Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Resistance to fluconazole is becoming an increasing problem in the management of oropharyngeal candidiasis in human immunodeficiency virus-infected patients. Strains obtained from five patients developed decreased fluconazole susceptibility over time. DNA strain typing confirmed the high degree of relatedness among isolates from one patient and the variability among isolates from different patients. Expression of genes involved in development of fluconazole resistance was monitored in each isolate using probes specific for ERG11 (lanosterol 14alpha-demethylase), MDR1 (a major facilitator), and CDR (ATP-binding cassette or ABC transporter) genes. Increased expression of CDR genes was detected in the series of isolates from two patients. Isolates from one of the two patients also demonstrated increased ERG11 expression, whereas isolates from the other patient did not. Increased levels of MDR1 mRNA correlated with increased resistance in sequential isolates from another patient. Initial overexpression of MDR1 with subsequent overexpression of CDR genes and a final isolate again overexpressing MDR1 were detected in serial isolates from another patient. In another patient, overexpression of these genes was not detected despite an eightfold increase in fluconazole MIC. In this patient, sequence data of the ERG11 gene revealed no point mutations associated with decreased susceptibility. Five different patterns of gene expression were observed in isolates recovered from five patients who developed resistance. Therefore, these experiments demonstrate that a variety of mechanisms or combinations of mechanisms are associated with the development of fluconazole drug resistance. Additional studies are needed to estimate the frequency and clinical impact of these mechanisms of resistance.
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PMID:Distinct patterns of gene expression associated with development of fluconazole resistance in serial candida albicans isolates from human immunodeficiency virus-infected patients with oropharyngeal candidiasis. 979 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.
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PMID:Transcriptional analyses of antifungal drug resistance in Candida albicans. 1095 71

7B4, B6 and D12 are murine monoclonal antibodies (MoAb) that bind to some human immunoglobulin heavy chain products of the closely related V3-30, V3-30.3 and V3-33 genes from the VH3 family. B6 and D12 have additional reactivities with some immunoglobulins (Ig) encoded by the V3-11 and V3-7 genes; D12 also reacts with some V3-43 gene Ig. We show here, by site-directed mutagensis, that the lysine at position 57 in the complementarity-determining region 2 (CDR-2) of the V3-30 gene product is crucial for epitope recognition by all three anti-VH3 MoAbs. Further analysis of the amino-acid sequences of a large panel of Ig reactive, or nonreactive, with MoAb 7B4 indicates that the determinant recognized by 7B4 is dependent on the presence of the tetrapeptide sequence NKYY between positions 56 and 59 in the CDR-2. Comparing the efficiency of 7B4 reactivity with VH3 gene-encoded human Ig indicates that amino-acid position 4 in the frame region 1 (FR-1) may also influence the binding of 7B4 to Ig encoded by three very closely related germline genes, V3-30, V3-30.3 and V3-33. NKYY is also found on the gp120 V3 region of human immunodeficiency virus (HIV)-2, SIV and HTLV-4. We also report that other tetrapeptide sequences found on the 56-59 motif of heavy chain variable regions encoded by germline genes are expressed on the solvent exposed V2 region of gp120 of HIV-1 isolates. The possible significance of these observations is discussed.
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PMID:Molecular analysis of human immunoglobulin heavy chain variable region associated determinants recognized by anti-VH3 antibodies 7B4, B6 and D12. 1101 4

We present the crystal structure at 2.7 angstrom resolution of the human antibody IgG1 b12. Antibody b12 recognizes the CD4-binding site of human immunodeficiency virus-1 (HIV-1) gp120 and is one of only two known antibodies against gp120 capable of broad and potent neutralization of primary HIV-1 isolates. A key feature of the antibody-combining site is the protruding, finger-like long CDR H3 that can penetrate the recessed CD4-binding site of gp120. A docking model of b12 and gp120 reveals severe structural constraints that explain the extraordinary challenge in eliciting effective neutralizing antibodies similar to b12. The structure, together with mutagenesis studies, provides a rationale for the extensive cross-reactivity of b12 and a valuable framework for the design of HIV-1 vaccines capable of eliciting b12-like activity.
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PMID:Crystal structure of a neutralizing human IGG against HIV-1: a template for vaccine design. 1149 95

Molecular mechanisms of azole resistance in Candida albicans, including alterations in the target enzyme and increased efflux of drug, have been described, but the epidemiology of the resistance mechanisms has not been established. We have investigated the molecular mechanisms of resistance to azoles in C. albicans strains displaying high-level fluconazole resistance (MICs, > or =64 microg/ml) isolated from human immunodeficiency virus (HIV)-infected patients with oropharyngeal candidiasis. The levels of expression of genes encoding lanosterol 14alpha-demethylase (ERG11) and efflux transporters (MDR1 and CDR) implicated in azole resistance were monitored in matched sets of susceptible and resistant isolates. In addition, ERG11 genes were amplified by PCR, and their nucleotide sequences were determined in order to detect point mutations with a possible effect in the affinity for azoles. The analysis confirmed the multifactorial nature of azole resistance and the prevalence of these mechanisms of resistance in C. albicans clinical isolates exhibiting frank fluconazole resistance, with a predominance of overexpression of genes encoding efflux pumps, detected in 85% of all resistant isolates, being found. Alterations in the target enzyme, including functional amino acid substitutions and overexpression of the gene that encodes the enzyme, were detected in 65 and 35% of the isolates, respectively. Overall, multiple mechanisms of resistance were combined in 75% of the isolates displaying high-level fluconazole resistance. These results may help in the development of new strategies to overcome the problem of resistance as well as new treatments for this condition.
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PMID:Prevalence of molecular mechanisms of resistance to azole antifungal agents in Candida albicans strains displaying high-level fluconazole resistance isolated from human immunodeficiency virus-infected patients. 1155 54

Candida dubliniensis is a newly identified species of Candida that is phenotypically similar to but genetically distinct from C. albicans. This organism has been recovered with increasing frequency from the oral cavities of human immunodeficiency virus (HIV)-infected and AIDS patients and has been implicated as a causative agent of oral candidiasis and systemic disease. In the present study we characterized the molecular mechanisms of resistance to fluconazole (FLC) in C. dubliniensis clinical isolates from two different HIV-infected patients with oropharyngeal candidiasis. Isolates were identified to the species level by phenotypic and genotypic tests. DNA-typing techniques were used to assess strain identity. Antifungal susceptibility testing was performed by NCCLS techniques. Northern blotting analysis was used to monitor the expression of genes encoding lanosterol demethylase (ERG11) and efflux transporters (CDR and MDR1) in matched sets of C. dubliniensis-susceptible and -resistant isolates by using probes generated from their homologous C. albicans sequences. In addition, ERG11 genes were amplified by PCR, and their nucleotide sequences were determined in order to detect point mutations with a possible effect in the affinity for azoles. Decreasing susceptibilities to FLC were detected in C. dubliniensis isolates recovered from both patients during the course of treatment. FLC-resistant C. dubliniensis isolates from one patient demonstrated combined upregulation of the MDR1, CDR1, and ERG11 genes. Among the isolates from the second patient, all isolates showing decreased susceptibility to FLC demonstrated upregulation of MDR1, whereas the levels of mRNA for the ERG11 genes remained constant and the expression of CDR genes was negligible. Fourteen point mutations were found in the ERG11 genes of the isolates with decreased susceptibility to FLC. These data demonstrate that the development of azole resistance in C. dublinensis clinical isolates from HIV-infected patients treated with FLC is mediated by multiple molecular mechanisms of resistance, similar to the observations found in the case of C. albicans.
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PMID:Molecular mechanisms of fluconazole resistance in Candida dubliniensis isolates from human immunodeficiency virus-infected patients with oropharyngeal candidiasis. 1201 78

The human monoclonal antibody 2F5 neutralizes primary human immunodeficiency virus type 1 (HIV-1) with rare breadth and potency. A crystal structure of a complex of 2F5 and a peptide corresponding to its core epitope on gp41, ELDKWAS, revealed that the peptide interacts with residues at the base of the unusually long (22-residue) third complementarity-determining region of the heavy chain (CDR H3) but not the apex. Here, we perform alanine-scanning mutagenesis across CDR H3 and make additional substitutions of selected residues to map the paratope of Fab 2F5. Substitution of residues from the base of the H3 loop or from CDRs H1, H2, and L3, which are proximal to the peptide, significantly diminished the affinity of Fab 2F5 for gp41 and a short peptide containing the 2F5 core motif. However, nonconservative substitutions to a phenylalanine residue at the apex of the H3 loop also markedly decreased 2F5 binding to both gp41 and the peptide, suggesting that recognition of the core epitope is crucially dependent on features at the apex of the H3 loop. Furthermore, substitution at the apex of the H3 loop had an even more pronounced effect on the neutralizing activity of 2F5 against three sensitive HIV-1. These observations present a challenge to vaccine strategies based on peptide mimics of the linear epitope.
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PMID:The long third complementarity-determining region of the heavy chain is important in the activity of the broadly neutralizing anti-human immunodeficiency virus type 1 antibody 2F5. 1499 Jul 36

We have determined the crystal structure of the Fab fragment from F105, a broadly reactive human antibody with limited potency that recognizes the CD4 binding site of gp120. The structure reveals an extended CDR H3 loop with a phenylalanine residue at the apex and shows a striking pattern of serine and tyrosine residues. Modeling the interaction between gp120 and F105 suggests that the phenylalanine may recognize the binding pocket of gp120 used by Phe(43) of CD4 and that numerous tyrosine and serine residues form hydrogen bonds with the main chain atoms of gp120. A comparison of the F105 structure to that of immunoglobulin G1 b12, a much more potent and broadly neutralizing antibody with an overlapping epitope, suggests similarities that contribute to the broad recognition of human immunodeficiency virus by both antibodies. While the putative epitope for F105 shows significant overlap with that predicted for b12, it appears to differ from the b12 epitope in extending across the interface between the inner and outer domains of gp120. In contrast, the CDR loops of b12 appear to interact predominantly with the outer domain of gp120. The difference between the predicted epitopes for b12 and F105 suggests that the unique potency of b12 may arise from its ability to avoid the interface between the inner and outer domains of gp120.
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PMID:Structure of the Fab fragment of F105, a broadly reactive anti-human immunodeficiency virus (HIV) antibody that recognizes the CD4 binding site of HIV type 1 gp120. 1618 8

Elicitation of potent and broadly neutralizing antibodies is an important goal in designing an effective human immunodeficiency virus-1 (HIV-1) vaccine. The HIV-1 gp41 inner-core trimer represents a functionally and structurally conserved target for therapeutics. Here we report the 2.0-A-resolution crystal structure of the complex between the antigen-binding fragment of D5, an HIV-1 cross-neutralizing antibody, and 5-helix, a gp41 inner-core mimetic. Both binding and neutralization depend on residues in the D5 CDR H2 loop protruding into the conserved gp41 hydrophobic pocket, as well as a large pocket in D5 surrounding core gp41 residues. Kinetic analysis of D5 mutants with perturbed D5-gp41 interactions suggests that D5 persistence at the fusion intermediate is crucial for neutralization. Thus, our data validate the gp41 N-peptide trimer fusion intermediate as a target for neutralizing antibodies and provide a template for identification of more potent and broadly neutralizing molecules.
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PMID:Structural basis for HIV-1 neutralization by a gp41 fusion intermediate-directed antibody. 1686 57

AIDS is mainly a sexually transmitted disease, and accordingly, mucosal tissues are the primary sites of natural human immunodeficiency virus type-1 (HIV-1) transmission. Mucosal immunoglobulin A (IgA) antibody specific for HIV-1 envelope gp41 subunit is one correlate of protection in individuals who are highly sexually exposed to HIV-1 but remain persistently IgG seronegative (HEPS). Understanding these peculiar IgAs at the gene and functional level is possible only with monoclonal IgAs. We have constructed a mucosal Fab IgA library from HEPS and have characterized a series of HIV-1 IgAs specific for gp41 that, in vitro, are transcytosis-blocking and infection-neutralizing. Characterization of their IgA genes shows that Fab specific for the gp41 membrane-proximal region harbors a long heavy-chain CDR3 loop (CDRH3) similar to the two broadly neutralizing IgG monoclonal antibodies, 2F5 and 4E10. Furthermore, the selected Fab IgA shows extensive somatic mutations that cluster in the CDR regions, indicating that affinity maturation due to an antigen-driven process had occurred in HEPS individuals, presumably upon multiple exposures to HIV. This analysis of HEPS monoclonal IgA gives a unique opportunity to correlate an antibody function (resistance to a pathogen in vivo) with an antibody gene. Such neutralizing monoclonal IgAs could be used in microbicide formulation.
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PMID:HIV-1 gp41-specific monoclonal mucosal IgAs derived from highly exposed but IgG-seronegative individuals block HIV-1 epithelial transcytosis and neutralize CD4(+) cell infection: an IgA gene and functional analysis. 1958 40


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