Liposomal and CpG-ODN formulation elicits strong humoral immune responses to recombinant Staphylococcus aureus antigens in heifer calves

•Cationic liposomes combined with CpG-ODN had strong adjuvant activity in calves.•The formulation induced high specific IgG1 levels, both in serum and whey.•The formulation was able to induce long-term humoral memory and specific IgG2.•A single pre-calving boost induced high IgG levels during the calving period.