Antibody production and blastogenic response in pigs experimentally infected with porcine reproductive and respiratory syndrome virus

Seven five-week piglets were infected intranasally with 10(5) TCID50 of porcine reproductive and respiratory syndrome (PRRS) virus strain IAF.exp91. All virus-exposed pigs developed fever, labored abdominal breathing, conjunctivitis, and lymph node enlargement within the first 96 h postexposure (PE), which continued to d 10 to 14 PE. Two pigs that were necropsied at d 7 and 10 PE had diffuse interstitial pneumonitis, cardiopathy and lymphadenopathy. All 5 remaining pigs produced serum IgM and IgG antibodies against PRRS virus by 7 or 14 days PE, as demonstrated by indirect immunofluorescence. This corresponded with the capability of isolating the virus from serum d 7 to d 49 or d 63 PE. Low serum neutralizing antibody titers were detected in 3 of the virus-exposed pigs by 35 days PE. A transient episode of diminished proliferative response of peripheral blood lymphocytes to mitogens phytohemagglutinin (PHA) and concanavalin A (Con A) was observed in the virus-exposed pigs at d 3 PE. However, in vitro spontaneous uptake of [3H]-thymidine was significantly increased in lymphocyte cultures of the same pigs at d 7 or d 14 PE. These results suggest polyclonal activation of peripheral blood lymphocytes.

Kinetics of humoral immune response to the major structural proteins of the porcine reproductive and respiratory syndrome virus

The kinetics of appearance of antibodies directed to the major structural proteins N, M and E of porcine reproductive and respiratory syndrome virus (PRRSV) was followed in pigs naturally- and experimentally-exposed to the virus. Specific IgM antibody titers were first detected by indirect immunofluorescence (IIF) at the end of the first week of PRRSV infection, peaked by day 14 to 21 post-inoculation (p.i.), then rapidly decreased to undetectable levels by day 35 to 42 p.i. On the other hand, specific IgG antibody titers peaked by day 21 to 28 p.i. and remained unchanged to the end of the 6- or 9-week observation period; in addition, a persistent viremia was observed. Virus neutralizing (VN) antibody titers > 8 were not detected until 3 to 4 weeks p.i. Taken together, the results obtained by Western blotting analyses using purified virus and E. coli-expressed ORFs 5 to 7 gene products, suggested that antibodies directed against the envelope E protein appear by day 7 p.i., whereas antibodies directed against the nucleocapsid N and membrane M proteins can only be detected by the end of the second week p.i. No correlation could be demonstrated between VN and IIF antibody titers, viremia, and viral protein specificities of circulating antibodies at various times p.i.

Sequence determination of the extreme 5' end of equine arteritis virus leader region

The extreme 5' end of the leader sequence of four equine arteritis virus (EAV) strains was obtained by using rapid amplification of cDNA end method (5' RACE), and sequenced. Seventeen more nucleotides were added upstream of the 5' end of the EAV published genomic sequence. A common feature among the analyzed EAV isolates was the presence of an AUG start codon within the added sequence and the appearance of an intraleader open reading frame (ORF) of 111 nucleotides which was predicted to encode a peptide of 37 amino acids. The role of this putative intraleader ORF has yet to be determined.

Comparison of nucleic and amino acid sequences and phylogenetic analysis of the Gs protein of various equine arteritis virus isolates

The genetic variation in equine arteritis virus (EAV) Gs protein encoding gene was investigated. Nucleic and deduced amino acid sequences from eight different EAV isolates (one European, two American and five Canadian isolates) were compared with those of the Bucyrus reference strain. Nucleotide and amino acid identities between these isolates and the Bucyrus reference strain ranged from 92.3 to 96.4%, and 93.2 to 95.5%, respectively. However, phylogenetic tree analysis and estimation of genetic distances based on the Gs protein encoding gene sequences showed that the European prototype Vienna strain, the American 87AR-A1 isolate and all other North American EAV isolates could be classified into three genetically divergent groups. Our results showed that the Gs protein-encoding gene can be subjected on the basis of phylogenetic analysis to genetic variation, as previously shown for the other three EAV structural protein (M, N and GL)-encoding genes.

Cloning of porcine cytokine-specific cDNAs and detection of porcine tumor necrosis factor alpha, interleukin 6 (IL-6), and IL-1 beta gene expression by reverse transcription PCR and chemiluminescence hybridization

A reverse transcription PCR assay with porcine cytokine-specific primers was developed to clone cDNA fragments and generate cDNA probes that were specific for porcine tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), and IL-1 beta. The specificities of the cDNA PCR products were confirmed by sequence analysis on the basis of known porcine cytokine gene sequences. The reverse transcription PCR assay was also used to study cytokine mRNA expression in lipopolysaccharide (LPS)-stimulated and control unstimulated porcine alveolar macrophages. The cDNA products were analyzed in ethidium bromide-stained agarose gels, and the transcription level of each cytokine was determined relative to the endogenous glyceraldehyde-3-phosphate dehydrogenase (GAPDH) RNA level of each cytokine by measuring the intensity of the chemiluminescence hybridization signals by densitometric scanning. Various levels of cytokine mRNAs were detected in both LPS-stimulated and control unstimulated cells. Thus, TNF-alpha mRNA levels were enhanced in the cell cultures stimulated for 6 h with LPS compared with those in control cell cultures. No differences in TNF-alpha transcription levels between LPS-stimulated and control cells were observed after incubation for 24 or 55 h. Enhancements of IL-6 and IL-1 beta mRNA levels were also observed in the cultures stimulated with LPS for 6 and 24 h compared with the cytokine mRNA levels in control cell cultures. The presence of cytokine mRNA transcripts in the LPS-stimulated macrophage cultures correlated with the detection of these soluble cytokines by the bioassays. In contrast, no soluble cytokine was detected in control macrophage culture supernatants in the presence of cytokine mRNA transcripts.

Persistence of porcine reproductive and respiratory syndrome virus infection in a swine operation

A herd of Quebec seedstock pigs experienced in early 1992 a typical outbreak of porcine reproductive and respiratory syndrome (PRRS) associated with lesions of interstitial, proliferative and necrotizing pneumonia in weaned piglets. The nature of the infection was confirmed by serology using indirect immunofluorescence (IIF) and virus isolation in primary cultures of porcine alveolar macrophages (PAM). Farm production recovered after eight weeks of losses. In order to evaluate the persistence of infection in the herd, five SPF-piglets were introduced in two different sections of the PRRS-affected barn four months after the disappearance of clinical symptoms, and two others were placed in a neighboring building with apparently healthy farrow-to-finnish pigs. Clinical signs, body temperature, humoral immune response, virological and histopathological findings were recorded over a 42-day period. Clinical signs were evident in all of the sentinels and prolonged fever (> or = 40 degrees C) was recorded one day post-exposure (PE). Antibody titers to PRRS virus could be detected by IIF on PAM seven days PE, and reached 1:1024 by day 21 PE. Three of the sentinels developed significant virus neutralizing antibody titers (> 1:8 to < or = 1:128) by day 35 PE. In all cases, the virus could be isolated from the serum between day 7 and 42 PE. Thus, the virus and specific antibodies coexisted for several weeks. Lesions of interstitial pneumonia was demonstrated in few animals. In experimental inoculation studies, the viral strain isolated from the sentinel pigs produced severe reproductive disorders in two sows inoculated at 95 days of gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Influences of renal nerves and pregnancy on renin secretion in sheep

To investigate the role of the renal nerves in the control of renin secretion during pregnancy, we prepared sheep with one denervated kidney, bilateral renal vein catheters, and an inflatable aortic occluder. The renin secretory responses to step reductions of renal perfusion pressure (RPP) of the innervated and denervated kidneys were compared in eight nonpregnant and nine pregnant (115-130 days gestation) sheep in a normal conscious state. Nonpregnant sheep had average basal levels of mean arterial pressure (MAP) of 91 +/- 3 mmHg, plasma renin activities (PRA) of 2.3 +/- 0.4 ng ANG I.ml-1.3 h-1, and plasma angiotensin (ANG) concentrations of 8.4 +/- 1.1 pg/ml. Pregnant sheep had reduced levels (P < 0.01) of MAP (76 +/- 3 mmHg) but elevated levels of PRA (3.8 +/- 0.4 ng ANG I.ml-1.h 3-1; P < 0.5) and ANG II (12.0 +/- 1.6 pg/ml; P = 0.08). Four successively reduced levels of RPP were observed for 15 min each in both groups of sheep. In both groups, RPP was reduced to a final level of 51 +/- 2 mmHg. The renal venous-arterial difference of PRA (v-aPRA) from the innervated kidneys was increased as RPP was reduced. However, there was little response of v-aPRA to RPP in denervated kidneys. In nonpregnant sheep, the relationship between RPP and renin secretion rate was characterized by an initially slow phase, over which small reductions of RPP resulted in small increases in renin secretion. As RPP fell, this relationship became progressively steeper in nonpregnant ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphorothioate oligonucleotides inhibit the replication of lentiviruses and type D retroviruses, but not that of type C retroviruses

Phosphorothioate analogs of oligodeoxynucleotides at a concentration of 2 microM protected Himalayan tahr cells from infection by caprine arthritis encephalitis virus (CAEV) and equine dermis cells from infection by equine infectious anemia virus (EIAV). The characteristics of this inhibition against these lentiviruses are similar to those previously described for the inhibition of HIV-1 in ATH8 cells [17]. Thus, the 28-mer homo-oligomer of cytidine [S-(dC)28] was at least as effective as three anti-sense sequences targeted to the LTR, gag, and env regions of CAEV. The effectiveness of homo-oligomers of equal length was in the order C >> A > T, and a random 28-copolymer with a composition of 2C:1G was as effective as S-(dC)28. Shorter oligonucleotides were less effective (28 > 14 > 5 mers) for all base compositions tested. While replication of a simian type D retrovirus was inhibited by S-(dC)28, this compound did not inhibit the cytopathogenicity of two type C retroviruses, amphotropic murine leukemia virus (MuLV), and baboon endogenous virus, when they were tested in the same cell lines used to support the replication of lentiviruses. Southern blot analysis of the high molecular weight DNA of drug-treated CAEV-infected cells showed that S-(dC)28 was acting at or before the reverse transcription step. Our present data and the earlier finding that S-(dC)28 is a potent in vitro inhibitor of the MuLV reverse transcriptase [15] suggest that S-(dC)28 is acting very early in the replication cycle of these lentiviruses. Since MuLV reverse transcriptase is inhibited in vitro, but its replication is not blocked in permissive cells, our data suggest that the phosphorothioate oligonucleotides are preventing virus attachment.

Detection of equine arteritis virus following amplification of structural and nonstructural viral genes by reverse transcription-PCR

A reverse transcription (RT)-PCR assay was developed for the detection of equine arteritis virus (EAV) in cell culture supernatant and in horse semen. Four different sets of oligonucleotide primers complementary to sequences located in the 3' end of the polymerase gene (open reading frame [ORF] 1b) and to sequences representing the entire ORFs 3, 4, and 7, which encode for nonstructural (ORFs 3 and 4) or viral nucleocapsid (ORF 7) proteins, were compared for their abilities to amplify the targeted EAV sequences by the RT-PCR procedure. The sensitivities of the RT-PCR for amplification of EAV sequences located in the 3' end of ORF 1b and ORF 4 were 2 median tissue culture infective doses (TCID50s) of viral particles in the EAV-infected cell culture supernatant for both ORFs and 20 and 200 TCID50s of viral particles, respectively, in virus-containing horse semen. The sensitivities were much lower when primers complementary to ORFs 3 and 7 were used in the RT-PCR, with a minimum detection limit of only 2 x 10(4) TCID50s of viral particles in virally infected cell culture supernatant, as determined by analyzing the resulting RT-PCR products on ethidium bromide-stained agarose gels. The specificities of the RT-PCR assays for all primer sets tested were confirmed when the amplified cDNA products of the expected size reacted positively with the corresponding virus-specific digoxigenin-labeled cDNA probes in the chemiluminescence assays. Although the sensitivity of the RT-PCR for amplification of ORF 3 and 7 sequences was lower, all sets or primers were capable of amplifying several cell culture-adapted EAV field isolates when the virus was present in high enough quanities in the test sample. When horse semen samples were analyzed for the presence of EAV by the RT-PCR with primers specific to the ORF 1b 3' end and ORF 4 sequences and by virus isolation in cell cultures, there was 100% concordance among the assays. The RT-PCR assay targeting the 3' end of ORF 1b and/or ORF 4 EAV RNA may be an alternative to conventional methods for the diagnosis of EAV infection in horses.

Defective viral particles in caprine arthritis encephalitis virus infection

Attempts to isolate full-length unintegrated circular forms of the caprine arthritis encephalitis virus (CAEV) genome yielded only a large number of molecules with deletions. The 3' borders of most of these deletions were near the U3 region of the long terminal repeat whereas the 5' edges were found at various upstream sites within pol or env. With one exception, gag sequences were always present. Analysis of molecular clones derived from integrated proviral CAEV genomes from the same infected cells showed a similar spectrum of deletions. The presence of transcriptionally active elements within the U3 domain of the defective genomes, as well as cis-acting elements within the leader sequences known to be required for efficient encapsidation of viral RNA, suggested that the defective viral DNA genomes could be transcribed into defective RNA molecules which could then be packaged into virions. Isopycnic density gradient centrifugation of supernatants of infected cell cultures indicated the presence of particles with densities less than that expected for intact virions (1.16 g/cc). Northern analysis revealed the presence of smaller viral-specific RNAs that lacked env sequences. These data, along with the structures of the molecular clones, suggest that CAEV stocks contain particles with defective genomes. The role of these particles in influencing the course of virus infection remains to be determined.

Characterization and comparative bactericidal activity of monoclonal antibodies to Bordetella pertussis lipo-oligosaccharide A

Spleen cells from mice immunized with a Bordetella pertussis N-lauroyl sarcosine membrane extract (SME) were used to generate hybridoma cells lines producing monoclonal antibodies (mAbs). Seven mAbs were shown to be specific to B. pertussis lipo-oligosaccharide (LOS) by immunoblotting of SME or purified LOS following SDS-PAGE. All mAbs reacted with the B. pertussis Tohama I strain of the LOS AB phenotype, and did not react with the atypical variant strain 134 of the LOS B phenotype. The immune reactivity of the mAbs was retained after treatment of SME with proteinase K and was lost after sodium periodate treatment. No cross-reactivity was observed with the mAbs when tested against B. parapertussis and other Gram-negative bacteria. However, all mAbs reacted with B. bronchiseptica. Binding assays with live B. pertussis cells demonstrated that mAbs strongly reacted with cell surface exposed antigenic determinants. High bacterial cell lytic capability was observed for five of these mAbs. Concentrations between 0.22 and 2.2 micrograms mAb ml-1 (0.1 and 1 microgram per 450 microliter assay) purified by protein A were required to kill at least 50% of the bacteria. Competition immunoassays with biotinylated antibodies showed that the bacteriolytic and non-bacteriolytic mAbs were directed to different epitopes of the B. pertussis LOS A.

Equine infectious anemia virus derived from a molecular clone persistently infects horses

A full-length molecular clone of equine infectious anemia virus (EIAV) was isolated from a persistently infected canine fetal thymus cell line (Cf2Th). Upon transfection of equine dermis cells, the clone, designated CL22, yielded infectious EIAV particles (CL22-V) that replicated in vitro in both Cf2Th cells and an equine dermis cell strain. Horses infected with CL22-V developed an antibody response to viral proteins and possessed viral DNA in peripheral blood mononuclear cells, as determined by polymerase chain reaction assays. In addition, horses infected with CL22-V became persistently infected and were capable of transmitting the infection by transfer of whole blood to uninfected horses. However, CL22-V, like the parental canine cell-adapted virus, did not cause clinical signs in infected horses. Reverse transcriptase assays of CL22-V- and virulent EIAV-infected equine mononuclear cell cultures indicated that the lack of virulence of CL22-V was not due to an inability to infect and replicate in equine mononuclear cells in vitro.

Study of virus excretion in feces of diarrheic and asymptomatic calves infected with rotavirus

Infection of calves by rotavirus could lead to diarrhea or subclinical disease. Therein, kinetic of viral excretion from a group of asymptomatic calves, previously exposed to a virulent strain of rotavirus, is compared to that of a group the calves of which had diarrhea associated with rotavirus infection. As determined by an enzyme-linked immunosorbent assay (ELISA), duration of rotavirus shedding in feces and maximum yield of virus antigen were similar within the two groups of calves. Rotaviruses isolated from the two above groups of animals were antigenically related as shown by neutralization tests, and showed a similar RNA electrophoretic profile. In conclusion, it is likely that both asymptomatic and diarrheic calves infected by rotavirus are equally a major source of contamination to contact healthy calves.

Development of an enzyme-linked immunosorbent assay for equine infectious anemia virus detection using recombinant Pr55gag

To provide more sensitive and convenient methods for the detection of equine infectious anemia virus (EIAV), we developed an enzyme-linked immunosorbent assay (ELISA) employing the EIAV gag precursor (Pr55gag) produced by using recombinant DNA techniques. The antigenic reactivity of the recombinant EIAV Pr55gag was found to be equivalent to that of the virion p24gag and elicited high-titered antiserum in rabbits. When a large number of horse sera were analyzed for the presence of antibodies to EIAV by this ELISA, a radioimmunoassay for EIAV p15gag, or the standard agar gel immunodiffusion test, there was 98.7% concordance among the assays. By using the ELISA it was possible to specifically detect antibodies earlier after experimental infection of horses with EIAV than with the other two tests. A competition ELISA developed in order to detect EIAV gag antigens was found to be approximately 15 times more sensitive than the radioimmunoassay for EIAV p15gag. Antigens of other animal lentiviruses as well as those of the prototype oncovirus failed to compete in this assay.

Effect of sodium diethyldithiocarbamate, Corynebacterium parvum and mycobacterium cell wall extract on in vitro blastogenic responses of bovine blood lymphocytes

In vivo inoculation of three-month-old calves with sodium diethyldithiocarbamate (DTC), killed Corynebacterium parvum or mycobacterium cell wall extract (MCWE) resulted in an enhancement of in vitro peripheral blood lymphocyte blastogenic responses to mitogens phytohemagglutinin (PHA) and Concanavalin A (Con A) in the first three days after treatment. In a separate experiment, blood lymphocytes isolated from a healthy nontreated calf were incubated in vitro in presence of each of the same immunostimulating agents and tested for their blastogenic responses to PHA and Con A. The results showed that all immunostimulants, excepting DTC, enhanced the in vitro blastogenic responses of lymphocytes to PHA and Con A. Finally, addition of MCWE to cultures of blood lymphocytes isolated from calves vaccinated intramuscularly with bovine rotavirus and adjuvant resulted in an enhancement of the in vitro lymphocyte transformation to rotavirus. Our study demonstrated that DTC, killed Corynebacterium parvum and mycobacterium cell wall extract were able to enhance bovine T cell proliferation in vitro.

Influence of immunomodulatory agents on bovine humoral and cellular immune responses to parenteral inoculation with bovine rotavirus vaccines

Sodium diethyldithiocarbamate (DTC), mycobacterium cell wall extract (MCWE, Regressin), killed Corynebacterium parvum (C. parvum, Immunoregulin) and muramyldipeptide (MDP) were each combined with purified, live bovine rotavirus and inoculated into 3 month-old Holstein-Friesian calves in order to examine their ability to potentiate specific humoral and cellular immune responses. The vaccinated calves were boosted twice at 3 and 6 weeks after initial vaccine inoculation. The rotavirus was administered intramuscularly either in an aqueous suspension or in a water-in-oil (WIO) emulsion, prepared with incomplete Freund's adjuvant (IFA). DTC and C. parvum were given by the intravenous route, while MCWE and MDP were incorporated directly in the rotavirus suspension. Two groups of calves were also vaccinated either with rotavirus and IFA or with rotavirus emulsified in mineral oil and a mannide oleate compound (MOC, Montanide 888). A control group of calves was given phosphate-buffered saline (PBS) solution emulsified with IFA. The different vaccine preparations were then compared by studying the kinetics of serum rotavirus-neutralizing antibody production and of proliferative response by blood lymphocytes following in vitro stimulation with bovine rotavirus. The results showed that: (1) the bovine rotavirus should be incorporated in a WIO emulsion in order to induce a cell-mediated immune response as detected by the rotavirus-specific in vitro stimulation test with blood lymphocytes, and to produce higher neutralizing antibody titers in the serum; (2) the vaccines prepared with the mineral oil-MOC complex or IFA both induced comparable levels of humoral and cellular immune responses. The use of mineral oil and MOC as adjuvant may be preferred to IFA, because of the facility of preparing the vaccine and of the low viscosity of the resulting WIO emulsion: (3) the addition of MDP to the WIO emulsion prepared with IFA resulted in a higher cell-mediated immune response as determined by the in vitro blood lymphocyte transformation index specific for bovine rotavirus.

Immune response of pregnant heifers and cows to bovine rotavirus inoculation and passive protection to rotavirus infection in newborn calves fed colostral antibodies or colostral lymphocytes

The efficacy of an adjuvanted bovine rotavirus vaccine in pregnant cattle (15 heifers and 2 cows) was studied. Each of 4 animals was inoculated IM at 8, 5, and 2 weeks before parturition with a water-in-oil emulsion containing live purified bovine rotavirus, mineral oil, and a mannide oleate compound. Four other animals were treated identically, except that muramyl dipeptide was added to the virus preparation. Five additional animals were inoculated orally at the same time intervals with adjuvant-free viral suspension, and 4 other pregnant animals inoculated only with buffer served as uninoculated controls. Kinetic studies of the specific immune responses were determined by quantification of the rotavirus-neutralizing antibodies and by a rotavirus lymphocyte stimulation test in vitro. Results showed that only the emulsions induced marked enhancement of rotavirus antibody titers in the serum, colostrum, and milk of inoculated cows. Colostral and milk lymphocytes isolated from these cows had a positive in vitro proliferative response to rotavirus stimulation, which lasted at least 21 days after parturition. The values of the stimulation index obtained with the colostral/milk lymphocytes were higher than those of the blood lymphocytes, reflecting increased lymphocyte activity in the colostrum/milk. However, addition of muramyl dipeptide to the emulsion preparation did not exert any potentiating effect on the immune response to rotavirus. Calves fed for the first 5 days after birth with a rotavirus-immune cell-free colostrum supplement were protected from a rotavirus challenge exposure on the third day after birth. Virus was not detectable in their feces.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of an enzyme-linked immunosorbent assay for caprine arthritis-encephalitis virus

Because relatively few caprine arthritis-encephalitis virus (CAEV)-infected animals exhibit clinical signs of illness, efforts to control and eradicate this virus will depend heavily on a sensitive diagnostic test that can be easily carried out. The currently utilized tests are of limited usefulness because of relatively low sensitivity or because of incomplete cross-reactivity of goat sera with heterologous test antigens. An enzyme-linked immunosorbent assay (ELISA) with purified CAEV antigen and biotin-avidin amplification steps was therefore developed and compared with a radioimmunoassay (RIA) against CAEV p28. Of over 500 sera tested, there was 99% concordance between the two tests. On the other hand, 23 of 24 sera obtained from animals with clinical signs of disease that were negative by agar gel immunodiffusion test (with ovine progressive pneumonia virus antigen) were positive by ELISA and RIA. These results suggest that an ELISA with CAEV antigen is superior to the agar gel immunodiffusion test and is easier and faster than an RIA, and therefore may be the method of choice for diagnosing CAEV infection.

Adjuvants et stimulants de l'immunité: propriétés immunorégulatrices du muramyl-dipeptide, des corynébactéries anaérobies et du diéthyldithiocarbamate de sodium

Several immunomodulator agents may influence the host immune system. Among them there are the adjuvants and the immunostimulant agents. In this paper, after a brief review of the mechanism of action of adjuvants, we have described the adjuvant and stimulant properties of muramyl-dipeptide, anaerobic corynebacteria and sodium diethyldithiocarbamate.

Standardization and kinetics of in vitro bovine blood lymphocyte stimulation with bovine rotavirus

Two groups of 3-month old calves were immunized intramuscularly with attenuated bovine rotavirus and boosted 21 and 42 days later. The first group of three calves were vaccinated with live virus emulsified with incomplete Freund's adjuvant (IFA) and the second group was immunized with live virus suspended in phosphate buffered saline (PBS). Three other calves, serving as controls, were inoculated with PBS emulsified with IFA. The specific cell-mediated and antibody responses of the animals were studied. Preliminary analysis of in vitro peripheral blood lymphocyte transformation to bovine rotavirus determined optimal conditions as: 96 h culture period, 5 X 10(5) cells per culture in RPMI 1640 medium containing 10% heat-inactivated bovine fetal serum and the use of inactivated virus in the cell culture at a concentration of 5 X 10(6) median tissue culture infective dose before inactivation. Specific blastic stimulation was observed on calves immunized with the rotavirus emulsified with IFA after the second and third vaccine inoculation with stimulation index values varying from 2.00 to 5.73. Serum neutralizing antibody titers of 1/25,600 were also induced in the same calves. Calves immunized with rotavirus-PBS suspension developed a mean antibody titer of 1/1,600, but showed no specific lymphocyte stimulation. No increase in specific immune responses was detected in the control animals.

Comparison by plaque assay of bovine rotavirus and a bovine enterovirus-like agent

Enterovirus-like particles from feces of calves are a frequent source of contamination of bovine rotavirus isolates. A study of plaque formation using BSC-1 cells indicated differences in behaviour of the viruses which could be used for differentiation the purification. The enterovirus-like particles produced well-defined plaques earlier and reached their optimal size much more rapidly than did the rotavirus. Furthermore, plaques produced by bovine enterovirus-like particles were significantly larger than those of bovine rotavirus. The viral cytopathic effects on the cells within the plaques were also characteristic for each virus.

Genomic variations and antigenic relationships among cytopathic rotavirus strains isolated in Quebec dairy herds

Twelve isolates of bovine rotavirus, originating from eight dairy herds in Quebec known to have frequent epizootics of diarrhea in young calves in the last five years, were successfully propagated in cell cultures. The 12 isolates produced clear-cut plaques in BSC-1 cells and, except for one isolate, agglutinated human group "O" erythrocytes to an higher titer than bovine erythrocytes. Antisera to each isolate were produced in rabbits and used to study their antigenic relationships. All the isolates shared the group-specific immunofluorescent antigen and were antigenically related as demonstrated by the seroneutralization and hemagglutination-inhibition tests. However, the relationships to the Nebraska rotavirus was quite weak in cases of two Quebec isolates. When the genomes of the various isolates were compared by polyacrylamide gel electrophoresis, at least three different reproducible fractionation patterns could be identified.