Spot synthesis of overlapping peptides on paper membrane supports enables the identification of linear monoclonal antibody binding determinants on morbillivirus phosphoproteins

In order to map antigenic domains on the P-protein of morbillivirus, a series of overlapping peptides, representing the P-protein sequences of phocid distemper virus strain 2558/Han88 and canine distemper virus strain Onderstepoort, were synthesized on a paper support by the spot-technique. The reactivity of six monoclonal antibodies with the peptides was tested in an enzyme immunoassay and compared to their reactivity in Western blots and in an ELISA using detergent extracts from virus-infected cells. Three linear determinants could be localized on the P-protein. Two antibody-binding sites were delineated within the C-terminal (between amino acids 307-322 and 382-400, respectively), and a third one was located on the N-terminal part (amino acids 13-31) of the protein. Fine mapping of this binding site revealed that this was a part of an antigenic domain. In Western blots, the monoclonal antibodies reacting with this domain also reacted with a second protein which was possibly the V-protein.

[Methods for the detection of viral contamination in food of animal origin]

Contamination of foods of animal origin with pathogenic human viruses may occur during handling or through polluted water. Most of these viruses are pathogens originating from the human gastrointestinal tract. They can be transmitted by the consumption of contaminated food and often cause disease. A survey is given of DNA- and RNA-viruses that may occur as contaminants of foods. In addition, the classical methods for detecting viral contaminations in foods are summarized. They are based on the effects after virus inoculation of cell cultures. Besides the fact that these methods are not economic and time consuming, they do not permit detection of some of the most important foodborne gastroenteritis viruses. The possibility of replacing these methods by detecting the viral genomes using hybridization and polymerase chain reaction (PCR) is discussed.

Demonstration of Sindbis virus antigen in Lowicryl-embedded cultured cells by immunogold staining

Eight monoclonal antibodies (MAbs) were tested for the use in immunogold staining of Sindbis virus (SIN) antigen in cultured Baby Hamster kidney (BHK) cells. The antibodies were directed against the capsid (C) protein (5) or against the glycoprotein E1 (3), respectively. Four out of five anti-C MAbs and two out of three anti-E1 Mabs reacted on frozen sections, whereas two of the anti-C antibodies and none of the anti-E1 antibodies reacted on Lowicryl K4M-embedded cells. The MAbs reacting, in particular the anti-C Mabs which react on Lowicryl K4M-sections, will allow further studies of the pathogenesis and replication of alphaviruses on the cellular level. The results also confirm the conformation-dependence of the glycoprotein epitopes.

Sensibilidade e especificidade de um teste imunoenzimático competitivo no diagnóstico sorológico da brucelose bovina

O trabalho teve por objetivo avaliar a sensibilidade e a especificidade de um teste imunoenzimático competitivo, empregando como conjugado os anticorpos monoclonais BM-38 e BM-40, no diagnóstico sorológico da brucelose bovina. Foram examinados 74 soros de bovinos dos quais havia sido isolada Brucella abortus e 2.118 soros de bovinos procedentes de rebanhos livres de brucelose e que apresentaram resultado negativo quando submetidos ao teste Rosa Bengala. O teste imunoenzimático competitivo, usando qualquer dos dois conjugados, foi capaz de revelar a presença de anticorpos contra o lipopolissacáride bacteriano em todos os soros de bovinos infectados, o que resulta em uma sensibilidade de 100%. A especificidade do teste usando o conjugado BM-38 foi de 98.82% e usando o conjugado BM-40 foi de 99,95%. Estes resultados indicam que o teste imunoenzimático competitivo, principalmente ao se empregar o conjugado BM-40, consiste em um método bastante útil para ser usado como teste confirmatório no diagnóstico sorológico da brucelose bovina.

[Use of a modified "antigen-capture" enzyme immunoassay for the identification of virus persistence in cattle infected with bovine virus diarrhea (BVD)]

Bovine viral diarrhoea (BVD)/mucosal disease (MD) is an economically important infectious disease of cattle, and persistently infected animals are of central epidemiological significance. The identification of these animals is a prerequisite for further sanitary measures in affected herds. In order to process large numbers of samples an antigen capture enzyme immunoassay (AC-ELISA) for the detection of bovine viral diarrhoea viral antigen in peripheral blood leukocytes of cattle of all ages has been developed. In this communication an improved method for the preparation of samples is described. A total of 563 blood samples was tested using the AC-ELISA and a routine virus isolation procedure on susceptible bovine cells. When compared to virus isolation in cell culture, the sensitivity of the AC-ELISA was 97%. From the samples that were virus negative in cell culture, 99.1% were also negative in the AC-ELISA. There is some evidence that the AC-ELISA discriminated between transiently and persistently infected animals.

Prolonged persistence of cytopathogenic bovine viral diarrhea virus (BVDV) in a persistently viremic cattle

A bull persistently viremic with noncytopathogenic (ncp) BVDV was inoculated with the cytopathic (cp) BVDV strain TGAC, which had been found to be antigenically different from the endogenous ncpBVDV (ncpW8). Neutralizing antibodies against strains NADL and TGAC were detectable 12 days and four weeks post infection, respectively. The animal developed fever and diarrhea 15 weeks post infection. On days 3 and 8 after onset of diarrhea a cpBVDV (cpX) was isolated from feces. Antigenic analysis using monoclonal antibodies (MoAbs) showed that cpX and the endogenous ncpBVDV (ncpW8) had identical reactivity patterns except for one epitope that was neither expressed on TGAC nor on ncpW8. Using polymerase chain reaction analysis it was shown that both TGAC and cpX contained a p8 phi gene duplication combined with genomic insertions of identical size. Restriction enzyme analysis of the TGAC and cpX amplicons using four enzymes showed an identical cleavage pattern, except for HaeIII digestion where an additional fragment was observed with cpX. These results suggest that cpBVDV strain TGAC persisted in the viremic animal and apparently caused disease after 15 weeks.

Diagnosis of bovine virus diarrhoea by two enzyme-linked immunosorbent assays

Two enzyme-linked immunosorbent assays (ELISAs) for the diagnosis of bovine virus diarrhoea (BVD) are described: CHEKIT-BVD-VIRUS and CHEKIT-BVD-SERO. The first test detects virus antigen in leucocytes, resulting in identification of persistently-infected animals, while the second detects antibodies to BVD virus (BVDV). It is well known that even persistently-infected animals may have antibodies to heterologous BVDV strains. These animals are still negative to the CHEKIT-BVD-SERO test because of immunotolerance to conserved virus antigens. Data on these two tests are summarised and a scheme is presented for the diagnosis of BVD using a combination of these two tests.

RNA insertions and gene duplications in the nonstructural protein p125 region of pestivirus strains and isolates in vitro and in vivo

Sixteen cytopathogenic (cp) bovine viral diarrhea virus (BVDV) strains/isolates were screened for the existence of RNA insertions in the p125 gene region and/or for p80 gene duplications using the polymerase chain reaction after reverse transcription. Three strains/isolates were shown to contain insertions, and in three others gene duplications were demonstrated. One strain was shown to contain a gene duplication in addition to an insertion. Insertions or duplications were absent in the genomes of 10 non-cp BVD virus strains/isolates, in 4 hog cholera (HC) virus strains, and in 9 of the 16 cp BVD virus strains/isolates analyzed. These results indicate that RNA insertions and gene duplications, although significant, are not the only mechanism contributing to cytopathogenicity in vitro. The RT-PCR was also applied to RNA isolated from tissues of a calf suffering from mucosal disease. Insertion-containing amplification products could be demonstrated in an organ-specific pattern.

An immunoplaque assay distinguishing between cytopathogenic and noncytopathogenic biotypes of bovine viral diarrhoea virus

Cytopathogenic (cp) and noncytopathogenic (ncp) biotypes of bovine virus diarrhoea virus (BVDV) could be clearly distinguished by hollow plaques with peripheral immunostaining in infected fetal calf kidney (FCK) monolayers cultures or the appearance of homogenously stained immunoplaques (IPs), respectively. Of 70 BVDV isolates formerly classified as cytopathogenic according to microscopic observations in FCK cell cultures, 46 produced IPs of both types while the remaining 24 isolates induced only the IP type characteristic of the ncp BVDV biotype. The same was true for 24 additional isolates classified by light microscopy as ncp after ten blind passages in FCK cell cultures. Thus it appeared that in 1/3 of the cases changes in FCK cell cultures had been formerly misinterpreted as BVDV induced cytopathic effects (CPE). Of the 46 isolates which produced both ncp and cp immunoplaques 5 BVDV isolates were selected and successfully subjected to cloning. Clones of the cp biotype were developed by picking native plaques from unfixed FCK cell monolayers. In case of ncp IP, cloning was attempted by picking randomly in the spaces between visible native plaques. Pairs of clones from each of the field isolates proved to consist of pure plaque populations of cp BVDV and ncp BVDV biotypes, respectively, at the dilution of viral suspension which allowed the classification of a single IP according to morphology. Analysis of the clones using 15 monoclonal antibodies against the major viral glycoprotein revealed far-reaching antigenic homogeneity for each pair with only few but distinct exceptions.

Distribution of cytopathogenic and noncytopathogenic bovine virus diarrhea virus in tissues from a calf with experimentally induced mucosal disease using antigenic and genetic markers

A comparative analysis of the distribution of cytopathogenic (cp) and noncytopathogenic (ncp) bovine virus diarrhea disease (BVD) virus in tissues from a calf with experimentally induced mucosal disease was performed using immunohistology and polymerase chain reaction after reverse transcription (RT-PCR) of viral RNA. For immunohistology, an antigenic marker on the superinfecting cp BVD virus defined by a monoclonal antibody (mab) was used, and overall presence of antigen was assessed with a pestivirus specific mab. The primers selected for RT-PCR detected the genomic insertion in the p125 region of the superinfecting cp BVD virus. Both methods gave consistent results.

An antigen capture test for the detection of cattle viremic with bovine viral diarrhoea virus--a comparison with BVD virus isolation from buffy coat cells in bovine kidney cells

An antigen capture enzyme immunoassay (EIA) for the detection of bovine viral diarrhoea (BVD) viral antigen in peripheral blood lymphocytes of cattle was used for the screening of 241 animals. The test used a monoclonal antibody directed against a conserved antigenic domain of a nonstructural protein (p125/p80) of pestiviruses for antigen capture. Bound antigen was detected with a pestivirus-specific polyclonal peroxidase conjugate. In parallel the samples were analysed by routine virus isolation procedures based on cell culture. Virus isolation and antigen capture EIA were positive in 54 cases. The latter test scored one additional sample.

Heterogeneous expression of the non-structural protein p80/p125 in cells infected with different pestiviruses

In order to analyse the expression of the non-structural (ns) protein p80/p125 in cells infected with different pestiviruses at the protein level, radioimmunoprecipitations with the pestivirus-specific monoclonal antibody (MAb) BVD/C16 were performed. Cell lysates infected with cytopathic (cp) and non-cytopathic (ncp) bovine viral diarrhoea (BVD) virus strains and isolates, and with hog cholera (HC) virus strains were analysed. From cpBVD virus-infected cells, the MAb precipitated one or more proteins corresponding to ns p125, displaying a marked size heterogeneity. In contrast, the lower Mr ns p80 proteins from all cpBVD virus strains and isolates analysed had identical electrophoretic motility. The ncpBVD virus strains displayed either one single band or a doublet of the p125 protein and no p80 cleavage products. The p125 proteins precipitated from HC virus-infected cells showed no size heterogeneity. The possibility is discussed that multiple recombination events, including both insertions or deletions in the genomes of ncpBVD viruses, may lead to the heterogeneous expression of the ns p125 in cpBVD virus populations.

Analysis of antigenic differences between sixteen phocine distemper virus isolates and other morbilliviruses

Monoclonal antibodies against a phocine morbillivirus isolate (PDV 2558/Han 88) were able to discriminate sixteen PDV isolates from any other morbillivirus species providing further evidence that PDV should be regarded a new species in the morbillivirus genus.

Immunofluorescence studies of biotype-specific expression of bovine viral diarrhoea virus epitopes in infected cells

The expression of biotype-specific epitopes in cells infected with cytopathic (cp) and non-cytopathic (ncp) bovine viral diarrhoea virus (BVDV) was analysed by immunofluorescence. Four monoclonal antibodies (MAbs) directed against different epitopes on the viral glycoprotein gp48 were used. With cells infected with cpBVDV strain NADL, the four MAbs yielded a strong and granular cytoplasmic fluorescence. The same pattern was observed when cells were infected with ncpBVDV 7443 with two of the MAbs (BVD/C12, BVD/C42). In contrast, reactivity with the other two MAbs (BVD/C38, BVD/C46) was restricted to a narrow perinuclear zone. These biotype-specific differences were not observed either with a gp53-specific MAb, or with an MAb specific for the non-structural protein p125/p80. Double immunofluorescence staining of living cells with a polyclonal BVDV-specific serum and with the MAbs revealed that expression of viral proteins on the surface of cells infected with cp- or ncpBVDV, respectively, was not detectable.

[Analysis of sera from two cattle herds suspected of brucellosis using a competition enzyme immunoassay with monoclonal antibodies]

The milk pools of two cattle herds in Lower Saxony were found to give positive results in an enzyme-linked immunosorbent assay (ELISA). The sera from these cattle were tested in competition enzyme immunoassays (cEIA) using two monoclonal antibodies. The results were compared to those obtained in the serum agglutination assay (SLA) and in an ELISA. The cEIAs detected more positive samples than the other tests. All sera that were positive in the SLA and in the ELISA were also positive in the cEIAs. Due to the higher sensitivity, these tests may be an alternative for the SLA.

[A sensitive enzyme-linked immunosorbent assay (ELISA) for the serological detection of antibodies against the European hog cholera virus]

An ELISA for the detection of antibodies against hog cholera virus (HCV) was developed. The HCV-specific glycoprotein gp53 served as diagnostic antigen after immobilization using a monoclonal capture antibody. Due to the higher affinity of HCV-specific antibodies to the viral gp53, sera cross reacting with bovine viral diarrhea (BVD) virus were discriminated by the slope of the titration curves.

[A new enzyme immunoassay for the detection of antibodies against the bovine viral diarrhea virus]

An enzyme-linked immunosorbent assay (ELISA), using the nonstructural protein p125/80 of the bovine viral diarrhoea (BVD) virus as antigen, was used for screening BVD-specific antibodies in 468 bovine sera. The results were compared with those obtained in a standard neutralization test (NT). Both tests reacted positive with 457 sera. The ELISA gave positive results with eight sera which were negative in the NT whereas one serum was positive in the NT and negative in the ELISA. Two sera could not be tested in the NT because they were toxic for the cultured cells. In addition the sera were screened in an ELISA using the equivalent heterologous nonstructural protein of hog cholera virus as antigen. The results obtained in both ELISAs showed a correlation of 94%.

Correlation of bovine viral diarrhoea virus induced cytopathic effects with expression of a biotype-specific marker

The purpose of this study was the identification antigenic differences between cytopathic (cp) and noncytopathic (ncp) bovine viral diarrhoea viruses (BVDV). Cells infected with 19 strains of each viral biotype were analyzed for reactivity with the monoclonal antibody (mab) BVD/C38. Reactivity was examined using an enzyme immunoassay on fixed infected monolayers of fetal calf kidney cells. In the majority of cases, the mab discriminated between cells infected with each of the two viral biotypes. Three reactivity patterns could be distinguished. Most cpBVDV strains yielded monolayers where 80-100% of infected cells reacted with the mab. Most of the ncpBVDV infected cells showed either no reaction, or only single cells of foci were stained. However, about one third of either cp- or ncpBVDV strains tested yielded infected monolayers where 30-50% of the cells reacted with the antibody. Cell damage other than the typical cytopathic effect might be responsible for the BVD/C38 reactivity of cells infected with BVDV. In addition, it was analyzed whether the antigenic marker associated with cpBVDV was expressed in cells infected with viral isolates from 21 animals with clinical mucosal disease. In 14 cases cpBVDV was isolated and the antigenic marker was found throughout. In seven cases ncpBVDV was cultivated and the antigenic marker was detected in four isolates.

Identification of conserved epitopes on a hog cholera virus protein

Eight monoclonal antibodies directed against the hog cholera virus (HCV) strain Alfort/187 and displaying broad cross-reactivity with other HCV strains were characterized. An enzyme immunoassay on fixed monolayers of porcine or bovine cells infected with 14 different strains and isolates of HCV and 12 bovine viral diarrhea viruses (BVDV), respectively, showed that all antibodies reacted with HCV only. Seven antibodies recognized all HCV tested, thus indicating that they were directed against conserved epitopes. All antibodies neutralized the homologous strain and different patterns of the other HCV tested. Radioimmunoprecipitation analysis showed that the monoclonal antibodies were directed against a doublet of 56-60 kDa, presumably representing the major envelope glycoprotein of HCV. The results of reciprocal antibody blocking assays allowed the mapping of two distinct conserved antigenic domains on this protein.

Attempts to characterize bovine viral diarrhea virus isolated from cattle after immunization with a contaminated vaccine

Bovine viral diarrhea virus (BVDV) was isolated from 28 animals with a history of immunization against respiratory disease with a vaccine contaminated with BVDV. The vaccine-derived parental virus strain and the 28 isolates were analyzed using 10 monoclonal antibodies (MAbs) directed against different epitopes and antigenic domains on the major envelope glycoprotein of BVDV. None of the isolates displayed a reaction pattern identical with the parental virus. Instead, seven different reaction patterns (#A-G) emerged. Circumstantial evidence indicated that six of these were vaccine related whereas in one case (pattern #F) the origin of the isolate was unclear. The results indicated that BVDV rapidly changed during animal passages and that the tracing of the vaccine contaminant using Mabs was impossible.

A competition enzyme immunoassay for brucellosis diagnosis

Two monoclonal antibodies (MAbs) conjugated with horseradish peroxidase were used independently in a competitive enzyme immunoassay (cEIA) to detect Brucella specific antibodies in 1120 sera from Brucella-free cattle, 61 from cattle known to be infected with B. abortus, and 207 sera from vaccinated calves. The results were compared to those obtained in the complement fixation test (CFT). The cEIA with both MAbs proved to be more sensitive than the CFT because no false-negative results were obtained. In addition, discrimination between sera from infected and vaccinated animals was more evident.

A new approach for the diagnosis of hog cholera

Pestiviruses were isolated from seven cases of suspect hog cholera. Using peroxidase conjugates of monoclonal antibodies (Mabs) six isolates were identified as hog cholera viruses (HCV), while one isolate was of ruminant origin, possibly bovine viral diarrhea virus. In parallel attempts were made to develop an ELISA for the detection of HCV-specific antibodies in pig sera. The Mab HCTC26 coated to polystyrol plates efficiently captured the major viral glycoprotein gp53 from crude antigen suspensions prepared from infected cells. The immobilized gp53 served as diagnostic antigen. Five pigs experimentally infected with the HCV strain Glentorf were sequentially bled and the development of antibodies was monitored by neutralization tests and the ELISA. Results showed that both tests detected antibodies simultaneously after infection. Titres measured by ELISA were slightly higher than those registered by neutralization.

Monoclonal antibodies reacting specifically with Francisella sp

Twenty two hybridoma strains producing monoclonal antibodies against Francisella tularensis ATCC 6223, var. tularensis, were characterized. In an enzyme-linked-immunosorbent-assay (ELISA) using formaldehyde fixed bacteria as antigens, neither cross-reactions with six different Brucella spp., with Yersinia enterocolitica 0:9 nor with two biotypes of Yersinia pseudotuberculosis could be detected. The antibodies gave comparable titres with the three strains of F.tularensis tested. ELISA binding studies indicated that fifteen of the antibodies bound with high affinities to their epitopes of the three Francisella strains, while the others each seemed to bind with low affinity to at least one of the antigens. Immunoblot analysis showed that six of the antibodies were directed to epitopes on the core moiety of the lipopolysaccharide molecule, while the other 16 antibodies bound to O side chain components.

Comparative analysis of monoclonal antibodies against pestiviruses: report of an international workshop

Thirty-three pestivirus strains were grown in cell culture and characterized by immunostaining with 19 monoclonal antibodies (MAbs) raised against hog cholera virus (HCV), with 42 MAbs against bovine viral diarrhoea virus (BVDV) and with 13 MAbs against border disease virus (BDV). Seven MAbs reacted with all pestivirus strains tested, eight MAbs detected only the seven HCV strains, three detected only the 16 BVDV strains. No MAb was found that was specific for BDV. BVDV and BDV strains were broadly cross-reactive with the MAbs, indicating a close relationship between these two species, whereas HCV strains were characterized as distinct from BVDV and BDV.

Most alphaviruses share a conserved epitopic region on their nucleocapsid protein

Fourteen hybridoma cell lines secreting antibodies against the Semliki Forest virus nucleocapsid protein were established and employed for identification of conserved epitopes among 27 alphavirus types and subtypes. Using an antibody capture test, the antibodies were found to cross-react to variable degree with alphaviruses belonging to the Semliki Forest, western encephalitis and eastern encephalitis complexes, as well as Middelburg and Ndumu. None of the antibodies reacted with either Venezuelan equine encephalitis or Barmah Forest virus. Due to their reactivity with Fort Morgan, Y62-33, Whataroa and chikungunya, the monoclonal antibodies were divided into six reactive types. Competition assays showed that the epitopes for all the types were either identical or clustered on a single domain of the nucleocapsid protein.