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Biomedical subjects

R C Wardley

Publications and source records attributed to R C Wardley.

At least 19 recordsLinked to original sources
PubMed1995

Defective entry of herpes simplex virus types 1 and 2 into porcine cells and lack of infection in infant pigs indicate species tropism.

We have determined if a defect at entry of the human pathogen herpes simplex virus type 1 (HSV-1) into cultured porcine cells extends to HSV-2 and if the poor susceptibility of porcine cells for these viruses is indicative of in vivo species tropism. HSV-1 replicates poorly in swine testis (ST) and other porcine cells which lack a functional non-heparan sulphate receptor(s) required for virus entry. By several criteria, ST cells resist infection by either HSV-1 or HSV-2. Infection can be restored if normal entry is bypassed by PEG-mediated virion-cell membrane fusion. Neither HSV serotype infects, replicates or produces clinical symptoms in infant pigs. No virus was isolated from any of multiple sites and seroconversion did not occur. The in vitro defect in porcine cells blocking HSV entry correlates with, and is likely to be at least partly responsible for, in vivo resistance of pigs to infection.

Animals↗
PubMed1994

Dose and load studies for subcutaneous and oral delivery of poly(lactide-co-glycolide) microspheres containing ovalbumin.

Poly(lactide-co-glycolide) microspheres containing different loads of OVA (0.05, 0.1, 0.5 and 1.0% w/w) were manufactured by a w/o/w emulsion/solvent evaporation method. Low load efficiencies of less than 20% were observed. Normal size distributions with mean volume diameters ranging from 3.7 to 4.7 microns were obtained for different batches. The in vitro release of OVA from different loaded microspheres showed an expected burst release with all batches. The in vivo dose study (1, 10, 25, 50 micrograms of OVA) was performed by subcutaneous and oral inoculation in mice by single (0 week) or double (0 and 3 weeks) administration of PLGA 50/50 microspheres containing 0.1% OVA. Subcutaneous administration showed an immune response (serum Ig levels by ELISA) statistically (Fisher's paired t-test; P < 0.05) above OVA saline negative controls at 3, 6 and 12 weeks after administration. Oral administration of microspheres produced statistically higher systemic immune responses at the higher doses. Single and double inoculation orally and subcutaneously produced similar serum antibody levels. The in vivo load study was performed by subcutaneous and oral administration to mice of 25 micrograms OVA contained in various loaded (0.05, 0.1, 0.5 and 1.0% w/w) microspheres. Serum immune responses at 3, 6, and 12 weeks after inoculation were statistically above OVA saline controls and were inversely proportional to the OVA load using either route. This observation suggested a relationship between the number of microspheres delivered and the in vivo serum response. Single subcutaneous administration of 0.05 or 0.1% OVA loaded PLGA 50/50 microspheres induced larger immune responses compared with complete Freund's adjuvant.

Administration, Oral↗
PubMed1992

The use of feline herpesvirus and baculovirus as vaccine vectors for the gag and env genes of feline leukaemia virus.

The env and gag genes from feline leukaemia virus were expressed in a thymidine kinase-negative feline herpes-virus and a baculovirus. Cats were vaccinated with various combinations of these recombinant viruses and 100% protection against feline leukaemia virus challenge was achieved using an immunization schedule which utilized both env and gag products delivered at both a mucosal and systemic site.

Animals↗
PubMed1991

Immune response in pigs to Aujeszky's disease viruses defective in glycoprotein g1 or gX.

Two Aujeszky's disease virus glycoprotein genes, gX and g1, have been used to produce deletion mutants which have then been developed into vaccines. These deletions then allow differentiation between pigs infected with wild type virus and those given the vaccine. It is not clear whether the glycoproteins encoded for by these genes are needed to induce a full protective immune response, in which case deletion mutants would suffer from lack of potency. To test this, commercially available Aujeszky's virus vaccines which lacked either gX or g1 were compared and isogenic constructs were made which differed only in the absence or presence of gX and, or, g1. These constructs and vaccines were used to vaccinate the natural host of Aujeszky's disease, the pig, and potency was measured using challenge with wild type virus. In all cases vaccines which lacked g1 performed significantly less well than those in which g1 was present, whereas deletions of gX had no significant effect on vaccine performance.

Animals↗
PubMed1990

Genetic engineering of the pseudorabies virus genome to construct live vaccines.

Pseudorabies virus (PRV) is a herpesvirus of pigs. Homologous recombination with plasmids offers a method to engineer precise changes in the PRV genome to produce advantageous live vaccines. Safety can be ensured by using a non-reverting deletion to inactivate the thymidine kinase gene. One particularly important feature of new PRV vaccines is deletion of an antigen, so that vaccinated pigs are serologically distinguishable from infected pigs. We have constructed a live vaccine strain with deletions in the thymidine kinase gene and in the gene for a glycoprotein, gX. Molecular engineering techniques made it possible to choose deletion of gX, which has no known immunological significance, over deletion of other glycoproteins that contribute to protective immunity. Extensive experiments in pigs with isogenic virus pairs show that deletion of gX does not compromise efficacy of a vaccine as gI deletions do. Deletion of gX also suggests a site for replacement with antigens from other pathogens. In addition to molecular engineering of a live vaccine strain, research on PRV glycoproteins has led to the discovery that expression of the glycoprotein gp50 makes cells resistant to PRV infection. Perhaps this observation could be extrapolated to the level of a whole animal to allow engineering of pigs to become an alternative to engineered vaccines.

Animals↗
PubMed1989

Infection of pigs with the Cameroon isolate (Cam/82) of African swine fever virus.

African swine fever (ASF) was produced in eight pigs by exposure to donors infected with the Cameroon/82 isolate of African swine fever virus. The primary clinical sign was pyrexia of more than 40 degrees C first observed 10 to 13 days post-exposure (dpe) in all pigs; other clinical signs were rarely observed. The most frequent post-mortem lesion was haemorrhage in the visceral lymph nodes. Other lesions included excess fluid in the abdominal cavity and petechial haemorrhages in the kidneys. Viraemia was first observed 1 to 2 days before the onset of pyrexia and maximal titres of more than 10(7.5) HAD50 per ml occurred 11 to 14 dpe. Virus excretion by the pharyngeal route was observed at 2 to 4 days before the onset of pyrexia and continued throughout the course of infection. Susceptible pigs, mixed directly with infected ones, contracted infection within 2 h; transmission time increased to 2 to 6 h when recipient pigs were separated by wire mesh from the infected pigs. The comparatively low mortality, ill-defined clinical signs and clinical recovery of many of the infected pigs show that the Cam/82 ASF virus is of relatively low virulence and thereby resembles recent European, South American and Caribbean isolates.

African Swine Fever↗
PubMed1988

ADCC and complement-dependent lysis as immune mechanisms against EHV-1 infection in the horse.

Immunity to equine herpesvirus type 1 (EHV-1) was evaluated using sera collected from yearling horses involved in a trial of a commercial vaccine. Measurement of the ability of these sera to mediate antibody-dependent cellular cytotoxicity and complement-dependent lysis revealed that these mechanisms, although potentially important in recovery from EHV-1 infection, do not play a role in protection following vaccination.

Animals↗
PubMed1987

A reassessment of the dual vaccine against rinderpest and contagious bovine pleuropneumonia.

In the light of the recent outbreaks of rinderpest in Africa a further assessment of the efficacy of the simultaneous inoculation of rinderpest virus vaccine and contagious bovine pleuropneumonia vaccine was undertaken. Groups of cattle were inoculated with a dual preparation of rinderpest vaccine virus and Mycoplasma mycoides subspecies mycoides or M mycoides alone. These groups were then challenged with M mycoides, first unsuccessfully by an in-contact challenge method and then by subcutaneous challenge. All animals were examined clinically after challenge for evidence of contagious bovine pleuropneumonia and serologically for rinderpest virus and M mycoides mycoides antibodies. There was no evidence that the serological response to the dual vaccine was in any way less than that to either agent given alone and no clinical disease was detected in these animals after in-contact challenge. However, after subcutaneous challenge, the dual vaccinated groups reacted similarly to an unvaccinated control group and unlike the group vaccinated only with M mycoides. This would indicate that the rinderpest virus component of the dual vaccine interfered with the ability of the M mycoides component to induce a fully effective immune response. In the pan African rinderpest campaign the use of the dual vaccine in areas where contagious bovine pleuropneumonia occurs should be carefully considered; in areas where the disease does not occur it is contraindicated.

Animals↗
PubMed1987

A vaccine strain of pseudorabies virus with deletions in the thymidine kinase and glycoprotein X genes.

A pseudorabies virus (PRV) mutant with deletions in genes for glycoprotein X (gX) and thymidine kinase, designated delta GX delta TK, was constructed and evaluated as a vaccine for protecting swine against PRV-induced mortality. Doses greater than or equal to 10(3) plaque-forming units (PFU) of this strain given to mice provided protection from challenge exposure with virulent PRV. Sera tested from mice inoculated with delta GX delta TK had high titers of neutralizing antibody to PRV, but reactivity in the same sera was not significantly different from that in sera from noninoculated mice (controls) when sera from both groups were evaluated by use of an ELISA with gX antigen produced in Escherichia coli. Compared with noninoculated pigs (controls), those given delta GX delta TK (greater than or equal to 10(2) PFU) were protected completely from lethal challenge exposure, without experiencing adverse effects on weight gain and with reduction of shedding of virulent challenge virus. Serotest results indicated that, although inoculated pigs responded with strong neutralizing antibody titers, the response of delta GX delta TK-inoculated pigs to gX, as determined by ELISA before challenge exposure, was not significantly greater than the ELISA values obtained from control pigs. The ELISA values from a group of pigs inoculated with a commercially available vaccine were significantly (P less than 0.05) higher than those of control pigs. The experimental vaccine, delta GX delta TK, was avirulent for mice, swine, and sheep, but was mildly virulent for calves (mortality, 1 of 12) and more virulent for dogs (mortality, 3 of 6) and cats (mortality, 2 of 6).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Local humoral and cellular responses in Aujeszky's disease virus infection in pigs.

Mucosal and tracheal washings from pigs vaccinated parenterally and intranasally with Aujeszky's disease virus were tested for specific anti-Aujeszky's disease virus responses. Antibody tests included complement dependent antibody lysis, antibody dependent cellular cytotoxicity, virus neutralisation, and anti-Aujeszky's disease virus IgA and IgG levels. There was no correlation between the levels of these antibodies and protection from subsequent challenge. Direct lymphocyte cytotoxicity against cells infected with Aujeszky's disease virus was found in lymph nodes draining the tonsillar area.

Animals↗
PubMed1987

Antibody and complement mediated lysis of felid herpesvirus 1 infected cells in vitro.

The lysis of cells infected by felid herpesvirus 1 (FHV) by feline anti-FHV antibody and complement was demonstrated. Lytic activity was sensitive to dilution of both antibody and, especially, complement. It was first detected within 10 to 20 minutes, increased rapidly during the next 30 minutes of incubation and then rose more slowly in a linear manner. Using standard antibody and complement concentrations and assay duration, it was shown that FHV infected cells underwent significant (P less than 0.05) lysis from eight hours after infection in a system in which FHV-specific membrane antigen was first detected at three hours after infection and spread of FHV by the intracellular route began eight to nine hours after infection. The ability of antibody and complement to reduce FHV spread in this system was demonstrated by a significant (P less than 0.05) reduction in FHV plaque numbers, although the restriction of spread was not absolute. Chelation of divalent cations and heat inactivation of complement factor B revealed that the lytic system was dependent on factor B and Mg2+ but not Ca2+, suggesting involvement of the alternative pathway of complement activation.

Animals↗
PubMed1987

Cross reactions between porcine, bovine and ovine interleukin-2 preparations.

Optimum conditions for the production of porcine interleukin-2 were found to include a delay of 24 hours before the addition of mitogen. Porcine and bovine interleukin-2 responded optimally in homologous systems whereas bovine interleukin-2 gave a better response in the ovine system than homologous ovine interleukin-2. Interleukin-2 produced from a continuous gibbon cell line reacted well with porcine, ovine and bovine T cell blasts indicating that it could act as a universal growth factor for T cell clones produced from these species.

Animals↗
PubMed1986

Serial inoculation of sheep with two bluetongue virus types.

Groups of sheep inoculated with bluetongue virus type 4 were challenged at various intervals after inoculation (from seven to 70 days) with bluetongue virus type 3. Examination of the clinical and serological response showed that animals were protected from challenge with a second bluetongue virus for up to 14 days after the inoculation of the first virus type. An adoptive transfer experiment in monozygotic sheep involving both antibody and T lymphocytes was carried out. Only partial protection was observed against heterologous virus challenge, indicating that although the T cell response has a cross-protective component, antibody is not involved. These observations indicate that current vaccination procedures should be reappraised, particularly in terms of revaccination with multiple bluetongue virus type.

Animals↗
PubMed1986

Functional antibody responses in pigs vaccinated with live and inactivated Aujeszky's disease virus.

Functional antibody tests, including virus neutralising activity of serum, antibody dependent cellular cytotoxicity and complement mediated lysis, were used to measure the response of pigs given either live or inactivated Aujeszky's disease virus vaccines. Pigs were then challenged with virulent Aujeszky's disease virus and antibody responses were analysed and found not to correlate with protection. Reasons for this lack of correlation are discussed and it is suggested that these results indicate that more emphasis should be placed on measuring the local immune response.

Animals↗
PubMed1985

The role of antibody in protection against African swine fever virus.

Intraperitoneal immunization of pigs with anti-African swine fever virus (ASFV) antibody protected them against the effects of challenge with ASFV. This protection, which was exemplified by a reduction in pyrexia and viraemia plus an increased survival time, appeared to be mediated through the effects of complement-dependent antibody-mediated cytotoxicity (CDAC) or antibody dependent cell mediated cytotoxicity (ADCC). Experiments suggested that the reduction in viraemia was associated with complement lysis whereas protection was conferred by ADCC.

African Swine Fever↗
PubMed1985

An immunological approach to vaccines against African swine fever virus.

Until recently there were no published reports of any immunological mechanism which could curtail the replication of African swine fever virus (ASFV). We have now described three such mechanisms--complement dependent lysis, antibody dependent cellular cytotoxicity and cytotoxic T lymphocytes. This paper discusses the likely role which each might play during ASFV infection and indicates where this research might help with a disease where no effective vaccine is available.

African Swine Fever↗
PubMed1985

Bluetongue vaccine: cells and/or antibodies.

Immunological studies with bluetongue virus have indicated that protection from re-infection involves components of both the humoral and cellular immune response. However, it was found that the humoral response was type-specific, whilst the cellular immune response, particularly through the action of cross-reactive cytotoxic T lymphocytes, gave rise to heterotypic protection. Work involving simultaneous and sequential inoculation of live virus and the inoculation of various inactivated preparations has further characterized the type of vaccine formulation needed for efficient protection in multitype endemic areas. The authors cite these studies on bluetongue virus as an example of an immunological approach to vaccine design that is too often ignored by vaccine manufacturers and yet clearly yields results.

Animals↗