毒载体转录“通读”改进研究进展

自2002年以来,在用γ-逆转录病毒载体治疗X连锁重度复合性免疫缺陷病 (X-SCID) 的10例病人中已有4例因载体整合在原癌基因lmo2等附近而得了白血病。这一事件提高了人们对基因治疗载体安全性的关注。与γ-逆转录病毒载体相比,慢病毒载体因尚未发现有整合在lmo2附近的现象,被认为是安全性较好的基因治疗载体。然而自灭活慢病毒载体与γ-逆转录病毒载体一样存在着转录“通读”的现象。近些年来,科学家们在改善自灭活慢病毒载体的通读率上做了一些工作并取得了一些积极成果。以下对慢病毒载体转录“通读”现象的发生机理和解决途径作了综合描述。     

人星状病毒研究进展

人星状病毒是引起婴幼儿病毒性腹泻的重要病原之一,本文回顾了其分子生物学特征、型别、所致疾病特征、致病机制、流行病学特征及检测方法等方面的文献,指出人星状病毒目前存在多种型别,尤其是近年来发现了多种新型的星状病毒,主要的流行型别是血清型1型,不仅引起肠道内感染,还可以引起其他系统疾病,所致疾病特征和其他腹泻相关病毒相似,但是其致病机制的研究尚不清楚,对于几种新发现的星状病毒,其与疾病的相关性研究较少,且未建立完善的实验室检测方法,还需要进一步的研究。     

博尔纳病病毒与人类神经精神性疾病

博尔纳病病毒是一种宿主范围很广的动物病毒,因其可能与人类的某些神经精神性疾病有关而备受重视.但其在人体的感染,致病还存在很多争议.需要通过建立高效灵敏和准确的检测技术进行更加全面的研究,同时对其可能致病机制的分子生物学研究也会有助于澄清有关争议.如果能够确认某些人类的神经精神性疾病与博尔纳病病毒有关,将会极大地帮助人们控制这类危害越来越大的疾病.     

诺如病毒爆发与HBGAs受体关系的研究

目的:研究诺如病毒爆发与HBGAs受体的关系.方法:选择2010年1月-2011年12月两年期间诺如病毒爆发的患者60例,作为实验组,同时,随机选择同期健康志愿者60例,作为对照组.收集患者和志愿者唾液,采用凝集抑制实验法检测唾液中HBGAS血型物质;用EIA法检测NoV-VLP与HBGAs的结合特性;比较不同型别诺如病毒爆发在实验组和对照组中HBGAs分布差异.结果:在感染诺如病毒的患者中,并无患者是唾液非分泌型,提示非分泌型HBGAs受体不与G Ⅱ 24型诺如病毒毒株结合与OD450值测定结果一致.其中检出分泌型中A型1例(1.67％),B型48例(80.00％),O型3例(5.00％),AB型2例(13.33％),60例患者的检测结果与其本身的血型相一致.无论是分泌型还是非分泌型的分布比例,两组存在明显的差异(P＜0.05),具有统计学意义.结论:B型患者为诺如病毒感染的高度敏感人群,提示在我国人群的感染类型多以分泌型B型人群为主.     

人类T淋巴细胞白血病病毒流行区无偿献血人群筛查研究

人类T淋巴细胞白血病病毒(human T-lym-photropic virus,HTLV)是最早发现的人类逆转录病毒,分为I型和II型。HTLV感染后,会在人体内长期存在,潜伏期长达20年以上,并在多年后引起白血病或下肢瘫痪等致死性或致残性疾病,迄今有效的治疗药物和预防性疫苗仍未研制成功[1]。因此,唯一积极的控制办法就是及时发现HTLV感染者,并采取措施切断其传播途径。由于HTLV可经血传播,日本、美国、澳大利亚、法国及其它一些国家和地区已将其列为献血员必检项目之一,但我国各地均一直未开展此项目。自1986年以来,我国先后在多个省、市发现了HTLV感染…     

EB病毒致病机制研究进展

EB病毒(Epstein-Barr virus,EBV)是一种常见的人类4型疱疹病毒,原发感染后可终身携带病毒。EBV感染无法从宿主中清除,呈现潜伏状态,一旦激活即可成为很多疾病的相关病因,与人类多种疾病特别是恶性肿瘤相关,包括Burkitt淋巴瘤、鼻咽癌、胃癌等。EBV致病机制复杂多样,目前致病机制的具体分子遗传机制尚未明确。本文主要从EBV与宿主细胞相互作用、免疫逃逸、EBV感染周期表达的相关产物与宿主的相互作用等几个方面,综述目前EBV致病机制的研究进展。     

Antibody responses against xenotropic murine leukemia virus-related virus envelope in a murine model

Background

Xenotropic murine leukemia virus-related virus (XMRV) was recently discovered to be the first human gammaretrovirus that is associated with chronic fatigue syndrome and prostate cancer (PC). Although a mechanism for XMRV carcinogenesis is yet to be established, this virus belongs to the family of gammaretroviruses well known for their ability to induce cancer in the infected hosts. Since its original identification XMRV has been detected in several independent investigations; however, at this time significant controversy remains regarding reports of XMRV detection/prevalence in other cohorts and cell type/tissue distribution. The potential risk of human infection, coupled with the lack of knowledge about the basic biology of XMRV, warrants further research, including investigation of adaptive immune responses. To study immunogenicity in vivo, we vaccinated mice with a combination of recombinant vectors expressing codon-optimized sequences of XMRV gag and env genes and virus-like particles (VLP) that had the size and morphology of live infectious XMRV.

Results

Immunization elicited Env-specific binding and neutralizing antibodies (NAb) against XMRV in mice. The peak titers for ELISA-binding antibodies and NAb were 1∶1024 and 1∶464, respectively; however, high ELISA-binding and NAb titers were not sustained and persisted for less than three weeks after immunizations.

Conclusions

Vaccine-induced XMRV Env antibody titers were transiently high, but their duration was short. The relatively rapid diminution in antibody levels may in part explain the differing prevalences reported for XMRV in various prostate cancer and chronic fatigue syndrome cohorts. The low level of immunogenicity observed in the present study may be characteristic of a natural XMRV infection in humans.     

Local replication of simian immunodeficiency virus in the breast milk compartment of chronically-infected, lactating rhesus monkeys

Retroviruses have been linked to a variety of diseases such as neoplastic and immunodeficiency disorders and neurologic and respiratory diseases. Recently, a novel infectious human retrovirus, the xenotropic murine leukemia virus-related virus (XMRV), has been identified in cohorts of patients with either a familial type of prostate cancer or chronic fatigue syndrome. The apparent unrelatedness of these diseases raised the question of the potential involvement of XMRV in other diseases. Here, we investigated the presence of XMRV in a selection of pediatric idiopathic infectious diseases with symptoms that are suggestive of a retroviral infection, as well as in children with respiratory diseases and in adult patients with spondyloarthritis (SpA). Using a XMRV env-nested PCR, we screened 72 DNA samples obtained from 62 children hospitalized in the Montpellier university hospital (France) for hematological, neurological or inflammatory pathologies, 80 DNA samples from nasopharyngeal aspirates from children with respiratory diseases and 19 DNA samples from SpA. None of the samples tested was positive for XMRV or MLV-like env sequences, indicating that XMRV is not involved in these pathologies.     

In-Depth Investigation of Archival and Prospectively Collected Samples Reveals No Evidence for XMRV Infection in Prostate Cancer

XMRV, or xenotropic murine leukemia virus (MLV)-related virus, is a novel gammaretrovirus originally identified in studies that analyzed tissue from prostate cancer patients in 2006 and blood from patients with chronic fatigue syndrome (CFS) in 2009. However, a large number of subsequent studies failed to confirm a link between XMRV infection and CFS or prostate cancer. On the contrary, recent evidence indicates that XMRV is a contaminant originating from the recombination of two mouse endogenous retroviruses during passaging of a prostate tumor xenograft (CWR22) in mice, generating laboratory-derived cell lines that are XMRV-infected. To confirm or refute an association between XMRV and prostate cancer, we analyzed prostate cancer tissues and plasma from a prospectively collected cohort of 39 patients as well as archival RNA and prostate tissue from the original 2006 study. Despite comprehensive microarray, PCR, FISH, and serological testing, XMRV was not detected in any of the newly collected samples or in archival tissue, although archival RNA remained XMRV-positive. Notably, archival VP62 prostate tissue, from which the prototype XMRV strain was derived, tested negative for XMRV on re-analysis. Analysis of viral genomic and human mitochondrial sequences revealed that all previously characterized XMRV strains are identical and that the archival RNA had been contaminated by an XMRV-infected laboratory cell line. These findings reveal no association between XMRV and prostate cancer, and underscore the conclusion that XMRV is not a naturally acquired human infection.     

Restricted replication of xenotropic murine leukemia virus-related virus in pigtailed macaques

Although xenotropic murine leukemia virus-related virus (XMRV) has been previously linked to prostate cancer and myalgic encephalomyelitis/chronic fatigue syndrome, recent data indicate that results interpreted as evidence of human XMRV infection reflect laboratory contamination rather than authentic in vivo infection. Nevertheless, XMRV is a retrovirus of undefined pathogenic potential that is able to replicate in human cells. Here we describe a comprehensive analysis of two male pigtailed macaques (Macaca nemestrina) experimentally infected with XMRV. Following intravenous inoculation with >10(10) RNA copy equivalents of XMRV, viral replication was limited and transient, peaking at ≤2,200 viral RNA (vRNA) copies/ml plasma and becoming undetectable by 4 weeks postinfection, though viral DNA (vDNA) in peripheral blood mononuclear cells remained detectable through 119 days of follow-up. Similarly, vRNA was not detectable in lymph nodes by in situ hybridization despite detectable vDNA. Sequencing of cell-associated vDNA revealed extensive G-to-A hypermutation, suggestive of APOBEC-mediated viral restriction. Consistent with limited viral replication, we found transient upregulation of type I interferon responses that returned to baseline by 2 weeks postinfection, no detectable cellular immune responses, and limited or no spread to prostate tissue. Antibody responses, including neutralizing antibodies, however, were detectable by 2 weeks postinfection and maintained throughout the study. Both animals were healthy for the duration of follow-up. These findings indicate that XMRV replication and spread were limited in pigtailed macaques, predominantly by APOBEC-mediated hypermutation. Given that human APOBEC proteins restrict XMRV infection in vitro, human XMRV infection, if it occurred, would be expected to be characterized by similarly limited viral replication and spread.     

Apobec 3G Efficiently Reduces Infectivity of the Human Exogenous Gammaretrovirus XMRV

Background

The human exogenous gammaretrovirus XMRV is thought to be implicated in prostate cancer and chronic fatigue syndrome. Besides pressing epidemiologic questions, the elucidation of the tissue and cell tropism of the virus, as well as its sensitivity to retroviral restriction factors is of fundamental importance. The Apobec3 (A3) proteins, a family of cytidine deaminases, are one important group of host proteins that control primary infection and efficient viral spread.

Methodology/Principal Findings

Here we demonstrate that XMRV is resistant to human Apobec 3B, 3C and 3F, while being highly susceptible to the human A3G protein, a factor which is known to confer antiviral activity against most retroviruses. We show that XMRV as well as MoMLV virions package Apobec proteins independent of their specific restriction activity. hA3G was found to be a potent inhibitor of XMRV as well as of MoMLV infectivity. In contrast to MoMLV, XMRV infection can also be partially reduced by low concentrations of mA3. Interestingly, established prostate cancer cell lines, which are highly susceptible to XMRV infection, do not or only weakly express hA3G.

Conclusions

Our findings confirm and extend recently published data that show restriction of XMRV infection by hA3G. The results will be of value to explore which cells are infected with XMRV and efficiently support viral spread in vivo. Furthermore, the observation that XMRV infection can be reduced by mA3 is of interest with regard to the current natural reservoir of XMRV infection.     

No detection of XMRV in blood samples and tissue sections from prostate cancer patients in Northern Europe

Background

We recently published the rare detection of xenotropic murine leukemia virus-related virus (XMRV) (1/105) in prostate cancer (PCA) tissue of patients in Northern Europe by PCR. The controversial discussion about the virus being detected in PCA tissue, blood samples from patients suffering from chronic fatigue syndrome (CFS), as well as from a significant number of healthy controls prompted us to deepen our studies about detection of XMRV infection applying different detection methods (PCR, cocultivation and immunohistochemistry [IHC]).

Methodology/Principal Findings

Peripheral blood mononuclear cells (PBMCs) from 92 PCA and 7 healthy controls were isolated, PHA activated and cocultivated with LNCaP cells for up to 8 weeks. Supernatant of these cells was applied to a reporter cell line, DERSE-iGFP. Furthermore, the PBMCs and cocultivated LNCaP cells were tested for the presence of XMRV by PCR as well as Western Blot analysis. While all PCR amplifications and Western Blot analyses were negative for signs of XMRV infection, DERSE-iGFP cells displayed isolated GFP positive cells in three cases. In all three cases XMRV presence could not be confirmed by PCR technology. In addition, we performed XMRV specific IHC on PCA tissue sections. Whole tissue sections (n = 20), as well as tissue microarrays (TMA) including 50 benign prostate hyperplasia (BPH), 50 low grade and 50 high grade PCA sections and TMAs including breast cancer, colon cancer and normal tissues were stained with two XMRV specific antisera. XMRV protein expression was not detected in any cancer sections included. One BPH tissue displayed XMRV specific protein expression in random isolated basal cells.

Conclusion

We were unable to conclusively detect XMRV in the blood from PCA patients or from healthy controls and there is no conclusive evidence of XMRV protein expression in PCA, breast cancer and colon cancer tissue sections tested by IHC staining.     

Membrane fusion and cell entry of XMRV are pH-independent and modulated by the envelope glycoprotein's cytoplasmic tail

Xenotropic murine leukemia virus-related virus (XMRV) is a gammaretrovirus that was originally identified from human prostate cancer patients and subsequently linked to chronic fatigue syndrome. Recent studies showed that XMRV is a recombinant mouse retrovirus; hence, its association with human diseases has become questionable. Here, we demonstrated that XMRV envelope (Env)-mediated pseudoviral infection is not blocked by lysosomotropic agents and cellular protease inhibitors, suggesting that XMRV entry is not pH-dependent. The full length XMRV Env was unable to induce syncytia formation and cell-cell fusion, even in cells overexpressing the viral receptor, XPR1. However, truncation of the C-terminal 21 or 33 amino acid residues in the cytoplasmic tail (CT) of XMRV Env induced substantial membrane fusion, not only in the permissive 293 cells but also in the nonpermissive CHO cells that lack a functional XPR1 receptor. The increased fusion activities of these truncations correlated with their enhanced SU shedding into culture media, suggesting conformational changes in the ectodomain of XMRV Env. Noticeably, further truncation of the CT of XMRV Env proximal to the membrane-spanning domain severely impaired the Env fusogenicity, as well as dramatically decreased the Env incorporations into MoMLV oncoretroviral and HIV-1 lentiviral vectors resulting in greatly reduced viral transductions. Collectively, our studies reveal that XMRV entry does not require a low pH or low pH-dependent host proteases, and that the cytoplasmic tail of XMRV Env critically modulates membrane fusion and cell entry. Our data also imply that additional cellular factors besides XPR1 are likely to be involved in XMRV entry.     

Failure to Detect the Novel Retrovirus XMRV in Chronic Fatigue Syndrome

Background

In October 2009 it was reported that 68 of 101 patients with chronic fatigue syndrome (CFS) in the US were infected with a novel gamma retrovirus, xenotropic murine leukaemia virus-related virus (XMRV), a virus previously linked to prostate cancer. This finding, if confirmed, would have a profound effect on the understanding and treatment of an incapacitating disease affecting millions worldwide. We have investigated CFS sufferers in the UK to determine if they are carriers of XMRV.

Methodology

Patients in our CFS cohort had undergone medical screening to exclude detectable organic illness and met the CDC criteria for CFS. DNA extracted from blood samples of 186 CFS patients were screened for XMRV provirus and for the closely related murine leukaemia virus by nested PCR using specific oligonucleotide primers. To control for the integrity of the DNA, the cellular beta-globin gene was amplified. Negative controls (water) and a positive control (XMRV infectious molecular clone DNA) were included. While the beta-globin gene was amplified in all 186 samples, neither XMRV nor MLV sequences were detected.

Conclusion

XMRV or MLV sequences were not amplified from DNA originating from CFS patients in the UK. Although we found no evidence that XMRV is associated with CFS in the UK, this may be a result of population differences between North America and Europe regarding the general prevalence of XMRV infection, and might also explain the fact that two US groups found XMRV in prostate cancer tissue, while two European studies did not.