Supplementing a Saccharomyces cerevisiae fermentation product modulates innate immune function and ameliorates bovine respiratory syncytial virus infection in neonatal calves.

The objectives of this study were to determine the effects of oral supplementation with Saccharomyces cerevisiae fermentation products (SCFP; SmartCare and NutriTek; Diamond V, Cedar Rapids, IA) on immune function and bovine respiratory syncytial virus (BRSV) infection in preweaned dairy calves. Twenty-four Holstein × Angus, 1- to 2-d-old calves (38.46 ± 0.91 kg initial body weight [BW]) were assigned two treatment groups: control or SCFP treated, milk replacer with 1 g/d SCFP (SmartCare) and calf starter top-dressed with 5 g/d SCFP (NutriTek). The study consisted of one 31-d period. On days 19 to 21 of the supplementation period, calves were challenged via aerosol inoculation with BRSV strain 375. Calves were monitored twice daily for clinical signs, including rectal temperature, cough, nasal and ocular discharge, respiration effort, and lung auscultation. Calves were euthanized on day 10 postinfection (days 29 to 31 of the supplementation period) to evaluate gross lung pathology and pathogen load. Supplementation with SCFP did not affect BW (P = 0.762) or average daily gain (P = 0.750), percentages of circulating white blood cells (P < 0.05), phagocytic (P = 0.427 for neutrophils and P = 0.460 for monocytes) or respiratory burst (P = 0.119 for neutrophils and P = 0.414 for monocytes) activity by circulating leukocytes either before or following BRSV infection, or serum cortisol concentrations (P = 0.321) after BRSV infection. Calves receiving SCFP had reduced clinical disease scores compared with control calves (P = 0.030), reduced airway neutrophil recruitment (P < 0.002), reduced lung pathology (P = 0.031), and a reduced incidence of secondary bacterial infection. Calves receiving SCFP shed reduced virus compared with control calves (P = 0.049) and tended toward lower viral loads in the lungs (P = 0.051). Immune cells from the peripheral blood of SCFP-treated calves produced increased (P < 0.05) quantities of interleukin (IL)-6 and tumor necrosis factor-alpha in response to toll-like receptor stimulation, while cells from the bronchoalveolar lavage (BAL) of SCFP-treated calves secreted less (P < 0.05) proinflammatory cytokines in response to the same stimuli. Treatment with SCFP had no effect on virus-specific T cell responses in the blood but resulted in reduced (P = 0.045) virus-specific IL-17 secretion by T cells in the BAL. Supplementing with SCFP modulates both systemic and mucosal immune responses and may improve the outcome of an acute respiratory viral infection in preweaned dairy calves.

A peptide-based vaccine for Mycobacterium avium subspecies paratuberculosis.

Recent efforts to develop a live attenuated vaccine against Mycobacterium avium subsp. paratuberculosis (Map), the causative agent of Johne's disease (JD), revealed relA is important in Map virulence. Deletion of the relA gene impairs the ability of Map to establish a persistent infection. Analysis of the basis for this observation revealed infection with a relA deletion mutant (ΔrelA) elicits development of cytotoxic CD8 T cells (CTL) with the ability to kill intracellular bacteria. Further analysis of the recall response elicited by ΔrelA vaccination showed a 35 kDa membrane peptide (MMP) is one of the targets of the immune response, suggesting it might be possible to develop a peptide-based vaccine based on MMP. To explore this possibility, ex vivo vaccination studies were conducted with MMP alone and incorporated into a nanoparticle (NP) vector comprised of poly (D, L-lactide-co-glycolide) and monophosphoryl lipid A (PLGA/MPLA). As reported, ex vivo vaccination studies showed CD8 CTL were elicited with classic and monocyte derived dendritic cells (cDC and MoDC) pulsed with MMP alone and incorporated into a PGLA/MPLA vector. Incorporation of MMP into a NP vector enhanced the ability of CD8 CTL to kill intracellular bacteria. The findings indicate incorporation of MMP into a PGLA/MPLA nanoparticle vector is one of the possible ways to develop a MMP based vaccine for Johne's disease.