Experimental reactivation of equid herpesvirus 1 (EHV 1) following the administration of corticosteroids

Abstract

Summary Eight ponies were experimentally infected with equid herpesvirus 1 (EHV 1) (subtype 1). All animals showed clinical and serological evidence of infection and virus was isolated from nasal swabs and leucocytes. These ponies were kept in isolation for a further three months during which time complement fixing antibody decreased at least four‐fold. Following immunosuppression with dexamethasone and prednisolone subtype 1 virus was recovered from six of the eight animals within 14 days. Five of these six ponies were viraemic and three of them shed virus in nasal secretions; only four displayed significant rises in complement fixing antibody and only two in neutralising antibody. Clinical abnormalities were not detected during reactivation.

In vitro reactivation of latent equid herpesvirus-1 from CD5+/CD8+ leukocytes indirectly by IL-2 or chorionic gonadotrophin.

“…The reverse is true for EHV-1 in the horse, where leukocytes were first identified as the site of latency (Edington et al, 1985(Edington et al, , 1994Welch et al, 1992), while detection in the trigeminal ganglia has shown a low frequency of neurones expressing LATs (Baxi et al, 1995) and with either no recovery or only low frequencies of infectious virus from latently infected neurones (Burrows & Goodridge, 1984 ;Edington et al, 1994 ;Slater et al, 1994). The present work is consistent with the range of variation in the predominant sites of latency that is seen between alphaherpesviruses in different hosts.…”

“…Leukocytes also have been identified as a site of latency for EHV-1 (Edington et al, 1985(Edington et al, , 1994Welch et al, 1992).…”

Identification and control of the cis-acting elements of the immediate early gene of equid herpesvirus type 1

“…However, recent work using polymerase chain reaction and co-cultivation studies has shown that latent EHV-1 in outbred animals is always detected in lymphoid tissues in the presence of EHV-2 (for review see Edington, 1991). It is also reported that recovery of EHV-2 precedes EHV-1 when corticosteroids are used in immunosuppression (Edington et al, 1985). In contrast to previous findings (Allen & Turtinen, 1982;Staczeck et al, 1983), recent work in our laboratory has shown that EHV-I DNA cross-hybridizes significantly with EHV-2 DNA.…”

Equid herpesvirus 1 is neurotropic in mice, but latency from which infectious virus can be reactivated does not occur

“…Latent EHV-1 and EHV-4 infections in horse have been shown to reactivate from lymphoid tissues following the administration of corticosteroids (Edington et al, 1985;Edington et al, 1994a, b;Browning et al, 1988;Welch et al, 1992) and also by IL-2 or chorionic gonadotrophin stimulation of leukocytes (Smith et al, 1998). Borchers et al (1999) also have been able to detect latency associated transcripts of EHV-1 and EHV-4 by PCR from trigeminal ganglia of the latently infected horses.…”