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

---

Query: UMLS:C0021051 (immunodeficiency)
71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The high affinity binding site for human immunodeficiency virus (HIV) envelope glycoprotein gp120 resides within the amino-terminal domain (D1) of CD4. Mutational and antibody epitope analyses have implicated the region encompassing residues 40-60 in D1 as the primary binding site for gp120. Outside of this region, a single residue substitution at position 87 abrogates syncytium formation without affecting gp120 binding. We describe two groups of CD4 monoclonal antibodies (mAbs) which recognize distinct epitopes associated with these regions in D1. These mAbs distinguish between the gp120 binding event and virus infection and virus-induced cell fusion. One cluster of mAbs, which bind at or near the high affinity gp120 binding site, blocked gp120 binding to CD4 and, as expected, also blocked HIV infection of CD4+ cells and virus-induced syncytium formation. A second cluster of mAbs, which recognize the CDR-3 like loop, did not block gp120 binding as demonstrated by their ability to form ternary complexes with CD4 and gp120. Yet, these mAbs strongly inhibited HIV infection of CD4+ cells and HIV-envelope/CD4-mediated syncytium formation. The structure of D1 has recently been solved at atomic resolution and in its general features resembles IgVk regions as predicted from sequence homology and mAb epitopes. In the D1 structure, the regions recognized by these two groups of antibodies correspond to the C'C" (Ig CDR2) and FG (Ig CDR3) hairpin loops, respectively, which are solvent-exposed beta turns protruding in two different directions on a face of D1 distal to the D2 domain. This face is straddled by the longer BC (Ig CDR1) loop which bisects the plain formed by C'C'' and FG. This structure is consistent with C'C'' and FG forming two distinct epitope clusters within D1. We conclude that the initial interaction between gp120 and CD4 is not sufficient for HIV infection and syncytium formation and that CD4 plays a critical role in the subsequent virus-cell and cell-cell membrane fusion events. We propose that the initial binding of CD4 to gp120 induces conformational changes in gp120 leading to subsequent interactions of the FG loop with other regions in gp120 or with the fusogenic gp41 potion of the envelope gp160 glycoprotein.
...
PMID:A region in domain 1 of CD4 distinct from the primary gp120 binding site is involved in HIV infection and virus-mediated fusion. 170 42

Infection of mononuclear cells by human immunodeficiency virus (HIV) begins with binding of the viral envelope glycoprotein, gp120, to its receptor, CD4. CD4 contains four extracellular immunoglobulin-like domains, the first of which (V1) is sufficient for HIV binding. V1 contains three sequences homologous to the antigen-complementarity-determining regions (CDR1 to -3) of immunoglobulin variable domains. While all three immunoglobulin CDRs are involved in antigen binding, only amino acids within and flanking the CDR2-like region of CD4 have been shown previously to be involved in gp120 binding. To investigate whether other regions in V1 take part in gp120 binding, we substituted alanine for each of 64 amino acids, including all of the hydrophilic residues in this domain. Mutations at four locations outside the CDR2-like sequence (amino acids 29, 59-64, 77-81, and 85) markedly affected gp120 binding, but not the overall structure of V1 as probed with eight conformationally sensitive monoclonal antibodies. Thus, the gp120-binding site of CD4 is not limited to the CDR2-like sequence and consists of several discontinuous segments. Several amino acids were identified that are critical for the conformation of V1; the importance of these residues suggests some differences in the folding of this domain compared to immunoglobulin variable domains. Three amino acid substitutions were found that increase the affinity for gp120 significantly (1.7- to 2-fold individually and 4.2-fold when combined), suggesting that it may be possible to improve the HIV-blocking ability of CD4-based molecules by increasing their gp120 binding affinity.
...
PMID:Mapping the CD4 binding site for human immunodeficiency virus by alanine-scanning mutagenesis. 240 98

Murine AIDS, induced by LP-BM5 murine leukemia retrovirus infection, causes a progressive and profound immunodeficiency in female C57B1/6 mice. Previously, we reported that autoantibodies were elevated during the initiation phases of this murine retrovirus infection and bound peptide determinants corresponding to CDR1 of several TCR V beta-chains. Therefore, we designed studies to determine whether administration of a major autoimmunogenic TCR V beta CDR1 peptide before or after infection with LP-BM5 retrovirus would modulate retrovirus-induced dysregulation of T cell function. Administration of the TCR V beta CDR1 peptide before murine retrovirus infection significantly prevented its suppression of splenic NK cell activity, T and B cell proliferation, and monokine (IL-6 and TNF-alpha) and Th1 cytokine (IL-2 and IFN-gamma) release by splenocytes, and inhibited retrovirus-induced elevation of Th2 cytokine (IL-5 and IL-10). Similar data were obtained with peptide immunization 2 wk after murine retrovirus infection at 6 and 16 wk postinfection. However, delaying peptide immunization until severe suppression of T and B cell mitogenesis had occurred did not restore their functions. Immunization with TCR V beta peptide prevents development of retrovirus-induced immune dysfunction, which suggests a possible pathogenic role of autoreactive T cells as regulatory elements.
...
PMID:T cell receptor V beta complementarity-determining region 1 peptide administration moderates immune dysfunction and cytokine dysregulation induced by murine retrovirus infection. 763 74

Autoantibodies (AAbs) directed against particular segments of the variable region of TCR beta chains occur in normal humans and in certain autoimmune diseases, but the factors regulating the appearance of such antibodies are unknown. We report that AAbs binding a peptide determinant corresponding to the CDR1 of the V beta domain are elevated in C57BL/6 mice following infection with the LP-BM5 murine leukemia retrovirus mixture, a treatment used to induce murine AIDS. The elevation of the level of these AAbs is an early event following retroviral infection which corresponds in part to the general polyclonal activation of the B cells, but a selectivity for particular V beta sequences is apparent later. This suggests that the appearance of these antibodies may play a part in the subsequent development of immunodeficiency. Since the antibodies studied are of the IgG isotype, both T cells and B cells are involved in their elaboration.
...
PMID:Production of IgG autoantibodies to TCRs in mice infected with the retrovirus LP-BM5. 771 13

Autoimmune reactivity is a consequence of infection with human immunodeficiency virus (HIV). We studied serological cross-reactions of purified pooled IgG from sera of HIV-infected individuals by using nested sets of synthetic overlapping peptides duplicating the covalent structures of T-cell receptors (TCRs) and immunoglobulin light chains and report that two processes of autoantibody production occur. (i) IgG autoantibodies to putative regulatory variable domain CDR1 and FR3 epitopes (where CDR is complementarity-determining region and FR is framework region) are present in pooled IgG from HIV-infected individuals at levels 10-fold greater than that in pooled IgG from healthy humans. (ii) Anti-TCR autoimmunization involves antigenic mimicry between a conserved peptide stretch of the major neutralizing V3 loop determinant of HIV-1 gp120 and the conserved FR4 segment of the TCR V beta. Affinity-purified antibodies to the synthetic V3 loop peptide bound to a recombinant single-chain TCR and to a synthetic TCR joining segment peptide containing the FR4 sequence. Conversely, affinity-purified autoantibodies from pooled IgG from HIV-infected individuals to the TCR peptide bound the V3 loop peptide and a single-chain TCR. Inhibition studies indicated that the cross-reactive immunizing antigen was the V3 loop. These results bear upon the impact of HIV infection on immune regulation and on the selection of peptides for vaccine development.
...
PMID:Autoantibodies to the alpha/beta T-cell receptors in human immunodeficiency virus infection: dysregulation and mimicry. 797 73

Autoantibodies directed against peptide-defined epitopes of T-cell receptors occur in the serum of healthy humans with the levels and isotypic expression dependent upon physiological changes (aging, pregnancy) or upon the development of autoimmune disease. We carried out investigations of autoantibodies against Tcr peptide-defined epitopes in retroviral infections of humans (HIV-1) and mice (LP-BM5 strain of murine leukemia virus) to determine whether infection with these agents disrupted the regulation of the production of these antibodies. Retroviral infection in humans resulted in increased levels of autoantibody production against putative immunoregulatory regions of the Tcr beta chain (V beta CDR1 and Fr3), a result reflecting a disruption of regulation. In addition, antigenic mimicry was observed with a cross-reaction shared between the common portion of the V3 neutralizing loop of the HIV-1 gp120 molecule and the joining segment of T-cell receptors (J beta). Infection of mice with the defective retrovirus resulted in the induction of antibodies directed particularly against V beta CDR1 peptide-defined determinants. Analysis of the virally induced response to a set of 8 CDR1 peptide epitopes indicated a selectivity to the process. It was possible to partially reverse aberrant cytokine changes correlated with the onset of murine MAIDS by administration of T-cell receptor peptides in saline. These results show that retroviral infection in humans and mice has a profound dysfunctional effect on the regulation of autoantibodies to T-cell receptors. The function of these autoantibodies in the immunopathogenesis of acquired immunodeficiency remains to be determined.
...
PMID:Autoantibodies against peptide-defined epitopes of T-cell receptors in retrovirally infected humans and mice. 864 4

Individuals seropositive for human immunodeficiency virus type 1 (HIV) express elevated levels of autoantibodies (AAbs) directed against recombinant T-cell receptors (TCRs) and synthetic peptide epitopes duplicating beta chain markers. We performed longitudinal studies of anti-TCR AAbs in HIV-1-infected individuals, making comparisons with uninfected sera and sera from other individuals infected with a nonviral agent. We determined levels of autoantibodies by titration using enzyme-linked immunosorbent assay (ELISA) and developed a means for characterizing "autoantibody CDR recognition spectrotypes" for individual sera. Antibody levels against certain defined synthetic epitopes were substantially elevated in HIV-infected subjects relative to reactivities by control groups. Individual sera showed relatively high AAb levels to a subset of CDR1 peptide epitopes. Two patients who subsequently developed AIDS showed particular reactivity to Vbeta2.1, 8.1, 10.1, and 22.1 epitopes. Our results show that production AAbs to TCR Vbeta epitopes is a general consequence of HIV infection. The response is individual but shows some restriction and shifts in AAb subpopulations often occur with time.
...
PMID:Analysis of autoantibodies to T-cell receptors among HIV-infected individuals: epitope analysis and time course. 900 Apr 86

Resistance to antifungal drugs, specifically azoles such as fluconazole, in the opportunistic yeast Candida albicans has become an increasing problem in human immunodeficiency virus (HIV)-infected individuals. The molecular mechanisms responsible for this resistance have only recently become apparent and can include alterations in the target enzyme of the azole drugs (lanosterol 14alpha demethylase [14DM]), or in various efflux pumps from both the ABC transporter and major facilitator gene families. To determine which of these possible mechanisms was associated with the development of drug resistance in a particular case, mRNA levels have been studied in a series of 17 clinical isolates taken from a single HIV-infected patient over 2 years, during which time the levels of fluconazole resistance of the strain increased over 200-fold. Using Northern blot analysis of steady-state levels of total RNA from these isolates, we observed increased mRNA levels of ERG16 (the 14DM-encoding gene), CDR1 (an ABC transporter), and MDR1 (a major facilitator) in this series. The timing of the increase in mRNA levels of each of these genes correlated with increases in fluconazole resistance of the isolates. Increased mRNA levels were not observed for three other ABC transporters, two other genes in the ergosterol biosynthetic pathway, or the NADPH-cytochrome P-450 oxidoreductase gene that transfers electrons from NADPH to 14DM. Increases in mRNA levels of ERG16 and CDR1 correlated with increased cross-resistance to ketoconazole and itraconazole but not to amphotericin B. A compilation of the genetic alterations identified in this series suggests that resistance develops gradually and is the sum of several different changes, all of which contribute to the final resistant phenotype.
...
PMID:Increased mRNA levels of ERG16, CDR, and MDR1 correlate with increases in azole resistance in Candida albicans isolates from a patient infected with human immunodeficiency virus. 921 Jun 70

Candida dubliniensis is a recently described Candida species associated with oral candidosis in human immunodeficiency virus (HIV)-infected and AIDS patients, from whom fluconazole-resistant clinical isolates have been previously recovered. Furthermore, derivatives exhibiting a stable fluconazole-resistant phenotype have been readily generated in vitro from fluconazole-susceptible isolates following exposure to the drug. In this study, fluconazole-resistant isolates accumulated up to 80% less [3H] fluconazole than susceptible isolates and also exhibited reduced susceptibility to the metabolic inhibitors 4-nitroquinoline-N-oxide and methotrexate. These findings suggested that C. dubliniensis may encode multidrug transporters similar to those encoded by the C. albicans MDR1, CDR1, and CDR2 genes (CaMDR1, CaCDR1, and CaCDR2, respectively). A C. dubliniensis homolog of CaMDR1, termed CdMDR1, was cloned; its nucleotide sequence was found to be 92% identical to the corresponding CaMDR1 sequence, while the predicted CdMDR1 protein was found to be 96% identical to the corresponding CaMDR1 protein. By PCR, C. dubliniensis was also found to encode homologs of CDR1 and CDR2, termed CdCDR1 and CdCDR2, respectively. Expression of CdMDR1 in a fluconazole-susceptible delta pdr5 null mutant of Saccharomyces cerevisiae conferred a fluconazole-resistant phenotype and resulted in a 75% decrease in accumulation of [3H]fluconazole. Northern analysis of fluconazole-susceptible and -resistant isolates of C. dubliniensis revealed that fluconazole resistance was associated with increased expression of CdMDR1 mRNA. In contrast, most studies showed that overexpression of CaCDR1 was associated with fluconazole resistance in C. albicans. Increased levels of the CdMdr1p protein were also detected in fluconazole-resistant isolates. Similar results were obtained with fluconazole-resistant derivatives of C. dubliniensis generated in vitro, some of which also exhibited increased levels of CdCDR1 mRNA and CdCdr1p protein. These results demonstrate that C. dubliniensis encodes multidrug transporters which mediate fluconazole resistance in clinical isolates and which can be rapidly mobilized, at least in vitro, on exposure to fluconazole.
...
PMID:Identification and expression of multidrug transporters responsible for fluconazole resistance in Candida dubliniensis. 966 Oct 28

Oral infections with the pathogenic yeast Candida albicans are one of the most frequent and earliest opportunistic infections in human immunodeficiency virus-infected patients. The widespread use of azole antifungal drugs has led to the development of drug-resistant isolates. Several molecular mechanisms that contribute to drug resistance have been identified, including increased mRNA levels for two types of efflux pump genes: the ATP binding cassette transporter CDRs (CDR1 and CDR2) and the major facilitator MDR1. Using Northern blot analyses, the expression patterns of these genes have been determined during logarithmic and stationary phases of cell growth and during growth in different carbon sources in a set of matched susceptible and fluconazole-resistant isolates that have been characterized previously. MDR1, CDR1, and CDR2 are expressed early during logarithmic growth, CDR4 is expressed late during logarithmic growth, and CDR1 is preferentially expressed in stationary-phase cells. There is a small decrease in expression of these genes when the cells are grown in carbon sources other than glucose. While increased mRNA levels of efflux pump genes are commonly associated with azole resistance, the causes of increased mRNA levels have not yet been resolved. Southern blot analysis demonstrates that the increased mRNA levels in these isolates are not the result of gene amplification. Nuclear run-on assays show that MDR1 and CDR mRNAs are transcriptionally overexpressed in the resistant isolate, suggesting that the antifungal drug resistance in this series is associated with the promoter and trans-acting factors of the CDR1, CDR2, and MDR1 genes.
...
PMID:Transcriptional analyses of antifungal drug resistance in Candida albicans. 1095 71


1 2 Next >>

---