Does the immune stimulant Amplimune® modulate humoral and cytokine responses to commercial bovine respiratory disease vaccines in cattle?

Abstract

<p><b>Context.</b> Feedlot entry can be a period of stress for cattle due to transportation, altered diets and other influences. Stress can suppress host defence mechanisms. Innate immune stimulants, such as mycobacterial cell-wall fractions, attract attention for the primary objective of enhancing nonspecific immune resistance of cattle against microbial diseases during periods of stress-induced susceptibility. These stimulants are also recognised for their capacity to modify responses of the adaptive immune system to vaccines. <b>Aims.</b> This study aims to evaluate the potential for mycobacterial cell-wall fractions in Amplimune^® to modify adaptive immune responses to the commercial vaccines Rhinogard^® (modified live bovine alphaherpesvirus-1 (BoHV-1)) and Bovilis MH + IBR^® (inactivated <i>Mannheimia haemolytica</i> and BoHV-1) in yearling cattle during simulated feedlot induction. <b>Methods.</b> Fifty-four mixed-sex Angus yearling cattle were transported for 6 h on Day −1 and on Day 0. The cattle were assigned to the following six treatment groups (<i>n </i>= 9/group): Rhinogard plus 2 mL Amplimune, Rhinogard plus 5 mL Amplimune, Bovilis MH + IBR plus 2 mL Amplimune, Bovilis MH + IBR plus 5 mL Amplimune, Rhinogard plus 5 mL saline, and Bovilis MH + IBR plus 5 mL saline. Blood and nasal secretions were sampled at various time points following treatment and antigen-specific antibody (immunoglobulin G) responses to components of the vaccines were assessed. Interferon-γ production by peripheral blood mononuclear cellsin response to BoHV-1, Concanavalin A or media only were assessed. <b>Key results.</b> No adverse clinical reactions were observed to administration of Amplimune and vaccines. A systemic antibody response to vaccination was observed for the Bovilis MH + IBR vaccine. Vaccine-specific antibody and cytokine responses were not modified by Amplimune. <b>Conclusions.</b> Amplimune can be administered at the same time as Rhinogard or Bovilis MH + IBR vaccines, without undesirable effects on specific immune responses to vaccination. <b>Implications.</b> The primary interest in using Amplimune is to potentiate non-specific immune defences as an alternative to antibiotics for the prevention and/or treatment of microbial diseases such as bovine respiratory disease in production animals. In view of its adjuvant-like activities, administration of Amplimune might also confer beneficial or detrimental effects on antigen-specific responses of the adaptive immune system to contemporaneous vaccination.</p>