Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The impact of drug resistance mutations induced by nucleoside reverse transcriptase (RT) inhibitors (NRTI) on cytotoxic T-lymphocyte (CTL) recognition of human immunodeficiency virus type 1 strain LAI (HIV-1(LAI)) RT was addressed in 35 treated or untreated patients. Two HIV-1(LAI) RT regions encompassing mutation M41L, L74V, M184V, and T215Y/F were recognized in 75 and 83% mutated and in 33 and 42% unmutated samples, respectively. A total of 41 new CTL epitopes overlapping these mutations were predicted. Mutations enhanced HLA-binding scores of 17 epitopes, decreased scores of 5, and had no effect in 19. Four predicted epitopes containing mutations 41, 74, and 184 were tested and recognized by CD8 cells from mutated or unmutated samples, with frequencies up to 270 gamma interferon spot-forming cells per 10(6) peripheral blood mononuclear cells. Therefore, RT mutations induced by NRTI can increase the immunogenicity of RT for CTL and might allow a better immune control of resistant viruses in vivo, suggesting that specific immune therapy might help prevent these mutations.
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PMID:Immunogenicity of mutations induced by nucleoside reverse transcriptase inhibitors for human immunodeficiency virus type 1-specific cytotoxic T cells. 1098 78

During highly active antiretroviral therapy (HAART), HIV-1 can still persist in circulating, resting CD4+ T lymphocytes, lymph node mononuclear cells, and seminal cells of patients despite sustained suppression of plasma viremia to undetectable levels. Sanctuary sites where antiretroviral drug penetration is not optimal may allow local HIV-1 infection of cells within and passing through these tissues. Factors such as imperfect drug adherence due to complicated drug regimens may also result in tissue compartments with suboptimal drug concentrations allowing viral replication. We have examined blood monocytes from HIV-1-infected subjects being effectively treated with HAART to determine virus carriage in these cells. Monocytes were purified from peripheral blood of patients with plasma HIV-1 RNA below 50 copies/mL and who had maintained levels of plasma RNA below detection for 3 months or more. Replication-competent virus could be recovered from the majority of monocyte populations by co-culture with CD8-depleted, PHA-activated, peripheral blood mononuclear cells. Sequencing of the reverse transcriptase and protease genes of the recovered viruses did not reveal resistance to both reverse transcriptase and protease inhibitors. Continued new infection of this transitory, circulating population of cells even during prolonged, effective HAART most likely reflects ongoing, low-level HIV-1 replication within cellular reservoirs and sanctuary sites in the body.
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PMID:HIV-1 can be recovered from a variety of cells including peripheral blood monocytes of patients receiving highly active antiretroviral therapy: a further obstacle to eradication. 1098 50

There is an emerging body of knowledge defining the role of CD8(+) cells in the pathogenesis of allergic asthma. We have previously demonstrated in sensitized Sprague-Dawley (SD) rats that depletion of CD8(+) cells caused an increase in the late airway response (LAR) and cellular infiltration after antigen challenge. To better delineate the mechanism of CD8(+) cell involvement in the development of the LAR and airway inflammation, we investigated the pattern of chemokine and cytokine production after antigen challenge. SD rats were sensitized to ovalbumin (OA) and subsequently treated with anti-CD8 (OX-8) monoclonal antibody (mAb) for the depletion of CD8(+) cells or with control mouse anti-rat IgG(1) mAb as a control procedure. After OA challenge, CD8- depleted SD rats developed an increased LAR when compared with control rats (area under the curve: 16.65 +/- 6.6 in CD8- depleted rats versus 5.39 +/- 2.0 in control animals; p < 0.05). Compared with the control animals, the increase in the LAR was accompanied by a significantly increased eosinophilic infiltration of the airways and was associated with increased eotaxin expression (both messenger RNA [mRNA] and protein) in the CD8-depleted group. There were no differences between the groups in RANTES or monocyte chemoattractant protein-1 (MCP-1) expression. In addition, we found a significantly lower interferon gamma (IFN-gamma) mRNA expression in the CD8-depleted rats, without any effects on interleukin (IL)-4 and IL-5 mRNA expression when measured either by semiquantitative reverse transcriptase/polymerase chain reaction (RT-PCR) or by in situ hybridization for the number of cells expressing these cytokines. Taken together, these results suggest that CD8(+) cells from sensitized SD rats exhibit the functional capacity to suppress the LAR, possibly through downregulation of eotaxin expression and increased expression of IFN-gamma mRNA.
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PMID:CD8 depletion-induced late airway response is characterized by eosinophilia, increased eotaxin, and decreased IFN-gamma expression in rats. 1098 41

The functional status of circulating human immunodeficiency (HIV)-specific CD8 T cells in chronically infected subjects was evaluated. By flow cytometry, only 5 of 7 subjects had detectable CD8 T cells that produced IFN-gamma after stimulation with HIV-infected primary CD4 T cells. In 2 subjects, the frequency of IFN-gamma-producing cells increased 4-fold when IL-2 was added to the culture medium; in another subject, IFN-gamma-producing cells could be detected only after IL-2 was added. IFN-gamma-producing cells ranged from 0.4% to 3% of CD8 T cells. Major histocompatibility complex-peptide tetramer staining, which identifies antigen-specific T cells irrespective of function, was used to evaluate the proportion of HIV-specific CD8 T cells that may be nonfunctional in vivo. CD8 T cells binding to tetramers complexed to HIV gag epitope SLYNTVATL and reverse transcriptase epitope YTAFTIPSI were identified in 9 of 15 and 5 of 12 HLA-A2-expressing seropositive subjects at frequencies of 0.1% to 1.1% and 0.1 to 0.7%, respectively. Freshly isolated tetramer-positive cells expressed a mixed pattern of memory and effector markers. On average, IFN-gamma was produced by less than 25% of tetramer-positive CD8 T cells after stimulation with the relevant gag or reverse transcriptase peptide. In all subjects tested, freshly isolated CD8 T cells were not cytolytic against peptide-pulsed B lymphoblastoid cell line or primary HIV-infected CD4 T-cell targets. Exposure to IL-2 enhanced the cytotoxicity of CD8 T cells against primary HIV-infected CD4 targets in 2 of 2 subjects tested. These results suggest that a significant proportion of HIV-specific CD8 T cells may be functionally compromised in vivo and that some function can be restored by exposure to IL-2.
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PMID:Impaired function of circulating HIV-specific CD8(+) T cells in chronic human immunodeficiency virus infection. 1104 89

The objective of antiretroviral therapy is to obtain an almost complete and durable suppression of viral replication in all compartments to facilitate recovery of the immune system. We assessed the virologic effect in plasma, tonsillar tissue, and cerebrospinal fluid (CSF) in 94 HIV-1-infected patients with CD4 counts >500 x 106 cells per liter and viral load >5000 copies/ml randomly assigned to triple antiretroviral therapy (two nucleoside reverse transcriptase inhibitors (NRTIs) plus one protease inhibitor) versus double therapy (two NRTIs). We also analyzed the immunologic recovery in this cohort of patients. Lymphoid tissue and cerebrospinal fluid viral load, development of genotypic resistance, proliferative responses to HIV-1 specific antigens, and other immunophenotypic markers were analyzed. The proportion of patients who achieved a decrease in HIV RNA levels to <200 copies/ml was significantly greater in the triple therapy group than in the two drug groups (p =.0002 for each pair-wise difference). At week 52, tonsillar tissue HIV RNA from 5 patients treated with triple therapy was lower than the limit of detection, whereas the mean +/- standard error in patients with double therapy (n = 5) was 5.03 +/- 0.34 copies/mg/tissue. In all 10 patients, CSF viral load (VL) was <20 HIV-1 RNA copies/ml at week 52. CSF cell counts and protein levels tended to decrease after 52 weeks of antiretroviral therapy. After 1 year of therapy, 13 of 21 patients (62%) in the double-therapy groups (zidovudine plus lamivudine [n = 9] and stavudine plus lamivudine [n = 12]) had evidence of M184V mutation. None of the 10 samples of patients receiving triple therapy could be amplified because of low HIV RNA levels. The mean increase in CD4 cells at week 52 was greater in the stavudine and lamivudine and indinavir group than in the double-treatment arms (186 versus 67 and 102, respectively; p =.03). In patients treated with triple therapy, the increase in naive T cells (CD4 and CD8) was greater than in patients treated with double therapy. Markers of activation decreased further in patients treated with the regimen that included protease inhibitors. Proliferative responses to HIV-1 p24 antigen were never recovered after double or triple therapy. Our study suggests that even in very early stages of HIV-1 disease only therapy with two NRTIs and one protease inhibitor reduces plasma, lymphoid tissue, and CSF VL to undetectable levels. HIV-1-related immune system abnormalities improved but were still defective after 1 year of antiretroviral therapy.
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PMID:Comparison of immunologic restoration and virologic response in plasma, tonsillar tissue, and cerebrospinal fluid in HIV-1-infected patients treated with double versus triple antiretroviral therapy in very early stages: The Spanish EARTH-2 Study. Early Anti-Retroviral Therapy Study. 1106 1

We report that simian immunodeficiency virus (SIV) infection in macaques is a valuable animal model for studying post-exposure chemoprophylaxis (PECP). PECP with the acyclic nucleoside reverse transcriptase inhibitors 9-(2-phosphonylmetho-xyethyl)adenine (PMEA) and (R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA) at early viral infection can provide long-term protection against subsequent heterologous SIV challenge. Eight macaques previously treated with PECP (called PECP macaques) and four naive controls were challenged intravenously with the most virulent form of SIV, SIV(PBj14). All controls showed signs of SIV(PBj14)-induced acute disease syndrome on days 6 and 7 post-inoculation (PI). One had a fatal viral infection and two surviving controls had persistent infection and decreased CD4+ cell count. Virologic studies of the three surviving controls revealed SIV in multiple lymphoid tissues and peripheral blood mononuclear cells (PBMCs) at necropsy. In contrast, the PECP macaques showed none to mild signs of acute disease syndrome at day 9 PI and exhibited only transient SIV infection in PBMCs between weeks 1 and 8 PI. In virologic studies of five PECP macaques necropsied, two macaques were SIV-negative and the other three were SIV-positive only in either lymph node or bone marrow. Three SIV(PBj14)-challenged PECP macaques, that were randomly reserved for a follow-up study for > 4.0 years PI showed extremely low to undetectable levels of PBMC-associated viremia and normal to increased levels of CD4 + and CD8 + cell counts throughout the study. Our results indicate that early PECP could activate immune responses to protect against subsequent infection with heterologous challenge virus.
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PMID:Post-exposure chemoprophylaxis (PECP) against SIV infection of macaques as a model for protection from HIV infection. 1108 87

Nonreplicating vectors are being considered in HIV-1 vaccine design. However, nonreplicating viruses are typically weak immunogens, leading to efforts to target the vaccine to mature dendritic cells (DCs). We have studied a single-cycle form of HIV-1, prepared by pseudotyping envelope-defective HIV-1 plasmids with the envelope from vesicular stomatitis virus (VSV) G protein (VSV-G), to which most humans lack preexisting immunity. The nonreplicating, VSV/HIV-1 efficiently infected the immature stage of DC development, in this case represented by monocytes cultured with GM-CSF and IL-4. A majority of the cells reverse transcribed the HIV-1 RNA, and a minority expressed gag protein. The infected populations were further matured with CD40 ligand, leading to strong stimulation of autologous T cells from HIV-1-infected individuals, but not controls. Enriched CD8(+) T cells from 12/12 donors released IFN-gamma (50-300 enzyme-linked immunospots/200,000 T cells) and proliferated. Macrophages were much less efficient in expanding HIV-1-responsive T cells, and bulk mononuclear cells responded weakly to VSV/HIV-1. CD4(+) T cells from at least half of the donors showed strong responses to VSV/HIV-1-infected DCs. Presentation to CD8(+) T cells, but not to CD4(+), was primarily through an endogenous pathway, because the responses were markedly reduced if envelope-defective virus particles or reverse transcriptase inhibitors were added. Therefore, nonreplicating vaccines can be targeted to immature DCs, which upon further maturation induce combined and robust CD4(+) and CD8(+) immunity.
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PMID:Dendritic cells, infected with vesicular stomatitis virus-pseudotyped HIV-1, present viral antigens to CD4+ and CD8+ T cells from HIV-1-infected individuals. 1108 7

CD8(+) T lymphocytes, which are major immune effectors, require primary stimulation by dendritic cells (DC) presenting MHC class I molecule-bound epitopes. Sensitization to exogenous protein epitopes that are not synthesized in DC, such as cross-priming, is obtained through pathways leading to their association with MHC class I. To follow class I-restricted pathways in human DC, we have tracked a lipopeptide derived from the conserved HLA-A*0201-restricted HIV-1 reverse transcriptase 476-484 epitope, by N-terminal addition of an Nepsilon-palmytoyl-lysine. Indeed, lipopeptides elicit cytotoxic responses from CD8(+) T lymphocytes, whereas peptides without a lipid moiety do not. The lipopeptide and its parent peptide were labeled unequivocally by rhodamine to study their entry into immature monocyte-derived human DC by confocal microscopy. The lipid moiety induced endocytosis of the lipopeptide, assessed by rapid entry into vesicles, colocalization with Dextran-FITC and dependence on energy. Internalization occurred even when actin filaments were depolymerized by Cytochalasin B. This internalization induced functional stimulation of specific CD8(+) T lymphocytes in IFN-gamma ELISPOT assays. The peptide alone was not visualized inside the DC and was presented through direct surface association to HLA-A*0201. Therefore, lipopeptides are a unique opportunity to define precisely the pathways that lead exogenous proteins to associate with MHC class I molecules in DC. The results will also be useful to design lipopeptide vaccines.
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PMID:Endocytosis of an HIV-derived lipopeptide into human dendritic cells followed by class I-restricted CD8(+) T lymphocyte activation. 1109 41

Potential live vaccines for HIV were developed using an Lpp-OmpA system to target an HIV antigen, reverse transcriptase, or an immunodominant epitope of this enzyme, to the outer membrane of an attenuated strain of Salmonella SL3261. These live vaccines were administered orally to mice, and fecal IgA and helper T cell responses were measured. Results indicated a fecal IgA response specific to HIV reverse transcriptase, as well as a reverse transcriptase-specific helper T cell response, as measured by proliferation assays. Additionally, tests with the epitope vaccines showed a selective cytotoxic CD8 T cell response. These results suggest that this method of antigen targeting to the outer membrane of attenuated bacterial vectors is very promising not only for HIV vaccine development, but also for antigens from other viral or bacterial pathogens, which could be inserted into the Lpp-OmpA protein construct, to elicit mucosal IgA and T cell responses.
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PMID:Potential live vaccines for HIV. 1111 94

Chemokines appear to have an important role in the seeding of lymphoid progenitors in the thymus, the regulation of the coordinated movements of the maturing T cells within this organ, and the egress of the resulting naive T cells to secondary lymphoid organs. CCR9, the specific receptor for the beta-chemokine TECK/CCL25, is selectively expressed in thymus, lymph node, and spleen. Using a specific anti-CCR9 polyclonal antibody, K629, and a semiquantitative reverse transcriptase-polymerase chain reaction procedure, a detailed study of CCR9 expression in the thymus and secondary lymphoid organs was performed. The results show that CD4(+)CD8(+) double-positive thymocytes have the highest CCR9 expression in thymus. Single-positive CD8(+) thymocytes continue to express this receptor after abandoning the thymus as mature naive T cells, as suggested by the existence of a CD8(+)CD69(low)CD62L(high) CCR9(+) cell subset. Consistent with this, CD8(+) lymphocytes from lymph nodes, spleen, and Peyer patches express a functional CCR9, as its expression correlates with migration in response to CCL25. Conversely, CD4(+) thymocytes lose CCR9 before abandoning the thymus, and CD4(+) T cells from secondary lymphoid organs also lack CCR9 expression. Analysis of CCR9 expression in thymocytes from mice of different ages showed that CCR9 levels are affected by age, as this receptor is more abundant, and its response to CCL25 is more potent in newborn animals. Collectively, these results suggest that CCR9 has a role in thymocyte development throughout murine life, with clear differences between the CD4(+) and CD8(+) lineages.
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PMID:Expression of CCR9 beta-chemokine receptor is modulated in thymocyte differentiation and is selectively maintained in CD8(+) T cells from secondary lymphoid organs. 1115 7


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