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Biomedical subjects

R D Woods

Publications and source records attributed to R D Woods.

At least 19 recordsLinked to original sources

Seroconversion of pigs in contact with dogs exposed to canine coronavirus.

In order to determine if canine coronavirus (CCV) could be transmitted to pigs, two dogs were inoculated orally with virulent CCV. After 24 h, the dogs were moved to an isolation room that contained three three-day-old pigs. A wire mesh fence, allowing close contact between the animals, separated the dogs from the pigs. The dogs and pigs were observed for 14 days for clinical signs of disease. Samples of blood were obtained from dogs and pigs immediately before the dogs were inoculated with virus and 14 and 28 days later. The dogs developed mild clinical signs of an infection, but the pigs remained normal throughout the observation period. The dogs shed CCV for eight days after exposure. All three pigs developed neutralizing antibodies against CCV and transmissible gastroenteritis virus by 14 days after they were exposed to the dogs.

Animals

Efficacy of antiserum produced in goats and pigs to passively protect piglets against virulent transmissible gastroenteritis virus.

The protective effect of sera produced in swine and goats exposed to virulent transmissible gastroenteritis virus (TGEV) or modified-live TGEV was tested in hysterectomy-derived, colostrum-deprived three-day-old pigs. Pigs were given serum with their daily ration of milk, and their immunity to virulent TGEV was determined. The pigs were observed for ten days for clinical signs of TGEV infection. One of nine pigs receiving goat serum was protected whereas all three pigs receiving three doses of swine serum per day were protected. Because virus was not isolated from the goats after oral/intranasal vaccination, it is suggested the virus did not replicate in either the respiratory or digestive tract of the goat.

Animals

Genetic analysis of porcine respiratory coronavirus, an attenuated variant of transmissible gastroenteritis virus.

The genome and transcriptional pattern of a newly identified respiratory variant of transmissible gastroenteritis virus were analyzed and compared with those of classical enterotropic transmissible gastroenteritis virus. The transcriptional patterns of the two viruses indicated that differences occurred in RNAs 1 and 2(S) and that RNA 3 was absent in the porcine respiratory coronavirus (PRCV) variant. The smaller RNA 2(S) of PRCV was due to a 681-nucleotide (nt) deletion after base 62 of the PRCV peplomer or spike (S) gene. The PRCV S gene still retained information for the 16-amino-acid signal peptide and the first 6 amino acid residues at the N terminus of the mature S protein, but the adjacent 227 residues were deleted. Two additional deletions (3 and 5 nt) were detected in the PRCV genome downstream of the S gene. The 3-nt deletion occurred in a noncoding region; however, the 5-nt deletion shortened the potential open reading frame A polypeptide from 72 to 53 amino acid residues. Significantly, a C-to-T substitution was detected in the last base position of the transcription recognition sequence upstream of open reading frame A, which rendered RNA 3 nondetectable in PRCV-infected cell cultures.

Base Sequence

Differentiation between transmissible gastroenteritis virus and porcine respiratory coronavirus using a cDNA probe.

A plasmid, pG3BS, containing a cDNA clone from the 5' coding region of the peplomer glycoprotein gene appears to be specific for enteric transmissible gastroenteritis virus (TGEV) strains and for live-attenuated TGEV vaccines. This cDNA probe is used to differentiate porcine respiratory coronavirus (PRCV) isolates from TGEV field and vaccine strains by a slot blot hybridization assay. Probe pG3BS also hybridizes to canine coronavirus (CCV) RNA but does not hybridize to antigenically related feline infectious peritonitis virus (FIPV) RNA. The RNAs of 13 enteric TGEV isolates from the United States, Japan, and England, 4 US-licensed live-attenuated TGEV vaccines, and antigenically closely related CCV were detected by pG3BS. The RNAs of FIPV and 3 US isolates of PRCV did not react with pG3BS but were detected by a TGEV-derived plasmid, pRP3. Pigs infected with either PRCV or TGEV test serologically positive for TGEV antibody by the serum neutralization test. Characterization of the virus circulating in a swine herd by the pG3BS probe will differentiate between an enteric TGEV and a respiratory PRCV infection.

Animals

Genetic basis for the pathogenesis of transmissible gastroenteritis virus.

Intracellular RNAs of an avirulent small-plaque (SP) transmissible gastroenteritis virus variant and the parent virulent Miller strain of transmissible gastroenteritis virus were compared. Northern RNA blotting showed that the Miller strain contained eight intracellular RNA species. RNAs 1, 2(S), 5, 6(M), 7(N), and 8 were similar in size for both viruses; however, the SP variant lacked subgenomic RNAs 3 and 4. Instead, the SP virus contained an altered RNA species (delta 4) that was slightly smaller than RNA 4. S1 nuclease protection experiments showed a deletion of approximately 450 nucleotides in the SP genome downstream of the peplomer S gene. Sequencing of cDNA clones confirmed that SP virus contained a 462-nucleotide deletion, eliminating the transcriptional recognition sequences for both RNAs 3 and 4. These RNAs encode open reading frames A and B, respectively. An alternative consensus recognition sequence was not readily apparent for the delta 4 RNA species of SP virus. Since open reading frame A is missing in SP virus, it is not essential for a productive infection. The status of the potential protein encoded by open reading frame B is not clear, because it may be missing or just truncated. Nevertheless, these genes appear to be the contributing entities for transmissible gastroenteritis virus virulence, SP morphology, tissue tropism, and/or persistence in swine leukocytes.

Animals

Evidence for a porcine respiratory coronavirus, antigenically similar to transmissible gastroenteritis virus, in the United States.

A respiratory variant of transmissible gastroenteritis virus (TGEV), designated PRCV-Ind/89, was isolated from a swine breeding stock herd in Indiana. The virus was readily isolated from nasal swabs of pigs of different ages and induced cytopathology on primary porcine kidney cells and and on a swine testicular (ST) cell line. An 8-week-old pig infected oral/nasally with the respiratory variant and a contact pig showed no signs of respiratory or enteric disease. These pigs did not shed virus in feces but did shed the agent from the upper respiratory tract for approximately 2 weeks. Baby pigs from 2 separate litters (2 and 3 days old) also showed no clinical signs following oral/nasal inoculation with PRCV-Ind/89. In a third litter, 5 of 7 piglets (5 days old) infected either oral/nasally or by stomach tube developed a transient mild diarrhea with villous atrophy. However, virus was not isolated from rectal swabs or ileal homogenates of these piglets, and viral antigen was not detected in the ileum by fluorescent antibody staining even though the virus was easily recovered from nasal swabs and lung tissue homogenates. Swine antisera produced against PRCV-Ind/89 or enteric TGEV cross-neutralized either virus. In addition, an anti-peplomer monoclonal antibody, 4F6, that neutralizes TGEV also neutralized the PRCV-Ind/89 isolate. Radioimmunoassays with a panel of monoclonal antibodies indicated that the Indiana respiratory variant and the European PRCV are antigenically similar.

Animals

Serologic survey for transmissible gastroenteritis virus neutralizing antibodies in selected feral and domestic swine sera in the southern United States.

Serum samples collected from feral and domestic swine (Sus scrofa) in Florida and feral swine in Georgia and Texas were assayed by plaque reduction for their virus neutralizing (VN) antibodies against the porcine transmissible gastroenteritis virus (TGE). None of 560 samples collected from feral swine contained VN antibodies for TGE virus, but experimentally infected feral swine seroconverted. None of 665 samples from domestic swine contained TGE-VN antibodies. These results indicate feral swine are not a significant reservoir for TGE virus in southern states, but are capable of becoming infected and developing VN antibodies against TGE.

Animals

Humoral and cellular responses in swine exposed to transmissible gastroenteritis virus.

Swine exposed to attenuated transmissible gastroenteritis virus had higher virus-neutralizing antibody titers than did swine exposed to virulent virus. The cellular response, measured by the direct leukocyte migration-inhibition (LMI) procedure, was greater in swine exposed to virulent virus than in swine exposed to the attenuated virus. Leukocytes from exposed swine were inhibited more in the LMI procedure in the presence of the homologeous sensitizing antigen than in the presence of the heterologous viral antigen. The humoral response measured by virus neutralizing reached a peak 21 days after exposure, and the cellular response measured by LMI reached a peak 28 days after exposure.

Animals

Small plaque variant transmissible gastroenteritis virus.

A small plaque (SP) variant transmissible gastroenteritis (TGE) virus strain that may be useful in the control of TGE in swine has been developed and tested. This strain was derived from a persistently infected swine leukocyte cell line originally infected with a virulent TGE virus. The SP viral strain was avirulent for 3-day-old susceptible pigs and pregnant gilts. The SP virus elicited protective antibody when inoculated into pregnant gilts oral/intranasally, or intramammarily, or by both of these routes. The morbidity and mortality of their passively immune suckling pigs were 62% and 14%, respectively.

Animals

Quantitative transmissible gastroenteritis virus shedding patterns in lactating sows.

To test the role of sows in spreading transmissible gastroenteritis (TGE), 11 sows were intravenously, intranasally, or intramammarily inoculated with virulent virus within 5 days of farrowing. Six of the sows were separated from their offspring, and 5 were allowed to nurse their litters. All sows became clinically ill with sign of anorexia, depression, and fever that persisted until postinoculation day 4 or 5. They shed virus through milk, nasal secretions, and feces, with individual variations occurring in degree and duration of shedding in the 1st week after inoculation. Of 40 pigs separately fed milk samples from the 6 inoculated sows, 19 pigs (47.5%) became sick in 24 to 40 hours, and virus was isolated from them at necropsy. Of 43 pigs in the 5 litters that nursed exposed dams, all became sick with typical signs of TGE, and 29 (67.4%) died in 2 to 9 days. Sows given the single intramammary inoculation of virus developed statistically significant higher levels of TGE virus-neutralizing antibodies than did sows inoculated intravenously or intranasally.

Administration, Intranasal

Leukocyte migration-inhibition procedure for transmissible gastroenteritis viral antigens.

Swine exposed to transmissible gastroenteritis viral antigens developed humoral and cell-mediated immunity. Migration of leukocytes from exposed swine was inhibited in the presence of the sensitizing antigens, whereas migration of leukocytes from nonexposed swine was not inhibited in the presense of these same antigens. In virus-neutralization-positive animals, it was not possible to correlate degree of inhibition with virus-neutralization titer. Inhibition was observed 7 days after exposure and was found to persist for at least 35 days.

Animals

Immunogenicity of experimental Streptococcus equisimilis vaccines in swine.

The protective and complement-fixing antibody immune responses to Streptococcus equisimilis vaccines were evaluated in young, surgically derived, colostrum-deprived swine. Comparable levels of protection against live S equisimilis challenge exposure developed in response to sonic-extract, acid-extract, and whole-cell vaccines combined with incomplete Freund adjuvant. The extract vaccines induced higher levels of complement-fixing antibody than did killed, whole cells. Protection, as well as complement-fixing antibody immune responses, were comparable when swine were given doses of vaccine beginning at 3 or 8 weeks of age.

Animals

Efficacy of isolated colostral IgA, IgG, and IgM(A) to protect neonatal pigs against the coronavirus of transmissible gastroenteritis.

To ascertain what class of immunoglobulin (Ig; IgA, IgG, or IgM) is most efficacious in protection, a large quantity of colostrum from sows immunized with virulent transmissible gastroenteritis (TGE) virus was fractionated by chromatographic and gel filtration methods. The isolated IgG, IgA, and IgM(A) had specific virus-neutralizing activities of 1:7.6, 1:342, and 1:302 per milligram of protein, respectively. Each Ig was fed to groups of hysterectomy-derived colostrum-deprived neonatal pigs before and after exposure (challenge) with virulent TGE virus. The 7 pigs fed IgG survived the challenge exposure, but 2 of 7 fed IgA and 1 of 7 fed IgM(A) died of TGE. Three of the survivor pigs that had been fed IgG and 2 of the survivor pigs that had been fed IgA had increased serum antibody titers between 8 and 19 days after challenge exposure, but none of the survivor pigs fed IgM(A) had TGE antibody. In contrast, 12 of 14 virus-control pigs died of TGE and the 2 survivors had antibody conversion. The data show that all 3 Ig classes in immune colostrum will protect neonatal pigs against exposure with virulent TGE virus.

Animals

An iridovirus from bees.

An iridovirus, Apis iridescent virus (AIV), isolated from sick adult specimens of Apis cerana (Hymenoptera) from Kashmir, closely resembles iridescent viruses from Tipula and Sericesthis spp. (TIV and SIV). However, AIV is only distantly related serologically to TIV and SIV and is even more remotely related to several other similar viruses that were tested in tube precipitation tests with intact particles. AIV multiplies in Apis mellifera, forming cytoplasmic iridescent crystalline aggregates in several tissues, but unlike all the other iridoviruses tested, it failed to multiply in Galleria mellonella.

Animals

Leukocyte-aggregation assay for transmissible gastroenteritis of swine.

An in vitro leukocyte-aggregation assay was developed to detect the exposure of swine to transmissible gastroenteritis virus. Leukocytes in heparinized blood samples aggregated when mixed with test antigen prepared from transmissible gastroenteritis-infected swine testicle cell cultures. Twenty-two of 23 swine exposed 3 days or more were positive or suspects in the assay; 6 nonexposed swine were negative. Aggregation was shown as early as 3 days postexposure in 1 sow and persisted for as long as 14 months in another. Persistence of the assay was proved by repeated evaluations on 2 experimentally exposed swine.

Animals

Inhibition of multiplication of tobacco mosaic virus in protoplasts by antibiotics and its prevention by divalent metals.

At concentrations that inhibit bacterial growth, some antibiotics including gentamicin completely inhibited virus multiplication in protoplasts, and other antibiotics partially inhibited virus multiplication. The inhibition caused by each antibiotic was largely prevented by adding a divalent metal; MnC1(2) was more effective than CaC1(2) and other salts of divalent metals when added at 10 mM to the incubation medium. When added immediately after infection, 1 mug/ml of gentamicin halved the final virus concentration and 3 mug/ml completely inhibited virus multiplication, although 10 mug/ml was required to stop bacterial growth. Gentamicin inhibited virus multiplication even when added 24 h after virus inoculation. Also, when protoplasts were exposed to gentamicin for only 1 or 2 h, either immediately after inoculation or 2 h later, the virus concentration was considerably decreased. Gentamicin seemed not to affect virus multiplication in whole plants. Sap from Dianthus barbatus also strongly inhibited virus multiplication in protoplasts but, unlike gentamicin, it acted in the presence of MnC1(2). By contrast, chelating agents such as 1 mM-EDTA or 5 mM-potassium citrate was strong inhibitors of virus multiplication that were inactive in the presence of MnC1(2). It is suggested that gentamicin and other antibiotics may chelate metals from the protoplast membranes, thus disorganizing their function and affecting virus multiplication.

Anti-Bacterial Agents

Purification and serological characterization of a type-specific antigen of Streptococcus equisimilis.

A microtiter complement fixation (CF) procedure was developed for use in detection of antibodies in sera of swine and rabbits vaccinated with Streptococcus equisimilis. Crude ultrasonic as well as acid-extracted preparations contained CF antigen, but the ultrasonic procedure resulted in a higher yield of active antigen. Evidence of serotype specificity with varying degrees of cross reactivity was detected with the CF procedure when representative strains of four different serotypes of S. equisimilis were compared by using their respective unadsorbed antisera. Fractionation of crude sonic extract or acid extract by centrifugation, precipitation with ammonium sulfate, and chromatography on carboxymethyl cellulose yielded a purified, type-specific antigen that reacted only with the homologous antiserum in the CF test and formed a single band by immunodiffusion. Complement-fixing antibodies in immune swine sera were predominately immunoglobulin G.

Animals