Activation of CD8 T cells by antigen expressed in the pituitary gland

Ag expressed exclusively in the anterior pituitary gland and secreted locally by pituitary somatotrophs can gain access to the MHC class I presentation pathway and activate CD8 T cells. Influenza nucleoprotein (NP) was expressed as a transgene under the control of the human growth hormone (GH) locus control region. Activation of monoclonal F5 CD8 T cells specific for NP resulted in spontaneous autoimmune pathology of the pituitary gland in mice transgenic for both NP and the F5 TCR. Destruction of somatotrophs resulted in drastically reduced GH levels in adult mice and a dwarf phenotype. Adoptive transfer of F5 T cells into NP-transgenic hosts resulted in full T cell activation, first demonstrable in regional lymph nodes, followed by their migration to the pituitary gland. Despite the presence of activated, IFN-gamma-producing CD8 T cells in the pituitary gland and a slight reduction in pituitary GH levels, no effect on growth was observed. Thus, CD8 T cells have access to the neuroendocrine system and get fully activated in the absence of CD4 help, but Ag recognition in this location causes autoimmune pathology only in the presence of excessive CD8 T cell numbers.

Localization of avian leukosis virus subgroup J in naturally infected chickens by RNA in situ hybridization

The novel subgroup J of avian leukosis virus (ALV-J) has emerged as a significant cause of myeloid neoplasia and weight suppression in broiler chickens. We investigated viral tropism using RNA in situ hybridization (ISH) in naturally infected chickens. Formalin-fixed tissues were collected from 12-day-old embryos (seven infected, two control) and from 0-week-old (four infected, one control), 3-week-old (five infected, one control), 6-week-old (five infected, one control), and 9-week-old (10 infected, two control) chickens naturally infected with ALV-J in ovo. A 636-base antisense riboprobe complementary to the 3' and 5' ends of the pol and env viral genes, respectively, was constructed. Strong positive staining was present in cardiac myocytes, Purkinje fibers, vascular and pulmonary smooth muscle, renal glomeruli, distal tubules, and pituitary glands. Light staining was present in gastrointestinal smooth muscle, thyroid and adrenal glands, and follicular medullae in the cloacal bursa. Staining was not present in any hematopoietic precursors. Tissues from newly hatched chicks exhibited the strongest and most consistent staining, whereas staining in embryos was minimal. RNA ISH confirmed the presence of ALV-J-specific nucleic acid within cytoplasmic inclusions in cardiac myocytes, Purkinje fibers, pituitary glands, and renal glomeruli. Viral tropism for cardiac myocytes and Purkinje fibers may relate pathogenetically to the cardiomyopathy and congestive heart failure described in index chicken flocks infected with ALV-J. Viral tropism for endocrine organs may relate pathogenetically to the weight suppression associated with infection.

Adenovirus-mediated herpes simplex virus type-1 thymidine kinase gene therapy suppresses oestrogen-induced pituitary prolactinomas

We tested the hypothesis that gene transfer using recombinant adenovirus vectors (RAds) expressing herpes simplex virus type 1 thymidine kinase (HSV1-TK) might offer an alternative therapeutic approach for the treatment of pituitary prolactinomas that do not respond to classical treatment strategies. HSV1-TK converts the prodrug ganciclovir (GCV) to GCV monophosphate, which is in turn further phosphorylated by cellular kinases to GCV triphosphate, which is toxic to proliferating cells. One attractive feature of this system is the bystander effect, whereby untransduced cells are also killed. Our results show that RAd/HSV1-TK in the presence of GCV is nontoxic for the normal anterior pituitary (AP) gland in vitro, but causes cell death in the pituitary tumor cell lines GH3, a PRL/GH-secreting cell line, and AtT20, a corticotrophic cell line. We have used sulpiride- and oestrogen-induced lactotroph hyperplasia within the rat AP gland as an in vivo animal model. Intrapituitary infection of rats bearing oestrogen-induced lactotroph hyperplasia, with RAd/ HSV1-TK and subsequent treatment with GCV, decreases plasma PRL levels and reduces the mass of the pituitary gland. More so, there were no deleterious effects on circulating levels of other AP hormones, suggesting that the treatment was nontoxic to the AP gland in situ. In summary, our results show that suicide gene therapy using the HSV1-TK transgene could be further developed as a useful treatment to complement current therapies for prolactinomas.

Functional measurements of [Ca2+] in the endoplasmic reticulum using a herpes virus to deliver targeted aequorin

Changes in the free calcium concentration of the endoplasmic reticulum ([Ca2+]er) play a central role controlling cellular functions like contraction, secretion or neuronal signaling. We recently reported that recombinant aequorin targeted to the endoplasmic reticulum (ER) [Montero M., Brini M., Marsault R. et al. Monitoring dynamic changes in free Ca2+ concentration in the endoplasmic reticulum of intact cells. EMBO J 1995; 14: 5467-5475, Montero M., Barrero M.J., Alvarez J. [Ca2+] microdomains control agonist-induced Ca2+ release in intact cells. FASEB J 1997; 11: 881-886] can be used to monitor selectively [Ca2+]er in intact HeLa cells. Here we have used a herpes simplex virus type 1 (HSV-1) based system to deliver targeted aequorin into a number of different cell types including both postmitotic primary cells (anterior pituitary cells, chromaffin cells and cerebellar neurons) and cell lines (HeLa, NIH3T3, GH3 and PC12 cells). Functional studies showed that the steady state lumenal [Ca2+]er ranged from around 300 microM in granule cells to 800 microM in GH3 cells. InsP3-coupled receptor stimulation with agonists like histamine (in HeLa, NIH3T3 and chromaffin cells), UTP and bradykinin (in PC12 cells) or thyrotropin-releasing hormone (TRH, in GH3 cells) produced a very rapid decrease in lumenal [Ca2+]er. Caffeine caused a rapid Ca2+ depletion of the ER in chromaffin cells, but not in the other cell types. Depolarization by high K+ produced an immediate and reversible increase of [Ca2+]er in all the excitable cells (anterior pituitary, GH3, chromaffin cells and granule neurons). We conclude that delivery of recombinant aequorin to the ER using HSV amplicon provides the first direct quantitative and dynamic measurements of [Ca2+]er in several primary non-dividing cells.