Preovulatory follicle diameter, growth rate and time of ovulation during induced oestrus using a CIDR® in trypanotolerant female Bos taurus N'Dama cattle.

The aim of this study was to assess the dose (300 to 600 IU) effects of equine chorionic gonadotropin (eCG) on the preovulatory follicle diameter, growth rate and time of ovulation characterized by echography. The eCG was injected at the end (D0) of the 7-day treatment with a controlled internal device release (CIDR®) and a PGF2α being injected 2 days before the removal of the CIDR® (d-2). The 120 N'Dama female were distributed into five experimental groups. The control group (n = 26) was treated with physiological saline at the removal of the CIDR®, while the animals in the four treated groups received, respectively, 300 IU (n = 25), 400 IU (n = 24), 500 IU (n = 22) and 600 IU (n = 23) of eCG. The diameter of the preovulatory follicle was significantly higher (P < 0.05) in the animals treated with 300 IU (10.1 ± 1.4 mm) than in untreated animals (9.3 ± 1.2 mm). Follicle growth rate was significantly (P < 0.05) higher in treated animals (1.0 ± 0.4 mm/day) than in the control group (0.9 ± 0.4 mm/day). The average interval between the time of eCG injection and ovulation was similar in the non-treated (83.7 ± 14.4 h) and treated animals (79.7 ± 11.9). Treated animals showed a significant increase in the percentage of ovulation (94.7 % compared to 73.1 %) (P < 0.01). Use of eCG contributed towards synchronising the time of ovulation between 72 to 96 h, which would facilitate the use of systematic insemination.

CD40 triggering induces strong cytotoxic T lymphocyte responses to heat-killed Staphylococcus aureus immunization in mice: a new vaccine strategy for staphylococcal mastitis.

Staphylococcus (S.) aureus is a major pathogen involved in chronic bovine mastitis. Staphylococcal mastitis is difficult to control due to the ability of S. aureus to invade and survive within host cells. We therefore postulated that induction of CD8(+) cytotoxic T lymphocyte (CTL) responses leading to destruction of infected cells could help in the control of S. aureus mastitis. We demonstrate that immunization of mice with heat-killed S. aureus together with agonistic anti-CD40 monoclonal antibodies elicits strong CTL responses capable of reducing the severity of subsequent staphylococcal mastitis. Our study shows promise for CTL-dependent vaccination against S. aureus mastitis.

Resident CD11b(+)Ly6C(-) lung dendritic cells are responsible for allergic airway sensitization to house dust mite in mice.

Conventional dendritic cells (DCs) are considered to be the prime initiators of airway allergy. Yet, it remains unclear whether specific DC subsets are preferentially involved in allergic airway sensitization. Here, we systematically assessed the respective pro-allergic potential of individually sorted lung DC subsets isolated from house dust mite antigen (HDM)-treated donor mice, following transfer to naïve recipients. Transfer of lung CD11c(+)CD11b(+) DCs, but not CD11c(+)CD11b(-)CD103(+) DCs, was sufficient to prime airway allergy. The CD11c(+)CD11b(+) DC subpopulation was composed of CD11c(+)CD11b(+)Ly6C(+) inflammatory monocyte-derived cells, whose numbers increase in the lungs following HDM exposure, and of CD11c(+)CD11b(+)Ly6C(-) DCs, which remain stable. Counterintuitively, only CD11c(+)CD11b(+)Ly6C(-) DCs, and not CD11c(+)CD11b(+)Ly6C(+) DCs, were able to convey antigen to the lymph nodes and induce adaptive T cell responses and subsequent airway allergy. Our results thus support that lung resident non-inflammatory CD11c(+)CD11b(+)Ly6C(-) DCs are the essential inducers of allergic airway sensitization to the common aeroallergen HDM in mice.

Sirtuin 1 promotes Th2 responses and airway allergy by repressing peroxisome proliferator-activated receptor-γ activity in dendritic cells.

Sirtuins are a unique class of NAD(+)-dependent deacetylases that regulate diverse biological functions such as aging, metabolism, and stress resistance. Recently, it has been shown that sirtuins may have anti-inflammatory activities by inhibiting proinflammatory transcription factors such as NF-κB. In contrast, we report in this study that pharmacological inhibition of sirtuins dampens adaptive Th2 responses and subsequent allergic inflammation by interfering with lung dendritic cell (DC) function in a mouse model of airway allergy. Using genetic engineering, we demonstrate that sirtuin 1 represses the activity of the nuclear receptor peroxisome proliferator-activated receptor-γ in DCs, thereby favoring their maturation toward a pro-Th2 phenotype. This study reveals a previously unappreciated function of sirtuin 1 in the regulation of DC function and Th2 responses, thus shedding new light on our current knowledge on the regulation of inflammatory processes by sirtuins.

Viral induction of Zac1b through TLR3- and IRF3-dependent pathways.

Zinc finger protein regulator of apoptosis and cell cycle arrest (Zac1) is a transcription factor able to induce apoptosis or cell cycle arrest through independent pathways. In spite of the important potential functions attributed to Zac1, little is known of its physiological regulation and biological function. We discovered that variant Zac1b was expressed in murine embryonic fibroblasts (MEFs) treated with polyriboinosinic polyribocytidylic acid [poly(I:C)], a synthetic double-stranded RNA. This regulation occurred mainly through Toll-Like Receptor 3 (TLR3)- and Interferon Regulatory Factor 3 (IRF3)-dependent pathways. As TLR3 and IRF3 are central activators of antiviral immunity, we hypothesized that Zac1 may be implicated in antiviral responses. In line with this notion, we observed that Zac1b was expressed in MEFs infected with Encephalomyocarditis virus (EMCV). We also observed that Zac1-deficient MEFs were less sensitive to EMCV-induced cell death than wild-type MEFs. However, Zac1 gene inactivation had no effect on the survival of mice infected with EMCV. In conclusion, this study describes for the first time a transcriptional regulation of Zac1b, induced by synthetic dsRNA and RNA viruses, the functional significance of which remains to be further investigated.

Lung interstitial macrophages alter dendritic cell functions to prevent airway allergy in mice.

The respiratory tract is continuously exposed to both innocuous airborne antigens and immunostimulatory molecules of microbial origin, such as LPS. At low concentrations, airborne LPS can induce a lung DC-driven Th2 cell response to harmless inhaled antigens, thereby promoting allergic asthma. However, only a small fraction of people exposed to environmental LPS develop allergic asthma. What prevents most people from mounting a lung DC-driven Th2 response upon exposure to LPS is not understood. Here we have shown that lung interstitial macrophages (IMs), a cell population with no previously described in vivo function, prevent induction of a Th2 response in mice challenged with LPS and an experimental harmless airborne antigen. IMs, but not alveolar macrophages, were found to produce high levels of IL-10 and to inhibit LPS-induced maturation and migration of DCs loaded with the experimental harmless airborne antigen in an IL-10-dependent manner. We further demonstrated that specific in vivo elimination of IMs led to overt asthmatic reactions to innocuous airborne antigens inhaled with low doses of LPS. This study has revealed a crucial role for IMs in maintaining immune homeostasis in the respiratory tract and provides an explanation for the paradox that although airborne LPS has the ability to promote the induction of Th2 responses by lung DCs, it does not provoke airway allergy under normal conditions.

Malignant catarrhal fever induced by alcelaphine herpesvirus 1 is associated with proliferation of CD8+ T cells supporting a latent infection.

Alcelaphine herpesvirus 1 (AlHV-1), carried by wildebeest asymptomatically, causes malignant catarrhal fever (WD-MCF) when cross-species transmitted to a variety of susceptible species of the Artiodactyla order. Experimentally, WD-MCF can be induced in rabbits. The lesions observed are very similar to those described in natural host species. Here, we used the rabbit model and in vivo 5-Bromo-2'-Deoxyuridine (BrdU) incorporation to study WD-MCF pathogenesis. The results obtained can be summarized as follows. (i) AlHV-1 infection induces CD8(+) T cell proliferation detectable as early as 15 days post-inoculation. (ii) While the viral load in peripheral blood mononuclear cells remains below the detection level during most of the incubation period, it increases drastically few days before death. At that time, at least 10% of CD8(+ )cells carry the viral genome; while CD11b(+), IgM(+) and CD4(+) cells do not. (iii) RT-PCR analyses of mononuclear cells isolated from the spleen and the popliteal lymph node of infected rabbits revealed no expression of ORF25 and ORF9, low or no expression of ORF50, and high or no expression of ORF73. Based on these data, we propose a new model for the pathogenesis of WD-MCF. This model relies on proliferation of infected CD8(+) cells supporting a predominantly latent infection.