Humoral immune response induced by novel liposomal formulations using an hydrophobized mannan from Saccharomyces cerevisiae as immunostimulants

IVANA REIDEL; BARTALLINI LAURA ; RUSSI, ROMINA CECILIA; GARCÍA, MARÍA INES; MÜLLER, DIANA MARÍA ; VEAUTE, CAROLINA

Congreso; Reunión Conjunta de Sociedades de Biociencias (SAI, SAIC, SAFIS); 2018

Liposomes are vaccine adjuvant systems able to transport hydro-and liposoluble molecules, allowing the co-incorporation ofantigen and different immunostimulants. Our aim was to evaluatethe adjuvanticity of a cationic liposomal formulation (Lip) with theaddition of an hydrophobized mannan from Saccharomyces cerevisiae(Man) and/or CpG oligodeoxynucleotide (CpG-ODN) as immunostimulants,in the immunization against recombinant clumpingfactor of Staphylococcus aureus (rClf). Balb/c mice were immunizedwith: Lip+CpG-ODN+rClf, Lip+Man+rClf, or Lip+Man+CpG-ODN+r-Clf (n=6/group). Mice received two subcutaneous doses, every 3weeks of 10 μg of rClf and were bleed 10 days after every dose.Control groups received Lip+Man or Lip+Man+CpG. Anti-rClf IgG,IgG1 and IgG2 levels were assessed by indirect ELISA in plasma.No specific rClf antibodies were found in pre-immune serum. Controlgroups didn?t show specific humoral response. Lip+CpG-ODN+rClf,Lip+Man+rClf and Lip+Man+CpG-ODN+rClf (OD450nm: 1.196±0.303,1.199±0.259 and 1.064± 0.330) all induced higher IgG levelsthan control groups after the second dose (p˂0.001, Bonferronitest). Furthermore, the three formulations led to high IgG titters atthe end of the protocol, being the mean for each group: 0.8x106,1.2x106 and 1.5x106, respectively. IgG subclasses also presentedhigh titters in all experimental groups. For IgG1, the titters were1.8x106, 1.2x106 and 1.3x106 for the groups Lip+CpG-ODN+rClf,Lip+Man+rClf and Lip+Man+CpG-ODN+rClf, meanwhile the IgG2titters were 2.9x105, 1.9x105 and 2.0x105, respectively. No significantlydifferences were found between experimental groups for anytitration. The results suggest that both hydrophobized mannan andCpG-ODN act as immunostimulant. Furthermore, their combinationwith cationic liposomes results in an efficient induction of specifichumoral immune responses to recombinant antigens in mice, evenwith production of IgG2.