Depending on the type of virus used to manufacture a VLP construct, studies have shown that protective responses induced by VLPs can be elicited without co-administration of adjuvant [33] [34] [35] . In many cases, however, the induction of useful immune responses may require multiple doses [36, 37] , a regime that may be impractical to implement in the field or involve a viral vector to provide an initial priming dose followed by a boost using VLPs [22, 38] . Of relevance to the present study, the use of adjuvants to enhance VLP immunogenicity has been shown to induce strong antibody responses using dose-sparing amounts of HIV [39] or Norwalk virus-derived VLPs [40] and also elicits cell-mediated were incubated with VLPs (5 mg) alone or formulated with E 8 Pam 2 Cys (0.01 nmoles/ml) or Alhydrogel (5 mg) in a total volume of 1 ml. For comparative purposes within all experiments, cells were also either left untreated, exposed to LPS (5 mg/ml) or to similar amounts of each adjuvant alone. Cell surface MHC class II expression was determined after 16 hours using a PEconjugated anti-IA/IE antibody. Cells expressing low levels of MHC Class II molecules were deemed to be immature whilst those expressing high levels were considered to be mature. Shown are representative histograms depicting cell surface MHC class II expression from one of three experiments conducted separately. MHC Class II high expressing cells are shaded in grey. For dosing experiments, cells were also incubated with increasing amounts of (B) VLPs, (C) E 8 Pam 2 Cys, (D) Alhydrogel or VLPs (5 mg) formulated with increasing amounts of (E) E 8 Pam 2 Cys, or (F) Alhydrogel. doi:10.1371/journal.pone.0047492.g002 responses that culminate in improved protection against lethal influenza viral [41, 42] and tumorigenic challenge [43] .