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Biomedical subjects

H J Field

Publications and source records attributed to H J Field.

At least 55 records · Page 3Linked to original sources
PubMed1993

Interactions between equine herpesvirus type 1 and equine herpesvirus type 4: T cell responses in a murine infection model.

Interactions involving the immune responses to equine herpesvirus types 1 and 4 (EHV-1 and EHV-4) were studied in a murine infection model. When mice were inoculated intranasally with EHV-1, virus replication occurred in the respiratory tract and clinical signs were produced. In contrast, mice that were similarly inoculated with EHV-4 produced no evidence of virus replication and showed no clinical signs. When mice that had been inoculated with live EHV-4 were challenged 1 month later with EHV-1 they were partially protected. Although clinical signs were apparent on reinfection, virus replication in the respiratory tract was reduced in these mice compared with control mice that had not been previously immunized. Mice primed with heat-inactivated EHV-4, however, were not so protected. Live EHV-4-primed mice developed very low levels of antibody to EHV-1 and the humoral response could not account for this protection. However, the infected mice did give a strong delayed-type hypersensitivity reaction in a skin test using either EHV-1 or EHV-4 antigen. Spleen cells from EHV-4-primed donors provided a source of immune cells, including T cells which were used for transfer to recipient mice which were then challenged with EHV-1. The cells were protective; there was a reduction of virus replication on challenge with EHV-1 which correlated with the number of cells transferred. Modulation of the protective effect of primed cell populations was tested after depletion in vivo by means of complement-mediated lysis. The depletion of CD4-bearing cells produced the least effect on the protection afforded by cell transfer. In contrast, depletion of CD8-bearing cells markedly reduced the protection in recipients. EHV-1 and EHV-4 are widespread in horses and cross-infections are common. These results gained from a murine model indicate that important interactions occur at the level of T cell immunity between the two virus types which warrant further investigation in the natural host.

Animals↗
PubMed1993

Cell-mediated antiviral response to equine herpesvirus type 1 demonstrated in a murine infection model by means of adoptive transfer of immune cells.

Protection against equine herpesvirus type 1 (EHV-1) infection in a mouse model has been studied by means of delayed-type hypersensitivity (DTH) and adoptive transfer of immune spleen cells. Mice were found to develop a positive DTH response to EHV-1 antigen which was sustained for several months after primary inoculation. The response was found to cross-react with EHV-4-derived antigen. Immune cells (from mice primed with live or heat-inactivated EHV-1) conferred an enhanced DTH response on recipients; however, only the immune cells that were previously primed with live EHV-1 gave protection against re-infection. The degree of protection was also dependent on the number of spleen cells transferred. Immune cells from mice primed with heat-inactivated EHV-1 appeared to enhance virus replication following subsequent inoculation. The serum antibody response to EHV-1 appeared to be slightly suppressed in recipients of spleen cells from mice primed with either live or heat-inactivated virus. These results support the important role for cell-mediated responses in protective immunity to EHV-1 and provide clues to the nature of protection and immunopathology in the natural host.

Animals↗
PubMed1993

Pathogenicity of a thymidine kinase-deficient mutant of equine herpesvirus 1 in mice and specific pathogen-free foals.

Both intranasal (i.n.) and intracerebral (i.c.) inoculation of mice with wild-type equine herpesvirus type 1 (wt EHV-1) caused clinical signs and mortality. Virus could be recovered from target organs (turbinates, lungs and blood) for several days. By contrast, the thymidine kinase (TK)-deficient deletion mutant PR1 produced markedly less clinical disease following both i.n. and i.c. inoculation, and, in particular, no mortality occurred. PR1 did, however, establish productive infections following either route of inoculation. High titres of virus were recovered from target organs although virus did not persist for as long as wt EHV-1 and no viraemia was detected. Primary i.n. infection of mice with either wt EHV-1 or PR1 protected against subsequent challenge with wt EHV-1 5 weeks later. I.n. inoculation of specific pathogen-free (EHV-free) foals with PR1 produced results similar to those observed after infection of mice. Clinical signs were milder than for wt EHV-1 and pyrexia was short-lived or absent. PR1 could be recovered from nasal mucus at high titres but it persisted for only 5 days post-infection compared to 11 days in the case of wt EHV-1. No viraemia was detected in foals infected with PR1. On challenge with wt EHV-1, foals given a primary infection with the mutant were partially protected; but a viraemia with a TK+ EHV-1 was observed. These results demonstrate that our TK- mutant PR1 is markedly less pathogenic than wt EHV-1, despite being able to replicate in the host. The use of TK-deficient mutants of EHV-1 as potential vaccines in the horse is discussed.

Animals↗
PubMed1993

Effects of phosphonylmethoxyalkyl derivatives studied with a murine model for abortion induced by equine herpesvirus 1.

(S)-9-(3-Hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) and (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) were tested in a mouse model for equine herpesvirus 1-induced abortion. HPMPA, given twice daily, reduced virus replication, but the compound was embryotoxic. A single dose of HPMPC, however, reduced the incidence of abortion and transfer of virus to the fetuses while producing no obvious toxic effects.

Abortion, Spontaneous↗
PubMed1992

Pathogenesis of equine herpesvirus-1 in specific pathogen-free foals: primary and secondary infections and reactivation.

Six specific pathogen-free foals shown to be free of equine herpesvirus-1 and 4 (EHV-1 and -4) and lacking in maternally-derived antibodies were used to investigate the pathogenesis of EHV-1 in horses. Following primary intranasal inoculation with EHV-1 all foals showed signs of a mild, self-limiting upper respiratory tract infection. A leucopenia was observed, comprising both a lymphopenia and neutropenia. Virus was isolated from nasal mucus and buffy coat cells over several days during the clinical episode and after the animals became clinically normal. Notwithstanding the mildness of the clinical disease, virus was not eliminated completely and intravenous administration of dexamethasone resulted in reactivation of latent EHV-1 in animals which had received only a single dose of the virus. In a second infection given to four foals, 61 days after the primary inoculation, no clinical signs were observed, haematological changes were minimal and viraemia was absent.

Animals↗
PubMed1992

Reinfection and reactivation of equine herpesvirus-1 in the mouse.

Balb/c mice were inoculated with equine herpesvirus-1 (EHV-1) by the intranasal (i.n.) route. Mice developed respiratory signs; virus replication occurred in the respiratory tract and viraemia was detected; some mice died. Recovered mice were given a second inoculation with the same strain 5 months later. Following the second infection no mice died, however, virus replication was again observed in the respiratory tract and viraemia was detected once more. Administration of an antiviral agent during the acute infection prevented mice from developing severe clinical signs and all survived. These mice, and some that had survived an acute infection without chemotherapy, were given a variety of stimuli, for example X-irradiation or corticosteroid injection. Reappearance of infectious virus was detected in approx. 1/3 animals in either the respiratory tract or blood. We speculate on the possible sites of latency in the model.

Animals↗
PubMed1992

The pathogenicity of Ab4p, the sequenced strain of equine herpesvirus-1, in specific pathogen-free foals.

The sequencing of the genome of equine herpesvirus-1 (EHV-1) is reported in Elizabeth A. R. Telford, Moira S. Watson, Kathryn McBride, and Andrew J. Davison, 1992, Virology, 189, 304-316. The sequence was derived using a plaque-purified clone of EHV-1 strain Ab4 (designated Ab4p). To ensure that Ab4p shares the pathogenic characteristics of parental Ab4 (hereafter Ab4), both were inoculated intranasally into foals, specifically free from EHV-1 and EHV-4. Clinical signs, including rectal temperature, were similar for both viruses. In addition, nasal shedding of virus was observed over a 1- to 2-week period postinfection, and viremia was established with both Ab4 and Ab4p. Isolation of virus from one foal following intravenous administration of steroids indicates that Ab4p can establish latency and undergo reactivation. Finally, retinal lesions were observed and these were similar to those seen with Ab4. In conclusion, several pathogenic characteristics of Ab4 are retained in the plaque-purified clone, Ab4p.

Animals↗
PubMed1992

The acyclic nucleoside analogue penciclovir is a potent inhibitor of equine herpesvirus type 1 (EHV-1) in tissue culture and in a murine model.

Equine herpesvirus type 1 (EHV-1) was sensitive to the nucleoside analogue penciclovir (PCV) when tested in tissue culture; the ED50 was 1.6 micrograms/ml. Drug-resistant mutants were selected which were found to be TK-defective and approx. 45-fold less sensitive to PCV compared with the parental strain. PCV was compared with the phosphonyl derivative, HPMPA in mice infected with EHV-1. Both drugs were shown to be effective in vivo, limiting wild-type virus replication in respiratory tissues, and reducing viraemia. The treated mice also showed less clinical signs and reduced histopathology compared with placebo-treated controls. The establishment of latent EHV-1 in the mice, however, was not prevented. The results obtained with mice suggest that antiviral chemotherapy may be practical in the horse and that this possibility is worthy of further investigation in the natural host.

Acyclovir↗
PubMed1992

The activity of (S)-1-[(3-hydroxy-2-phosphonyl methoxy) propyl] cytosine (HPMPC) against equine herpesvirus-1 (EHV-1) in cell cultures, mice and horses.

The activity of the nucleotide analogue, (S)-1-[(3-hydroxy-2-phosphonyl methoxy) propyl] cytosine (HPMPC), against equine herpesvirus-1 (EHV-1) was tested in cell culture, mice and foals. The ED50 for plaque reduction was found to be 0.07 and 0.03 microgram/ml in RK-13 and EEL cells respectively. In mice, a single administration of HPMPC (20 mg/kg, s.c.) was very effective at reducing clinical signs and virus replication if given on the day before intranasal inoculation with EHV-1. Treatment on the day of infection or day 1 p.i. was less effective, but still significantly reduced clinical signs and virus titres in the target organs (lungs and nasal tissue). Furthermore, HPMPC was found to protect mice partially from an intracerebral inoculation with EHV-1. Experiments in the horse suggested that HPMPC was also very active against EHV-1 in the natural host. Thus a single administration of HPMPC at 20 mg/kg, s.c., on the day of infection, markedly reduced clinical signs and nasal excretion of virus following intranasal inoculation with EHV-1. HPMPC given as a divided dose of 1 mg/kg on day 0 and day 3 p.i. had no effect on clinical signs but did reduce nasal excretion of virus. The significance of these results is discussed.

Administration, Intranasal↗
PubMed1992

Serological responses of specific pathogen-free foals to equine herpesvirus-1: primary and secondary infection, and reactivation.

Serum antibody (virus neutralisation, complement fixation, IgM and IgG) responses to equine herpesvirus-1 (EHV-1) infection were measured in six foals which were initially free from EHV-1 and EHV-4 infection and maternally-derived antibodies. Following primary infection, high titres of virus neutralisation and complement fixation antibodies were detectable against EHV-1, however, corresponding antibody levels against EHV-4 were low or inapparent, although the two viruses share a number of cross-reactive epitopes. In addition, following the primary infection with EHV-1, IgM levels increased before those of IgG, virus neutralisation and complement fixation antibodies, peaked sooner and thereafter declined. Stimulation of IgM levels was observed on secondary infection with EHV-1 given 61 days later. In contrast, IgG, virus neutralisation and complement fixation antibodies following primary infection were more sustained and no increase in their levels was observed on secondary infection. No consistent changes in IgM or IgG levels were seen after administration of dexamethasone to reactivate latent virus.

Animals↗
PubMed1991

A murine model for studying EHV-1-induced abortion.

Balb/c mice were infected with two abortigenic strains of equine herpesvirus-1 (EHV-1) by intranasal inoculation. The inoculation of one strain produced subclinical disease while the other produced a disease characterised by weight loss, constitutional signs, and death in the most severely affected animals. When pregnant mice were infected by the same method of inoculation, one strain of virus produced premature parturition; both strains produced fetal abnormalities. In some cases, virus could be detected in the aborted fetuses by means of virus isolation and immunofluorescent staining.

Abortion, Veterinary↗
PubMed1991

Isolation of equine herpesvirus-1 mutants in the presence of (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine: demonstration of resistance in vitro and in vivo.

The compound (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) had been previously shown to be highly effective in treatment of EHV-1 in a murine model for the equine disease. This paper describes the isolation of a series of mutants resistant to the drug. Resistance was demonstrated in cell culture and one mutant was tested in a murine model. The resistant mutant was pathogenic for mice; infectious virus was recovered from respiratory tissues and blood at levels similar to the parental virus. However, the mutant showed a significant degree of resistance in vivo, thus proving the virus-specific mode of action of the antiviral compound.

Adenine↗
PubMed1991

The raising of equine colostrum-deprived foals; maintenance and assessment of specific pathogen (EHV-1/4) free status.

Over a period of two years, a total of 22 full term foals from Welsh Mountain pony mares were raised in conditions that were free from infection by Equid herpesvirus (EHV-1/4). Parturition dates were predicted by monitoring colostrum electrolytes, and the mares allowed to foal naturally under supervision or following induction with intravenous oxytocin. Immediately following birth, foals were separated from their dams and transferred to a specially built, positive pressure isolation unit. They were given antibiotic prophylaxis and fed bovine colostrum during the first 24 h, and then mare's milk replacer until weaned. Out of 22 specific pathogen free (SPF) foals one that had not been given antibiotic prophylaxis died of an E. coli septicaemia aged eight days. Two foals developed a streptococcal upper respiratory tract infection, which responded to antibiotic therapy and did not spread to the rest of the herd. A self limiting upper respiratory tract infection was seen in a fourth foal and mild diarrhoea was observed in six foals. Physical development in all SPF foals appeared normal and behavioural patterns resembled those of conventional handreared foals. Newborn foals were held in a separate quarantine area, within the isolation unit, and checked extensively for evidence of EHV-1/4 infection, before being transferred to the main holding unit. Periodic checks were then made for EHV-1/4 over a period ranging from 2 to 4 months; none of the SPF foals showed evidence of infection with EHV-1/4 in terms of clinical disease, virus isolation, sero-conversion or specific lymphocyte transformation.

Animals↗
PubMed1990

Experimental reactivation of bovine herpesvirus 1 (BHV-1) by means of corticosteroids in an intranasal rabbit model.

Intranasal inoculation of the rabbit was shown to be a viable alternative to eye inoculation as a model to study latency and reactivation of bovine herpesvirus 1 (BHV-1). In four different experiments, separate groups of rabbits were intranasally inoculated with BHV-1. In two experiments some rabbits were inoculated instead with a TK-defective (TK-) mutant strain of BHV-1. The development of a specific antibody response was monitored by both virus neutralization and ELISA assays. Cell-mediated immunity was measured by means of a skin test. Many weeks after virus inoculation the rabbits were treated with corticosteroid. Antibody formation after treatment was markedly different in wild type and in TK- virus inoculated groups. In the former, virus reactivation was suggested by a sudden rise in serum antibody levels with kinetics closely resembling those reported in infected calves following corticosteroid administration, whereas in the case of the TK- group no significant increase in antibody activity was measured. Histopathological changes in trigeminal ganglia also indicated reactivation of virus in the wild-type virus infected animals. Further evidence for reactivation was obtained by virus isolation from nasal swabs after corticosteroid treatment.

Adrenal Cortex Hormones↗
PubMed1990

A reliable method for establishing viral infection in the rabbit by intranasal inoculation.

Bovine herpesvirus 1 (BHV-1) infection was established in the rabbit by a novel procedure which involved virus being injected through trephine openings on either side of the nose of anaesthetised animals. This method of intranasal inoculation produced more consistent reactions to BHV-1 inoculation, and both humoral and cell-mediated immune responses to the virus were of greater magnitude compared with those following per naris instillation of virus.

Animals↗
PubMed1990

Identification of the gene homologous to HSV major DNA binding protein in the BHV-1 genome.

By means of Southern blot hybridisation using a cloned herpes simplex virus (HSV) major DNA binding protein (MDBP) gene as probe, the putative MDBP gene of BHV-1 was located within the Hind III G fragment which mapped between 0.352 and 0.381 map units of the BHV-1 genome. Moreover, an antiserum raised to HSV MDBP precipitated a 120kD polypeptide in a radio-immunoprecipitation test.

Animals↗