The impact of new cloning techniques on the diagnosis and treatment of infectious diseases

Experimental and clinical applications of molecular cell biology in nutrition and metabolism

Rapid advances in molecular biology have yielded important new techniques for understanding the cellular mechanisms of normal homeostasis and disease. In particular, molecular laboratory methodologies have become important investigative tools for nutritional studies. Detection techniques for specific DNAs, RNAs, and proteins allow direct examination of cellular regulation of protein expression in health and illness. Construction of transgeneic models by recent techniques of inserting foreign genes into experimental animals has provided novel models for studies of cellular metabolism. In addition, molecular biology has had impact on clinical nutrition and therapy. Molecular techniques not only allow for early diagnosis of many inborn genetic errors of metabolism, recombinant technology has also provided for large-scale production of proteins and hormones of potential therapeutic value. The possibility for direct gene therapies is also nearing reality. Hence, understanding the language of molecular biology and the recent developments in this field is not only of research interest, but is also of clinical relevance.

An Anaplasma centrale DNA probe that differentiates between Anaplasma ovis and Anaplasma marginale DNA

An Anaplasma centrale genomic library was constructed in pUC13. Two clones pAC5 and pAC137 hybridising to A. centrale and A. marginale DNA were isolated from this library. One of these, pAC5, also hybridised to DNA from A. ovis. The total insert of pAC5 was subcloned into pBR322. This subclone, pAC5-12, could detect 1 ng A. centrale, 0.5 ng A. marginale and 3.9 ng A. ovis DNA. The hybridisation pattern obtained with pAC5-12 on digests of A. centrale, A. marginale and A. ovis DNA suggests that this probe detects EcoR1 and Hind111-polymorphisms. Probe pAC5-12 could detect A. ovis DNA in 36% of blood samples tested compared to the 33% detectability obtained with microscopy.

E5 monoclonal immunoglobulin M antibody for the treatment of gram-negative sepsis

Despite the advent of aminoglycoside and beta-lactam antibiotics and early antimicrobial intervention, overall morbidity and mortality associated with gram-negative sepsis and bacteremia remain high. Complications of sepsis have been related to the release of endotoxin from the cell walls of gram-negative bacilli. Although antibiotics can effectively kill gram-negative bacteria, they have no effect on lipopolysaccharide lipopolysaccharide (LPS) and may, in fact, enhance its release when cell lysis occurs. Lipid A, the lipid portion of LPS, is composed of glucosamines, polar phosphate groups, and fatty acids. It represents the endotoxic component of gram-negative bacteria and is responsible for host responses to LPS, including fever, hypotension, and shock. E5 is a murine monoclonal immunoglobulin M antibody directed against the lipid A portion of the cell-wall endotoxin that is common to clinically important gram-negative bacilli. A clinical evaluation program of E5 included patients who were moderately to severely ill with clinical evidence of an infection usually caused by gram-negative bacteria. In pharmacokinetic and safety studies, laboratory tests revealed no evidence of antibody-mediated toxicity and serum antibody concentrations in the desired therapeutic range (greater than 5 microgramS/mL) were found as late as 72 hours after initial infusion of E5. In a Phase II study, mortality rates at seven days in patients with documented gram-negative infection were 22 percent in the placebo group compared with 7 percent in the E5-treated groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitation of canine distemper virus and antibodies by enzyme-linked immunosorbent assays using protein A and monoclonal antibody capture

Monoclonal antibodies produced from 19 cloned hybridomas were selected for this study. Specific canine distemper virus (CDV) antibodies in medium from cloned hybridomas were detected by direct enzyme-linked immunosorbent assays (ELISA) and by indirect immunofluorescence. Three different sandwich ELISA systems were developed either to detect CDV in cell cultures and clinical specimens or to detect specific antibody in canine sera. Protein A and monoclonal antibodies attached in sequence to a solid phase constituted the capture system in the assays. Viral antigens were detected by sandwiching extracts of clinical specimens (or infected cell cultures), monoclonal antibody, and peroxidase-labeled protein A in sequence onto the capture layer. In 1 procedure, biotin-labeled antibody and peroxidase-labeled avidin were used as the last 2 layers in the assay. The CDV antibodies in dog sera were quantitated in a similar manner, but the sequential sandwiching levels consisted of partially purified CDV, serum specimen, and peroxidase-labeled protein A, respectively. The procedures were specific and highly sensitive.

Detection and quantitation of Anaplasma marginale in carrier cattle by using a nucleic acid probe

Cattle which have recovered from acute infection with Anaplasma marginale, a rickettsial hemoparasite of cattle, frequently remain persistently infected with a low-level parasitemia and serve as reservoirs for disease transmission. To fully understand the role of these carriers in disease prevalence and transmission, it is essential that low levels of parasitemia can be accurately detected and quantitated. We have developed a nucleic acid probe, derived from a portion of a gene encoding a 105,000-molecular-weight surface protein, that can detect A. marginale-infected erythrocytes. The probe is specific for A. marginale and can detect 0.01 ng of genomic DNA and 500 to 1,000 infected erythrocytes in 0.5 ml of blood, which is equivalent to a parasitemia of 0.000025%. This makes the probe at least 4,000 times more sensitive than light microscopy. Hybridization of the probe with treated blood from animals proven to be carriers of anaplasmosis showed that parasitemia levels were highly variable among carriers, ranging from greater than 0.0025 to less than 0.000025%. Parasitemia levels of individual animals on different dates were also variable. These results imply that, at any given time, individuals within a group of cattle may differ significantly in their abilities to transmit disease.

Detection of bovine viral diarrhea virus by spot hybridization with probes prepared from cloned cDNA sequences

A cytopathic strain of bovine viral diarrhea virus (BVDV) was purified from infected cell culture fluids by isopycnic density-gradient centrifugation. Genomic RNA was extracted and tailed with adenine residues at the 3' end with poly-A polymerase. Double-stranded complementary DNA (cDNA) was synthesized, using the poly-A-tailed RNA as a template and oligo-dT as a primer, and then cloned into the pUC9 plasmid. Virus-specific cDNA sequences, varying in length from 0.5 to 2.5 kilobases (kb), were obtained. One BVDV-specific sequence of cloned cDNA, 1.1 kb in length and with an internal Pst I restriction endonuclease cleavage site, was selected for use as a probe. The cloned cDNA insert was removed from the plasmid either with or without flanking plasmid sequences and labeled with 32P-nucleotides by nick translation for use as hybridization probes for BVDV. The performance of probes of smaller fragments of the insert was compared to that of the intact sequence in hybridization assays. In addition, 2 methods of specimen preparation were compared to establish optimum parameters for hybridization. The hybridization assay was 10-100 times more sensitive than infectivity assays for BVDV in infected cell cultures. Freezing of specimens reduced by 10-fold the sensitivity of hybridization for BVDV target sequences. The probes prepared from the cloned cDNA hybridized with all cytopathic and noncytopathic BVDV strains tested but not with uninfected cell cultures, cellular ribosomal RNA, bovine coronavirus, bluetongue virus, or bovine adenovirus 3. Probes prepared with native plasmid DNA did not hybridize with BVDV or uninfected cell cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of an rDNA probe filter hybridization assay for the detection of Rift Valley fever virus RNA in human serum samples from the Mauritanian epidemic

The Rift Valley fever virus (RVFV) epidemic that occurred in southern Mauritania during the 1987 rainy season provided a unique opportunity to test and evaluate a recently developed, M-segment-specific, nucleic acid filter hybridization assay on a large collection of infected human serum samples. It afforded the opportunity to compare the procedure with two other methods for detecting virus: virus isolation and antigen detection by ELISA. The filter hybridization procedure employed a polyethylene-glycol-precipitation and proteinase-K-digestion sample treatment step developed specifically for preparing serum samples for hybridization. The procedure was less sensitive for detecting RVFV in the Mauritanian human viremic samples than in sera from experimentally infected monkeys used to evaluate this procedure. It was also less sensitive than an antigen detection procedure used to test the Mauritanian samples. However, we were able to detect virus RNA in a significant proportion of the virus-isolation-positive samples. Advances in sample preparation, labelling and detection procedures, and hybridization methods will improve the sensitivity, precision and ease of use of this assay and increase its value as a diagnostic tool.

DNA probe technology for rapid detection of Haemophilus influenzae in clinical specimens

In a previous study, we reported that a 5-kilobase Haemophilus influenzae DNA fragment involved in penicillin-binding protein expression could be used as a probe for specific detection of H. influenzae strains (F. Malouin and L. E. Bryan, Mol. Cell. Probes 1:221-232, 1987). Here, we report the ability of this probe to detect H. influenzae in clinical specimens. In a bacterial dot experiment, there was strong hybridization of the 32P-labeled probe to nonencapsulated and serotype a through f H. influenzae strains. The detection of H. influenzae in body fluids was then evaluated by using pooled human serum, urine, cerebrospinal fluid, and sputum as dilution media for H. influenzae, Haemophilus aegyptius, Haemophilus parainfluenzae, and Escherichia coli cells. At 65 degrees C, the probe hybridized to H. influenzae and H. aegyptius (greater than or equal to 10(5) cells) in all fluids. There was no hybridization with the E. coli negative control, and H. parainfluenzae hybridized when greater than or equal to 10(7) cells were used. Experiments performed at 73 and 80 degrees C permitted elimination of H. parainfluenzae hybridization. The detection of H. influenzae in 232 sputa from patients with respiratory tract infections was very specific (96 to 97%) and sensitive (74 to 100%) when the total time of the procedure was sufficient (6 to 24 h) and when the experiments were performed at 80 degrees C. In addition, the probe detected three of three and four of four H. influenzae-infected cerebrospinal fluids and blood cultures, respectively, and did not react with pneumococcus- or streptococcus-infected cerebrospinal fluids. Finally, by using a small-scale procedure, the probe rapidly detected H. influenzae in cerebrospinal fluid and sputum specimens (4 and 8 h, respectively). These results imply prompt diagnosis of H. influenzae infections caused by nonencapsulated and serotype a through f strains.

Detection of herpes simplex virus type 1 in herpetic ocular diseases by DNA-DNA hybridization using a biotinylated DNA probe

A diagnostic hybridization assay for detecting herpes simplex virus type 1 (HSV-1) in ocular specimens was developed using cloned viral DNA as a probe. This hybridization assay is based on visualizing a biotinylated probe that is hybridized to the target DNA by a streptavidin/alkaline phosphatase system. The time required for performing this assay system is only two days. This assay system could detect a probe which had been hybridized to as little as 1 pg of homologous DNA and did not cross-react with DNA of other human herpes viruses except that of herpes simplex virus type 2 (HSV-2) which showed weak cross-reactivity. The assay system was applied to experimental keratitis in albino rabbits and clinical specimens. In experimental keratitis in rabbits it was possible to detect HSV-1 DNA in the eye swab samples at least until the ninth day after virus inoculation. Five clinical specimens collected from patients with corneal ulcer or blepharitis contained HSV-1 DNA in spite of the failure of demonstration of viral antigen and/or virus isolation in two cases.

Clinical laboratory applications of monoclonal antibodies

Monoclonal antibody (MAb) technology is well recognized as a significant development for producing specific serologic reagents to a wide variety of antigens in unlimited amounts. These reagents have provided the means for developing a number of highly specific and reproducible immunological assays for rapid and accurate diagnosis of an extensive list of diseases, including infectious diseases. The impact that MAbs have had in characterizing infectious disease pathogens, as well as their current and future applications for use in clinical microbiology laboratories, is reviewed. In addition, the advantages (and disadvantages) of the use of MAbs in a number of immunoassays, such as particle agglutination, radioimmunoassays, enzyme-linked immunosorbent assays, immunofluorescent-antibody assays, and immunohistology, are explored, including the use of these reagents in novel test system assays. Also, nucleic acid probe technology is compared with the use of MAbs from the perspective of their respective applications in the diagnosis of infectious disease agents. There is no question that hybridoma technology has the potential to alter significantly the methods currently used in most clinical microbiology laboratories.

Rapid methods for the molecular diagnosis of infectious diseases: current trends and applications

Methods for the rapid diagnosis of infectious diseases have become increasingly common in the last decade. The impetus for the development of such techniques has stemmed from the need to provide clinically relevant information without the length of time and complexity inherent to traditional cultivation methods. This is particularly important in high-risk populations for which more effective antibiotics and antiviral compounds are now available. Assay systems for the immunological detection of microbial agents occupy a central role in the molecular diagnosis of infectious diseases and are rapidly appearing on the market. Novel methods of organism detection by nucleic acid hybridization, long considered usable only in highly specialized laboratories, have the potential for use in routine microbiological laboratories and some systems are now commercially available. As more efficient and rapid diagnostics systems are being developed, the selection of the optimal method will depend on the environment in which the system is to be used. Rapid methods for the detection of infectious agents might markedly improve health care in a variety of clinical, laboratory and epidemiologic situations.

DNA probe technology for detection of Haemophilus influenzae

A 5 kb Haemophilus influenzae DNA fragment involved in penicillin-binding proteins expression was used as a probe for specific detection of H. influenzae strains. The 32p-labeled probe specificity was assessed by hybridization to bacterial dots and 75 strains were tested. All H. influenzae (18) and H. aegyptius (1) strains reacted very strongly with the probe. The H. influenzae serotypes tested (a, b, and non-typable strains) did not differ in their hybridization. Some hybridization was also found with the 12 other Haemophilus species tested as well as other Pasteurellaceae such as Actinobacillus lignieresii and Pasteurella multocida. Two other less related species (Klebsiella ozaenae and Providencia stuartii) also showed low hybridization. The probe detected as low as 10(5)-10(6) H. influenzae cells and 0.1 microgram of DNA in a dot sensitivity test. Hybridization to electroblotted, digested DNA from different species which reacted in the bacterial dot test revealed strong hybridization to H. influenzae and H. aegyptius only. This DNA probe should prove useful for H. influenzae and possibly H. aegyptius detection due to its high specificity and sensitivity under stringent hybridization conditions.

DNA analysis in human disease

The analysis of human DNA using recombinant DNA technology is fast becoming an integral part of the diagnosis, assessment, and prevention of inherited and somatic genetic disease. The rationale underlying these methods of analysis is discussed, and the nature and extent of mutational change in heritable disorders and neoplastic development is outlined.

Pyrolysis mass spectrometry of bacteria from infected human urine. I. Influence of culturing and antibiotics

Curie-point pyrolysis mass spectrometry was performed on three bacterial isolates obtained from infected human urine using a novel, direct isolation method. Bacterial samples were analysed directly after isolation, as well as after free growth in broth and after exposure to solutions containing penicillin and gentamicin. The spectra of bacteria directly from urine showed no detectable contamination from urinary constituents. Discriminant analysis indicated genetic strain differences to be greater than the combined variances due to sample preparation or the growth phase. Characteristic biochemical changes related to growth or non-growth were detectable after only 2 h of incubation. The potential usefulness of pyrolysis mass spectrometry techniques for rapid susceptibility testing is discussed.

Clinical considerations in the diagnosis of viral respiratory infections

Recent advances are allowing the transfer of sensitive and precise rapid viral antigen detection technology from sophisticated research laboratories to standardly equipped clinical diagnostic facilities. It is now possible to identify many viral respiratory pathogens directly from clinical specimens in less than 1 hr. Rapid antigen detection promises to be of the most value in the identification of respiratory viruses 1) for which antiviral therapy is available, 2) which can be prevented by employing isolation precautions, chemoprophylaxis, and/or immunization, 3) whose presence usually is associated with acute respiratory disease, not just asymptomatic colonization, and 4) which ordinarily are not associated with concomitant bacterial infection, and thus, whose early detection may allow withholding or withdrawing antibiotics. Based on these considerations, the relative usefulness of rapid viral antigen detection of commonly encountered respiratory pathogens will be discussed. In addition, the role of rapid viral detection in diagnosis of respiratory infections in high risk versus otherwise healthy individuals will be explored.

Serospecificity of a cloned protease-resistant Treponema pallidum--specific antigen expressed in Escherichia coli

We evaluated the serological reactivity of a protease-resistant antigen designated 4D which was encoded by Treponema pallidum DNA and was expressed in Escherichia coli from recombinant plasmid pAW329. This 19,000-molecular-weight antigen was purified in its native, non-protease-treated form from E. coli sonic extracts by molecular sieving and ion-exchange chromatography. Antibody binding to antigen 4D was detected by a radioimmunoassay. Antigen 4D-specific antibody was detected in 95% of the sera in a Centers for Disease Control syphilis serum panel. It was also detected in 55% of 121 primary syphilis patients, whereas syphilis antibody was detected in 83% of the sera by a fluorescent treponemal antibody absorption test and in 88% of the sera by a T. pallidum microhemagglutination test. In tests of 118 normal sera, less than 3% demonstrated antibody to antigen 4D; these results are similar to microhemagglutination and fluorescent treponemal antibody absorption test results. Rabbit antisera against Treponema phagedenis, Treponema refringens, Treponema denticola, and Treponema vincentii did not react with antigen 4D.

Current and Future Applications of Monoclonal Antibodies against Bacteria in Veterinary Medicine

This chapter discusses the current and future applications of monoclonal antibodies against bacteria in veterinary medicine. It discusses the existing applications of monoclonal antibodies, including the use of pilus-specific monoclonal antibodies for passive immunization of calves and piglets against enteropathogenic E. coli (EPEC) infections as well as the development of rapid diagnostic test kits for field diagnosis of EPEC infections. The potential applications of monoclonal antibodies for passive immunization against a variety of veterinary pathogens are passive immunization against Moraxella bovis (pinkeye), Bacteroides nodosus (foot rot), EPEC enterotoxin (enteric colibacillosis), Pasteurella haemolytica (pneumonic pasteurellosis), and Streptococcus equi (strangles). Three main areas of application for monoclonal antibodies against bacterial antigens in veterinary medicine are passive immunization, improved immunodiagnostics, and immunotherapy. Monoclonal antibodies, because of their specificity, unlimited availability, and high titer, represent excellent passive immunizing agents. However, their potential usefulness in preventing infection must be evaluated on a case-by-case basis.

Escherichia coli as a genetic tool

The study of Escherichia coli and its plasmids and bacteriophages has provided a vast body of genetical information, much of it relevant to the whole of biology. This was true even before the development of the new techniques, for cloning and analysing DNA, that have revolutionized biological research during the past decade. Thousands of millions of dollars are now invested in industrial uses of these techniques, which all depend on discoveries made in the course of academic research on E. coli. Much of the background of knowledge necessary for the cloning and expression of genetically engineered information, as well as the techniques themselves, came from work with this organism.

Monoclonal antibodies and the skin biopsy: current and potential clinical applications

Monoclonal antibodies are becoming increasingly useful in the clinical diagnosis and/or treatment of a number of unrelated diseases. Discussion will be directed to those monoclonal antibodies recognizing antigens within the skin which appear to have either proven or potential application in the diagnostic evaluation of the skin biopsy.

In situ hybridization with biotinylated DNA probes: a rapid diagnostic test for adenovirus upper respiratory infections

Adenovirus DNA was detected in cells from nasopharyngeal secretions of children with acute respiratory infections by in situ hybridization with biotinylated probes. The technique was easy to perform, giving rapid results which were well correlated with those of immunofluorescence assays of the same samples. Adenoviruses of subgroups B, C and E were detected equally well by probes prepared either from purified adenovirus type 5 or from a plasmid (A1) carrying a cloned insertion of BamH1 fragments C and D of adenovirus type 2 in pAT 153. The use of stable non-radioactive probes makes in situ hybridization a feasible assay for use in clinical laboratories with moderate resources.

Respiratory tract infections. Goals for 1995

Goals to be identified for 1995, a decade hence, in the prevention, diagnosis, and management of respiratory tract infections may conveniently be divided into diagnostic goals and goals in therapy and prophylaxis. Major diagnostic goals for bacterial, viral, and mycoplasmal infections of the respiratory tract focus on the development of systems to identify microbial components, such as specific antigens or segments of DNA, using monoclonal antibody techniques or DNA probes for hybridization. Sputum cultures, in the traditional sense, should ultimately become obsolete. Management goals include the development of algorithms to identify patients who should be hospitalized, in contrast to those who can safely be treated on an outpatient basis. New antibiotic drug development should include drugs active against methicillin-resistant staphylococci, broad-spectrum beta-lactam drugs that are orally active against gram-negative bacilli, and drugs that can be used parenterally on a once-daily basis in settings other than the acute care hospital. There are certainly needs to enhance the present spectrum of antiviral drugs and to develop therapeutically useful immunomodulators. There are promising prospects for vaccine development, including live attenuated influenza virus vaccine, parainfluenza virus vaccine, respiratory syncytial virus vaccine, and a Mycoplasma pneumoniae vaccine. With major research support, such vaccines could possibly be fully developed by 1995. Finally, of greatest importance is the need to achieve greater utilization of existing vaccines, that is, inactivated influenza vaccine and the current 23-valent pneumococcal vaccine. A legitimate goal for 1995 would be to achieve 70 percent or greater utilization of these vaccines within the recommended target populations.