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PubMed1977

Biological properties of Shigella flexneri 2A toxin and its serological relationship to Shigella dysenteriae 1 toxin.

A toxin extracted from heat-inactivated, alkaline-treated Shigella flexneri 2a showed biological properties similar to those of Shigella dysenteria 1 toxin. The S, flexneri 2a toxin was lethal to mice, enterotoxic for ileal loops of rabbits, and cytotoxic for HeLa cells. A serological relationship between S. flexneri 2a and S. dysenteriae 1 toxin was shown with cross neutralization tests.

Antigens, Bacterial↗
PubMed1979

Growth, plaque assay and immunofluorescent studies on Tataguine virus in cell culture.

The growth characteristics of Tataguine virus were studied in Cercopithecus monkey kidney (Vero); rhesus monkey kidney (LLC-MK2), baby hamster kidney (BHK-21); porcine kidney (PK-15), mouse fibroblasts (L-929) and Aedes albopictus cell monolayers. The virus replicated without producing any cytopathology in Vero, BHK-21 and Aedes albopictus: but not in the other three cell culture systems. Two or three subsequent serial blind passages in those cultures supporting the growth of the virus did not produce any appreciable increase in virus titre. Immunofluorescent staining of inoculated Vero cells demonstrated the presence of Tataguine virus antigen in the cytoplasm of infected cells. Plaques 1--1.5 mm in diameter were produced only in Vero cell culture. In neutralization tests performed on Tataguine virus, immune mouse and hamster sera, higher antibody titres were obtained by plaque reduction than mouse protection tests.

Aedes↗
PubMed1988

Isolation of TBE virus from the tick Ixodes hexagonus.

Tick-borne encephalitis (TBE) virus was isolated from a sample of Ixodes hexagonus ticks collected from the hair of the western European hedgehog (Erinaceus europaeus) which had been captured on the edge of a new housing estate in Ceské Budĕjovice at the end of September 1986. This was the first isolation of TBE virus from this vector, supporting the previous experimental results. The virus was identified in immunofluorescent and plaquereduction neutralization tests.

Animals↗
PubMed1973

Enterovirus type 70: the etiologic agent of pandemic acute haemorrhagic conjunctivitis.

A new enterovirus, now classified as enterovirus type 70, was isolated from the conjunctiva of patients with acute haemorrhagic conjunctivitis during the 1971 epidemics that occurred in Japan, Singapore, and Morocco. These epidemics were parts of a pandemic involving Africa (Algeria, Ghana, Morocco, Nigeria, and Tunisia), Asia (Cambodia, China (Province of Taiwan), Hong Kong, India, Indonesia, Japan, Malaysia, the Philippines, Singapore, and Thailand), and England during 1969-71. A representative strain from each of the three epidemic areas was studied cooperatively. The strains exhibited the physicochemical characteristics of enteroviruses. Cross-neutralization tests showed that these viruses were distinct from all known human enterovirus immunotypes, but that they were antigenically closely related. The human origin of the viruses was demonstrated by the appearance of homologous neutralizing antibodies during convalescence in patients with acute haemorrhagic conjunctivitis.

Acute Disease↗
PubMed1975

A chick-embyo cell microtest for typing of Herpesvirus hominis (38531).

Oral type 1 and genital type 2 Herpesvirus hominis (HVH) strains demonstrate distinctive biological properties in primary chick embryo cells (PCE) cultivated in microtest plates. With this procedure four reference strains of known types and 106 clinical isolates were differentiated as type 1 or 2. The type 1 strains showed low efficiency of infection and either no cytopathic effect (CPE) or only an incomplete CPE characterized by uniform thinning of the cell sheet in test wells. Type 2 strains had a high efficiency of infection and with CPE characterized by patchy plaque-like lesions readily distinguished from CPE of type 1 strains. A 96% correlation (27/28) between the PCE microtyping and kinetic neutralization tests and a 94% correlation (60/64) between the PCE microtyping and immunofluorescence test was obtained. The microplate PCE test is a simple, clear-cut, and reliable procedure for the typing of HVH.

Animals↗
PubMed1985

A preliminary survey of the epidemiology of bluetongue in Costa Rica and northern Colombia.

Recent evidence of bluetongue (BT) virus infection of livestock in scattered localities in the neotropics prompted a serologic survey of cattle in Colombia and Costa Rica. In Costa Rica 48.1% of 1435 bovine animals had BT virus antibody in the agar gel precipitation test (AGPT). In Colombia 51.8% of 635 cattle were AGPT-positive for BT virus. Antibody prevalence ranged from over 50% in the lowlands to 0% in Costa Rica and 19% in Colombian cattle above 2000 m altitude. Neutralization tests indicated that Costa Rican cattle had been exposed to BT virus types 6, 12, 14 and 17.

Altitude↗
PubMed1997

Evaluation of an enzyme immunosorbent assay for the diagnosis of Argentine haemorrhagic fever.

To elaborate a set of serological tests for the diagnosis of Argentine haemorrhagic fever (AHF), an enzyme-linked immunosorbent assay (ELISA) for detection of specific anti-Junin virus (JV) IgG is described, and its performance is compared with that of the plaque reduction neutralization test (PRNT). The reproducibility, sensitivity, specificity, and confidence limits for positive and negative results for ELISA were statistically analysed. The value of 800 was demonstrated as the lowest positive titer. Titers > or = 800 varied within one (two-fold) dilution in 95.6% of the tests, while the sensitivity and specificity were 99.2% and 98.8%, respectively. The assay yielded 1% of false positives and 0.05% of false negatives. A comparison of ELISA to PRNT in detecting the seroconversion for JV was studied by the chi square test (comparison of proportions in paired samples) and the K parameter for agreement proportion. Comparison of ELISA to PRNT showed no significant difference in the proportions of positive and negative results of these assays (P < 0.01), demonstrating an equivalent performance (K = 0.98) in the diagnosis of AHF. In addition, the simplicity and safety of the procedures involved make this ELISA the most suitable test to detect natural human JV infections.

Antibodies, Viral↗
PubMed1999

Use of anti-glycoprotein monoclonal antibodies to characterize rabies virus in formalin-fixed tissues.

Seventy anti-rabies virus monoclonal antibodies (Mabs) were tested for reactivity with rabies and rabies-related viruses in formalin-fixed (FF) tissues. Forty-three of the Mabs were directed against the glycoprotein and 27 were directed against the nucleocapsid as determined by enzyme immunoassays and neutralization tests. Twenty of the anti-glycoprotein Mabs and one of the anti-nucleocapsid Mabs reacted with the rabies challenge virus strain (CVS) in FF tissue. These 21 Mabs were screened against other lyssaviruses in FF tissues: five rabies virus strains (coyote, skunk, raccoon, red bat, and silver-haired bat), and four rabies-related viruses (Australian bat lyssavirus, Duvenhage virus, Lagos bat virus, and Mokola virus). One of the anti-glycoprotein Mabs was reactive with all the virus strains screened. Another of the anti-glycoprotein Mabs reacted with all of the rabies virus strains tested, but not with any of the rabies-related virus strains tested. The remaining Mabs had reactivity patterns that could be useful for characterizing lyssaviruses in FF tissues.

Animals↗
PubMed1976

Use of the hemadsorption phenomenon for determining virus and neutralizing antibody titers of rabies.

Chicken embryo cells infected with the HEP Flury strain of rabies virus adapted to tissue culture produced a hemadsorption (HAD) phenomenon by using goose erthyrocytes. The optimal conditions for HAD included the incubation of cell cultures at 37C for 3 days after virus inoculation, the use of a 0.4% suspension of goose erythrocytes in phosphate buffer adjusted at pH 6.2, and adsorption of erythrocytes at 4C. This phenomenon was inhibited with anti-rabies serum. Virus titer obtained with the HAD technique was almost the same as with the fluorescent antibody technique or the intracerebral inoculation of suckling mice. Results of the neutralization test by using the HAD technique could be easily determined 3 days after inoculation of chicken embryo cells with the mixture of 100 mean tissue culture infective doses of virus and diluted serum. The neutralizing antibody titers coincided with those obtained in mice.

Animals↗
PubMed1998

Association of Venezuelan equine encephalitis virus subtype IE with two equine epizootics in Mexico.

Two outbreaks of encephalitis consistent with an etiology of Venezuelan equine encephalitis (VEE) virus occurred in equines on the Pacific coast of southern Mexico in 1993 (Chiapas State) and in 1996 (Oaxaca State). In Chiapas, there were 125 cases, of which 63 were fatal and in Oaxaca, there were 32 cases and 12 fatalities. Virus was isolated from two horses from each outbreak, including three brain isolates and one from blood. Virus isolates (93-42124, ISET-Chi93, Oax131, and Oax142) were shown by indirect immunofluorescence, hemagglutination inhibition, monoclonal antibody ELISA, and nucleotide sequencing to be VEE virus, subtype IE, a type previously thought to be equine-avirulent. Genetic characterization and phylogenetic analysis indicated that the outbreak viruses were identical or nearly identical to one another and that they were closely related to equine-avirulent IE strains from Guatemala and the Gulf coast of Mexico. In a plaque-reduction neutralization test, sera collected from healthy horses in Chiapas and Oaxaca reacted significantly better with isolate 93-42124 than with Guatemala IE isolate 68U201, suggesting that subtle genetic changes may have resulted in alteration of neutralization domains. It is not clear whether these differences may also influence equine virulence. However, renewed VEE virus subtype IE activity in Mexico, and its apparent conversion to equine virulence, underscores the need for increased surveillance, additional laboratory and epidemiologic studies in VEE-endemic regions, and possibly new vaccines.

Amino Acid Sequence↗
PubMed1974

Host DNA synthesis-suppressing factor in culture fluid of tissue cultures infected with measles virus.

Host DNA synthesis is suppressed by the culture fluid of cell cultures infected with measles virus. This activity in the culture fluid is initiated somewhat later than the growth of infectious virus. Ninety percent of host DNA synthesis in HeLa cells is inhibited by culture fluid of 3-day-old cell cultures of Vero or HeLa cells infected with measles virus. This suppressing activity is not a property of the virion, but is due to nonvirion-associated component which shows none of the activities of measles virus such as hemagglutination, hemolysis, or cell fusion nor does it have the antigenicity of measles virus as tested by complement-fixation or hemagglutination-inhibiting antibody blocking tests. Neutralization of the activity of this component is not attained with the pooled sera of convalescent measles patients. This component has molecular weights of about 45,000, 20,000, and 3,000 and appears to be a heat-stable protein. The production of host DNA suppressing factor (DSF) is blocked by cycloheximide. Neither UV-inactivated nor antiserum-neutralized measles virus produce DSF. Furthermore, such activity of nonvirion-associated component is not detected in the culture fluid of cultures infected with other RNA viruses such as poliovirus, vesicular stomatitis virus, or Sindbis virus.

Animals↗
PubMed1981

Neutralization of adenovirus infectivity and cytotoxin in various cell cultures.

The neutralization of human adenovirus 5 and 11 by homologous and heterologous rabbit antisera was determined by CPE inhibition in various cell cultures (HeLa, HEL, Vero, secondary kidney cells from cercopithecus, rabbit, mouse), or in HeLa cells made impermissive by IUdR inhibition. The results concerning sensitivity and specificity were similar in all cases. Crude and purified virus showed similar neutralization. Immunofluorescence neutralization in HeLa cell cultures gave similar results; this method is suitable for demonstrating subtle immunological relations between adenovirus types. The neutralization of the early cytopathic factor ('cytotoxin') showed a pattern of cross-reactivity different from the virion; the cytotoxin was found to be active in part of the cell cultures only. It is concluded from the results that the virus function(s) blocked by antibody appear to be identical for the replicative cycle in infection and for the initiation of the abortive infection in non-permissive cells. Hence, either kind of cells may be used for neutralization tests.

Adenoviruses, Human↗
PubMed1978

Mink lung cells: a non-primate cell line highly susceptible for varicella-zoster virus.

Mink lung cells (MvILu) are highly susceptible to varicella-zoster virus (VZV). The titres of cell-free VZV suspensions reached 1.0 x 10(7) p.f.u./ml at 3 days post-infection, with subsequent cell degeneration, if MvILu cells were infected with a multiplicity of infectious virus of 0.01 p.f.u./cell. In contrast, during the same period and under the same conditions the titres of cell-free VZV were 10(2) to 10(3) times lower when grown on human foreskin fibroblasts. A fast and reliable plaque assay and a neutralization test for VZV on MvILU cells, were developed.

Animals↗
PubMed1967

Studies on bluetongue. IV. Studies of three strains in primary bovine foetal kidney cell cultures.

Three different strains of bluetongue virus were adapted to grow in primary bovine foetal kidney cell cultures. The cytopathic effects observed from the three strains were similar, and were characterized by shrinkage of cells and increased granularity. The specificity of the changes was confirmed by the fluorescent antibody technique. No significant immunological cross-reaction was detected by serum-virus neutralization tests from the strains studied.

Culture Techniques↗
PubMedDate not supplied

Changes in VP2 gene during the attenuation of very virulent infectious bursal disease virus strain Gx isolated in China.

Very virulent (vv) infectious bursal disease virus (IBDV) Gx strain with high pathogenicity was attenuated through replication in specific-pathogen-free (SPF) chicken embryos and in chicken embryo fibroblast (CEF) cell cultures. The changes in VP2 nucleotide and the deduced amino acid sequences were obtained during attenuation of vvIBDV in CEF culture. Sequence analysis of selected passages from numbers 0 to 20 in CEFs (designated here Gx to CEF-20) showed that no changes were detectable in the VP2 gene before CEF-7. There were a few changes in the nucleotide sequence of the VP2 gene but no amino acid substitutions at CEF-8. The virus of CEF-9 was an intermediate with some amino acid changes that possibly were related to virulence. CEF-10 virus had become similar to CU-1 strain. The VP2 gene sequence remained the same from CEF-10 to CEF-20. The results of pathogenicity tests showed that the mortalities of Gx, CEF-5, CEF-8, and CEF-9 in 4-wk-old SPF chickens were 64%, 60%, 60%, and 32%, respectively; whereas CEF-10, CEF-15, and CEF-20 were nonpathogenic. Virus neutralization tests with Gx strain showed that the antigenicities are similar from Gx to CEF-20.

Amino Acid Sequence↗
PubMed1978

Radioimmunoprecipitation assay for quantitation of serum antibody to the hemagglutinin of type A influenza virus.

A double-antibody radioimmunoprecipitation (RIP) assay has been developed to provide a sensitive and specific measure of antibody to hemagglutinins of H3N2 influenza viruses. Chloramine T was used to radiolabel purified hemagglutinins to high specific activity without loss of antigenicity. The purity of the labeled hemagglutinin was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, which also established that both the HA(1) and HA(2) polypeptides were iodinated. Radiolabeled hemagglutinins with a specific activity that did not exceed 12 muCi/mug of protein could be maintained for up to 30 days at -70 degrees C in the presence of supplemental protein. The RIP assay was compared with conventional methods, hemagglutination inhibition and viral neutralization tests, using H3N equine 1 hybrid viruses for determining serum antihemagglutinin antibody titers. The geometric mean titers for human convalescent sera after infection with A/England/72 virus were 118, 161, and 18,822 for hemagglutination inhibition, viral neutralization, and RIP tests, respectively, and the three tests demonstrated significant rises in antihemagglutinin antibody titers with equal efficiency. In general, a positive correlation existed between antihemagglutinin antibody titers determined by these three procedures; however, the antibody level determined by RIP assay for each individual could not be related to hemagglutination inhibition or viral neutralization titers by a constant factor. A similar lack of a constant relationship was found by using hyperimmune guinea pig antisera, which suggests that the RIP assay can detect antibody populations that exhibit differing efficiencies for inhibition of viral hemagglutination and replication.

Animals↗
PubMed1980

Serological survey to detect subclinical Junín virus infection in laboratory personnel.

Serological survey for detecting subclinical infections with Junín virus, the etiological agent of Argentine hemorrhage fever, was carried out in a group of 107 individuals working in laboratories where this virus was handled. The group was divided into high risk and low risk personnel according to the degree of exposure to the virus. Neutralizing tests were performed in Vero cell cultures to detect circulating antibodies. Results were evaluated comparatively with those obtained in a previous survey. This study shows that among high risk personnel three out of 52 developed neutralizing antibodies (NA) against Junín virus; one of them had a mild clinical illness, and the other two showed no overt disease during this period. No one among the low risk group developed NA against Junín virus.

Antibodies, Viral↗
PubMed2001

Genetic and antigenic analysis of type A foot-and-mouth disease viruses isolated in India during 1987-1996.

Twenty-three foot-and-mouth disease virus (FMDV) type A field isolates, recovered from different outbreaks during 1987-1996 in India, were subjected to antigenic and genetic analysis. The isolates showed a close antigenic relationship to the current vaccine strain (IND 17/77) in micro-neutralization test conducted using a vaccine strain (IND 17/77) antiserum and a peptide (aa 136-151 of VP1 protein of the A22/Azerbaijan/65 strain) antiserum. However, the isolates revealed minor antigenic differences in their reactivity with three neutralizing monoclonal antibodies (MAbs) recognizing trypsin-sensitive conformation-independent epitopes of the vaccine virus strains. Phylogenetic relationship between the isolates was carried out employing a part of the 1D gene (168 nucleotides at the 3'-end). Additional seven type A Indian field isolates reported earlier were included in the analysis. The percent similarity among the Indian isolates varied from 82.7% to 99.4% at nucleotide level, and from 83.9% to 100% at amino acid level. These observations clearly demonstrate genetic heterogeneity of the field isolates. The current vaccine strain IND 17/77 showed divergence of 9.7% at nucleotide level and 5.6% at amino acid level from the A22 Iraq 24/64 isolate. The field strains were divergent from the vaccine strain IND 17/77 by 5.6%-14.6% and 3.7% 13.7% at nucleotide and amino acid level, respectively. In the phylogenetic tree, the isolates were distributed into 21 genetic groups. The clustering pattern of the isolates in the phylogenetic tree revealed no specific distribution pattern of the foot-and-mouth disease (FMD) outbreaks in relation to their geographical locations, caused by unrestricted animal movement and endemic nature of the disease.

Amino Acid Sequence↗