A nontoxic derivative of lipopolysaccharide increases immune responses to Gardasil HPV vaccine in mice

Protective antigen of Bacillus anthracis in combination with TLR4 or TLR5 agonist confers superior protection against lethal challenge in mouse model

The immunogenicity and protective ability of recombinant PA (rPA) with two innate immune system modulators, i.e., monophosphoryl lipid A (MPLA), a TLR4 agonist, and recombinant flagellin C (FliC), a TLR5 agonist, were studied in the mouse model. BALB/c mice were inoculated with three doses of rPA + alum (Alum group), rPA + FliC + alum (FliC group), rPA + MPLA + alum (MPLA group), or only alum adjuvant (Alum alone group). Significant increases in anti-PA IgG titers were observed in the Alum, FliC and MPLA groups when compared to control Alum alone group. Similarly, a significant enhancement of proinflammatory (TNF-α, IL-1β), Th1 (IFN-γ, IL-12(p70), IL-2) and Th2 (IL-10, IL-4) cytokines were also noticed in Alum, FliC and MPLA groups compared to Alum alone group. The rPA-specific IgG and cytokine responses in MPLA and FliC groups were significantly higher than the Alum group, suggesting enhancement of immune response by these TLR agonists. MPLA was also found to skew the IgG1:IgG2a ratio towards IgG2a. At a challenge dose of 25 LD50, complete protection was observed in mice of MPLA group whereas lesser protection was observed in FliC (87%) and Alum (50%) groups. Therefore, we suggest the use of MPLA in further development of rPA based anthrax vaccines.

Advance in strategies to build efficient vaccines against tuberculosis

Tuberculosis is a chronic consumptive infectious disease, which can cause great damage to human and animal health all over the world. The emergence of multi-drug resistant strains, the unstable protective effect of Bacillus Calmette-Guérin (BCG) vaccine on adults, and the mixed infection with HIV all warn people to exploit new approaches for conquering tuberculosis. At present, there has been significant progress in developing tuberculosis vaccines, such as improved BCG vaccine, subunit vaccine, DNA vaccine, live attenuated vaccine and inactivated vaccine. Among these candidate vaccines, there are some promising vaccines to improve or replace BCG vaccine effect. Meanwhile, the application of adjuvants, prime-boost strategy, immunoinformatic tools and targeting components have been studied concentratedly, and verified as valid means of raising the efficiency of tuberculosis vaccines as well. In this paper, the latest advance in tuberculosis vaccines in recent years is reviewed to provide reliable information for future tuberculosis prevention and treatment.

Dose finding for new vaccines: The role for immunostimulation/immunodynamic modelling

Current methods to optimize vaccine dose are purely empirically based, whereas in the drug development field, dosing determinations use far more advanced quantitative methodology to accelerate decision-making. Applying these established methods in the field of vaccine development may reduce the currently large clinical trial sample sizes, long time frames, high costs, and ultimately have a better potential to save lives. We propose the field of immunostimulation/immunodynamic (IS/ID) modelling, which aims to translate mathematical frameworks used for drug dosing towards optimizing vaccine dose decision-making. Analogous to Pharmacokinetic/Pharmacodynamic (PK/PD) modelling, the mathematical description of drug distribution (PK) and effect (PD) in host, IS/ID modelling approaches apply mathematical models to describe the underlying mechanisms by which the immune response is stimulated by vaccination (IS) and the resulting measured immune response dynamics (ID). To move IS/ID modelling forward, existing datasets and further data on vaccine allometry and dose-dependent dynamics need to be generated and collate, requiring a collaborative environment with input from academia, industry, regulators, governmental and non-governmental agencies to share modelling expertise, and connect modellers to vaccine data.

A De-O-acylated Lipooligosaccharide-Based Adjuvant System Promotes Antibody and Th1-Type Immune Responses to H1N1 Pandemic Influenza Vaccine in Mice

Vaccine adjuvants are agents that are used to promote immune responses to vaccine antigens and thereby to enhance the protective efficacy of the vaccines. In this study, we investigated the adjuvant activity of CIA06, an adjuvant system that is composed of a toll-like receptor 4 agonist de-O-acylated lipooligosaccharide (dLOS) and aluminum hydroxide, on the H1N1 pandemic influenza vaccine Greenflu-S® in mice. CIA06 significantly enhanced influenza-specific serum IgG, hemagglutination-inhibition, and virus-neutralizing antibody titers, which eliminated vaccine dose-dependency in the antibody response. Mice immunized with the CIA06-adjuvanted Greenflu-S showed Th1-type-predominant cytokine profiles, and both CD4⁺ and CD8⁺ T cell responses were induced. Immunization of mice with the CIA06-adjuvanted vaccine reduced the mortality and morbidity of mice upon lethal challenges with influenza virus, and no excessive inflammatory responses were observed in the lung tissues of the immunized mice after viral infection. These data suggest that the dLOS-based adjuvant system CIA06 can be used to promote the immune responses to influenza vaccine or to spare antigen dose without causing harmful inflammatory responses.

Influence of Brucella abortus lipopolysaccharide as an adjuvant on the immunogenicity of HPV-16 L1VLP vaccine in mice

Brucella abortus lipopolysaccharide (LPS) has less toxicity and no pyrogenic properties in comparison with other bacterial LPS. It is a toll-like receptor 4 agonist and has been shown to have the potential use as a vaccine adjuvant. In this study, the immunostimulatory properties of LPS from smooth and rough strains of B. abortus (S19 and RB51) as adjuvants were investigated for the human papillomavirus type 16 (HPV16) L1 virus-like particles (L1VLPs) vaccines. C57BL/6 mice were immunized subcutaneously three times either with HPV-16 L1VLPs alone, or in combination with smooth LPS (S-LPS), rough LPS (R-LPS), aluminum hydroxide or a mixture of them as adjuvant. The humoral immunity was evaluated by measuring the specific and total IgG levels, and also the T-cell immune response of mice was evaluated by measuring different cytokines such as IFN-γ, TNF-α, IL-4, IL-10 and IL-17. Results showed that serum anti-HPV16 L1VLP IgG antibody titers was significantly higher in mice immunized with a combination of VLPs and R-LPS or S-LPS compared with other immunized groups. Co-administration of HPV-16 L1VLPs with R-LPS elicited the highest levels of splenocytes cytokines (IFN-γ, IL-4, IL-17 and TNF-α) and also effectively induced improvement of a Th1-type cytokine response characterized with a high ratio of IFN-γ/IL-10. The data indicate that B. abortus LPS particularly RB51-LPS enhances the immune responses to HPV-16 L1VLPs and suggests its potential as an adjuvant for the development of a potent prophylactic HPV vaccine and other candidate vaccines.

Characterization of the structure and immunostimulatory activity of a vaccine adjuvant, de-O-acylated lipooligosaccharide

Lipopolysaccharide (LPS) is a major component of the outer membrane of Gram-negative bacteria. LPS elicits strong immunopathological responses during bacterial infection, and the lipid A moiety of LPS is responsible for this immunostimulatory activity. Lipid A exerts its biological activity by sending signals via TLR4 present on immune cells, and TLR4 agonists have been a target for vaccine adjuvant. Previously, we demonstrated an adjuvant activity of deacylated lipooligosaccharide (dLOS) to viral and bacterial antigens. In this study, we characterized the chemical structure of dLOS and evaluated its immunostimulatory activity on mouse and human immune cells in comparison with monophosphoryl lipid A (MPL). dLOS consists of a core oligosaccharide lacking the terminal glucose residue, a glucosamine disaccharide with two phosphate groups, and two N-linked acyl groups. dLOS was similar to MPL in induction of cytokine production in mouse peritoneal macrophages, but was a more potent activator in human monocytes and dendritic cells (DCs). Results of an analysis of allogeneic T cell responses revealed that dLOS induces Th1, Th2, and Th17-type immune responses in a dose-dependent manner. The immunostimulatory activities of dLOS were completely abrogated in TLR4^−/− mice, which confirms its TLR4-dependency. These results suggest that in the presence of the core oligosaccharide, O-linked acyl groups of LPS are dispensable for activating the TLR4 signaling pathway. dLOS did not cause any pathological effects or death at 0.25, 0.5, or 1 mg per kg body weight in mice in the acute toxicity tests. This result suggests that dLOS has a low toxicity. dLOS should be considered for further development as a safe and effective adjuvant for human vaccines.

Increased long-term immunity to Bacillus anthracis protective antigen in mice immunized with a CIA06B-adjuvanted anthrax vaccine

Anthrax is an acute infectious disease caused by Bacillus anthracis. We previously reported that the adjuvant CIA06B, which consists of TLR4 agonist CIA05 and aluminum hydroxide (alum), enhanced the immune response to anthrax protective antigen (PA) in mice. This study was carried out to determine whether CIA06B can enhance long-term immune responses to PA in mice. BALB/c mice were immunized intramuscularly three times at 2-week intervals with recombinant PA alone or PA combined with alum or CIA06B. At 8 and 24 weeks post-immunization, the immunological responses including serum anti-PA IgG antibody titer, toxin-neutralizing antibody titer, splenic cytokine secretion and the frequency of PA-specific memory B cells were assessed. Compared with mice injected with PA alone or PA plus alum, mice injected with PA plus CIA06B had higher titers of serum anti-PA IgG antibodies, and higher frequencies of PA-specific memory B cells and interferon-γ secreting cells. Furthermore, anti-PA antibodies induced by CIA06B were more effective in neutralizing anthrax toxin. These results demonstrated that CIA06B is capable of providing long-term immunity when used as an adjuvant in a PA-based anthrax vaccine.

Comparison of the immune responses to the CIA06-adjuvanted human papillomavirus L1 VLP vaccine with those against the licensed HPV vaccine Cervarix™ in mice

CIA05 is a toll-like receptor (TLR) 4 agonist derived from an Escherichia coli lipopolysaccharide (LPS) mutant and has been shown to have potential as a vaccine adjuvant. In this study, we investigated the immunopotentiating activity of the adjuvant system CIA06, which is comprised of CIA05 and aluminum hydroxide (alum), when used with the human papillomavirus (HPV) L1 virus-like particles (VLPs) vaccine. BALB/c mice were immunized intramuscularly three times at 2-week intervals with HPV16 L1 VLPs alone or in the presence of various combinations of CIA05 and alum, and the immune responses were assessed. We found that the combination of CIA05 and alum at a ratio of 1:50 (designated CIA06B) yielded the highest immune response in terms of serum anti-HPV L1 VLP IgG antibody titers, splenocyte interferon (IFN)-γ secretion, and antigen-specific memory B cell responses. The immunogenicity of the CIA06B-adjuvanted HPV16/18 L1 VLP vaccine was compared with that of the currently licensed HPV vaccine Cervarix™. The CIA06B-adjuvanted vaccine was similar to Cervarix™ with regard to eliciting serum antigen-specific IgG antibodies and virus-neutralizing antibodies but more effective at inducing splenic cytokine production and memory B cells. We also observed that the antigen-specific IgG antibody titers, splenic IFN-γ secretion and memory B cells induced by the CIA06B-adjuvanted HPV vaccine remained high up to 24 weeks post-immunization. Based on these data, we concluded that CIA06B may have potential as an adjuvant in a potent prophylactic vaccine against HPV infection.

A combination of the TLR4 agonist CIA05 and alum promotes the immune responses to Bacillus anthracis protective antigen in mice

Anthrax is an infectious disease caused by Bacillus anthracis. The currently licensed human anthrax vaccines contain protective antigen (PA) as a major protective component and alum as an adjuvant. In this study, we investigated whether CIA05, a TLR4 agonist, is able to promote the immune response to an anthrax vaccine adjuvanted with alum. BALB/c mice were immunized intraperitoneally three times at 2-week intervals with a recombinant B. anthracis PA alone or in combination with CIA05 in the absence or presence of alum, and immune responses were determined 2 or 3 weeks after the third immunization. The results showed that the combination of CIA05 and alum significantly increased both serum anti-PA IgG antibody and toxin-neutralizing antibody titers, and the adjuvant effects were greater when lower antigen doses were used for immunization. Both CIA05 and alum stimulated PA-specific splenocyte secretion of interleukin (IL)-4, IL-5, and IL-6. A combination of the two yielded synergistic effects on IL-4 secretion, but CIA05 tended to repress IL-5 and IL-6 secretions induced by alum. Co-administration of CIA05 and alum also increased GL7 expression in B220(+)CD24(+) splenic cells, indicating the ability to activate B cells. These data suggest that CIA05, combined with alum, could be used to achieve higher immune responses to PA, leading to the development of an effective anthrax vaccine.

Simple and convenient chromatography-based methods for purifying the pseudovirus of human papillomavirus type 58

The currently available purification protocol for human papillomavirus (HPV) pseudovirus (PsV), as a substitute for the native HPV virion, utilizes Optiprep gradients (OG), which require costly equipment such as ultracentrifuges, and 4-7 h of working time, and cannot cope with large PsV samples. To develop a convenient method for purifying HPV type 58 PsV (HPV58 PsV) we have examined the use of heparin chromatography (HC) and cation-exchange chromatography (CC), which utilize open column systems and do not require expensive equipment. We confirmed that the PsVs resulting from HC and CC have correctly assembled conformations and are neutralized by anti-HPV58 PsV mouse serum, indicating that their antigenic characteristics make them suitable to substitute for native HPV58 virion. The recoveries of infectious PsV resulting from HC and CC were 39% and 11%, respectively, while that from OG was 58%. The two new purification methods are advantageous with respect to working time (only 30 min) and expense over the OG method, and have considerable potential for large scale purification.