Biomedical subjects

Gary J Vora

Publications and source records attributed to Gary J Vora.

11 recordsLinked to original sources

PubMed2006

Fluorescent signal amplification of carbocyanine dyes using engineered viral nanoparticles.

We report enhancement in the fluorescent signal of the carbocyanine dye Cy5 by using an engineered virus as a scaffold to attach >40 Cy5 reporter molecules at fixed locations on the viral capsid. Although cyanine dye loading is often accompanied by fluorescence quenching, our results demonstrate that organized spatial distribution of Cy5 reporter molecules on the capsid obviates this commonly encountered problem. In addition, we observe energy transfer from the virus to adducted dye molecules, resulting in a highly fluorescent viral nanoparticle. We have used this enhanced fluorescence for the detection of DNA-DNA hybridization. When compared with the most often used detection methods in a microarray-based genotyping assay for Vibrio cholerae O139, these viral nanoparticles markedly increased assay sensitivity, thus demonstrating their applicability for existing DNA microarray protocols.

Avidin↗

PubMed2006

Broad-spectrum respiratory tract pathogen identification using resequencing DNA microarrays.

The exponential growth of pathogen nucleic acid sequences available in public domain databases has invited their direct use in pathogen detection, identification, and surveillance strategies. DNA microarray technology has offered the potential for the direct DNA sequence analysis of a broad spectrum of pathogens of interest. However, to achieve the practical attainment of this potential, numerous technical issues, especially nucleic acid amplification, probe specificity, and interpretation strategies of sequence detection, need to be addressed. In this report, we demonstrate an approach that combines the use of a custom-designed Affymetrix resequencing Respiratory Pathogen Microarray (RPM v.1) with methods for microbial nucleic acid enrichment, random nucleic acid amplification, and automated sequence similarity searching for broad-spectrum respiratory pathogen surveillance. Successful proof-of-concept experiments, utilizing clinical samples obtained from patients presenting adenovirus or influenza virus-induced febrile respiratory illness (FRI), demonstrate the ability of this approach for correct species- and strain-level identification with unambiguous statistical interpretation at clinically relevant sensitivity levels. Our results underscore the feasibility of using this approach to expedite the early surveillance of diseases, and provide new information on the incidence of multiple pathogens.

Bacterial Typing Techniques↗

PubMed2006

Identifying influenza viruses with resequencing microarrays.

Identification of genetic variations of influenza viruses is essential for epidemic and pandemic outbreak surveillance and determination of vaccine strain selection. In this study, we combined a random amplification strategy with high-density resequencing microarray technology to demonstrate simultaneous detection and sequence-based typing of 25 geographically distributed human influenza virus strains collected in 2004 and 2005. In addition to identification, this method provided primary sequence information, which suggested that distinct lineages of influenza viruses co-circulated during the 2004-2005 season, and simultaneously identified and typed all component strains of the trivalent FluMist intranasal vaccine. The results demonstrate a novel, timely, and unbiased method for the molecular epidemiologic surveillance of influenza viruses.

Amino Acid Sequence↗

PubMed2006

Co-infections of adenovirus species in previously vaccinated patients.

Despite the success of the adenovirus vaccine administered to US military trainees, acute respiratory disease (ARD) surveillance still detected breakthrough infections (respiratory illnesses associated with the adenovirus serotypes specifically targeted by the vaccine). To explore the role of adenoviral co-infection (simultaneous infection by multiple pathogenic adenovirus species) in breakthrough disease, we examined specimens from patients with ARD by using 3 methods to detect multiple adenoviral species: a DNA microarray, a polymerase chain reaction (PCR)-enzyme-linked immunosorbent assay, and a multiplex PCR assay. Analysis of 52 samples (21 vaccinated, 31 unvaccinated) collected from 1996 to 2000 showed that all vaccinated samples had co-infections. Most of these co-infections were community-acquired serotypes of species B1 and E. Unvaccinated samples primarily contained only 1 species (species E) associated with adult respiratory illness. This study highlights the rarely reported phenomenon of adenoviral co-infections in a clinically relevant environment suitable for the generation of new recombinational variants.

Adenovirus Infections, Human↗

PubMed2005

Microarray-based detection of genetic heterogeneity, antimicrobial resistance, and the viable but nonculturable state in human pathogenic Vibrio spp.

The morbidity and mortality associated with Vibrio-mediated waterborne diseases necessitates the development of sensitive detection technologies that are able to elucidate the identity, potential pathogenicity, susceptibility, and viability of contaminating bacteria in a timely manner. For this purpose, we have designed a single multiplex PCR assay to simultaneously amplify 95 diagnostic regions (encompassing species/serogroup-specific, antimicrobial resistance, and known toxin markers) and combined it with a long oligonucleotide microarray to create a platform capable of rapidly detecting and discriminating the major human pathogenic species from the genus Vibrio: V. cholerae, V. parahaemolyticus, V. vulnificus, and V. mimicus. We were able to validate this strategy by testing 100 geographically and temporally distributed isolates and observed an excellent concordance between species- and serotype-level microarray-based identification and traditional typing methods. In addition to accurate identification, the microarray simultaneously provided evidence of antibiotic resistance genes and mobile genetic elements, such as sulfamethoxazole-trimethoprim constins and class I integrons, and common toxin (ctxAB, rtxA, hap, hlyA, tl, tdh, trh, vvhA, vlly, and vmhA) and pathogenicity (tcpA, type III secretion system) genes that are associated with pathogenic Vibrio. The versatility of this method was further underscored by its ability to detect the expression of known toxin and virulence genes from potentially harmful viable but nonculturable organisms. The results suggest that this molecular identification method provides rapid and definitive information that would be of value in epidemiological, environmental, and health risk assessment surveillance.

Anti-Infective Agents↗

PubMed2004

Cell surface display of the chlamydial glycolipid exoantigen (GLXA) demonstrated by antibody-dependent complement-mediated cytotoxicity.

The chlamydial species are Gram-negative bacterial pathogens critical to human health. Their developmental cycle is associated with the formation and release of the broadly conserved glycolipid exoantigen (GLXA), which has been implicated in the chlamydial elementary body-host cell interaction. This study examines the potential surface display of this glycolipid by chlamydiae-infected cells and the ability of the GLXA they secrete to associate with the plasma membranes of uninfected cells, a prerequisite for exerting influence on them. The sequential incubation of anti-GLXA antibody and complement with Chlamydia trachomatis serovar K or C. pneumoniae AR-39-infected HeLa 229 or macrophage cells resulted in significant cellular cytotoxicity, which preceded the formation of mature elementary bodies. For uninfected cells, co-incubation of GLXA, purified from supernatants of either C. trachomatis or C. pneumoniae-infected HeLa 229 cells, followed by the successive addition of mouse anti-GLXA antibody and complement, yielded similar levels of cellular cytotoxicity. Thus, GLXA indeed is displayed on the surface of infected cells and, therefore, if antibody of appropriate specificity were present, this GLXA could serve to target these infected cells for elimination. Furthermore, released GLXA can associate with uninfected cells and therefore would be positioned to influence their behavior, especially in the context of infection.

Antibody Specificity↗

PubMed2004

Nucleic acid amplification strategies for DNA microarray-based pathogen detection.

DNA microarray-based screening and diagnostic technologies have long promised comprehensive testing capabilities. However, the potential of these powerful tools has been limited by front-end target-specific nucleic acid amplification. Despite the sensitivity and specificity associated with PCR amplification, the inherent bias and limited throughput of this approach constrain the principal benefits of downstream microarray-based applications, especially for pathogen detection. To begin addressing alternative approaches, we investigated four front-end amplification strategies: random primed, isothermal Klenow fragment-based, phi29 DNA polymerase-based, and multiplex PCR. The utility of each amplification strategy was assessed by hybridizing amplicons to microarrays consisting of 70-mer oligonucleotide probes specific for enterohemorrhagic Escherichia coli O157:H7 and by quantitating their sensitivities for the detection of O157:H7 in laboratory and environmental samples. Although nearly identical levels of hybridization specificity were achieved for each method, multiplex PCR was at least 3 orders of magnitude more sensitive than any individual random amplification approach. However, the use of Klenow-plus-Klenow and phi29 polymerase-plus-Klenow tandem random amplification strategies provided better sensitivities than multiplex PCR. In addition, amplification biases among the five genetic loci tested were 2- to 20-fold for the random approaches, in contrast to >4 orders of magnitude for multiplex PCR. The same random amplification strategies were also able to detect all five diagnostic targets in a spiked environmental water sample that contained a 63-fold excess of contaminating DNA. The results presented here underscore the feasibility of using random amplification approaches and begin to systematically address the versatility of these approaches for unbiased pathogen detection from environmental sources.

Antigens, Bacterial↗

PubMed2004

Use of oligonucleotide microarrays for rapid detection and serotyping of acute respiratory disease-associated adenoviruses.

The cessation of the adenovirus vaccination program for military trainees has resulted in several recent acute respiratory disease (ARD) outbreaks. In the absence of vaccination, rapid detection methods are necessary for the timely implementation of measures to prevent adenovirus transmission within military training facilities. To this end, we have combined a fluorogenic real-time multiplex PCR assay with four sets of degenerate PCR primers that target the E1A, fiber, and hexon genes with a long oligonucleotide microarray capable of identifying the most common adenovirus serotypes associated with adult respiratory tract infections (serotypes 3, 4, 7, 16, and 21) and a representative member of adenovirus subgroup C (serotype 6) that is a common cause of childhood ARD and that often persists into adulthood. Analyses with prototype strains demonstrated unique hybridization patterns for representative members of adenovirus subgroups B(1), B(2), C, and E, thus allowing serotype determination. Microarray-based sensitivity assessments revealed lower detection limits (between 1 and 100 genomic copies) for adenovirus serotype 4 (Ad4) and Ad7 cell culture lysates, clinical nasal washes, and throat swabs and purified DNA from clinical samples. When adenovirus was detected from coded clinical samples, the results obtained by this approach demonstrated an excellent concordance with those obtained by the more established method of adenovirus identification as well as by cell culture with fluorescent-antibody staining. Finally, the utility of this method was further supported by its ability to detect adenoviral coinfections, contamination, and, potentially, recombination events. Taken together, the results demonstrate the usefulness of the simple and rapid diagnostic method developed for the unequivocal identification of ARD-associated adenoviral serotypes from laboratory or clinical samples that can be completed in 1.5 to 4.0 h.

Acute Disease↗

PubMed2004

Detection and genotyping of Entamoeba histolytica, Entamoeba dispar, Giardia lamblia, and Cryptosporidium parvum by oligonucleotide microarray.

Entamoeba histolytica, Giardia lamblia, and Cryptosporidium parvum are the most frequently identified protozoan parasites causing waterborne disease outbreaks. The morbidity and mortality associated with these intestinal parasitic infections warrant the development of rapid and accurate detection and genotyping methods to aid public health efforts aimed at preventing and controlling outbreaks. In this study, we describe the development of an oligonucleotide microarray capable of detecting and discriminating between E. histolytica, Entamoeba dispar, G. lamblia assemblages A and B, and C. parvum types 1 and 2 in a single assay. Unique hybridization patterns for each selected protozoan were generated by amplifying six to eight diagnostic sequences/organism by multiplex PCR; fluorescent labeling of the amplicons via primer extension; and subsequent hybridization to a set of genus-, species-, and subtype-specific covalently immobilized oligonucleotide probes. The profile-based specificity of this methodology not only permitted for the unequivocal identification of the six targeted species and subtypes, but also demonstrated its potential in identifying related species such as Cryptosporidium meleagridis and Cryptosporidium muris. In addition, sensitivity assays demonstrated lower detection limits of five trophozoites of G. lamblia. Taken together, the specificity and sensitivity of the microarray-based approach suggest that this methodology may provide a promising tool to detect and genotype protozoa from clinical and environmental samples.

Animals↗

PubMed2003

A Role for the glycolipid exoantigen (GLXA) in chlamydial infectivity.

The chlamydial glycolipid exoantigen, GLXA, is associated with the bacterial membrane, intracellular inclusion, and can also be found secreted into the microenvironment of Chlamydia trachomatis-infected cells. The aim of this study was to investigate the function of GLXA in chlamydial pathogenesis. Pretreatment of HeLa 229 cells with affinity-purified GLXA resulted in a significant enhancement of chlamydial infectivity as determined by inclusion body enumeration. The GLXA-mediated enhancement was shown to be time- and dose-dependent and, more importantly, GLXA-specific, as the effect was abrogated by anti-GLXA antibody. In vitro neutralization assays on HEp-2 cells revealed that an anti-anti-idiotypic antibody to GLXA effectively reduced the infectivity of C. trachomatis, C. pneumoniae, and C. psittaci. In vivo, the co-inoculation of GLXA at the time of C. trachomatis serovar K intravaginal challenge of C3H/HeJ mice resulted in a significant increase in the numbers of shed organisms on days 4, 7, 14, 21, and 28. Taken together, these observations suggest that GLXA, both organism bound and secreted, is important in facilitating the initiation of infection.

Animals↗

PubMed2002

Potential applications of DNA microarrays in biodefense-related diagnostics.

Recent years have witnessed a logarithmic growth in the number of applications involving DNA microarrays. Extrapolation of their use for infectious diagnostics and biodefense-related diagnostics seems obvious. Nevertheless, the application of DNA microarrays to biodefense-related diagnostics will depend on solving a set of substantial, yet approachable, technical and logistical problems that encompass diverse topics from amplification efficiency to bioinformatics.

Bioterrorism↗