Vaccine Technology: Adjuvants for Increased Efficacy

The effect of Syntex adjuvant formulation (SAF-m) on humoral immunity to the influenza virus in the mouse

Syntex adjuvant in its microfluidized form (SAF-m) was equal to or superior to Freund's complete adjuvant in stimulating an enhanced hemagglutination inhibition (HI) antibody response in mice to trivalent influenza virus vaccine (TIV). There was an average 16-fold increase in HI titer for the three components of the vaccine with no significant differences among strains. The increased serum antibodies correlated with an increase in protection against infection. The threonyl-MDP (t-MDP) component of the adjuvant played no role in this activity. The vehicle, in contrast, was so effective that it could be diluted 1:202 (in the presence of (t-MDP) and still retain a statistically significant effect. Vaccine and adjuvant could be stored together at 4 degrees C for 2 years without a statistically significant change in potency. Mice were given a priming immunization with TIV, PBS, or adjuvanted TIV (AIV). A year later, the mice were boosted with heterotypic TIV or AIV. The nature of the priming immunization made no difference in the strong antibody response to an AIV boost. However, priming significantly improved the response to TIV with AIV being the best primer. The enhancement in the antibody response to AlShanghai of the unprimed (PBS) elderly mice caused by AIV (14-fold improvement over TIV) was similar to that in young mice. Female mice had antibody titers which overall were 2.6-fold higher than those of males (P < 0.0001) for AIV and TIV.

Relevance of the guinea-pig necrotic inflammation footpad reaction to safety concerns with MDP-based adjuvants

The guinea-pig necrotic inflammatory reaction described by Nagao and Tanaka was investigated to determine its possible relevance to tuberculin-positive individuals who may receive MDP-based adjuvants. The reaction was induced by a preparatory footpad injection of Mycobacterium tuberculosis in Freund's incomplete adjuvant (FIA) followed three weeks later by a provocative gluteal injection of muramyl dipeptide (MDP). Increased footpad swelling and necrosis occurred within 24 h. The reaction was also caused to a significantly lesser degree by a gluteal injection of the threonyl-MDP component of Syntex adjuvant SAF-m. Elicitation of the reaction in responsive animals was absolutely dependent on the presence of both FIA and M. tuberculosis at the reaction site. Animals injected in the right footpad with FIA plus M. tuberculosis and in the left footpad with M. tuberculosis alone responded to the provocative injection with necrosis in the right footpad only. The reaction therefore appears to have little potential relevance to the vaccination of tuberculin-positive humans.

The subclass IgG responses of mice to influenza surface proteins formulated into liposomes

Unprimed mice and mice primed by prior infection with an H1N1 subtype of influenza virus were used to assess the total and subclass IgG serum antibody responses to influenza virus A/Sichuan/2/87 (H3N2) surface haemagglutinin and neuraminidase proteins incorporated into four different formulations of liposomes. Only one of these liposome preparations, DSPC(B), induced greater total IgG, and subclass IgG1 and IgG2a antibody levels, in sera from both primed and unprimed mice than the aqueous A/Sichuan surface preparations alone administered at equivalent levels of haemagglutinin protein. The same DSPC(B) liposome formulation of A/Sichuan antigens was also the only preparation found to elicit levels of IgG2b and IgG3 subclass antibodies above baseline values in these animals.

Comparative analysis of the immunostimulatory properties of different adjuvants on the immunogenicity of a prototype parainfluenza virus type 3 subunit vaccine

The immunogenicity of a parainfluenza virus type 3 (PIV-3) subunit vaccine consisting of affinity-purified haemagglutinin-neuraminidase (HN) and fusion (F) surface glycoproteins was tested in guinea-pigs and hamsters. The ability of several different immunopotentiating agents to enhance the antibody response of animals to the PIV-3 surface glycoproteins was evaluated. The immunity induced by HN and F alone was compared with the response elicited by purified proteins combined with Freund's complete adjuvant, aluminium phosphate, Syntex's threonyl-muramyl dipeptide (MDP) SAF-MF formulation, or Ribi's adjuvant formulation containing BCG cell wall skeleton (CWS), trehalose dimycolate (TDM) and monophosphoryl lipid A (MPL) in a 2% squalene-in-water emulsion. Purified proteins were also incorporated into three different liposome formulations prepared by the detergent dialysis procedure. Immunization of guinea-pigs and hamsters with two 15 micrograms doses of the PIV-3 surface glycoproteins administered in the absence of adjuvant elicited high haemagglutination inhibition, neutralization and anti-fusion titres. The liposome preparations failed to enhance the antibody titres. Ribi's adjuvant formulation was effective at inducing a good secondary response to the purified proteins while the immunostimulatory effects of aluminium phosphate, Syntex and Freund's adjuvants were clearly demonstrated in both primary and secondary responses. When administered without adjuvant, a 15 microgram dose of the HN and F mixture was capable of protecting hamsters against live virus challenge. The immunoprotective dose of the purified proteins could be reduced to at least 0.1 microgram by the addition of aluminium phosphate, Syntex or Freund's adjuvants.