Tropism of subgroup J avian leukosis virus as detected byin situhybridization

Abstract

The HPRS-103 strain of avian retrovirus is the prototype of subgroup J avian leukosis virus (ALV-J) and causes myeloid leukosis in meat-type chickens. Using immunohistochemical detection of the viral groupspecific antigen (Gag) we have previously demonstrated that the induction of myeloid leukosis by ALV-J is associated with viral tropism for myelomonocytic cells. In this paper we describe an in situ hybridization (ISH) technique using digoxigenin (DIG)-labelled probes for detecting RNA transcripts in tissues from chickens infected with avian leukosis viruses (ALV) of subgroups J (HPRS-103 strain) and A (RAV-1 strain). Virus-specific RNA was detected mainly in the heart, kidney, proventriculus and adrenal in locations similar to those of the Gag protein. Viral gene expression could not be detected in the bone marrow or tumour tissues using this test. Higher levels of viral gene expression in the bursa of Fabricius infected with RAV-1, but not with HPRS-103, might help explain the inability of the latter virus to induce lymphoid leukosis.

Localization of Avian Leukosis Virus Subgroup J in Naturally Infected Chickens by RNA In Situ Hybridization

“…3 Transcripts also were detected in Purkinje fibers and vascular smooth muscle, and intracytoplasmic inclusions were noted in both cardiac myofibers and Purkinje fibers in HE-stained sections from 3-, 6-, and 9-week-old infected chickens. Similar inclusions have been reported in myocardium, ventricular smooth mus-cle, arterioles, feather follicles, and skeletal muscle of adult chickens naturally infected with lymphoid leukosis virus, and ultrastructural examination of these inclusions revealed ribonucleic acid and protein.…”

“…3,30 Nucleic acid probes failed to detect ALV-J proviral DNA but could detect viral transcripts in tissues from experimentally infected chickens. 3 Therefore, we used a riboprobe specific for the same region of the SU domain to detect viral transcripts in chickens naturally infected in ovo. Our results agree with those previously published for chickens experimentally inoculated with the prototype ALV-J strain HPRS-103 and an acutely transforming derivative virus, strain 966, with some exceptions.…”

“…Both immunohistochemical detection of group-specific antigen and ISH detection of viral transcripts have been used to determine viral tropism in chickens experimentally infected with ALV-J in ovo. 2,3 Group-specific antigen and viral nucleic acid expression were greatest in heart, kidney, adrenal gland, and proventricular glandular epithelium. Although the experimental model of ALV-J infection reliably reproduces the neoplastic manifestations typical of natural infection, studies using this model have not reported any other adverse manifestations, such the body weight suppression described in chickens naturally infected in ovo.…”

“…1,2,26 The lowered tropism for lymphocytes has been suggested as the cause for a predominance of myeloid tumors instead of lymphosarcoma in natural ALV-J infection. 2,3 The nonneoplastic effects of ALV-J in poultry, particularly in younger chickens, have not been well described. Initial isolates of ALV-J came from meat-type chicken flocks with a high prevalence of ascites and retroviral particles present in the myocardium.…”

Na + /H + exchanger type 1 is a receptor for pathogenic subgroup J avian leukosis virus

“…chNHE1 probably carries out housekeeping functions similar to mammalian NHE1, and its expression is likely required in all lines of chickens, possibly accounting for the broad susceptibility of chickens to ALV-J. Analysis of ALV-J tropism in infected chickens by in situ hybridization demonstrates infection of many tissues (33,34) consistent with the presumed extensive expression of chNHE1. High levels of viral RNA were seen in the heart, kidney, pituitary, adrenal, and thyroid glands.…”