bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid and Inexpensive Drug Susceptibility Testing of
Mycobacterium tuberculosis
with a Nitrate Reductase Assay
Authors: Ängeby K. A. Kristian , Klintz Lisbeth , Hoffner Sven E. 
Published: July 2002

ABSTRACT

Multidrug-resistant tuberculosis is an increasing public health concern in many parts of the world, especially in low-income countries, where most cases occur. Traditional drug susceptibility testing is either time-consuming, such as the proportion method on solid media, or expensive, such as the BACTEC 460 system. We have evaluated a new nitrate reductase assay (NRA) that depends on the ability of
Mycobacterium tuberculosis
to reduce nitrate to nitrite. The reduction can be detected using specific reagents, which produce a color change. We tested a panel of 57
M. tuberculosis
strains with various resistance patterns. The bacteria were inoculated on Löwenstein-Jensen medium, either without drugs or with rifampin, isoniazid, streptomycin, or ethambutol and with potassium nitrate (KNO
3
) incorporated. After incubation for 7, 10, or 14 days, the reagents were added and nitrate reduction, indicating growth, could be detected by a color change. Sensitivities to and specificities for drugs as determined by the NRA method compared to those determined by the BACTEC 460 method were 100 and 100% for rifampin, 97 and 96% for isoniazid, 95 and 83% for streptomycin, and 75 and 98% for ethambutol, respectively. The results were in the majority of the cases available in 7 days. The evaluated method is rapid and inexpensive and could correctly identify most resistant and sensitive
M. tuberculosis
strains. It has the potential to become an interesting alternative to existing methods, such as the proportion and BACTEC methods, particularly in resource-poor settings.
Rapid Identification ofCandidaSpecies by Confocal Raman Microspectroscopy
Authors: Maquelin K. , Choo-Smith L.-P. , Endtz H. P. , Bruining H. A. , Puppels G. J. 
Published: July 2002

ABSTRACTCandidaspecies are important nosocomial pathogens associated with high mortality rates. Rapid detection and identification ofCandidaspecies can guide a clinician at an early stage to prescribe antifungal drugs or to adjust empirical therapy when resistant species are isolated. Confocal Raman microspectroscopy is highly suitable for the rapid identification ofCandidaspecies, since Raman spectra can be directly obtained from microcolonies on a solid culture medium after only 6 h of culturing. In this study, we have used a set of 42Candidastrains comprising five species that are frequently encountered in clinical microbiology to test the feasibility of the technique for the rapid identification ofCandidaspecies. The procedure was started either from a culture on Sabouraud medium or from a positive vial of an automated blood culture system. Prior to Raman measurements, strains were subcultured on Sabouraud medium for 6 h to form microcolonies. Using multivariate statistical analyses, a high prediction accuracy (97 to 100%) was obtained with the Raman method. Identification with Raman microspectroscopy may therefore be significantly faster than identification with commercial identification systems that allow various species to be identified and that often require 24 to 48 h before a reliable identification is obtained. We conclude that confocal Raman microspectroscopy offers a rapid, accurate, and easy-to-use alternative for the identification of clinically relevantCandidaspecies.
Frequency of Mutations Conferring Resistance to Nucleoside Reverse Transcriptase Inhibitors in Human Immunodeficiency Virus Type 1-Infected Patients in Korea
Authors: Cho Young Keol , Sung Heungsup , Ahn Sun Hee , Bae In Gyu , Woo Jun Hee , Won Young Ho , Kim Dae Ghon , Kang Moon Won 
Published: July 2002

ABSTRACT

A nested PCR and direct sequencing methods were used to define human immunodeficiency virus type 1(HIV-1) reverse transcriptase codons 41 to 219 in DNA from 127 peripheral blood mononuclear cell samples obtained from 35 patients treated with nucleoside reverse transcriptase inhibitors (NRTI). The follow-up period after the initiation of NRTI therapy was 61.8 ± 31 months (mean and standard deviation). In addition to NRTI therapy, 32 of 35 patients were simultaneously treated with Korean red ginseng. The annual decrease in the CD4
+
T-cell count over 5 years was 13.2/μl. Twenty-eight (80%) of the 35 patients had mutations conferring resistance to NRTI. The frequencies of K70R, T215S/Y/F (i.e., mutation of T at codon 215 to S, Y, or F), D67N/E, K219Q, T69N/S/A, M41L, and L210W mutations conferring resistance to zidovudine were 57.6, 36.4, 36.4, 27.2, 24.2, 21.2, and 12.1%, respectively. Mutations conferring resistance to didanosine and lamivudine were detected in 2 (L74V and M184I; 14.2%) of 11 patients tested and in 4 (M184V; 57%) of 7 patients tested, respectively. In particular, the frequency of T69N/S/A increased sharply after more than 48 months of zidovudine monotherapy. However, Q151M was not detected. As the first report on the frequency of NRTI resistance mutations in Korea, our data suggest that genotypic antiretroviral drug testing should be considered for the design of better drug regimens to improve the management of HIV-1-infected patients.
Prevalent Bacterial Species and Novel Phylotypes in Advanced Noma Lesions
Authors: Paster B. J. , Falkler, W. A. , Enwonwu C. O. , Idigbe E. O. , Savage K. O. , Levanos V. A. , Tamer M. A. , Ericson R. L. , Lau C. N. , Dewhirst F. E. 
Published: July 2002

ABSTRACTThe purpose of this study was to determine the bacterial diversity in advanced noma lesions using culture-independent molecular methods. 16S ribosomal DNA bacterial genes from DNA isolated from advanced noma lesions of four Nigerian children were PCR amplified with universally conserved primers and spirochetal selective primers and cloned intoEscherichia coli. Partial 16S rRNA sequences of approximately 500 bases from 212 cloned inserts were used initially to determine species identity or closest relatives by comparison with sequences of known species or phylotypes. Nearly complete sequences of approximately 1,500 bases were obtained for most of the potentially novel species. A total of 67 bacterial species or phylotypes were detected, 25 of which have not yet been grown in vitro. Nineteen of the species or phylotypes, includingPropionibacterium acnes,Staphylococcusspp., and the opportunistic pathogensStenotrophomonas maltophiliaandOchrobactrum anthropiwere detected in more than one subject. Other known species that were detected includedAchromobacterspp.,Afipiaspp.,Brevundimonas diminuta,Capnocytophagaspp.,Cardiobacteriumsp.,Eikenella corrodens,Fusobacteriumspp.,Gemella haemoylsans, andNeisseriaspp. Phylotypes that were unique to noma infections included those in the generaEubacterium,Flavobacterium,Kocuria,Microbacterium, andPorphyromonasand the relatedStreptococcus salivariusand generaSphingomonasandTreponema. Since advanced noma lesions are infections open to the environment, it was not surprising to detect species not commonly associated with the oral cavity, e.g., from soil. Several species previously implicated as putative pathogens of noma, such as spirochetes andFusobacteriumspp., were detected in at least one subject. However, due to the limited number of available noma subjects, it was not possible at this time to associate specific species with the disease.
Dense Bodies of Human Cytomegalovirus Induce both Humoral and Cellular Immune Responses in the Absence of Viral Gene Expression
Authors: Pepperl Sandra , Münster Jürgen , Mach Michael , Harris J. Robin , Plachter Bodo 
Published: July 2002

ABSTRACTInfection of fibroblast cell cultures with human cytomegalovirus (HCMV) leads to the production of significant amounts of defective enveloped particles, termed dense bodies (DB). These noninfectious structures contain major antigenic determinants which are responsible for induction of both the humoral and the cellular immune response against HCMV. We tested the hypothesis that, by virtue of their unique antigenic and structural properties, DB could induce a significant immune response in the absence of infectious virus. Mice were immunized with gradient-purified DB, which were either left untreated or subjected to sequential rounds of sonication and freeze-thawing to prevent cellular entry. Titers of neutralizing antibodies induced by DB were in a range comparable to levels present in convalescent human sera. The virus-neutralizing antibody response was surprisingly durable, with neutralizing antibodies detected 12 months following primary immunization. The HCMV-specific major histocompatibility complex class I-restricted cytolytic T-cell (CTL) response was assayed using mice transgenic for the human HLA-A2 molecule. Immunization with DB led to high levels of HCMV-specific CTL in the absence of de novo viral protein synthesis. Maximal total cytolytic activity in mice immunized with DB was nearly as efficient as the cytolytic activity induced by a standard immunization with murine cytomegalovirus. Furthermore, DB induced a typical T-helper 1 (Th1)-dominated immune response in mice, as determined by cytokine and immunoglobulin G isotype analysis. Induction of humoral and cellular immune responses was achieved without the concomitant use of adjuvant. We thus propose that DB can serve as a basis for the future development of a recombinant nonreplicating vaccine against HCMV. Finally, such particles could be engineered for efficient delivery of antigens from other pathogens to the immune system.
Vaccination against Canine Distemper Virus Infection in Infant Ferrets with and without Maternal Antibody Protection, Using Recombinant Attenuated Poxvirus Vaccines
Authors: Welter Janet , Taylor Jill , Tartaglia James , Paoletti Enzo , Stephensen Charles B. 
Published: July 2002

ABSTRACTCanine distemper virus (CDV) infection of ferrets is clinically and immunologically similar to measles, making this a useful model for the human disease. The model was used to determine if parenteral or mucosal immunization of infant ferrets at 3 and 6 weeks of age with attenuated vaccinia virus (NYVAC) or canarypox virus (ALVAC) vaccine strains expressing the CDV hemagglutinin (H) and fusion (F) protein genes (NYVAC-HF and ALVAC-HF) would induce serum neutralizing antibody and protect against challenge infection at 12 weeks of age. Ferrets without maternal antibody that were vaccinated parenterally with NYVAC-HF (n= 5) or ALVAC-HF (n= 4) developed significant neutralizing titers (log10inverse mean titer ± standard deviation of 2.30 ± 0.12 and 2.20 ± 0.34, respectively) by the day of challenge, and all survived with no clinical or virologic evidence of infection. Ferrets without maternal antibody that were vaccinated intranasally (i.n.) developed lower neutralizing titers, with NYVAC-HF producing higher titers at challenge (1.11 ± 0.57 versus 0.40 ± 0.37,P= 0.02) and a better survival rate (6/7 versus 0/5,P= 0.008) than ALVAC-HF. Ferrets with maternal antibody that were vaccinated parenterally with NYVAC-HF (n= 7) and ALVAC-HF (n= 7) developed significantly higher antibody titers (1.64 ± 0.54 and 1.28 ± 0.40, respectively) than did ferrets immunized with an attenuated CDV vaccine (0.46 ± 0.59;n= 7) or the recombinant vectors expressing rabies glycoprotein (RG) (0.19 ± 0.32;n= 8,P= 7 × 10−6). The NYVAC vaccine also protected against weight loss, and both the NYVAC and attenuated CDV vaccines protected against the development of some clinical signs of infection, although survival in each of the three vaccine groups was low (one of seven) and not significantly different from the RG controls (none of eight). Combined i.n.-parenteral immunization of ferrets with maternal antibody using NYVAC-HF (n= 9) produced higher titers (1.63 ± 0.25) than did i.n. immunization with NYVAC-HF (0.88 ± 0.36;n= 9) and ALVAC-HF (0.61 ± 0.43;n= 9,P= 3 × 10−7), and survival was also significantly better in the i.n.-parenteral group (3 of 9) than in the other HF-vaccinated animals (none of 18) or in controls immunized with RG (none of 5) (P= 0.0374). Multiple routes were not tested with the ALVAC vaccine. The results suggest that infant ferrets are less responsive to i.n. vaccination than are older ferrets and raises questions about the appropriateness of this route of immunization in infant ferrets or infants of other species.
CD4-Independent Infection of Two CD4−/CCR5−/CXCR4+Pre-T-Cell Lines by Human and Simian Immunodeficiency Viruses
Authors: Borsetti Alessandra , Parolin Cristina , Ridolfi Barbara , Sernicola Leonardo , Geraci Andrea , Ensoli Barbara , Titti Fausto 
Published: July 2002

ABSTRACTThe infection of CD4-negative cells by variants of tissue culture-adapted human immunodeficiency virus type 1 (HIV-1) or HIV-2 strains has been shown to be mediated by the CXCR4 coreceptor. Here we show that two in vitro-established CD4−/CCR5−/CXCR4+human pre-T-cell lines (A3 and A5) can be productively infected by wild-type laboratory-adapted T-cell-tropic HIV-1 and HIV-2 strains in a CD4-independent, CXCR4-dependent fashion. Despite the absence of CCR5 expression, A3 and A5 cells were susceptible to infection by the simian immunodeficiency viruses SIVmac239 and SIVmac316. Thus, at least in A3 and A5 cells, one or more of the chemokine receptors can efficiently support the entry of HIV and SIV isolates in the absence of CD4. These findings suggest that to infect cells of different compartments, HIV and SIV could have evolved in vivo to bypass CD4 and to interact directly with an alternative receptor.
Infectivity of Moloney Murine Leukemia Virus Defective in Late Assembly Events Is Restored by Late Assembly Domains of Other Retroviruses
Authors: Yuan Bing , Campbell Stephen , Bacharach Eran , Rein Alan , Goff Stephen P. 
Published: July 2002

ABSTRACT

The p12 region of the Moloney murine leukemia virus (M-MuLV) Gag protein contains a PPPY motif important for efficient virion assembly and release. To probe the function of the PPPY motif, a series of insertions of homologous and heterologous motifs from other retroviruses were introduced at various positions in a mutant
gag
gene lacking the PPPY motif. The assembly defects of the PPPY deletion mutant could be rescued by insertion of a wild-type PPPY motif and flanking sequences at several ectopic positions in the Gag protein. The late assembly domain (L-domain) of Rous sarcoma virus (RSV) or human immunodeficiency virus type 1 (HIV-1) could also fully or partially restore M-MuLV assembly when introduced into matrix, p12, or nucleocapsid domains of the mutant M-MuLV Gag protein lacking the PPPY motif. Strikingly, mutant viruses carrying the RSV or the HIV-1 L-domain at the original location of the deleted PPPY motif were replication competent in rodent cells. These data suggest that the PPPY motif of M-MuLV acts in a partially position-independent manner and is functionally interchangeable with L-domains of other retroviruses. Electron microscopy studies revealed that deletion of the entire p12 region resulted in the formation of tube-like rather than spherical particles. Remarkably, the PPPY deletion mutant formed chain structures composed of multiple viral particles linked on the cell surface. Many of the mutants with heterologous L-domains released virions with wild-type morphology.
Follicular Dendritic Cells and Dissemination of Creutzfeldt-Jakob Disease
Authors: Manuelidis Laura , Zaitsev Igor , Koni Pandelakis , Yun Lu Zhi , Flavell Richard A. , Fritch William 
Published: July 2002

ABSTRACTThe contribution of immune system cells to the propagation of transmissible encephalopathies is not well understood. To determine how follicular dendritic cells (FDC) may act, we challenged lymphotoxin β null and wild-type (wt) controls with a Creutzfeldt-Jakob disease (CJD) agent. There was only a small difference in incubation time to clinical disease even after peripheral challenge with low infectious doses (31 in a total of 410 days). Brain pathology with extensive microglial infiltration, identified by keratan sulfate, as well as astrocytic hypertrophy, was also equivalent in all groups despite the fact that null mice had neither FDC nor splenic metallophilic macrophages that filter particulate antigen. Because FDC accumulate pathologic prion protein (PrP) in infected but not wt mice, we studied the cellular distribution of PrP by confocal microscopy. The majority of pathologic PrP collected on the plasma membrane of FDC, as identified by the Ca+2-binding protein S100A. This surface distribution suggested that agent aggregated with pathologic PrP might spread by cell-to-cell contacts. While several types of leukocytes may be involved in agent dissemination, cells of myeloid lineage were found to be infectious. Moreover, perivascular tracks of microglia and abnormal PrP after intraperitoneal inoculation were consistent with hematogenous spread. In summary, FDC are not required for CJD agent spread from the periphery, although FDC may enhance spread through surface accumulation of pathologic PrP. While it is still not clear where the infectious agent replicates, macrophages can sequester appreciable levels of infectivity and hence act as reservoirs for prolonged latent infection.
A Recombinant Human Immunodeficiency Virus Type 1 Envelope Glycoprotein Complex Stabilized by an Intermolecular Disulfide Bond between the gp120 and gp41 Subunits Is an Antigenic Mimic of the Trimeric Virion-Associated Structure
Authors: Binley James M. , Sanders Rogier W. , Clas Brian , Schuelke Norbert , Master Aditi , Guo Yong , Kajumo Francis , Anselma Deborah J. , Maddon Paul J. , Olson William C. , Moore John P. 
Published: July 2002

ABSTRACT
The few antibodies that can potently neutralize human immunodeficiency virus type 1 (HIV-1) recognize the limited number of envelope glycoprotein epitopes exposed on infectious virions. These native envelope glycoprotein complexes comprise three gp120 subunits noncovalently and weakly associated with three gp41 moieties. The individual subunits induce neutralizing antibodies inefficiently but raise many nonneutralizing antibodies. Consequently, recombinant envelope glycoproteins do not elicit strong antiviral antibody responses, particularly against primary HIV-1 isolates. To try to develop recombinant proteins that are better antigenic mimics of the native envelope glycoprotein complex, we have introduced a disulfide bond between the C-terminal region of gp120 and the immunodominant segment of the gp41 ectodomain. The resulting gp140 protein is processed efficiently, producing a properly folded envelope glycoprotein complex. The association of gp120 with gp41 is now stabilized by the supplementary intermolecular disulfide bond, which forms with approximately 50% efficiency. The gp140 protein has antigenic properties which resemble those of the virion-associated complex. This type of gp140 protein may be worth evaluating for immunogenicity as a component of a multivalent HIV-1 vaccine.
Cytotoxic T-Lymphocyte Responses to a Polymorphic Epstein-Barr Virus Epitope Identify Healthy Carriers with Coresident Viral Strains
Authors: Brooks J. M. , Croom-Carter D. S. G. , Leese A. M. , Tierney R. J. , Habeshaw G. , Rickinson A. B. 
Published: July 2002

ABSTRACTCytotoxic T-lymphocyte (CTL) responses to Epstein-Barr virus (EBV) tend to focus on a few immunodominant viral epitopes; where these epitope sequences are polymorphic between EBV strains, host CTL specificities should reflect the identity of the resident strain. In studying responses in HLA-B27-positive virus carriers, we identified 2 of 15 individuals who had strong CTL memory to the pan-B27 epitope RRIYDLIEL (RRIY) from nuclear antigen EBNA3C but whose endogenous EBV strain, isolated in vitro, encoded a variant sequence RKIYDLIEL (RKIY) which did not form stable complexes with B27 molecules and which was poorly recognized by RRIY-specific CTLs. To check if such individuals were also carrying an epitope-positive strain (either related to or distinct from the in vitro isolate), we screened DNA from freshly isolated peripheral blood mononuclear cells for amplifiable virus sequences across the EBNA3C epitope, across a different region of EBNA3C with type 1-type 2 sequence divergence, and across a polymorphic region of EBNA1. This showed that one of the unexplained RRIY responders carried two distinct type 1 strains, one with an RKIY and one with an RRIY epitope sequence. The other responder carried an RKIY-positive type 1 strain and a type 2 virus whose epitope sequence of RRIFDLIEL was antigenically cross-reactive with RRIY. Of 15 EBV-seropositive donors analyzed by such assays, 12 appeared to be carrying a single virus strain, one was coinfected with distinct type 1 strains, and two were carrying both type 1 and type 2 viruses. This implies that a small but significant percentage of healthy virus carriers harbor multiple, perhaps sequentially acquired, EBV strains.
N-Linked Glycosylation of CXCR4 Masks Coreceptor Function for CCR5-Dependent Human Immunodeficiency Virus Type 1 Isolates
Authors: Chabot Donald J. , Chen Hong , Dimitrov Dimiter S. , Broder Christopher C. 
Published: July 2002

ABSTRACTThe chemokine receptors CXCR4 and CCR5 are the principal coreceptors for infection of X4 and R5 human immunodeficiency virus type 1 (HIV-1) isolates, respectively. Here we report on the unexpected observation that the removal of the N-linked glycosylation sites in CXCR4 potentially allows the protein to serve as a universal coreceptor for both X4 and R5 laboratory-adapted and primary HIV-1 strains. We hypothesize that this alteration unmasks existing common extracellular structures reflecting a conserved three-dimensional similarity of important elements of CXCR4 and CCR5 that are involved in HIV envelope glycoprotein (Env) interaction. These results may have far-reaching implications for the differential recognition of cell type-dependent glycosylated CXCR4 by HIV-1 isolates and their evolution in vivo. They also suggest a possible explanation for the various observations of restricted virus entry in some cell types and further our understanding of the framework of elements that represent the Env-coreceptor contact sites.
Adeno-Associated Virus Serotype 4 (AAV4) and AAV5 Both Require Sialic Acid Binding for Hemagglutination and Efficient Transduction but Differ in Sialic Acid Linkage Specificity
Authors: Kaludov Nikola , Brown Kevin E. , Walters Robert W. , Zabner Joseph , Chiorini John A. 
Published: July 2002

ABSTRACTAdeno-associated virus serotype 4 (AAV4) and AAV5 have different tropisms compared to AAV2 and to each other. We recently reported that α2-3 sialic acid is required for AAV5 binding and transduction. In this study, we characterized AAV4 binding and transduction and found it also binds sialic acid, but the specificity is significantly different from AAV5. AAV4 can hemagglutinate red blood cells from several species, whereas AAV5 hemagglutinates only rhesus monkey red blood cells. Treatment of red blood cells with trypsin inhibited hemagglutination for both AAV4 and AAV5, suggesting that the agglutinin is a protein. Treatment of Cos and red blood cells with neuraminidases also indicated that AAV4 bound α2-3 sialic acid. However, resialylation experiments with neuraminidase-treated red blood cells demonstrated that AAV4 binding required α2–3 O-linked sialic acid, whereas AAV5 required N-linked sialic acid. Similarly, resialylation of sialic acid-deficient CHO cells supported this same conclusion. The difference in linkage specificity for AAV4 and AAV5 was confirmed by binding and transduction experiments with cells incubated with either N-linked or O-linked inhibitors of glycosylation. Furthermore, AAV4 transduction was only blocked with soluble α2-3 sialic acid, whereas AAV5 could be blocked with either α2–3 or α2-6 sialic acid. These results suggest that AAV4 and AAV5 require different sialic acid-containing glycoproteins for binding and transduction of target cells and they further explain the different tropism of AAV4 and AAV5.