TGF-b2 induction regulates invasiveness of theileria-transformed leukocytes and disease susceptibility

Theileria parasites invade and transform bovine leukocytes causing either East Coast fever (T. parva), or tropical theileriosis (T. annulata). Susceptible animals usually die within weeks of infection, but indigenous infected cattle show markedly reduced pathology, suggesting that host genetic factors may cause disease susceptibility. Attenuated live vaccines are widely used to control tropical theileriosis and attenuation is associated with reduced invasiveness of infected macrophages in vitro. Disease pathogenesis is therefore linked to aggressive invasiveness, rather than uncontrolled proliferation of Theileria-infected leukocytes. We show that the invasive potential of Theileria-transformed leukocytes involves TGF-b signalling. Attenuated live vaccine lines express reduced TGF-b2 and their invasiveness can be rescued with exogenous TGF-b. Importantly, infected macrophages from disease susceptible Holstein-Friesian (HF) cows express more TGF-b2 and traverse Matrigel with great efficiency compared to those from disease-resistant Sahiwal cattle. Thus, TGF-b2 levels correlate with disease susceptibility. Using fluorescence and time-lapse video microscopy we show that Theileria-infected, disease-susceptible HF macrophages exhibit increased actin dynamics in their lamellipodia and podosomal adhesion structures and develop more membrane blebs. TGF-b2-associated invasiveness in HF macrophages has a transcription-independent element that relies on cytoskeleton remodelling via activation of Rho kinase (ROCK). We propose that a TGF-b autocrine loop confers an amoeboid-like motility on Theileria-infected leukocytes, which combines with MMP-dependent motility to drive invasiveness and virulence

A bovine lymphosarcoma cell line infected with theileria annulata exhibits an irreversible reconfiguration of host cell gene expression

Theileria annulata, an intracellular parasite of bovine lymphoid cells, induces substantial phenotypic alterations to its host cell including continuous proliferation, cytoskeletal changes and resistance to apoptosis. While parasite induced modulation of host cell signal transduction pathways and NFκB activation are established, there remains considerable speculation on the complexities of the parasite directed control mechanisms that govern these radical changes to the host cell. Our objectives in this study were to provide a comprehensive analysis of the global changes to host cell gene expression with emphasis on those that result from direct intervention by the parasite. By using comparative microarray analysis of an uninfected bovine cell line and its Theileria infected counterpart, in conjunction with use of the specific parasitacidal agent, buparvaquone, we have identified a large number of host cell gene expression changes that result from parasite infection. Our results indicate that the viable parasite can irreversibly modify the transformed phenotype of a bovine cell line. Fifty percent of genes with altered expression failed to show a reversible response to parasite death, a possible contributing factor to initiation of host cell apoptosis. The genes that did show an early predicted response to loss of parasite viability highlighted a sub-group of genes that are likely to be under direct control by parasite infection. Network and pathway analysis demonstrated that this sub-group is significantly enriched for genes involved in regulation of chromatin modification and gene expression. The results provide evidence that the Theileria parasite has the regulatory capacity to generate widespread change to host cell gene expression in a complex and largely irreversible manner

Analysis of IL28B Variants in an Egyptian Population Defines the 20 Kilobases Minimal Region Involved in Spontaneous Clearance of Hepatitis C Virus

Spontaneous clearance of hepatitis C virus (HCV) occurs in ∼30% of acute infections. Host genetics play a major role in HCV clearance, with a strong effect of single nucleotide polymorphisms (SNPs) of the IL28B gene already found in different populations, mostly infected with viral genotypes 1 and 3. Egypt has the highest prevalence of HCV infection in the world, which is mostly due to viral genotype 4. We investigated the role of several IL28B SNPs in HCV spontaneous clearance in an Egyptian population. We selected nine SNPs within the IL28B genomic region covering the linkage disequilibrium (LD) block known to be associated with HCV clearance in European populations. These SNPs were genotyped in 261 HCV-infected Egyptian subjects (130 with spontaneous clearance and 131 with chronic infection). The most associated SNPs were rs12979860 (P = 1.6×10−7) and the non-synonymous IL28B SNP, rs8103142 (P = 1.6×10−7). Interestingly, three SNPs at the two bounds of the region were monomorphic, reducing the size of the LD block in which the causal variants are potentially located to ∼20 kilobases. HCV clearance in Egypt was associated with a region of IL28B smaller than that identified in European populations, and involved the non-synonymous IL28B SNP, rs8103142

CPP-ZFN: A potential DNA-targeting anti-malarial drug

<p>Abstract</p> <p>Background</p> <p>Multidrug-resistant <it>Plasmodium </it>is of major concern today. Effective vaccines or successful applications of RNAi-based strategies for the treatment of malaria are currently unavailable. An unexplored area in the field of malaria research is the development of DNA-targeting drugs that can specifically interact with parasitic DNA and introduce deleterious changes, leading to loss of vital genome function and parasite death.</p> <p>Presentation of the hypothesis</p> <p>Advances in the development of zinc finger nuclease (ZFN) with engineered DNA recognition domains allow us to design and develop nuclease of high target sequence specificity with a mega recognition site that typically occurs only once in the genome. Moreover, cell-penetrating peptides (CPP) can cross the cell plasma membrane and deliver conjugated protein, nucleic acid, or any other cargo to the cytoplasm, nucleus, or mitochondria. This article proposes that a drug from the combination of the CPP and ZFN systems can effectively enter the intracellular parasite, introduce deleterious changes in its genome, and eliminate the parasite from the infected cells.</p> <p>Testing the hypothesis</p> <p>Availability of a DNA-binding motif for more than 45 triplets and its modular nature, with freedom to change number of fingers in a ZFN, makes development of customized ZFN against diverse target DNA sequence of any gene feasible. Since the <it>Plasmodium </it>genome is highly AT rich, there is considerable sequence site diversity even for the structurally and functionally conserved enzymes between <it>Plasmodium </it>and humans. CPP can be used to deliver ZFN to the intracellular nucleus of the parasite. Signal-peptide-based heterologous protein translocation to <it>Plasmodium</it>-infected RBCs (iRBCs) and different <it>Plasmodium </it>organelles have been achieved. With successful fusion of CPP with mitochondrial- and nuclear-targeting peptides, fusion of CPP with 1 more <it>Plasmodium </it>cell membrane translocation peptide seems achievable.</p> <p>Implications of the hypothesis</p> <p>Targeting of the <it>Plasmodium </it>genome using ZFN has great potential for the development of anti-malarial drugs. It allows the development of a single drug against all malarial infections, including multidrug-resistant strains. Availability of multiple ZFN target sites in a single gene will provide alternative drug target sites to combat the development of resistance in the future.</p

CTL Escape Mediated by Proteasomal Destruction of an HIV-1 Cryptic Epitope

Cytotoxic CD8+ T cells (CTLs) play a critical role in controlling viral infections. HIV-infected individuals develop CTL responses against epitopes derived from viral proteins, but also against cryptic epitopes encoded by viral alternative reading frames (ARF). We studied here the mechanisms of HIV-1 escape from CTLs targeting one such cryptic epitope, Q9VF, encoded by an HIVgag ARF and presented by HLA-B*07. Using PBMCs of HIV-infected patients, we first cloned and sequenced proviral DNA encoding for Q9VF. We identified several polymorphisms with a minority of proviruses encoding at position 5 an aspartic acid (Q9VF/5D) and a majority encoding an asparagine (Q9VF/5N). We compared the prevalence of each variant in PBMCs of HLA-B*07+ and HLA-B*07- patients. Proviruses encoding Q9VF/5D were significantly less represented in HLA-B*07+ than in HLA-B*07- patients, suggesting that Q9FV/5D encoding viruses might be under selective pressure in HLA-B*07+ individuals. We thus analyzed ex vivo CTL responses directed against Q9VF/5D and Q9VF/5N. Around 16% of HLA-B*07+ patients exhibited CTL responses targeting Q9VF epitopes. The frequency and the magnitude of CTL responses induced with Q9VF/5D or Q9VF/5N peptides were almost equal indicating a possible cross-reactivity of the same CTLs on the two peptides. We then dissected the cellular mechanisms involved in the presentation of Q9VF variants. As expected, cells infected with HIV strains encoding for Q9VF/5D were recognized by Q9VF/5D-specific CTLs. In contrast, Q9VF/5N-encoding strains were neither recognized by Q9VF/5N- nor by Q9VF/5D-specific CTLs. Using in vitro proteasomal digestions and MS/MS analysis, we demonstrate that the 5N variation introduces a strong proteasomal cleavage site within the epitope, leading to a dramatic reduction of Q9VF epitope production. Our results strongly suggest that HIV-1 escapes CTL surveillance by introducing mutations leading to HIV ARF-epitope destruction by proteasomes

The protozoan parasite Theileria annulata alters the differentiation state of the infected macrophage and suppresses musculoaponeurotic fibrosarcoma oncogene (MAF) transcription factors

AbstractThe tick-borne protozoan parasite Theileria annulata causes a debilitating disease of cattle called Tropical Theileriosis. The parasite predominantly invades bovine macrophages (mϕ) and induces host cell transformation by a mechanism that has not been fully elucidated. Infection is associated with loss of characteristic mϕ functions and phenotypic markers, indicative of host cell de-differentiation. We have investigated the effect of T. annulata infection on the expression of the mϕ differentiation marker c-maf. The up-regulation of c-maf mRNA levels observed during bovine monocyte differentiation to mϕ was suppressed by T. annulata infection. Furthermore, mRNA levels for c-maf and the closely related transcription factor mafB were significantly lower in established T. annulata-infected cell-lines than in bovine monocyte-derived mϕ. Treatment of T. annulata-infected cells with the theileriacidal drug buparvaquone induced up-regulation of c-maf and mafB, which correlated with altered expression of down-stream target genes, e.g. up-regulation of integrin B7 and down-regulation of IL12A. Furthermore, T. annulata infection is associated with the suppression of the transcription factors, Pu.1 and RUNX1, and colony stimulating factor 1 receptor (CSF1R) which are also involved in the regulation of monocyte/mϕ differentiation. We believe these results provide the first direct evidence that T. annulata modulates the host mϕ differentiation state, which may diminish the defence capabilities of the infected cell and/or promote cell proliferation. Musculoaponeurotic fibrosarcoma oncogene (MAF) transcription factors play an important role in cell proliferation, differentiation and survival; therefore, regulation of these genes may be a major mechanism employed by T. annulata to survive within the infected mϕ

PP2A1 binding, cell transducing and apoptotic properties of Vpr77-92: A new functional domain of HIV-1 Vpr proteins

Background: The hallmark of HIV-1 pathogenesis is the progressive CD4(+) T cell depletion and high propensity of CD4(+) T cells to apoptosis. HIV-1 viral protein R (Vpr) is a major pro-apoptotic gene product. A first Vpr-mediated apoptotic mechanism that requires a physical interaction of HIV-1 Vpr(71-82) mitochondriotoxic domain containing the conserved sequence (71-)HFRIGCRHSRIG(-82) with the Adenine Nucleotide Translocator (ANT) has been characterized. The family of Ser/Thr protein phosphatase PP2A interacts with several viral proteins to regulate cell growth and apoptotic pathways. Previous studies based on yeast two hybrid assays and mutational experiments indicated that PP2A(1) is involved in the induction of G2 arrest by HIV-1 Vpr. [br/] Principal Findings: Experiments combining pull-down, cell penetration and apoptosis analyses in distinct human cells indicate that the PP2A(1) binding sequence from Vpr(77-92) is a new cell penetrating apoptotic sequence. We also found that the I84P mutation or the IIQ/VTR83-85 and T89A substitutions in the Vpr(77-92) sequence prevent PP2A(1) binding, cell penetration and apoptosis. In addition the double R77A and R80A mutation known to inactivate the mitochondriotoxic Vpr(71-82) domain, has no effect on the biological properties of the Vpr(77-92) domain. [br/] Conclusion: Together our data provide evidence for the first time that the Vpr(77-92) sequence delineates a biological active domain of Vpr with PP2A(1) binding and pro-apopototic capacities and, it is conceivable that this cell penetrating sequence may account for the Vpr internalization in uninfected cells. Finally, our data also implicate the existence of two partially overlapping pro-apoptotic domains in the Vpr C-terminal part, a redundancy that represents a new approach to address the question of biological relevance of HIV-1 Vpr. In this context, future studies will be required to determine the functional relevance of the Vpr(77-92) domain in full length Vpr protein and also in entire HIV provirus

A PKA survival pathway inhibited by DPT-PKI, a new specific cell permeable PKA inhibitor, is induced by T. annulata in parasitized B-lymphocytes

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