Goat endothelial cells may be infected in vitro by transmigration of caprine arthritis-encephalitis virus-infected leucocytes.

The caprine arthritis-encephalitis lentivirus (CAEV) causes a lifelong persistent infection in goats, and induces infiltrations of leucocytes and tissue reorganization in target organs, with a cyclical pattern of viral expression. The mammary gland is an important site of infection, associated with mother-to-kid transmission by infected cells in colostrum and milk. The monocyte/macrophage is the principal target cell, but other cell types, including epithelial and endothelial cells and fibroblasts, are susceptible to in vitro infection with varying levels of viral replication. Such cells, perhaps at specific differentiation states, might play a role in the regulation and transfer of in vivo infection in target organs. In this paper we describe the in vitro infection of endothelial cell monolayers by the transmigration of monocytes carrying the CAEV provirus. The infected endothelial cells progress to expression of the viral p30 capsid antigen, suggesting viral proliferation. Such a process occurring in vivo during angiogenesis and leucocyte homing to the mammary gland in the final third of mammogenesis, might contribute to viral spread in this crucial target organ.

Viral expression and leukocyte adhesion after in vitro infection of goat mammary gland cells with caprine arthritis-encephalitis virus.

A characteristic lesion in goats infected by the lentivirus CAEV is mastitis with lymphoid hyperplasia. In order to investigate the mechanism of lesion formation, cultures highly enriched in microvascular endothelial cells, mature and immature luminal epithelial cells, fibroblasts and myoepithelial cells were established from goat mammary gland biopsies. Their susceptibility to in vitro infection with two distinct types of CAEV was investigated by PCR, antigen expression and cytopathy. The capacity of infected mammary gland cells to bind uninfected caprine leukocytes was determined by flow cytometry. All cell types tested were susceptible to CAEV infection in vitro, with different levels of sensitivity according to cell phenotype. Our results suggest that the limited extent of natural infection of mammary gland cells reflects a protective local immune response, and that the myoepithelial cell could act as a reservoir cell. After infection, the mature luminal cell acquires the capacity to bind leukocytes in vitro, which could indicate a facilitation of cellular interactions. The distinct reactions of the different cell types to CAEV infection may be correlated with events leading to progressive lesion development during the natural infection.

Reduced expression of SLA Class 1 antigens by intestinal epithelium of newborn piglets.

Expression of major histocompatibility complex Class 1 by the small intestine mucosa of piglets was compared by indirect immunofluorescence during the 4 days following birth with both maternal and artificial feeding. The duodenal epithelium did not express Class I antigen during these 4 days. The jejunal epithelium did not express Class I antigen at Day 0 after birth but expression developed from Day 1. However ileal epithelium expressed Class 1 antigen throughout the study period. In contrast, cells from the lamina propria of all samples expressed Class 1 antigen. There was no difference between piglets receiving maternal colostrum and artificially reared piglets. This lack of Class 1 expression occurs at a time when the intestinal epithelium constitutes an interface between piglet and colostral maternal cells. This can be of biological relevance for mother-newborn interactions.

Cellular components of mammary secretions and neonatal immunity: a review.

Mammary secretions contain viable maternal cells that are mainly lymphocytes, macrophages, neutrophils and epithelial cells. Their biological functions in the neonate, though not yet clearly established, are strongly suggested by experimental data. This paper reviews current knowledge of the cellular components of mammary secretions: their nature, in vitro properties, and demonstrated in vivo effects in the neonate, and discusses possible future experimental approaches. It is thought that the main role of the cellular components from mammary secretions is to interact with the development of local immunity in the newborn, and to modulate active immunization of the neonatal intestine during this critical period when the development of adapted responses to antigens (protection/tolerance/alimentary allergy) is of crucial importance for the future of the young.

A study by flow cytometry of lymphocytes in sow colostrum.

Mammary secretions contain leucocytes which may be of value to the neonate. The cells obtained from sow colostrum (1 to 2.5 x 10(6) ml-1) are mainly lymphocytes (10 to 25 per cent) and epithelial cells (more than 20 per cent). In milk, there are few lymphocytes (0.5 to 2 per cent) and mostly alveolar epithelial cells. The study of lymphocytes in the mammary secretions of sows has been made difficult by the high proportion of epithelial cells, which could not be separated from lymphocytes, and by a high background in membrane immunofluorescence labelling. This paper describes a method for the study of the cells in the mammary secretions of sows by flow cytometry. It showed that 70 to 90 per cent of colostral lymphocytes were T lymphocytes, with T8 lymphocytes predominating over T4, and that the ratio T4/T8 was significantly lower in colostrum (0.57) than in blood (0.80). There were no lymphocytes expressing interleukin-2-receptors in the colostrum of sows.

Secretory component and IgA expression by epithelial cells in sow mammary gland and mammary secretions.

Secretory component (SC) and IgA expression of epithelial cells were studied in the mammary tissue and mammary secretions of sows. In mammary tissue, SC was not detected until day 105 of gestation. From the time of delivery (day 115) to the time of established lactation, the proportion of epithelial cells containing SC rose from 20 per cent to nearly 100 per cent. There was no IgA in alveolar epithelial cells until day 105 of gestation; on day 115, IgA positive epithelial cells were present in 10 per cent of the alveoli, which increased to 80 per cent during lactation. Epithelial cells represented more than 20 per cent of the total cells in colostrum, and predominated over leucocytes in milk. In colostrum, these epithelial cells (9 to 15 microns) showed weakly positive membrane, SC, contained cytoplasmic SC and had a limited capacity for in vitro proliferation. Ten per cent of epithelial cells contained intracytroplasmic IgA. In milk, the epithelial cells were larger (15 to 40 microns) with a higher expression of both membrane and intracytoplasmic SC; 66 per cent of these cells expressed intracytoplasmic IgA. These data showed that the capacity of mammary epithelium to process IgA to secretory IgA was complete at the end of mammary gland organisation, and established that the epithelial cells of milk contribute to the transfer of IgA to neonates.

Lymphocyte subsets in the mammary gland of sows.

The presence and localisation of lymphocyte subsets together with class II bearing cells in the mammary gland of sows, were studied at different periods of the reproductive cycle by immunohistochemistry and compared with blood. All cell types involved in the immune response were present in the mammary gland at the different stages of gestation and lactation and nearer the alveolar epithelium as gestation proceeded: T lymphocytes, including CD4+ and CD8+, B lymphocytes and class II bearing cells (epithelial cells and macrophages). The results indicated an early accumulation of T lymphocytes, specifically T helper cells, during pregnancy; the specific increase of IgA lymphocytes occurring after this phase could suggest a role for these T cells in the induction of IgA response. The local accumulation of immune cells sustains the view that the mammary gland is able to mount a true local immune response and the increase in CD8+ cells near the epithelium suggests a role in local immune defence.

[Therapeutic test in trachoma: putting in place a study model and preliminary results]. / Essai thérapeutique dans le trachome: mise en place d'un modèle d'étude et résultats préliminaires.

This study, performed in Atar and Nouakchott, has tested a new proceeding for biological diagnostic of trachoma (Chlamydia trachomatis direct specimen test, SYVA Merieux microtrak), and has controlled the efficiency of different therapeutic schemes against trachoma. An experimental pattern for subsequent studies is proposed.

Non-specific antiviral activity of bovine leukocytes against infectious bovine rhinotracheitis virus in vitro.

Leukocytes collected from bovine blood inhibit the multiplication of virus in IBR infected MDBK cells. This inhibition is non-specific and can be observed in the absence of serum. Number of infected cells, number of leukocytes per infected cell and time of placing of leukocytes onto infected cells are some of the important factors in this protection. We observed variations between animals, but for each animal the activity of leukocytes was constant for several months. Contact between leukocytes and the susceptible cell is a vital factor in this protection. We could not detect any soluble mediator in the supernatant fluid. The different types of cells which constitute the population of leukocytes are less efficient than the original heterogenous population (80% lymphocytes and 20% neutrophils and monocytes).

In vivo effect of levamisole on responses of blood lymphocytes to mitogens in calf.

In vivo administration of levamisole in calf enhances the capacities of peripheral blood lymphocytes to undergo blastic transformation in response to both phytohemagglutinin and concanavalin A. This effect is dose-dependent and persists at least five days. These results confirm that levamisole is efficient not only in immunodepressed but also in normal individual, and suggest that target cells susceptible to levamisole are different at systemic and local level.

[Induction of interferon activity in nasal mucus by association of levamisole by systemic route -- inactivated virus by local route (author's transl)]. / Induction d'une activité interféron dans le mucus nasal chex le veau par l'association lévamisole par voie gén,érale-virus inactivé par voie locale.

Calf respiratory disease could have a non-specific origin. The respiratory tract bacterial flora is pathogen only if the animal faces stress which decreases the defense capacities of the respiratory mucosa. The simultaneous administration of UV irradiated IBR virus by nasal route and of levamisole by systemic route induces a protection which is accompanied by interferon synthesis in the nasal mucus. This protection is evaluated experimentally with an infectious IBR virus challenge. In the natural conditions the respiratory disease loses its transmissible aspect in the treated calves.

Transfer of antibodies against the CPD virus through colostrum and milk.

Newborn lamb immunoglobulins are of maternal origin and the transfer is done exclusively by colostrum and milk (syndesmochorial placentation). Antibody levels in colostrum and in maternal serum are the same at the moment of lambing. Milk antibodies are synthesized by cells which invade the udder at the end of the milking period. We immunized ewes with C.P.D. virus during gestation or at the end of lactation and we evaluated the presence of specific neutralizing antibodies in colostrum, in milk and in the sera of the mother and lamb. We recommend vaccination during pregnancy for ewes which are not going to feed their lambs: colostral given protection persists for 3 or 4 weeks. Ewe vaccination when the udder dried up is the choice when natural suckling is used: the lamb is protected as long as it is with its mother. In the conditions used in this work the steroid injection did not interfere with colostral antibody transmission.