24 research outputs found
Cytomegalovirus and polyomavirus BK posttransplant
Virus replication and progression to disease in transplant patients is determined by patient-, graft- and virus-specific factors. This complex interaction is modulated by the net state of immunosuppression and its impact on virus-specific cellular immunity. Due to the increasing potency of immunosuppressive regimens, graft rejections have decreased, but susceptibility to infections has increased. Therefore, cytomegalovirus (CMV) remains the most important viral pathogen posttransplant despite availability of effective antiviral drugs and validated strategies for prophylactic, preemptive and therapeutic intervention. CMV replication can affect almost every organ system, with frequent recurrences and increasing rates of antiviral resistance. Together with indirect long-term effects, CMV significantly reduces graft and patient survival after solid organ and hematopoietic stem cell transplantation. The human polyomavirus called BK virus (BKV), on the other hand, only recently surfaced as pathogen with organ tropism largely limited to the reno-urinary tract, manifesting as polyomavirus-associated nephropathy in kidney transplant and hemorrhagic cystitis in hematopoetic stem cell transplant patients. No licensed anti-polyoma viral drugs are available, and treatment relies mainly on improving immune functions to regain control over BKV replication. In this review, we discuss diagnostic and therapeutic aspects of CMV and BKV replication and disease posttransplantatio
A Pathogen Secreted Protein as a Detection Marker for Citrus Huanglongbing.
The citrus industry is facing an unprecedented crisis due to Huanglongbing (HLB, aka citrus greening disease), a bacterial disease associated with the pathogen Candidatus Liberibacter asiaticus (CLas) that affects all commercial varieties. Transmitted by the Asian citrus psyllid (ACP), CLas colonizes citrus phloem, leading to reduced yield and fruit quality, and eventually tree decline and death. Since adequate curative measures are not available, a key step in HLB management is to restrict the spread of the disease by identifying infected trees and removing them in a timely manner. However, uneven distribution of CLas cells in infected trees and the long latency for disease symptom development makes sampling of trees for CLas detection challenging. Here, we report that a CLas secreted protein can be used as a biomarker for detecting HLB infected citrus. Proteins secreted from CLas cells can presumably move along the phloem, beyond the site of ACP inoculation and CLas colonized plant cells, thereby increasing the chance of detecting infected trees. We generated a polyclonal antibody that effectively binds to the secreted protein and developed serological assays that can successfully detect CLas infection. This work demonstrates that antibody-based diagnosis using a CLas secreted protein as the detection marker for infected trees offers a high-throughput and economic approach that complements the approved quantitative polymerase chain reaction-based methods to enhance HLB management programs
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An In Vitro Pipeline for Screening and Selection of Citrus-Associated Microbiota with Potential Anti-"Candidatus Liberibacter asiaticus" Properties.
Huanglongbing (HLB) is a destructive citrus disease that is lethal to all commercial citrus plants, making it the most serious citrus disease and one of the most serious plant diseases. Because of the severity of HLB and the paucity of effective control measures, we structured this study to encompass the entirety of the citrus microbiome and the chemistries associated with that microbial community. We describe the spatial niche diversity of bacteria and fungi associated with citrus roots, stems, and leaves using traditional microbial culturing integrated with culture-independent methods. Using the culturable sector of the citrus microbiome, we created a microbial repository using a high-throughput bulk culturing and microbial identification pipeline. We integrated an in vitro agar diffusion inhibition bioassay into our culturing pipeline that queried the repository for antimicrobial activity against Liberibacter crescens, a culturable surrogate for the nonculturable "Candidatus Liberibacter asiaticus" bacterium associated with HLB. We identified microbes with robust inhibitory activity against L. crescens that include the fungi Cladosporium cladosporioides and Epicoccum nigrum and bacterial species of Pantoea, Bacillus, and Curtobacterium Purified bioactive natural products with anti-"Ca. Liberibacter asiaticus" activity were identified from the fungus C. cladosporioides Bioassay-guided fractionation of an organic extract of C. cladosporioides yielded the natural products cladosporols A, C, and D as the active agents against L. crescens This work serves as a foundation for unraveling the complex chemistries associated with the citrus microbiome to begin to understand the functional roles of members of the microbiome, with the long-term goal of developing anti-"Ca Liberibacter asiaticus" bioinoculants that thrive in the citrus holosystem.IMPORTANCE Globally, citrus is threatened by huanglongbing (HLB), and the lack of effective control measures is a major concern of farmers, markets, and consumers. There is compelling evidence that plant health is a function of the activities of the plant's associated microbiome. Using Liberibacter crescens, a culturable surrogate for the unculturable HLB-associated bacterium "Candidatus Liberibacter asiaticus," we tested the hypothesis that members of the citrus microbiome produce potential anti-"Ca Liberibacter asiaticus" natural products with potential anti-"Ca Liberibacter asiaticus" activity. A subset of isolates obtained from the microbiome inhibited L. crescens growth in an agar diffusion inhibition assay. Further fractionation experiments linked the inhibitory activity of the fungus Cladosporium cladosporioides to the fungus-produced natural products cladosporols A, C, and D, demonstrating dose-dependent antagonism to L. crescens
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Two distinct viral suppressors of RNA silencing encoded by citrus tatter leaf virus
Two proteins of the citrus tatter leaf virus (CTLV), a strain of the apple stem grooving virus (ASGV), capable of inducing citrus bud union disorders on commercially important trifoliate and citrange rootstocks, were identified as viral suppressors of RNA silencing (VSR). Both the coat protein (CP) and the movement protein (MP) suppressed RNA silencing in GFP-transgenic Nicotiana benthamiana 16c plants in agrobacterium-mediated co-infiltration assays; the MP acted as a local VSR, while the CP acted as a systemic VSR. When the potato virus X (PVX) infectious vector harbored either the CTLV CP or MP gene, viral infection and symptom development were promoted in N. benthamiana. Deletions of amino acids in the CP sequence or the MP sequence resulted in failure to promote PVX infections as well as suppression of silencing in agrobacterium-mediated co-infiltration assays. Mass spectrometry-based immunoprecipitation proteomics showed that neither the CTLV CP nor the MP interacts with cellular components directly involved in host antiviral RNA silencing pathways. RNA immunoprecipitation (RIP) and RNA-protein pull-down assays indicated that the CTLV MP interacts with double-stranded RNA (dsRNA) presumably through a protein complex or proteins containing RNA binding domains. It is possible that the MP prevents dsRNA cleavage through this mechanism, leading to suppression of host antiviral RNA silencing. These findings confirmed that CTLV uses VSRs as part of its overall strategy to overcome host antiviral defenses and are indicative of the ability of ASGV and CTLV to infect a wide range of hosts including different species of woody and herbaceous plants
Quick Plant Sample Preparation Methods Using a Micro-Homogenizer for the Detection of Multiple Citrus Pathogens
Effective pathogen detection is essential for plant disease control. However, plant sample preparation for downstream assays, such as quantitative polymerase chain reaction (qPCR), is challenging to perform outside of a laboratory. This paper reports two sample preparation methods featuring chemical and mechanical lysis and nucleic acid extraction using a micro-homogenizer, followed by serial dilution or nucleic acid purification with a paper disk before assay. Five minutes of lysis and extraction resulted in DNA and RNA yields of up to 76.5% and 63.3%, respectively, compared to mortar and pestle controls. Crude lysates were unsuitable for direct use in qPCR assays; however, serial dilution or quick wash using chromatography paper rendered samples ready for such assays. Additionally, the nucleic acids stored on paper disks under various storage conditions remained stable for one month. These methods can facilitate the in-field preparation of citrus samples and allow for both onsite and mail-in diagnostics for growers
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Microsatellite characterization and marker development for the fungus Penicillium digitatum, causal agent of green mold of citrus.
Penicillium digitatum is one of the most important postharvest pathogens of citrus on a global scale causing significant annual losses due to fruit rot. However, little is known about the diversity of P. digitatum populations. The genome of P. digitatum has been sequenced, providing an opportunity to determine the microsatellite distribution within P. digitatum to develop markers that could be valuable tools for studying the population biology of this pathogen. In the analyses, a total of 3,134 microsatellite loci were detected; 66.73%, 23.23%, 8.23%, 1.24%, 0.16%, and 0.77% were detected as mono-, di-, tri-, tetra-, penta-, and hexanucleotide repeats, respectively. As consistent with other ascomycete fungi, the genome size of P. digitatum does not seem to correlate with the density of microsatellite loci. However, significantly longer motifs of mono-, di-, and tetranucleotide repeats were identified in P. digitatum compared to 10 other published ascomycete species with repeats of over 800, 300, and 900 motifs found, respectively. One isolate from southern California and five additional isolates from other countries ("global isolates") were used to initially screen microsatellite markers developed in this study. Twelve additional isolates, referred to as the "local isolates," were also collected from citrus at the University of California Riverside agricultural experiment station and were subsequently used to screen the primers that sequenced well and were polymorphic based on the global isolates. Thirty-six primers were screened, and nine trinucleotide loci and one hexanucleotide locus were chosen as robust markers. These loci yielded two to seven alleles and will be useful to study population genetic structure of P. digitatum populations
TUSC1, a putative tumor suppressor gene, reduces tumor cell growth in vitro and tumor growth in vivo.
We previously reported the identification of TUSC1 (Tumor Suppressor Candidate 1), as a novel intronless gene isolated from a region of homozygous deletion at D9S126 on chromosome 9p in human lung cancer. In this study, we examine the differential expression of TUSC1 in human lung cancer cell lines by western blot and in a primary human lung cancer tissue microarray by immunohistochemical analysis. We also tested the functional activities and mechanisms of TUSC1 as a tumor suppressor gene through growth suppression in vitro and in vivo. The results showed no expression of TUSC1 in TUSC1 homozygously deleted cells and diminished expression in some tumor cell lines without TUSC1 deletion. Interestingly, the results from a primary human lung cancer tissue microarray suggested that higher expression of TUSC1 was correlated with increased survival times for lung cancer patients. Our data demonstrated that growth curves of tumor cell lines transfected with TUSC1 grew slower in vitro than those transfected with the empty vector. More importantly, xenograph tumors in nude mice grew significantly slower in vivo in cells stably transfected with TUSC1 than those transfected with empty vector. In addition, results from confocal microscopy and immunohistochemical analyses show distribution of TUSC1 in the cytoplasm and nucleus in tumor cell lines and in normal and tumor cells in the lung cancer tissue microarray. Taken together, our results support TUSC1 has tumor suppressor activity as a candidate tumor suppressor gene located on chromosome 9p
Transcriptome Analysis of Citrus Dwarfing Viroid Induced Dwarfing Phenotype of Sweet Orange on Trifoliate Orange Rootstock
Dwarfed citrus trees for high-density plantings or mechanized production systems will be key for future sustainable citrus production. Citrus trees consist of two different species of scion and rootstock. Therefore, any observed phenotype results from gene expression in both species. Dwarfed sweet orange trees on trifoliate rootstock have been produced using citrus dwarfing viroid (CDVd). We performed RNA-seq transcriptome analysis of CDVd-infected stems and roots and compared them to non-infected controls. The identified differentially expressed genes validated with RT-qPCR corresponded to various physiological and developmental processes that could be associated with the dwarfing phenotype. For example, the transcription factors MYB13 and MADS-box, which regulate meristem functions and activate stress responses, were upregulated in the stems. Conversely, a calcium-dependent lipid-binding protein that regulates membrane transporters was downregulated in the roots. Most transcriptome reprogramming occurred in the scion rather than in the rootstock; this agrees with previous observations of CDVd affecting the growth of sweet orange stems while not affecting the trifoliate rootstock. Furthermore, the lack of alterations in the pathogen defense transcriptome supports the term “Transmissible small nuclear ribonucleic acid,” which describes CDVd as a modifying agent of tree performance with desirable agronomic traits rather than a disease-causing pathogen
Could Human Papillomaviruses Be Spread through Blood?
The human papillomaviruses (HPVs) are epitheliotropic viruses that require the environment of a differentiating squamous epithelium for their life cycle. HPV infection through abrasion of the skin or sexual intercourse causes benign warts and sometimes cancer. HPV DNA detected in the blood has been interpreted as having originated from metastasized cancer cells. The present study examined HPV DNA in banked, frozen peripheral blood mononuclear cells (PBMCs) from 57 U.S. human immunodeficiency virus (HIV)-infected pediatric patients collected between 1987 and 1996 and in fresh PBMCs from 19 healthy blood donors collected in 2002 to 2003. Eight patients and three blood donors were positive mostly for two subgroups of the HPV type 16 genome. The HPV genome detected in all 11 PBMC samples existed as an episomal form, albeit at a low DNA copy number. Among the eight patients, seven acquired HIV from transfusion (three associated with hemophilia) and one acquired HIV through vertical transmission; this patient also had received a transfusion before sampling. Our data suggest that PBMCs may be HPV carriers and might spread the virus through blood