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Biomedical subjects

D B Snyder

Publications and source records attributed to D B Snyder.

At least 19 recordsLinked to original sources
PubMed1996

Document management and scanning in the physician's office.

A popular PC magazine recently conducted a survey asking readers whether a paperless office or Santa Claus was more believable. Santa Claus won. Health care professionals would make that same choice. They come from an educational process that teaches, if it is not on paper, it never happened. However, the necessity for fast and easy access to medical documents, particularly in managed care networks, is causing the paperless office to rush forward at breakneck speed.

CD-ROM↗
PubMed1994

Molecular basis of antigenic variation in infectious bursal disease virus.

Four antigenically different strains of infectious bursal disease virus (IBDV), characterized by their reactivities with a panel of neutralizing monoclonal antibodies (MAbs), were selected to determine the molecular basis of antigenic variation. The large genome segment A, encoding the structural proteins of the U.S. variants GLS, DS326, E/Del and the vaccine strain D78, was cloned and sequenced. Comparison of the deduced amino acid sequences of the U.S. variants with other IBDV strains showed that most of the amino acid substitutions occur in the central region between residues 212 to 332, especially in the two hydrophilic regions between residues 212 to 223 and residues 314 to 324 of VP2 protein. By comparing the amino acid sequences of these variant viruses and their reactivities with IBDV specific MAbs, the putative amino acids involved in the formation of virus-neutralizing epitopes were identified. Comparison of the D78 versus PBG98 sequence showed that Gln at position 249 (Gln249) appears to be critical in binding with MAb B69. Similarly, comparison of the U.S. variant sequences with other serotype 1 sequences showed unique substitution(s) at residue Glu321 in GLS, residues Ile286, Asp318, Glu323 in E/Del, and residues Glu311 and Gln320 in DS326, which could be potential residue(s) involved in the recognition of MAb57, MAb67, and MAb179 epitopes, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Active and passive protection against variant and classic infectious bursal disease virus strains induced by baculovirus-expressed structural proteins.

Infectious bursal disease virus (IBDV) is responsible for a highly immunosuppressive disease in young chickens which causes significant economic losses to the poultry industry worldwide. The structural protein genes (VP2, VP3 and VP4) of a variant IBDV strain (GLS) were expressed in insect cells using a baculovirus expression system. Susceptible chickens vaccinated with a single dose of the recombinant IBDV antigens were completely protected against challenge with two variant strains of IBDV (GLS and Delaware), and partially protected against the standard challenge strain (STC). A booster dose of the recombinant antigens induced higher levels of neutralizing antibodies and afforded complete protection against both variant and standard virus challenges. Specific-pathogen-free hens vaccinated with a single dose of the same subunit vaccine produced virus-neutralizing antibodies that were capable of passively protecting the progeny from infection with variant IBDV.

Animals↗
PubMed1993

Infectious bursal disease virus structural proteins expressed in a baculovirus recombinant confer protection in chickens.

Plasmids were prepared that contained cDNA segments of the large genomic segment A of infectious bursal disease virus (IBDV) strain GLS-5. The genes encoding the IBDV structural proteins (VP2, VP3 and VP4) were introduced into the baculovirus transfer vector pBlueBacI to obtain a recombinant baculovirus vIBD-7. When insect cells were infected with recombinant viruses, the result was synthesis of IBDV precursor proteins which were processed by the viral protease. The recombinant IBDV antigens were characterized by immunoprecipitation with monoclonal antibodies (MAbs) and polyclonal antiserum to IBDV, and by antigen-capture ELISA using a panel of IBDV-specific MAbs. The recombinant IBDV antigens closely resembled the native IBDV proteins and reacted with all the GLS-5 strain-specific neutralizing MAbs that recognize only conformational epitopes of IBDV. When susceptible chickens were inoculated with the recombinant IBDV antigens, virus-neutralizing antibodies were induced that conferred up to 79% protection against IBDV challenge.

Animals↗
PubMed1992

Naturally occurring-neutralizing monoclonal antibody escape variants define the epidemiology of infectious bursal disease viruses in the United States.

A panel of two non-neutralizing and six neutralizing monoclonal antibodies (Mabs) were used in antigen-capture enzyme immunoassays (AC-ELISA) to examine the antigenicity of 1301 wild type infectious bursal disease viruses (IBDV) isolated from different poultry flocks throughout the United States over a three year period. Analysis of these isolates with protective, neutralizing Mabs directed against the VP2 structural protein of IBDV showed that four antigenically distinct groups of serotype 1 IBDV could be separated on the basis of the presence or absence of one or more Mab defined, conformation-dependent, multivalent neutralization site. AC-ELISA reactivity patterns of the Mabs with isolates demonstrated that IBDV field populations were relatively antigenically homogeneous per premise isolation. Geographically, various antigenic species were more or less prevalent, or nearly absent. Competition analysis with neutralizing Mabs coupled with AC-ELISA results suggested that neutralization epitopes for IBDV are distinct, spatially arranged, yet closely linked. Of 5 Mab defined neutralization epitopes, shown to be related to protection from virulent challenge by Classic IBDV strains isolated prior to 1985, only two of the epitopes remain unaltered on the most recent emergent variant field strain of IBDV isolated.

Animals↗
PubMed1988

Development of and serologic evaluation of acquired immunity to Cryptosporidium baileyi by broiler chickens.

Eighteen 2-wk-old broiler chickens that were inoculated orally with oocysts of Cryptosporidium baileyi (Group B) became infected, shed large numbers of oocysts in their feces on Days 6 to 12 post inoculation (PI), and suddenly cleared the parasites from the mucosal epithelium of the bursa of Fabricius (BF), cloaca, or both BF and cloaca on Days 14 to 16 PI. Eighteen uninoculated birds (Group A) did not shed oocysts during this time period. Five days after all birds in Group B stopped shedding oocysts, the 36 chickens comprising both groups were challenged orally with C. baileyi oocysts. At the time of necropsy, 10 days after oral challenge, all Group A birds (previously uninfected, challenged) had heavy C. baileyi infections in the mucosal epithelium of the BF or cloaca. No parasites were found in the BF or cloaca of the Group B birds (previously infected, recovered, challenged) at the time of necropsy. These data demonstrate that a single intestinal infection with C. baileyi can elicit an immune response of sufficient magnitude to clear the parasite from the intestinal (BF and cloaca) mucosa and to make broiler chickens resistant to subsequent oral challenge with oocysts of the same species. Development of resistance to reinfection was accompanied by the appearance of serum antibodies to C. baileyi that were detectable by two Cryptosporidium-specific assays; an indirect immunofluorescent antibody assay and an enzyme-linked immunosorbent antibody assay (ELISA). The ELISA described herein can now be incorporated into serologically based health monitoring programs.

Animals↗
PubMed1988

Serologic incidence of Cryptosporidium in Delmarva broiler flocks.

Banked serum samples collected from an industry-wide serologic survey of eighteen Delmarva broiler flocks conducted in 1985 were evaluated for the presence of Cryptosporidium- specific antibodies in an indirect enzyme-linked immunosorbent assay (ELISA). Evaluation of sera collected at 49-days posthatch showed that 38% of the broiler flocks were serologically positive, whereas 50% of samples obtained from flocks at 63-days during an extended growout were positive. From a performance standpoint, the top nine flocks in the study were essentially negative at the 49-day sampling. In order to more firmly establish the serologic prevalence of Cryptosporidium in Delmarva broiler flocks, a second serologic survey was conducted early in 1987. In this study, an estimated 22% of the 454 broiler flocks sampled at approximately 49 days of age were positive for Cryptosporidium. The negative Cryptosporidium serology in the top 25% of these flocks was associated with better performance, but positive Cryptosporidium serology was not clearly correlated with poor performance. Remarkable differences between Cryptosporidium serologic exposure rates of the growout companies were observed, with some companies having exposure rates as high as 40%, and others rates of less than 3%.

Animals↗
PubMed1988

Identification of species-specific and interspecies-specific polypeptides of Mycoplasma gallisepticum and Mycoplasma synoviae.

Temporal antisera (TA) prepared in susceptible Leg-horn-type chickens against Mycoplasma gallisepticum and M synoviae were evaluated to determine the extent of cross-reactivity in ELISA and hemagglutination inhibition tests. Species-specific and interspecies-specific polypeptides were identified after electrophoretic separation and protein immunoblotting with reference antisera, TA, and a monoclonal antibody specific for M gallisepticum. Mycoplasma gallisepticum antiserum cross-reacted with M synoviae polypeptides in ELISA and TA immunoblots. Two major M synoviae polypeptides (88 and 53 kilodaltons [kD]) cross-reacted with M gallisepticum antisera in TA immunoblots. An M gallisepticum polypeptide of 70 kD cross-reacted with M synoviae in TA immunoblots. In contrast, M gallisepticum and M synoviae reference antisera cross-reacted when immunoblotted with heterologous antigens. A monoclonal antibody specific for M gallisepticum bound to a 69-kD polypeptide in lectin-purified and whole-cell M gallisepticum protein fractions in immunoblot assays. The lectin-purified fraction hemagglutinated chicken RBC. Seemingly, the 69-kD polypeptide may constitute all or part of the M gallisepticum hemagglutinin.

Animals↗
PubMed1985

An enzyme-linked immunosorbent assay method for the simultaneous measurement of antibody titer to multiple viral, bacterial or protein antigens.

A model enzyme-linked immunosorbent assay (ELISA) system was developed which permits the user to evaluate replicate single sera dilutions of 46 test and control serum samples for the presence of specific antibody against up to eight different antigens in one assay. The system makes use of a transplanting device for the simultaneous transfer of aliquots of independently diluted replicate test samples along with conjugate and substrate from a serum reservoir plate or from a reagent reservoir onto different antigen coated target plates. Kinetically read, raw absorbance data from tests are transmitted to a microcomputer, where absorbance values from all tests are quickly reduced to predicted titer levels by computer analysis. All titer computations involve the use of a single prescribed standard curve for predicting antibody titer against the different antigens. Between assay repeatability of this procedure is high and its potential for replacing a number of different conventional assays for epidemiological studies has been evaluated.

Animals↗
PubMed1985

Presumptive diagnosis of subclinical infections utilizing computer-assisted analysis of sequential enzyme-linked immunosorbent assays against multiple antigens.

One-hundred-seventy-two serum samples, collected sequentially from four flocks of egg- and meat-type chickens, were evaluated for antibodies to multiple infectious agents by enzyme-linked immunosorbent assay (MELISA). The MELISA system used provided simultaneous measurement of antibody titers against avian infectious bronchitis (IB), infectious bursal disease (BD), Newcastle disease, avian encephalomyelitis and reovirus infections, and Mycoplasma gallisepticum. The use of computer-generated graphic print outs of relative MELISA titers provided immediate visulization of over 740 data points and convenient detection of any temporal changes in median titer class (MTC). The temporally changing MTC, or flock profiles obtained, indicated that negligible or waning IB immunity may be a common occurrence in previously vaccinated commercial chickens. These profiles further suggested that, despite no IB revaccination, these same flocks experienced episodes of reexposure to IB which otherwise may have been difficult to detect by conventional clinical or diagnostic laboratory protocols. MELISA profiles and sequential histologic examinations of bursas of Fabricius also provided evidence of a possible BD vaccination problem in young chickens that also experienced excessive losses from coccidiosis, ulcerative enteritis, and Marek's disease. Short sampling intervals were found to foster the detection and definition of fluctuations in MTC which otherwise may have been missed.

Animals↗
PubMed1984

Serologic cross-reaction between bovine herpesviruses 1 and 4 by the enzyme-linked immunosorbent assay.

Reciprocal cross-titrations using constant concentrations of bovine antiserum (1: 100) to either bovine herpesvirus (BHV) 1 or BHV 4 (obtained from controlled infection status) against varying concentrations of both viral antigens in enzyme-linked immunosorbent assay (ELISA) indicated a subtle difference between the antigenic composition of these 2 agents. Although control antiserum consistently yielded higher ELISA titers against homologous viral antigen, a considerable cross-reactivity between the 2 viruses was observed. Based on control sera results, serologic profiling of field bovine serum samples against both BHVs 1 and 4 antigen preparations indicated that the ELISA was unsatisfactory for distinguishing between previous BHV 1 or 4 exposure. The ELISA, however, was more sensitive than the virus neutralization test for detecting antibodies to BHVs 1 and 4 in cattle sera.

Animals↗
PubMed1981

Complement requirement for virus neutralization by antibody and reduced serum complement levels associated with experimental equine herpesvirus 1 infection.

Pony foals, negative for detectable serum-neutralizing antibody to equine herpesvirus 1 by the standard tube-culture virus neutralization test, were experimentally infected with equine herpesvirus 1. Complement-requiring (CR) and non-complement-requiring (NCR) serum-neutralizing antibodies were evaluated in preinfection and postinfection sera by means of a complement-enhanced plaque reduction assay. Low levels of CR antibodies were found in the preinfection sera of only group II ponies. Upon infection, CR antibodies were detected by day 2 postinfection and reached peak titers between 7 and 14 days postinfection in the antisera of all ponies. NCR antibodies were detected later than CR antibodies and at levels approximately 40 to 150 times lower than the latter. CR/NCR ratios indicated that complement requirement was greatest early in the acute stages of disease and that this requirement decreased during the convalescent phase. Fractionation of 1-week and 2-week postinfection antisera of group I ponies indicated the CR antibody activity resided in both the 7S and 19S fractions. Total serum complement levels of the ponies were quantified throughout the infection with an equine anti-goat erythrocyte hemolytic system. In vivo, complement levels were depressed for all ponies during the first 2 weeks of infection. A decline in complement levels was seen as early as day 2, and they decreased to an average of 35% of preinfection levels on day 10 postinfection for all ponies.

Animals↗
PubMedDate not supplied

Relationship of the enzyme-linked immunosorbent assay to indirect immunofluorescent antibody test for the detection of so-called chicken anemia agent antibodies in serum from broiler breeders.

Serum samples collected from breeder chickens ranging in age from 1 day to 55 weeks were tested for CAA antibodies by enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescent antibody (IFA) test. The relationship of ELISA to IFA test was determined. The sensitivity of the ELISA relative to the IFA test was 82.64%, and the specificity of the ELISA relative to the IFA test was 56.25%. Agreement between the ELISA and the IFA test was highly significant (Kappa = 0.74, Z = 5.78). We concluded that the ELISA is as good as the IFA test for detecting CAA antibody in sera from chickens.

Anemia↗
PubMedDate not supplied

Development and comparison of serologic methods for diagnosing chicken anemia virus infection.

This paper describes the development of an indirect immunoperoxidase assay (IIP) and an indirect enzyme-linked immunosorbent assay (ELISA) for detecting antibodies to chicken anemia virus (VAC). The IIP assay developed used CAV-infected MDCC-MSB1 cells for detecting antibody to CAV, whereas the ELISA utilized gradient-purified immunoadsorbed CAV as the target antigen. The IIP and ELISA were compared with the standard indirect immunofluorescent antibody (IFA) assay, which is more conventionally used to screen chicken serum for antibodies against CAV. Comparative test results of 185 field samples of chicken serum by these three methods were in agreement 84% of the time. Both IFA and IIP assays yielded fewer positive tests than did the ELISA. IFA and IIP assays were in agreement 93% of the time, as compared with 91% agreement of IIP and ELISA results, or 84% agreement for comparative IFA and ELISA results.

Anemia↗
PubMedDate not supplied

Pathogenicity of CL-1 chicken anemia agent.

Twelve-day-old broiler-type chickens had hemorrhagic necrotic wing tips. After 10 blind subcultures in an MDCC-MSB1 cell line, a virus (so-called chick anemia agent [CAA]) was isolated and designated CL-1 CAA. Five-day-old specific-pathogen-free chicken embryos from a commercial breeder flock that were found not to possess antibody against CAA were infected with CL-1 virus via yolk-sac injection. Many (49%) infected embryos were small and apparently had died from severe systemic hemorrhage. Hatched chicks were small and had pale feathers, skin, skeletal muscles, bone marrow, and viscera. All infected chicks had small thymuses. These thymuses often were so small that they could not be found grossly (P = 0.002). Anemia occurred within 4 days post-hatch. Microscopically, all hematopoietic organs were markedly atrophic. Septic necrotizing lesions were seen only in organs from CL-1-injected chicks. Physicochemical and pathological characteristics of this virus indicate that it is similar to other isolates of CAA found in Europe and Japan.

Anemia↗
PubMedDate not supplied

Isolation of a monoclonal antibody with specificity for commonly employed vaccine strains of Newcastle disease virus.

A monoclonal antibody, AVS-I, was produced from a hybridization of murine myeloma cells and splenocytes from mice immunized with the La Sota strain of Newcastle disease virus (NDV). The hybridoma producing AVS-I, selected from 184 NDV-positive supernatants, is one of two supernatants that reacted exclusively with lentogenic strains in an indirect enzyme-linked immunosorbent assay. AVS-I can also be assayed by hemagglutination-inhibition (HI), which was used to test selected reference avian paramyxovirus (PMV) strains of types 1 to 3. NDV vaccines La Sota and B1 and field isolates from chickens, turkeys, pigeons, and cockatoos were also used as antigens. AVS-I had a high binding affinity for all La Sota and B1 strains, including vaccines. The antibody bound with a lower titer to the Australian Queensland V4 and Ulster strains, but it did not bind to the F strain, a lentogenic strain from England. AVS-I was HI-negative against the other PMV reference strains. AVS-I may be valuable for identifying field isolates antigenically similar to La Sota and B1 and rapidly differentiate those vaccine strains from more virulent viruses.

Antibodies, Monoclonal↗