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L J Saif

Publications and source records attributed to L J Saif.

At least 55 records · Page 3Linked to original sources
PubMed1999

Comparisons of nucleotide and deduced amino acid sequences of NSP4 genes of virulent and attenuated pairs of group A and C rotaviruses.

The NSP4 protein of rotavirus is a nonstructural glycoprotein and has a crucial function in virus morphogenesis during infection of host cells. It was recently reported that NSP4 may also function as a viral enterotoxin in the induction of rotavirus diarrhea by causing Ca++ influx in the cytoplasm of the infected cells. We sequenced and analyzed two (Wa and M strains) pairs of NSP4 genes of virulent (v) and attenuated (a) (after 30 to 40 passages in cell culture) human group A rotaviruses and a pair of NSP4 genes of virulent and attenuated porcine group C rotavirus (Cowden strain). These strains were previously identified as virulent (induce diarrhea) or attenuated (no diarrhea) in a gnotobiotic pig model of rotavirus infection [Bohl et al. (4), Saif et al. (13), Ward et al. (17)]. The NSP4 genes of the Wa, M and Cowden strains were amplified with RT-PCR using a proof reading polymerase (Tli) and the RT-PCR product was sequenced directly. Analysis of the NSP4 deduced amino acid sequences showed that only 3 (Wa) and 2 (M and Cowden) amino acids differed between the virulent and attenuated strains. For the Wa strain, the changes from the virulent to attenuated strain were in amino acids 13 (V to A), 16 (L to S) and 34 (P to L); in the M strain, the difference was in amino acids 53 (T to I) and 104 (K to E), and in the Cowden strains, amino acids 50 (L to F) and 97 (D to N) differed between virulent and attenuated strains. To our knowledge, this is the first sequence comparison between NSP4 of a virulent and attenuated pair of group C rotaviruses. The potential impact of these few amino acid changes on the pathogenesis of the NSP4 protein for piglets is unclear, relative to previous findings in mice (1), but requires further study using purified recombinant NSP4 proteins or peptides.

Amino Acid Sequence↗
PubMed1999

Sequence analysis of the gene encoding VP4 of a bovine group C rotavirus: molecular evidence for a new P genotype.

Nucleotide sequence of the bovine group C rotavirus Shintoku strain gene 3 was determined. Segment 3 is 2253 nucleotides (nt) in length and contains a long open reading frame (ORF) beginning at nt 22 and terminating at nt 2223. This ORF encodes a polypeptide of 733 amino acids with a predicted molecular mass of 83 kDa. The deduced gene 3 amino acid sequence shares 79% and 73% identities with VP4 of the porcine Cowden and human Bristol strains, respectively. Lack of high amino acid sequence homology in VP4 of bovine, porcine, and human group C rotaviruses indicates that the Shintoku strain represents a new P genotype.

Amino Acid Sequence↗
PubMed1999

Serum and intestinal isotype antibody responses to Wa human rotavirus in gnotobiotic pigs are modulated by maternal antibodies.

The effects of passive antibodies on protection and active immune responses to human rotavirus were studied in gnotobiotic pigs. Pigs were injected at birth with saline or sow serum of high (immunized) or low (control) antibody titre and subsets of pigs were fed colostrum and milk from immunized or control sows. Pigs were inoculated at 3-5 days of age and challenged at 21 days post-inoculation (p.i.) with virulent Wa human rotavirus. Pigs receiving immune serum with or without immune colostrum/milk were partially protected against diarrhoea and virus shedding after inoculation, but had significantly lower IgA antibody titres in serum and small intestinal contents at 21 days p.i. and lower protection rates after challenge compared with pigs given control or no maternal antibodies. IgG antibody titres were consistently higher in small than in large intestinal contents. Pigs given control serum with control colostrum/milk had lower rates of virus shedding after inoculation than those given control serum alone. In summary, high titres of circulating maternal antibodies with or without local (milk) antibodies provided passive protection after inoculation but suppressed active mucosal antibody responses. These findings may have implications for the use of live, oral rotavirus vaccines in breast-fed infants.

Animals↗
PubMed1999

Characterization of group C rotaviruses associated with diarrhea outbreaks in feeder pigs.

Feces and serum specimens were collected from three farms in Michigan on which approximately 50-lb (8- to 9-week-old) pigs experienced diarrhea just after placement into all-in-all-out finishing barns. The clinical signs (profuse watery diarrhea lasting about 2 weeks and no vomiting) were similar on all farms, and the morbidity rate was high (ranging from 60 to 80%) but without mortality. Eleven diarrheic fecal samples from the farms were tested for group A and C rotaviruses by immune electron microscopy (IEM) and various assays. IEM indicated that the fecal samples reacted only with antiserum against group C rotaviruses, and polyacrylamide gel electrophoresis indicated that the samples had characteristic genomic electropherotypes for group C rotavirus. Group C rotavirus was detected by cell culture immunofluorescence (CCIF) tests in nine fecal samples, but no group A rotavirus was detected by enzyme-linked immunosorbent assay or CCIF. By reverse transcription (RT)-PCR, all 11 fecal samples were positive for group C rotaviruses, with only 2 samples positive for group A rotaviruses. However, a second amplification of RT-PCR products using nested primers detected group A rotaviruses in all samples. Analysis of nucleotide and deduced amino acid sequences of the RT-PCR product (partial-length VP7) of the group C rotavirus showed 87.2 to 91% nucleotide identity and 92.6 to 95.9% amino acid identity among two strong samples from the different farms and the Cowden strain of porcine group C rotavirus. All nine convalescent-phase serum samples tested had neutralizing antibodies to the Cowden strain, and the majority of them had neutralizing antibody against group A rotaviruses (OSU or/and Gottfried strains) by fluorescent focus neutralization tests. Although group C rotaviruses have been reported as a cause of sporadic diarrhea in suckling or weanling pigs, to our knowledge, this is the first report of epidemic diarrhea outbreaks associated with group C rotavirus in older pigs.

Animals↗
PubMed1999

Effects of maternal antibodies on protection and development of antibody responses to human rotavirus in gnotobiotic pigs.

Although maternal antibodies can protect against infectious disease in infancy, they can also suppress active immune responses. The effects of circulating maternal antibodies, with and without colostrum and milk antibodies, on passive protection and active immunity to human rotavirus (HRV) were examined in gnotobiotic pigs. Pigs received intraperitoneal injections of high-titer serum (immune pigs [groups 1 and 2]) from immunized sows, low-titer serum from naturally infected sows (control pigs [groups 3 and 4]), or no serum (group 5). Immune or control colostrum and milk were added to the diet of groups 2 and 4, respectively. After inoculation (3 to 5 days of age) and challenge (postinoculation day [PID] 21) with virulent HRV, the effects of maternal antibodies on protection (from diarrhea and virus shedding), and on active antibody responses (measured by quantitation of antibody-secreting cells [ASC] in intestinal and systemic lymphoid tissues by ELISPOT) were evaluated. Groups 1 and 2 had significantly less diarrhea and virus shedding after inoculation but higher rates of diarrhea and virus shedding after challenge than did groups 3 and 5. Group 1 and 2 pigs had significantly fewer immunoglobulin A (IgA) ASC in intestinal tissues at PID 21 and at postchallenge day (PCD) 7 compared to group 5. Significantly fewer IgG ASC were present in the intestines of group 2 pigs at PID 21 and PCD 7 compared to group 5. There was a trend towards fewer ASC in intestinal tissues of group 2 than group 1, from PID 21 on, with significantly fewer IgA ASC at PCD 7. IgG ASC in the duodenum and mesenteric lymph nodes of group 3 and 4 pigs were significantly fewer than in group 5 at PCD 7. These decreases in ASC emphasize the role of passive antibodies in impairing induction of ASC rather than in merely suppressing the function of differentiated B cells. To be successful, vaccines intended for populations with high titers of maternal antibodies (infants in developing countries) may require higher titers of virus, multiple doses, or improved delivery systems, such as the use of microencapsulation or immune stimulating complexes, to overcome the suppressive effects of maternal antibodies.

Animals↗
PubMed1999

Dual infection of gnotobiotic calves with bovine strains of group A and porcine-like group C rotaviruses influences pathogenesis of the group C rotavirus.

There is serological evidence that bovine group C rotaviruses exist in the United States, but there are no reports of their isolation. Ninety fecal samples from calves with diarrhea, 81 samples from adult cows with diarrhea (winter dysentery), and 20 fecal samples from healthy adult cows were tested for group C rotaviruses by polyacrylamide gel electrophoresis, immune electron microscopy, and reverse transcription-PCR (RT-PCR). Three samples from adult cow diarrhea cases were positive only by RT-PCR, and a group C rotavirus was isolated from a positive sample in monkey kidney (MA104) cells (WD534tc/C). Genetically and serologically, the WD534tc/C strain was more closely related to the Cowden porcine group C strain than to the Shintoku bovine strain. Because the original cow feces also contained a group A rotavirus (detected after passage in cell culture), we hypothesized that such dual-rotavirus infections might play a role in the pathogenesis and host adaptation of rotaviruses. Thus, we examined the pathogenesis of WD534tc/C alone or combined with virulent (IND/A) or attenuated (NCDV/A) bovine group A rotaviruses in gnotobiotic calves. WD534tc/C alone induced diarrhea without (or with limited) virus shedding in inoculated calves (n = 3). In contrast, all calves coinfected with WD534tc/C and IND/A (n = 2) developed diarrhea and shed both viruses, whereas calves coinfected with WD534tc/C and NCDV/A (n = 3) developed diarrhea but did not shed either virus. Infection with WD534tc/C or NCDV/A alone caused only mild villous atrophy (jejunum and/or ileum), whereas dual infection with both viruses induced lesions throughout the small intestine. Although IND/A alone caused villous atrophy, more-widespread small intestinal lesions occurred in calves coinfected with WD534tc/C and IND/A. In conclusion, coinfection of calves with group A rotaviruses enhanced fecal shedding of a bovine group C rotavirus and the extent of histopathological lesions in the small intestines. Thus, our findings suggest a potential novel hypothesis involving dual infections for the adaptation of heterologous rotaviruses to new host species.

Animals↗
PubMed1999

Molecular characterization of a porcine enteric calicivirus genetically related to Sapporo-like human caliciviruses.

Porcine enteric calicivirus (PEC) is associated with diarrhea in pigs, and to date it is the only cultivable enteric calicivirus (tissue culture-adapted [TC] PEC/Cowden). Based on sequence analysis of cDNA clones and reverse transcription-PCR products, TC PEC/Cowden has an RNA genome of 7,320 bp, excluding its 3' poly(A)(+) tail. The genome is organized in two open reading frames (ORFs), similar to the organizations of the human Sapporo-like viruses (SLVs) and the lagoviruses. ORF1 encodes the polyprotein that is fused to and contiguous with the capsid protein. ORF2 at the 3' end encodes a small basic protein of 164 amino acids. Among caliciviruses, PEC has the highest amino acid sequence identities in the putative RNA polymerase (66%), 2C helicase (49.6%), 3C-like protease (43.7%), and capsid (39%) regions with the SLVs, indicating that PEC is genetically most closely related to the SLVs. The complete RNA genome of wild-type (WT) PEC/Cowden was also sequenced. Sequence comparisons revealed that the WT and TC PEC/Cowden have 100% nucleotide sequence identities in the 5' terminus, 2C helicase, ORF2, and the 3' nontranslated region. TC PEC/Cowden has one silent mutation in its protease, two amino acid changes and a silent mutation in its RNA polymerase, and five nucleotide substitutions in its capsid that result in one distant and three clustered amino acid changes and a silent mutation. These substitutions may be associated with adaptation of TC PEC/Cowden to cell culture. The cultivable PEC should be a useful model for studies of the pathogenesis, replication, and possible rescue of uncultivable human enteric caliciviruses.

Amino Acid Sequence↗
PubMed1999

Evaluation of the baculovirus-expressed S glycoprotein of transmissible gastroenteritis virus (TGEV) as antigen in a competition ELISA to differentiate porcine respiratory coronavirus from TGEV antibodies in pigs.

The spike (S) glycoprotein of the Miller strain of transmissible gastroenteritis virus (TGEV) was recently cloned and expressed in baculovirus. The recombinant S protein was used as the coating antigen in a competition (blocking) enzyme-linked immunosorbent assay (ELISA) in combination with monoclonal antibodies to the S protein epitope A (conserved on TGEV and porcine respiratory coronavirus [PRCV]) or epitope D (present on TGEV only) to differentiate PRCV- from TGEV-induced antibodies. One set (set A) of 125 serum samples were collected at different times after inoculation of caesarean-derived, colostrum-deprived (n = 52) and conventional young pigs (n = 73) with 1 of the 2 porcine coronaviruses or uninoculated negative controls (TGEV/PRCV/negative = 75/30/20). A second set (set B) of 63 serum samples originated from adult sows inoculated with PRCV and the recombinant TGEV S protein or with mock-protein control and then exposed to virulent TGEV after challenge of their litters. Sera from set A were used to assess the accuracy indicators (sensitivity, specificity, accuracy) of the fixed-cell blocking ELISA, which uses swine testicular cells infected with the M6 strain of TGEV as the antigen source (ELISA 1) and the newly developed ELISA based on the recombinant S protein as antigen (ELISA 2). The sera from set B (adults) were tested for comparison. The plaque reduction virus neutralization test was used as a confirmatory test for the presence of antibodies to TGEV/PRCV in the test sera. The accuracy indicators for both ELISAs suggest that differential diagnosis can be of practical use at least 3 weeks after inoculation by testing the dual (acute/convalescent) samples from each individual in conjunction with another confirmatory (virus neutralization) antibody assay to provide valid and complete differentiation information. Moreover, whereas ELISA 1 had 10-20% false positive results to epitope D for PRCV-infected pigs (set A samples), no false-positive results to epitope D occurred using ELISA 2, indicating its greater specificity. The progression of seroresponses to the TGEV S protein epitopes A or D, as measured by the 2 ELISAs, was similar for both sets (A and B) of samples. Differentiation between TGEV and PRCV antibodies (based on seroresponses to epitope D) was consistently measured after the third week of inoculation.

Animals↗
PubMed1999

Isolation of bovine respiratory coronaviruses from feedlot cattle and comparison of their biological and antigenic properties with bovine enteric coronaviruses.

OBJECTIVE: To isolate bovine coronaviruses from the respiratory tracts of feedlot cattle and compare antigenic and biological properties of these strains with bovine enteric coronaviruses. ANIMALS: 5- to 8-month-old mixed-breed cattle at 4 feedlots. PROCEDURE: Samples were obtained from the nasal passages for testing. The 13 samples with the highest magnitude of positive values for bovine coronavirus (BCV) were cultured. Ten strains of bovine respiratory coronavirus (BRCV) were adapted successfully to serial passage. After observation of cytopathic effects (CPE) and confirmation of BRCV by immune electron microscopy and immunofluorescence testing, cell culture-adapted strains were cloned by limiting dilution. These isolates then were compared with a panel of bovine enteric coronaviruses (BECV), using hemagglutination (HA), receptor-destroying enzyme activity (RDE), hemagglutination inhibition (HI), and virus neutralization (VN) assays. Antigenic relatedness values then were calculated. RESULTS: The BRCV were detected in 105 of 488 (21.5%) of the cattle tested. Of 13 strains tested, 10 were isolated in cell culture. Six of the BRCV strains were similar to 2 strains obtained from neonatal calves with diarrhea and 2 strains from adult cattle with winter dysentery. The other 4 BRCV isolates had high RDE activity against mouse erythrocytes but differed from other strains of BECV Nine of 10 BRCV isolates had properties similar to the 2 BECV subtypes. CONCLUSIONS AND CLINICAL RELEVANCE: The BRCV can be isolated from nasal passages of cattle entering feedlots. Most BRCV were similar to BECV strains, although a few had unique properties. Vaccines developed to protect against enteric strains also may protect against respiratory tract strains.

Animals↗
PubMed1998

Passive immunity to bovine rotavirus in newborn calves fed colostrum supplements from cows immunized with recombinant SA11 rotavirus core-like particle (CLP) or virus-like particle (VLP) vaccines.

Heterotypic passive immunity to IND (P/5/G6) bovine rotavirus (BRV) was evaluated. Three groups of calves (n = 5 per group) were fed 1% pooled colostrum supplements (birth to 7 days of age) from BRV seropositive cows vaccinated with recombinant SA11(P/2/G3) rotavirus-like particles (VLPs), recombinant SA11 rotavirus core-like particles (CLPs), or inactivated SA11 rotavirus (SA11). Control calves (n = 5 per group) received either pooled colostrum from unvaccinated (BRV field exposure seropositive) control cows, or no colostrum. IgG1 antibody titers to IND BRV for the pooled colostrum were: 1,048,576 (VLP); 1,048,576 (CLP); 262,144 (SA11); and 16,384 (control colostrum). Elevated titers of BRV neutralizing (VN) antibodies were present in VLP colostrum (98,000), and SA11 colostrum (25,000), but not in CLP colostrum (1400), compared to colostrum from nonvaccinates (2081). Calves were orally inoculated with virulent IND BRV at 2 days of age and challenged at post-inoculation day (PID) 21. Calves were monitored daily for diarrhea and faecal BRV shedding through PID 10 and post-challenge day (PCD) 10. After colostrum feeding, the IgG1 antibody titers were highest in serum and faeces of calves fed VLP and CLP colostrum, but VN and IgA antibodies were highest in calves fed VLP colostrum. After BRV inoculation, calves fed colostrum from vaccinated cows had significantly fewer days of BRV-associated diarrhea and BRV shedding than control calves. All calves fed VLP colostrum were protected from diarrhea after BRV inoculation; two calves shed BRV. In the CLP colostrum group, one calf developed BRV-associated diarrhea and all calves shed virus. In the SA11 colostrum group, three calves developed BRV-associated diarrhea and four calves shed virus. BRV-associated diarrhea and shedding occurred in 9 of 10 control calves. Active IgM antibody responses occurred in faeces and/or serum of most calves after BRV inoculation. However, the highest active antibody responses (IgM and IgG1 in serum, and IgM, IgG1 or IgA in faeces) after BRV inoculation were in calves fed control or no colostrum, in association with clinical diarrhea in most of these calves. After challenge at PID 21, BRV-associated diarrhea and shedding were of short duration or absent, in all groups. These results demonstrate the efficacy of colostrum from VLP vaccinated cows to provide heterologous, passive protection against BRV diarrhea and shedding in calves. In comparison, calves fed CLP or SA11 colostrum were only partially protected against BRV diarrhea or shedding.

Animals↗
PubMed1998

Serum and intestinal isotype antibody responses and correlates of protective immunity to human rotavirus in a gnotobiotic pig model of disease.

We examined the antibody responses and protection to a human rotavirus (HRV) in gnotobiotic (Gn) pigs. Pigs were perorally (p.o.) inoculated with attenuated (group 1), virulent (group 2), or inactivated (group 3) Wa (P1A[8]G1) HRV. A fourth group was inoculated intramuscularly (i.m.) with inactivated Wa HRV in adjuvant. After p.o. challenge with virulent Wa HRV at post-inoculation day 21, most group 1, 3 and 4 pigs shed virus and developed diarrhoea, whereas this occurred in only a few group 2 pigs. Antibodies to HRV (IgM, IgA or IgG) were detected in serum and intestinal contents of pigs of all groups after virus inoculation or challenge, and the antibody titres in intestinal contents, although lower, showed similar kinetics to the serum responses. There was no correlation between protection and neutralizing antibody titres of serum or intestinal contents, but a positive correlation existed between protection and serum IgA, intestinal IgA and intestinal IgG antibody titres. These findings suggest that serum IgA antibodies to HRV could act as an indicator of IgA antibodies in the intestine after rotavirus infection. The virulent HRV elicited protective immunity and higher levels of serum and intestinal IgA antibodies to HRV compared to attenuated and inactivated HRV. These findings suggest that more efficient mucosal delivery systems and/or adjuvants are needed to enhance the intestinal immune responses to attenuated or inactivated HRV if more successful vaccination is to be achieved in neonates.

Animals↗
PubMed1998

Antibody-secreting cell responses and protective immunity assessed in gnotobiotic pigs inoculated orally or intramuscularly with inactivated human rotavirus.

Newborn gnotobiotic pigs were inoculated twice perorally (p.o.) (group 1) or intramuscularly (i.m.) (group 2) or three times i.m. (group 3) with inactivated Wa strain human rotavirus and challenged with virulent Wa human rotavirus 20 to 24 days later. To assess correlates of protection, antibody-secreting cells (ASC) were enumerated in intestinal and systemic lymphoid tissues from pigs in each group at selected postinoculation days (PID) or postchallenge days. Few virus-specific ASC were detected in any tissues of group 1 pigs prior to challenge. By comparison, groups 2 and 3 had significantly greater numbers of virus-specific immunoglobulin M (IgM) ASC in intestinal and splenic tissues at PID 8 and significantly greater numbers of virus-specific IgG ASC and IgG memory B cells in spleen and blood at challenge. However, as for group 1, few virus-specific IgA ASC or IgA memory B cells were detected in any tissues of group 2 and 3 pigs. Neither p.o. nor i.m. inoculation conferred significant protection against virulent Wa rotavirus challenge (0 to 6% protection rate), and all groups showed significant anamnestic virus-specific IgG and IgA ASC responses. Hence, high numbers of IgG ASC or memory IgG ASC in the systemic lymphoid tissues at the time of challenge did not correlate with protection. Further, our findings suggest that inactivated Wa human rotavirus administered either p.o. or parenterally is significantly less effective in inducing intestinal IgA ASC responses and conferring protective immunity than live Wa human rotavirus inoculated orally, as reported earlier (L. Yuan, L. A. Ward, B. I. Rosen, T. L. To, and L. J. Saif, J. Virol. 70:3075-3083, 1996). Thus, more efficient mucosal delivery systems and rotavirus vaccination strategies are needed to induce intestinal IgA ASC responses, identified previously as a correlate of protective immunity to rotavirus.

Administration, Oral↗
PubMed1998

Mutations in rotavirus nonstructural glycoprotein NSP4 are associated with altered virus virulence.

Rotaviruses are major pathogens causing life-threatening dehydrating gastroenteritis in children and animals. One of the nonstructural proteins, NSP4 (encoded by gene 10), is a transmembrane, endoplasmic reticulum-specific glycoprotein. Recently, our laboratory has shown that NSP4 causes diarrhea in 6- to 10-day-old mice by functioning as an enterotoxin. To confirm the role of NSP4 in rotavirus pathogenesis, we sequenced gene 10 from two pairs of virulent and attenuated porcine rotaviruses, the OSU and Gottfried strains. Comparisons of the NSP4 sequences from these two pairs of rotaviruses suggested that structural changes between amino acids (aa) 131 and 140 are important in pathogenesis. We next expressed the cloned gene 10 from the OSU virulent (OSU-v) and OSU attenuated (OSU-a) viruses by using the baculovirus expression system and compared the biological activities of the purified proteins. NSP4 from OSU-v virus increased intracellular calcium levels over 10-fold in intestinal cells when added exogenously and 6-fold in insect cells when expressed endogenously, whereas NSP4 from OSU-a virus had little effect. NSP4 from OSU-v caused diarrhea in 13 of 23 neonatal mice, while NSP4 from OSU-a caused disease in only 4 of 25 mice (P < 0.01). These results suggest that avirulence is associated with mutations in NSP4. Results from site-directed mutational analyses showed that mutated OSU-v NSP4 with deletion or substitutions in the region of aa 131 to 140 lost its ability to increase intracellular calcium levels and to induce diarrhea in neonatal mice, confirming the importance of amino acid changes from OSU-v NSP4 to OSU-a NSP4 in the alteration of virus virulence.

Amino Acid Sequence↗
PubMed1998

Field isolates of transmissible gastroenteritis virus differ at the molecular level from the Miller and Purdue virulent and attenuated strains and from porcine respiratory coronaviruses.

The diversity in selected regions of the transmissible gastroenteritis virus (TGEV) and porcine respiratory coronavirus (PRCV) genomes was analyzed among known TGEV and PRCV strains and field isolates. The N-terminal half of the spike (S) glycoprotein gene and open reading frames (ORF) 3, 3-1 and 4 were amplified by reverse transcriptase reaction and polymerase chain reaction (RT/PCR), and analyzed using restriction fragment length polymorphism (RFLP) patterns of the amplified DNA. Reference TGEV strains (Miller and Purdue) and a PRCV strain (ISU-1), and TGEV and PRCV field isolates were analyzed. Based on the size of the ORF 3, 3-1 and 4 RT/PCR products, TGEV and PRCV strains could be quickly and easily differentiated into three groups designated TGEV Miller, Purdue types and PRCV. By RFLP analysis of the N-terminal region of the S glycoprotein gene and ORFs 3, 3-1 and 4, TGEV and PRCV strains were differentiated into five groups using the restriction enzyme Sau3AI. Sequence analysis of a PCR product in the ORFs 3, 3-1 and 4 from virulent and attenuated Miller strains demonstrated additional differences in that region which have been correlated with a change in virulence of TGEV isolates.

Animals↗
PubMed1998

Further validation of antibody-capture and antigen-capture enzyme-linked immunosorbent assays for determining exposure of cattle to bovine coronavirus.

OBJECTIVE: To further validate an antibody-capture ELISA for measuring bovine coronavirus (BCV) exposure (antibody seroresponse) in cattle and to explain the apparent loss of sensitivity of a BCV antigen-capture ELISA when testing feces from adult versus neonatal cattle. ANIMALS: 98 adult cows from herds with and without winter dysentery; 10 gnotobiotic or colostrum-deprived calves. PROCEDURES: Results of an antibody-capture ELISA for BCV and a plaque reduction virus neutralization assay performed on paired serum samples from 24 cattle were compared with each other and with results of immunoelectron microscopy (IEM) of feces for BCV. For samples from 98 cattle, results of antibody-capture ELISA were compared with results of IEM. Calves were inoculated with feces ELISA-positive or IEM-positive for BCV and monitored for BCV infection. An ELISA was developed to detect BCV antigen-antibody complexes in feces and results were compared with results of an antigen-capture ELISA and IEM. RESULTS: Antibody-capture ELISA results correlated with neutralization assay results, but agreed more closely with results of IEM. Calves became infected with BCV following inoculation with either ELISA-positive or ELISA-negative but IEM-positive feces. Results of the antigen-antibody ELISA correlated with results of IEM and the antigen-capture ELISA. CLINICAL IMPLICATIONS: In adult cattle, testing of paired serum samples by use of an antibody-capture ELISA may be a better indicator of recent BCV exposure than results of virus neutralization tests. Antigen-antibody binding in feces may interfere with results of antigen-capture ELISA for BCV.

Animals↗
PubMed1998

Evaluation of cow-level risk factors for the development of winter dysentery in dairy cattle.

OBJECTIVE: To identify exposures to etiologic agents and to identify characteristics that could explain risk of disease for adult cattle in herds affected by winter dysentery (WD). ANIMALS: 229 lactating and nonlactating adult cattle (125 case and 104 control cattle) selected from 12 dairy herds. PROCEDURE: A case-control study, using multivariate conditional logistic regression and controlling for herd effects, was used to develop a model for risk factors associated with disease for each cow. RESULTS: Likelihood of developing disease increased as the ELISA value for bovine coronavirus (BCV) antigen detectable in feces increased (odds ratio [OR] = 2.94 for each 0.100 increase in BCV antigen ELISA value). Pregnant cattle were less likely to develop WD, compared with nonpregnant herdmates. Cows with high acute BCV antibody titers that seroresponded had greater odds of developing disease, compared with seroresponding cows with low acute titers. However, among those cows that did not serorespond, high acute antibody titers were associated with lower odds of developing the disease. CONCLUSION: In herds affected by WD, ill cows were more likely to shed detectable amounts of BCV antigen in their feces, and pregnancy appeared to protect cattle from the disease. The measured interaction between BCV seroresponse and acute BCV antibody titer may be evidence of an immunopathologic condition, but could also have been attributable to dynamics of the ELISA or study design. CLINICAL RELEVANCE: Factors that explained a cow's risk for illness within WD-affected herds may have been surrogate measures for that cow's nonspecific and BCV-specific immune profile.

Animals↗
PubMed1998

Epidemiologic herd-level assessment of causative agents and risk factors for winter dysentery in dairy cattle.

OBJECTIVE: To test the association between exposure to bovine coronavirus (BCV) and outbreaks of winter dysentery (WD) in dairy herds and to examine other risk factors for outbreaks of WD in dairy herds. ANIMALS: 12 dairy herds in Ohio affected with WD (case herds). For each case herd, 2 unaffected herds from the same area were concurrently used as control herds. PROCEDURE: A case-control study was conducted, using herds as the unit of investigation. Multivariate logistic regression modeling was used to identify risk factors for contracting disease. RESULTS: 4 factors appeared to increase a herd's risk for WD: increase in herd prevalence of adult cows that had a fourfold or more increase in BCV serum IgG antibody titer; increase in herd prevalence of adult cows that had a fourfold or more increase in bovine viral diarrhea virus (BVDV) titer; housing cattle in tiestall or stanchion barns rather than free-stall facilities; and use of equipment to handle manure and subsequently handle feed. The adjusted population-attributable risk for these variables was 71, 43, 53, and 31%, respectively, and 99% overall, indicating that these variables had considerable impact on WD outbreaks for the study population. CONCLUSIONS AND CLINICAL RELEVANCE: In dairies in Ohio, recent herd exposure to BCV appeared to increase the risk for WD outbreaks. Some WD outbreaks might have been associated with acute BVDV infection. Certain housing and management practices may have increased the risk of an outbreak of WD.

Animals↗