Synergistic action of cholera toxin B subunit (and Escherichia coli heat-labile toxin B subunit) and a trace amount of cholera whole toxin as an adjuvant for nasal influenza vaccine

Induction of systemic immune responses to measles virus synthetic peptides administered intranasally

A systemic antibody response was induced when a chimeric peptide containing two copies of a promiscuous T-cell epitope and one copy of a B-cell epitope (TTB) from the fusion protein of measles virus (MV) was administered to mice intranasally without adjuvant. A higher antibody titre was produced when the peptide was administered intranasally with cholera toxin B subunit (CTB) as an adjuvant and these antibodies crossreacted with the MV. Furthermore, splenocytes from intranasally immunized mice proliferated in vitro in the presence of the TTB peptide. The immune response following intranasal immunization with the peptide was influenced by the MHC haplotype of the strain of mice used. Thus CBA and BALB/c mice were high responders whereas C57BL/6 mice were low responders. Although peptide administered intranasally with CTB to CBA mice induced an immune response, no significant protection was observed against intra-cranial challenge with canine distemper virus which is antigenically related to MV.

Immune response and protection against influenza A infection in mice immunised with subunit influenza A vaccine in combination with whole cell or acellular DTP vaccine

Following the demonstration of the strong adjuvant effect of whole-cell DTP vaccine (wDTP) on the immune responses to influenza subunit vaccine, studies were undertaken to identify the component of wDTP responsible for the adjuvant effect, and to determine if acellular DTP (aDTP) vaccine was as effective since it is less reactogenic and likely to replace wDTP for primary or secondary immunisation. In addition, wDTP and aDTP were directly compared in a dose-response study. Experiments in mice indicated that the adjuvant effect of wDTP resided in the LPS component of B. pertussis, since purified LPS enhanced the IgG antibody response, the IgG subclass response and protection to the same level as wDTP. An adjuvant effect was detected using aDTP, but was statistically less pronounced than wDTP by a factor of some 100-fold. These results suggest that immunisation against influenza in infants and young children can be achieved combining small amounts of influenza antigen with wDTP or LPS, and to a lesser extent by combining vaccine with aDTP. However, these results were obtained in mice and should be confirmed in man since species vary considerably in response to adjuvant.

A mutant pertussis toxin molecule that lacks ADP-ribosyltransferase activity, PT-9K/129G, is an effective mucosal adjuvant for intranasally delivered proteins

We examined the capacity of a genetically detoxified derivative of pertussis toxin (PTX), PT-9K/129G, to act as a mucosal adjuvant for an intranasally (i.n.) administered tetanus vaccine. Groups of mice were immunized i.n. with the nontoxic C-terminal 50-kDa portion of tetanus toxin (fragment C [Frg C]) either alone or mixed with PT-9K/129G, PTX, or cholera toxin (CT) or were immunized subcutaneously (s.c.) with an equivalent amount of Frg C adsorbed to alhydrogel. In response to a single immunization, mice receiving Frg C plus PT-9K/129G or CT i.n. and parenterally immunized mice developed high-titer (> 20,000) anti-Frg C antibodies, whereas mice immunized i.n. with Frg C plus PTX or with Frg C alone seroconverted only after being boosted. The serum anti-Frg C response was dominated by immunoglobulin G1 (IgG1) in mice immunized with Frg C plus PT-9K/129G, with Frg C plus PTX, or s.c. In contrast, IgG1, IgG2a, and IgG2b contributed almost equally to the Frg C response when CT was the adjuvant. Anti-Frg C IgE was detected only in the sera of mice immunized i.n. with Frg C plus PTX and immunized s.c. with Frg C plus alhydrogel. High levels of IgA antibodies were present in nasal lavage fluid from mice immunized i.n. with Frg C plus PT-9K/129G, PTX, or CT but not in that from mice given Frg C alone i.n. or parenterally. The mucosal adjuvanticity of PT-9K/129G was manifested in inbred as well as outbred mice. A single i.n. dose of Frg C plus either PT-9K/129G or PTX (with high specific activity) was sufficient to protect all immunized mice from tetanus toxin challenge, in contrast to the case for mice that received Frg C alone i.n. We conclude that the pertussis toxin analog PT-9K/129G, which is devoid of ADP-ribosyltransferase activity, is a potent mucosal adjuvant for vaccines delivered via the respiratory tract.

Cross-protection against influenza virus infection in mice vaccinated by combined nasal/subcutaneous administration

The effects of a combination of intranasal (i.n.) and subcutaneous (s.c.) administration of inactivated influenza vaccine for priming and boosting on the cross-protection against antigenically drifted virus challenge were examined in Balb/c mice. Mice were primed through the i.n. or s.c. route with a CTB*-A/Kumamoto/37/79 (H1N1) combined vaccine (CTB*: cholera toxin B subunit supplemented with 0.2% of the holotoxin) and boosted through the i.n. or s.c. route with another drift virus vaccine, A/Bangkok/10/83 (H1N1), 4 weeks later. Two weeks after boosting, the mice were challenged with a third drift virus, A/Yamagata/120/86 (H1N1). The combination of i.n. priming and i.n. boosting afforded the highest cross-protection, while combinations of s.c. priming and i.n. or s.c. boosting afforded little cross-protection. In parallel with the protective activity, anti-A/Yamagata haemagglutinin-reactive IgA and IgG antibodies were detected in nasal and bronchoalveolar wash specimens. These results suggest that cross-protection against a variant virus challenge is most favourably provided by i.n. priming with the CTB* combined vaccine and i.n. boosting with the vaccine, which optimally induces cross-protective IgA and IgG antibodies.

Effects of cholera toxin adjuvant on IgE antibody response to orally or nasally administered ovalbumin

Effects of cholera toxin B subunits supplemented with 0.1% cholera toxin (CTB*) on systemic IgE antibody responses to ovalbumin (OVA) were examined in BDFI (H-2b/d), Balb/c (H-2d) and C3H (H-2k) mice given OVA intragastrically or intranasally. Two successive doses of OVA intragastrically administered to Balb/c and C3H mice induced little IgE response and resulted in almost complete unresponsiveness to subsequent intraperitoneal challenge with OVA in Al(OH)3, while the intragastric administration to BDF1 mice induced high IgE response and resulted in abrogation of the unresponsiveness to the subsequent challenge. The intranasal administration of OVA induced little IgE response and suppressed response to the subsequent challenge in any strain of mice. On the other hand, two successive doses of intragastric or intranasal OVA together with CTB* enhanced IgE response in all three strains and the subsequent challenge with OVA in Al(OH)3 induced higher IgE responses. These results suggest that CTB* augments IgE response to OVA and abrogates the unresponsiveness when administered orally or intranasally into mice together with OVA, regardless of the H-2 haplotype of the mice.

Escherichia coli heat-labile enterotoxin B subunits supplemented with a trace amount of the holotoxin as an adjuvant for nasal influenza vaccine

Escherichia coli heat-labile enterotoxin B subunit (LTB) (2 micrograms), supplemented with a trace amount of the holotoxin (LT) (0.02-20 ng), was examined for the adjuvant effect on antibody (Ab) responses against influenza inactivated haemagglutinin (HA) vaccine in Balb/c mice. Each mouse received a primary intranasal (i.n.) inoculation with the vaccine (1.5 micrograms), prepared from PR8 (H1N1) virus, together with LT-containing LTB and in 4 weeks a second i.n. inoculation of the vaccine alone. The inoculation of the vaccine with the LT-containing LTB induced significantly high primary and secondary anti-HA IgA and IgG Ab responses in the nasal wash and the serum, while the vaccine with LTB or less than 2 ng of LT induced little response. The synergistic adjuvant effect was maximal in the concentration of LTB supplemented with 0.2-2 ng of LT. Under these conditions, the augmented IgA and IgG Ab responses, which are cross-protective to PR8 HA molecules, provided complete cross-protection against PR8 virus challenge in mice immunized with heterologous vaccine within the same subtype. These results suggest that LTB containing a trace amount of LT can be used as a potent adjuvant for nasal vaccination of humans against influenza.