Biomedical subjects
Publications and source records attributed to R W Ellis.
This paper summarizes major technologies, with emphasis on applications to preventive vaccines for infectious diseases. A limited number of examples of each technology are provided.
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The highly conserved NspA protein has been found in the outer membrane of every Neisseria meningitidis strain tested so far. Two monoclonal antibodies (MAbs) directed against this protein were used to demonstrate that biologically important epitopes of the NspA protein are exposed at the surface of serologically distinct meningococcal strains. Analysis of sera collected from mice that survived a deadly meningococcal challenge following immunization with recombinant NspA protein (rNspA) revealed the presence of cross-reactive antibodies which efficiently attached to and killed the four serogroup B strains tested. These data are additional proof that the NspA protein is exposed at the surface of intact meningococcal cells, which is an important characteristic for a vaccine candidate.
The distribution of Neisseria meningitidis serogroup B and C polysaccharide antigen in blood and the prognostic significance of antigen concentration was examined by ultrasound-enhanced immunoagglutination of coated microparticles. Specimens (169 sera/plasma from 145 patients with confirmed meningococcal disease) were tested retrospectively. The ultrasonic immunoassay detected serum antigen in 136 samples from 112 patients. Titration of antigen-positive specimens allowed estimation of blood antigen concentration. The modal blood antigen titre was 1/16, corresponding to an estimated polysaccharide concentration of 0.85 microg/ml. The lowest mean blood antigen concentration found ultrasonically was 0.05 microg/ml; compared to the 1.98 microg/ml found by conventional latex agglutination, this represents an approximately 30-fold improvement in sensitivity. Three grades of outcome were correlated with the presenting antigen titre in 83 patients: (i) <2 weeks hospitalisation, (ii) > or =2 weeks hospitalisation and (iii) mortality. High polysaccharide concentrations correlated with mortality. Nine of 15 patients with a serum antigen titre of 1/64 or greater (> or =3.4 microg/ml polysaccharide) died, whereas no patient with titres equal to or less than 1/4 (< or = 0.21 microg/ml) died, including those patients in whom antigen was undetectable by ultrasonic immunoassay. Increasing antigen concentration significantly correlated with severity of outcome (P<0.001). Ultrasound-enhanced agglutination provides a rapid prognostic indicator by sensitive measurement of serum antigen level.
The purpose of this study is to prospectively evaluate a strategy in which prophylaxis with amphotericin B lipid complex at 3 different dosages was targeted to liver transplant recipients at high risk for the development of invasive fungal infection (IFI). High risk was defined as a postoperative requirement for prolonged (>/=5 days) intensive care unit (ICU) treatment. Consecutive high-risk patients were administered prophylaxis with amphotericin B lipid complex from day 5 after orthotopic liver transplantation (OLT) until ICU discharge or death. The first 10 eligible patients were administered 5 mg/kg/d, the next 10 patients were administered 2.5 mg/kg/d, and a final 10 patients were administered 1 mg/kg/d. Drug safety and efficacy were assessed before each dosage reduction. During the study period, 130 adult patients underwent 137 OLTs. Thirty patients fulfilled the entry criteria and were administered prophylaxis with amphotericin B lipid complex. No patient developed proven IFI during prophylaxis. Cultures from normally sterile sites (blood and abdominal drain fluid) always showed negative results. All fungal isolates were sensitive in vitro to amphotericin B. There was no significant difference in colonization scores among the groups of patients administered different dosages of amphotericin B lipid complex. No death, serious adverse reaction, or nephrotoxicity was attributed to amphotericin B lipid complex. We conclude that prophylaxis with amphotericin B lipid complex targeted to patients requiring prolonged ICU treatment after OLT appears to be well tolerated and may prevent IFI. Our current policy is to use amphotericin B lipid complex, 1 mg/kg/d, as antifungal prophylaxis in this high-risk group.
Application of a non-cavitating ultrasonic standing wave to suspended microparticles brings the particles into close approximation and has been used previously to enhance the performance of several diagnostic agglutination tests. The sensitivity of rotavirus detection by ultrasound enhanced latex agglutination was compared with conventional test-card agglutination. Application of ultrasound gave a 32-fold improvement in the sensitivity of detection of rotavirus antigen in buffer compared with the test card method. A novel turbidimetric approach was used to measure agglutination occurring following the test-card procedure (in place of visual examination) and following exposure of commercial rotavirus latex reagents to a 4.5 MHz ultrasonic field (in place of microscopy). The sensitivity enhancement over the conventional method achievable through ultrasonic exposure was comparable whether agglutination measurements were made visually or turbidimetrically and demonstrates the potential for turbidimetry in combination with the ultrasonic method. Turbidimetry offers an alternative to visual assessment that may be more easily incorporated into automated systems.
PURPOSE: The purpose of this in vitro study was to compare caries resistance of sound human enamel following argon laser (AL) irradiation, as well as, combinations of topical fluoride foams and AL irradiation. METHODS AND MATERIALS: Thirty extracted human teeth were sectioned into four buccal windows and assigned to one of the following treatment groups: (1) no treatment/control; (2) low fluence (11.5 J/cm2) AL irradiation for 10 seconds; (3) 1.23% APF foam for 4 minutes followed by low fluence AL irradiation; (4) 2.0% NaF foam for 4 minutes followed by low fluence AL irradiation. Caries-like lesions were created by submerging the teeth in ten Cate solution (pH 4.5). Following a 96-hour exposure period, 100 microns longitudinal sections were prepared for polarized light evaluation. Visilog 5.1.1. image analysis software was used to obtain quantitative lesion depths. The Scheffe F-test was used to compare the lesion depths for each of the four treatment groups. RESULTS: Lesion depths were: 16.1 +/- 6 microns for control; 13.7 +/- 4 microns for AL irradiation alone; 12.1 +/- 4.3 microns for 1.23% APF foam before AL irradiation; and 11.4 +/- 5.9 microns for 2.0% NaF foam before AL irradiation. Significant difference (p < 0.05) was found between the control group and the 2.0% NaF foam before AL irradiation group. AL irradiation alone reduced lesion depth by 15% compared with the control lesion. When AL irradiation was combined with 1.23% APF foam treatment, lesion depth decreased by 25% compared with control lesions, and by 29% when combined with 2.0% NaF foam. CONCLUSION: Combining AL irradiation and 2.0% NaF foam treatment significantly enhances the resistance of sound enamel to an in vitro cariogenic challenge.
Technologies for making active vaccines fall into 3 general groups: live, subunit (killed or inactivated) and genetic. Each of these groups is further divisible into multiple categories, which include recombinant-derived antigens as well as native microorganisms and their components. In addition, there are new enabling technologies such as delivery systems and vectors which can be applied to these approaches. Most disease targets, whether infectious or noninfectious in origin, can be approached by the application of several different vaccine technologies, as can be tested during the discovery phase of research. The criteria for choosing early in a development program which of the vaccine technologies are likely to ultimately be most fruitful for a given application include: knowledge of the pathogenesis of the given infection/disease; technical feasibility; immunobiology and associated mechanisms; preclinical efficacy profile; anticipated clinical safety; regulatory; manufacturing; and marketing. All of these criteria should be considered together in making selections for an R&D program. This paper is reviewing the major vaccine technologies and relevant examples of how these criteria are used to make decisions in vaccine development.
Breakthroughs in molecular biology, biochemistry, process development, immunology and related fields have provided the means for improving current vaccines and developing new ones. The increasing availability of these vaccines is providing the unprecedented opportunity to prevent serious infectious disease in different age groups and to significantly reduce associated morbidity and mortality. However, since the great majority of licensed and experimental vaccines in advanced clinical studies are injected, each new vaccine creates the need for additional needlesticks which could become so numerous as to discourage full compliance with immunization schedules. Therefore, the development of combination vaccines is a major way to assure compliance with immunization needs. The leading types of licensed and experimental vaccines which have been or may be made into combination vaccines will be described. In addition, key challenges common to the development of all combination vaccines will be discussed; these include pharmaceutical, immunological, clinical, regulatory, manufacturing, public health and marketing issues. In order to assure timely development and availability of such combination products, these issues must be integrated successfully early in a development program.
Detailed instructions for performance and interpretation of ultrasound-enhanced latex agglutination tests for the rapid identification of bacteria causing meningitis are described. This recently developed technique, which enhances the sensitivity of most latex immunoagglutination assays, has been studied mainly in the context of detection of antigens of meningitis-causing bacteria. The test concentrates on the Wellcogen bacterial antigen kit (Murex Diagnostics Ltd) that contains five latex suspensions specific for Haemophilus influenzae type b, Neisseria meningitidis ACYW135, N. meningitidis B/Escherichia coli K1, Streptococcus group B and Streptococcus pneumoniae. Light photomicrographs of positive agglutination are shown. Particular attention is paid to the appearance of the latex in negative control samples following exposure to ultrasound. Guidance is given on interpretation and assessment in clinical samples.
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A comparison was made of antibody responses generated to live varicella (Oka/Merck) vaccine (Varivax) produced during three different manufacturing campaigns to evaluate the quality of the antibody responses and demonstrate consistency of the manufacturing process. Anti-varicella zoster virus (VZV) antibody titers were measured by an enhanced neutralization assay and VZV glycoprotein-based enzyme-linked immunosorbent assay (gpELISA). For sera taken from children who had received one dose of vaccine an excellent linear concordance in titers was observed between the two assays. Sera from adults who had received two doses demonstrated continuing increased neutralization at high gpELISA titers. The immunogenicity measured by the two assays demonstrates that the overall performance of the vaccine was very similar over the three production series.
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A large body of evidence exists that implicates a number of microbial agents in the pathogenesis of coronary heart disease (CHD). This, if proven, may have far-reaching implications for the prevention and treatment of CHD and other atherosclerotic disease. The histopathology of atherosclerosis and its natural history suggest infectious causation at many points along the progression of disease, particularly with regard to CHD, and a number of pathogens have been the focus of study. Viral agents implicated include Coxsackie B4 virus, for which tenuous sero-epidemiological associations exist, and the Herpesviridae. The animal herpesvirus causing Marek's disease in chickens causes atherosclerotic lesions in these animals. Herpes simplex virus I and II have been found in aortic smooth muscle and produce changes in vitro in smooth muscle that are similar to those seen at the beginning of atherosclerosis and which may also explain some of the features of atherosclerotic complications. Cytomegalovirus is implicated more strongly sero-epidemiologically by in-vivo detection in atherosclerotic lesions and by its links with post-cardiac transplant vasculopathya syndrome similar to atherosclerosis. Bacteria have also been shown to have links with CHD. Chlamydia pneumoniae and Helicobacter pylori have both been associated sero-epidemiologically with CHD, and these findings have been consolidated by recent work showing their presence in atherosclerotic lesions in adults. Bacterial infections in general lead to many changes in lipid, thrombic and other acute-phase protein metabolism, and some of these changes occur with both C. pneumoniae and H. pylori infections. The ubiquity and similar epidemiological features to CHD of all these microbial pathogens make the resolution of the causative issue impossible by retrospective means. All that can be shown at present are a variety of weak and strong links, the significance of which can only be determined by large and perhaps lifetime prospective studies.
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Bovine rotavirus strain WC3 (P7[5], G6) administered at the 12th passage level was well tolerated clinically in infants and efficiently induced serum virus neutralizing antibody (VNA) with bovine rotavirus G6 specificity. The protective efficacy of WC3 vaccine against all rotavirus disease was inconsistent, varying in four separate trials from 76% to 0%; some selective protection against severe disease was seen in all trials. WC3 reassortants containing the gene for an individual human rotavirus VP7 (G) or VP4 (P) surface antigen were also well tolerated, but preferentially induced VNA to the WC3 parent. Efficacy trials of human G1 VP7 reassortant WI79-9 (P7[5], G1) consistently led to > 60% protection against all rotavirus disease. A quadrivalent WC3 reassortant vaccine was developed to contain four separate monovalent reassortants expressing human rotaviruses surface proteins G1, G2, G3, and P1A [8] respectively. In a multicenter trial including 439 infants, this vaccine induced 67.1% protection against all rotavirus disease (defined as positive for rotavirus antigen by ELISA only [p = < 0.001]) and 72.6% protection when the standard for rotavirus diagnosis was a positive test of stool for both rotavirus antigen by ELISA and rotavirus RNA by electropherotype analysis (p = < 0.001). In this trial, episodes of the most severe rotavirus disease (clinical severity score > 16.0 eight cases) occurred only in placebo recipients.
The live attenuated varicella vaccine, which is available for the prevention of chickenpox, was produced by a classic technology that also has been used for polio, measles, mumps, and rubella vaccines. There are many newer technologies that have been applied to the research and development of other vaccines. Each of these other approaches offers potential advantages and disadvantages relative to the current varicella vaccine.
There have been two major focal points for the development of recombinant viral subunit vaccines. Expression strategies for the candidate antigens have focused increasingly on producing more natural antigenic structures, for example, virus-like particles. Also, new adjuvants have been used in order to increase immunogenicity.