• Combination of inhibitors of lymphocyte activation (hydroxyurea, trimidox, and didox) and reverse transcriptase (didanosine) suppresses development of murine retrovirus-induced lymphoproliferative disease.

      Mayhew, Christopher N.; Sumpter, Ryan; Inayat, Mohammed; Cibull, Michael; Phillips, Jonathan D.; Elford, Howard L.; Gallicchio, Vincent S. (Elsevier Science Direct, 2005)
      The ribonucleotide reductase inhibitor hydroxyurea (HU) has demonstrated some benefit as a component of drug cocktails for the treatment of HIV-1 infection. However, HU is notoriously myelosuppressive and often administered only as salvage therapy to patients with late-stage disease, potentially exacerbating the bone marrow toxicity of HU. In this report we have compared the antiviral effects of HU and two novel RR inhibitors trimidox (3,4,5-trihydroxybenzamidoxime) and didox (3,4-dihydroxybenzohydroxamic acid) in combination with didanosine (2,3-didoxyinosine; ddI) in the LPBM5 MuLV retrovirus model (murine AIDS). We also evaluated the effects of these drug combinations on the hematopoietic tissues of LPBM5 MuLV-infected animals. The combination of RR inhibitors and ddI was extremely effective (DX>TX>HU) in inhibiting development of retrovirus-induced disease (splenomegaly, hypergammaglobulinemia, activated B-splenocytes and loss of splenic architecture). In addition, relative levels of proviral DNA were significantly lower in combination drug-treated animals compared to infected controls. Evaluation of femur cellularity, numbers of marrow-derived myeloid progenitor cells (CFU-GM and BFU-E) and peripheral blood indices revealed that TX and DX in combination with ddI were well-tolerated. However, treatment with HU and ddI induced moderate myelosuppression. These data demonstrate that RR inhibitors in combination with ddI provide significant protection against retroviral disease in murine AIDS. Moreover, the novel RR inhibitors TX and DX appear to be more effective and less myelosuppressive than HU when administered with ddI in this model.
    • Human endogenous retrovirus HERV-K10 implicated in rheumatoid arthritis and systemic lupus erythematosus: potential pathological triggers?

      Nelson, Paul N.; Shaw, M.; Roden, Denise A.; Freimanis, Graham L.; Nevill, Alan M.; Rylance, Paul (Czech Republic: Palacky University, Olomouc: Faculty of Medicine and Dentistry, 2006)
      Human endogenous retroviruses (HERVs) are a group of integrated RNA viruses within our human genome. Whilst many are regarded as defective, a number possess the potential to generate retroviral products. Indeed HERVs such as those belonging to the HERV-K family produce retroviral particles in the teratocarcinoma cell line GH and the breast cancer cell line T47D. It has been argued that some retroelements may be beneficial to the human host, perhaps conferring a selective advantage, whereas others may be harmful. Furthermore certain HERVs might be involved in the pathogenesis of autoimmune diseases. The precise mechanisms in diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) may include molecular mimicry and superantigen motifs that evoke and augment unwarranted immune responses. The precise mechanisms in diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) may include molecular mimicry and superantigen motifs that evoke and augment unwarranted immune responses. In the RA joint, tissue destruction is evident over time with recruitment of lymphoid and other cells plus the presence of rheumatoid factor that exhibits increased affinity and change in isotype; evidence of an antigen-driven immune response. The precise trigger of course, remains unknown although certain HERVs have been implicated. In a previous study we found evidence for increased expression of HERV-K10 mRNA in patients with RA. Here we have extended this work by investigating the serological expression to HERV-K10 in patients with RA, SLE, osteoarthritis, normals and other inflammatory disease groups. The study utilised a novel peptide ELISA immunoassay using segments of HERV-K10 identified through bioinformatic analysis. In particular, biotinylation of peptides was necessary for serological discrimination between patients. Overall a significant difference (p<0.05) was found for RA patients in terms of antibody activity to HERV-K10. There was also an increased level of antibodies to HERV-K10 in patients with renal lupus although this was below the level of significance. It is possible that HERV-K10 could act as a trigger in RA/SLE through regions of similarity to host proteins. In this case, the immune response to HERV-K10 could lead to collateral damage and pathogenesis of disease.
    • Human endogenous retroviruses: transposable elements with potential?

      Nelson, Paul N.; Hooley, Paul; Roden, Denise A.; Ejtehadi, H. Davari; Rylance, Paul; Warren, Phil; Martin, Jan H.; Murray, Paul G. (Wiley InterScience, 2004)
      Human endogenous retroviruses (HERVs) are a significant component of a wider family of retroelements that constitute part of the human genome. These viruses, perhaps representative of previous exogenous retroviral infection, have been integrated and passed through successive generations within the germ line. The retention of HERVs and isolated elements, such as long-terminal repeats, could have the potential to harm. In this review we describe HERVs within the context of the family of known transposable elements and survey these viruses in terms of superantigens and molecular mimics. It is entirely possible that these mechanisms provide the potential for undesired immune responses.
    • Suppression of retrovirus-induced immunodeficiency disease (murine AIDS) by trimidox and didox: novel ribonucleotide reductase inhibitors with less bone marrow toxicity than hydroxyurea.

      Mayhew, Christopher N.; Mampuru, Leseilane J.; Chendil, Damodoran; Ahmed, Mansoor M.; Phillips, Jonathan D.; Greenberg, Richard N.; Elford, Howard L.; Gallicchio, Vincent S. (Elsevier Science Direct, 2002)
      Recently, the use of the ribonucleotide reductase (RR) inhibitor hydroxyurea (HU) in combination with nucleoside analogs has gained attention as a potential strategy for anti-HIV-1 therapy. However, appeal for the long-term use of HU in HIV-1 infection may be limited by its propensity to induce hematopoietic toxicity. We report a comparison of the efficacy and bone marrow toxicity of HU (400 and 200 mg/kg/day) with the novel RR inhibitors and free radical-scavenging compounds didox (DX; 3,4-dihydroxybenzohydroxamic acid; 350 mg/kg/day) and trimidox (TX; 3,4,5-trihydroxybenzamidoxime; 175 mg/kg/day) in the murine AIDS (LPBM5 MuLV) model of retrovirus infection. Infected mice received daily drug treatment for 8 weeks. Efficacy was determined by measuring drug effects on retroviral-induced disease progression (i.e. development of splenomegaly and hypergammaglobulinemia) and by evaluating splenic levels of proviral DNA. Bone marrow toxicity was evaluated by measuring peripheral blood indices (WBC, hematocrit and reticulocyte counts), femoral cellularity and by determining the numbers of hematopoietic progenitor cells (CFU-GM, BFU-E) per femur and spleen. Compared to infected controls receiving no drug treatment, disease progression was significantly suppressed by TX, DX and HU. However, HU was associated with mortality and induced significant hematopoietic toxicity in a time- and dose-dependent manner. Conversely, TX and DX effectively inhibited retrovirus-induced disease but did not induce hematopoietic toxicity. These results suggest that due to their reduced hematopoietic toxicity and ability to inhibit disease progression in murine AIDS, TX and DX may offer effective alternatives to HU therapy in HIV-1 infection.
    • The Detection and Role of Human Endogenous Retrovirus K (HML-2) In Rheumatoid Arthritis

      Nelson, Paul N.; Hooley, Paul; Rylance, Paul; Freimanis, Graham L. (University of Wolverhampton, 2008)
      Human endogenous retroviruses are the remnants of ancient retroviral infections present within our genome. These molecular fossils show similarities with present day exogenous retroviruses but act as typical Mendelian elements that are passed vertically between generations. Despite being repeatedly linked to a number of autoimmune diseases and disorders, no conclusive proof has been identified. Rheumatoid arthritis (RA) is one such disease which has been associated with an increase in HERV expression, compared to controls. In order to elucidate a clear role for HERVs in RA pathogenesis, autoantigens implicated in disease pathogenesis were scanned for sequence homology to retroviral genes. Such epitopes would induce antibodies cross reactive with host proteins, resulting in disease. Short peptides mimicking these regions were synthesised and the prevalence of anti-HERV antibodies was determined in RA patients and disease controls. Additionally, a novel real-time Polymerase Chain Reaction (PCR) assay was developed to accurately quantify levels of HERV-K (HML-2) gag expression, relative to normalised levels of housekeeping gene expression. Both serological and molecular assays showed significant increases in HERV-K (HML-2) activity in RA patients compared to disease controls with CD4+ lymphocytes harbouring the highest activity. The real-time assay was also used to determine whether factors within the synovium could modulate HERVs, resulting in their upregulation. Exogenous viral protein expression and pro-inflammatory cytokines were shown to exert a significant modulatory effect over HERV-K (HML-2) transcription. From this data, it is clear that RA patients have increased levels of HERV-K (HML-2) gag activity compared to controls. Despite this it is likely that factors within the synovium such as exogenous viral expression and pro-inflammatory cytokines also influence HERV-K (HML-2) transcription possibly contributing to a role of bystander activation, i.e. being influenced by external factors, rather than actively contributing to disease processes. The exact role of HERVs in RA pathology remains elusive; however this research proposes several mechanisms by which HERV-K (HML-2) may contribute to disease.
    • The potential role of human endogenous retrovirus K10 in the pathogenesis of rheumatoid arthritis: a preliminary study.

      Ejtehadi, H. Davari; Freimanis, Graham L.; Ali, H.A.; Bowman, S.J.; Alavi, A.; Axford, John; Callaghan, R.; Nelson, Paul N. (BMJ Publishing, 2006)
      OBJECTIVE: To examine whether human endogenous retrovirus K10 is associated with autoimmune rheumatic disease. DESIGN: A novel multiplex reverse transcription polymerase chain reaction (RT-PCR) system was developed to investigate HERV-K10 mRNA expression in patients with rheumatoid arthritis. METHODS: 40 patients with rheumatoid arthritis, 17 with osteoarthritis, and 27 healthy individuals were recruited and total RNA was extracted from peripheral blood mononuclear cells (PBMCs) and analysed using multiplex RT-PCR for the level of HERV-K10 gag mRNA expression. Southern blot and DNA sequencing confirmed the authenticity of the PCR products. RESULTS: Using the histidyl tRNA synthetase (HtRNAS) gene as a housekeeping gene in the optimised multiplex RT-PCR, a significantly higher level of HERV-K10 gag mRNA expression was found in rheumatoid arthritis than in osteoarthritis (p = 0.01) or in the healthy controls (p = 0.02). CONCLUSION: There is enhanced mRNA expression of the HERV-K10 gag region in rheumatoid arthritis compared with osteoarthritis or healthy controls. This could contribute to the pathogenesis of rheumatoid arthritis.