Recombinant Baculovirus Associated with Bilosomes as an Oral Vaccine Candidate against HEV71 Infection in Mice

Abstract

BackgroundHuman enterovirus 71 (HEV71) is one of the major pathogen responsible for hand, foot and mouth disease (HFMD). Currently no effective vaccine or antiviral drugs are available. Like poliovirus, EV71 is transmitted mainly by the feco-oral route. To date the majority of the studied EV71 vaccine candidates are administered parenterally. Injectable vaccines induce good systemic immunity but mucosal responses are often unsatisfactory, whereas mucosal vaccines provide both systemic and mucosal immunity. Therefore, oral immunization appears to be an attractive alternative to parenteral immunization.Methodology/Principal FindingsIn this report, we studied the efficacy of an orally administered vaccine candidate developed using recombinant baculovirus displaying VP1 (Bac-VP1) in a murine model. Gastrointestinal delivery of Bac-VP1 significantly induced VP1-specific humoral (IgG) and mucosal (IgA) immune responses. Further, we studied the efficacy of the Bac-VP1 associated with bilosomes and observed that the Bac-VP1 associated with bilosomes elicited significantly higher immune responses compared to bilosomes non-associated with Bac-VP1. However, mice immunized subcutaneously with live Bac-VP1 had significantly enhanced VP1 specific serum IgG levels and higher neutralizing antibody titers compared with mice orally immunized with live Bac-VP1 alone or associated with bilosomes.ConclusionBilosomes have been shown to possess inherent adjuvant properties when associated with antigen. Therefore Bac-VP1 with bilosomes could be a promising oral vaccine candidate against EV71 infections. Thus, Bac-VP1 loaded bilosomes may provide a needle free, painless approach for immunization against EV71, thereby increasing patient compliance and consequently increasing vaccination coverage.

Bile salts-containing vesicles: promising pharmaceutical carriers for oral delivery of poorly water-soluble drugs and peptide/protein-based therapeutics or vaccines

“…The obtained end-point antibody titers from TTx-loaded bilosomes were superior to the oral administration of the un-entrapped antigen, but analogous to parenterally administrated ones. Premanand et al (2013) confirmed that baculovirus displaying VP1 (Bac-VP1) linked with bilosomes provoked significantly higher immune responses relative to bilosomes non-linked with Bac-VP1 suggesting that bilosomes have intrinsic adjuvant characters when linked with antigen. Wilkhu et al (2013) confirmed the protective property of bilosomes to antigens as low levels of antigen (39%) were measured across the GIT after oral administration of free antigen to mice in compared to 55% for antigen-loaded bilosomes.…”

“…Transmission electron microscopy (TEM) Shukla et al, 2008;Mann et al, 2009;Shukla et al, 2010a;Guan et al, 2011;Niu et al, 2011;Shukla et al, 2011;Dai et al, 2013;Premanand et al, 2013;Jain et al, 2014a,b Cryogenic-transmission electron microscopy (Cryo-TEM) Chen et al, 2009 Scanning electron microscopy (SEM) Gebril et al, 2014 Freeze fracture electron microscopy (FFEM) Mann et al, 2006 Separation of free drug from drug-loaded vesicles Molecular exclusion chromatography Singh et al, 2004;Shukla et al, 2008Shukla et al, , 2011Chen et al, 2009;Sun et al, 2010;Guan et al, 2011;Niu et al, 2011Niu et al, , 2012Niu et al, , 2014Dai et al, 2013;Hu et al, 2013;Jain et al, 2014a,b Ultracentrifugation Conacher et al, 2001Song et al, 2005;Mann et al, 2009;Premanand et al, 2013;Gebril et al, 2014 Entrapment efficiency percent High performance liquid chromatography (HPLC) Chen et al, 2009;Sun et al, 2010;Niu et al, 2011Niu et al, , 2012Niu et al, , 2014Hu et reported that increasing either homogenization pressure or cycles reduced the size of BS-liposomes (Chen et al, 2009;Niu et al, 2011). Oppositely, extremely high homogenization pressure increased particle size and PI of BS-vesicles due to rupturing and combination of the vesicles under high h...…”

“…After preparation of BS-vesicles suspension, the unencapsulated drug/protein was separated from the total amount of drug by techniques such as ultracentrifugation (Song et al, 2005;Mann et al, 2009;Gebril et al, 2014) or size exclusion chromatography using Sephadex column (Chen et al, 2009;Dai et al, 2013;Niu et al, 2014). The amount of encapsulated agents was quantified by HPLC (Niu et al, 2011(Niu et al, , 2012(Niu et al, , 2014, UV spectrophotometer (Guan et al, 2011;Dai et al, 2013) or using different protein analysis methods like bicinchoninic acid (Shukla et al, 2011;Jain et al, 2014a,b) and modified ninhydrin assay (Mann et al, 2006;Mann et al, 2009;Conacher et al, 2001;Premanand et al, 2013). …”

Multifaceted applications of bile salts in pharmacy: an emphasis on nanomedicine

“…However, pharmaceutical application of this route is marred by the harsh gastrointestinal environment that is detrimental to many vaccine formulations. 4,29,33,34,75 Obstacles to oral antigen delivery include degradation of oral antigens by proteolytic enzymes and hydrochloric acid in addition to poor absorption by gut-associated lymphoid tissue. As a consequence, larger and more frequent doses of oral vaccines would be required to give equal immunity to parenteral vaccines, leading to the formation of specific tolerance to such an antigen.…”

“…Bilosomes and modified bilosomes (including probilosomes and surface-engineered bilosomes) demonstrate higher oral stability, protective effect, and permeation-enhancing properties compared with conventional liposomes and niosomes. [29][30][31][32] Such novel nanocarriers could be employed to improve the oral bioavailability of vaccines, hydrophilic drugs, 4,29,[33][34][35][36][37][38][39][40] and insoluble actives as well. 41 In another avenue, injectable size-tunable cholate NPs have been recently developed for cancer targeting with superior properties to their peer nanocarriers.…”