Leiber (Germany)

Yeast-based feed additives have emerged as promising functional feed additives (FFAs) to promote sustainable aquaculture development through enhanced gut health and immune modulation in fish. The present study evaluated the impact of autolysed brewer's yeast (ABY) and soluble dried yeast extract (SDYE) in improving the intestinal and skin histology, immune response, and intestinal microbiome of Atlantic salmon parr (Salmo salar) over a 9-week feeding trial. Three experimental diets were produced: a control diet, a diet supplemented with ABY at 2.5 g/kg, and a diet supplemented with SDYE at 2.5 g/kg. These diets were administered to triplicate tanks of Atlantic salmon. The yeast-supplemented diets, especially ABY, improved intestinal mucosal fold length, lamina propria width, microvilli density, and intestinal goblet cell counts, as well as skin goblet cell counts. The yeast additives had no detrimental effects on the fish haematology, with no significant differences in haemoglobin concentration, red blood cell counts, and white blood cell counts among the treatment groups. Gene expression analysis revealed upregulation of il-1β and muc-2 in fish fed the ABY diet, indicating enhanced immune function and potentially mucosal protection. Intestinal microbiota analysis revealed Firmicutes as the most dominant phylum in all groups, followed by Actinobacteriota. Distinct bacterial community shifts were observed between the treatment groups, with a significant increase in the relative abundance of taxa such as Staphylococcus in yeast-supplemented diets and a significant decrease in Streptococcus and Weissella. Collectively, these findings suggest that the yeast additives, especially ABY, enhance gut health and immune function without compromising growth performance.

ABSTRACTWe evaluated antibody persistence against hepatitis B virus (HBV) in adolescents previously vaccinated with a hexavalent diphtheria-tetanus-acellular pertussis-HBV-inactivated poliovirus-Haemophilus influenzae type b conjugate vaccine (DTPa-HBV-IPV/Hib), as part of the national newborn immunization program in Germany. We also assessed the anamnestic response to a challenge dose of a monovalent HBV vaccine. In this phase 4, open-label, non-randomized study (NCT02798952), 302 adolescents aged 14–15 years, primed in their first 2 years of life with 4 DTPa-HBV-IPV/Hib doses, received one challenge dose of monovalent HBV vaccine. Blood samples were taken before and one month post-vaccination and used to determine antibody levels against hepatitis B surface antigen (HBs). Reactogenicity and safety were also assessed post-challenge dose. Pre-challenge dose, 53.7% of 268 participants included in the according-to-protocol cohort for immunogenicity had anti-HBs antibody concentrations ≥10 mIU/mL (seroprotection cut-off) and 16.8% had anti-HBs antibody concentrations ≥100 mIU/mL. One month post-challenge dose, 93.3% of adolescents had anti-HBs antibody concentrations ≥10 mIU/mL and 87.3% had antibody concentrations ≥100 mIU/mL. An anamnestic response was mounted in 92.5% of adolescents. Injection site pain (in 33.6% of participants) and fatigue (30.2%) were the most frequently reported solicited local and general symptoms, respectively. Six of the 55 unsolicited adverse events reported were considered vaccination-related. Two vaccination-unrelated serious adverse events were reported during the study. Long-term antibody persistence against hepatitis B was observed in 14–15 years old adolescents previously primed in infancy with DTPa-HBV-IPV/Hib. A challenge dose of monovalent HBV vaccine induced strong anamnestic response, with no safety concerns.

Beta-glucans are a heterogeneous group of natural polysaccharides mostly investigated for their immunological effects. Due to the low systemic availability of oral preparations, it has been thought that only parenterally applied beta-glucans can modulate the immune system. However, several in vivo and in vitro investigations have revealed that orally applied beta-glucans also exert such effects. Various receptor interactions, explaining possible mode of actions, have been detected. The effects mainly depend on the source and structure of the beta-glucans. In the meantime, several human clinical trials with dietary insoluble yeast beta-glucans have been performed. The results confirm the previous findings of in vivo studies. The results of all studies taken together clearly indicate that oral intake of insoluble yeast beta-glucans is safe and has an immune strengthening effect.