Adjuvant activity of muramyl dipeptide derivatives to enhance immunogenicity of a hantavirus-inactivated vaccine

Advancements in Vaccine Adjuvants: The Journey from Alum to Nano Formulations

Vaccination is a groundbreaking approach in preventing and controlling infectious diseases. However, the effectiveness of vaccines can be greatly enhanced by the inclusion of adjuvants, which are substances that potentiate and modulate the immune response. This review is based on extensive searches in reputable databases such as Web of Science, PubMed, EMBASE, Scopus, and Google Scholar. The goal of this review is to provide a thorough analysis of the advances in the field of adjuvant research, to trace the evolution, and to understand the effects of the various adjuvants. Historically, alum was the pioneer in the field of adjuvants because it was the first to be approved for use in humans. It served as the foundation for subsequent research and innovation in the field. As science progressed, research shifted to identifying and exploiting the potential of newer adjuvants. One important area of interest is nano formulations. These advanced adjuvants have special properties that can be tailored to enhance the immune response to vaccines. The transition from traditional alum-based adjuvants to nano formulations is indicative of the dynamism and potential of vaccine research. Innovations in adjuvant research, particularly the development of nano formulations, are a promising step toward improving vaccine efficacy and safety. These advances have the potential to redefine the boundaries of vaccination and potentially expand the range of diseases that can be addressed with this approach. There is an optimistic view of the future in which improved vaccine formulations will contribute significantly to improving global health outcomes.

Glycerol Monolaurate to Ameliorate Efficacy of Inactivated Pseudorabies Vaccine

The present study is aimed to evaluate the effect of glycerol monolaurate (GML) on the growth performance and immune enhancement of pseudorabies virus (PRV)-inactivated vaccine in the early-weaned piglets. One hundred and twenty-five 28-day-old weaned piglets were randomly assigned to a control group (CON, no vaccine and no challenge), challenge control group (C-CON), inactivated PRV vaccine group (IPV), IPV + 500 mg/kg GML group (L-GML), and IPV + 1,000 mg/kg GML group (H-GML) during the entire 28-day experimental period. All the data analyses were performed by one-way analysis of variance (ANOVA) and multiple comparisons. Our results showed that the final weight, average daily gain (ADG), and average daily feed intake (ADFI) of H-GML were the highest in each group, and F/G of H-GML was increased but there was no significant difference with CON (p > 0.05). Levels of PRV glycoprotein B (gB) antibody and immunoglobulin in serum of L-GML and H-GML were higher than those of IPV, but only gB antibody levels and immunoglobulin G (IgG) in H-GML were significantly increased (p < 0.05). Compared with IPV, the contents of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) in serum of L-GML (TNF-α and IL-1β: p > 0.05, IL-6: p < 0.05, respectively) and H-GML (p < 0.01, both) were all decreased, and the content of interleukin-10 (IL-10) in H-GML was increased (p > 0.05). Furthermore, reverse transcription-polymerase chain reaction (RT-PCR) experiments proved that L-GML and H-GML were both superior to IPV in inhibiting the expression of TNF-α (p < 0.01), IL-6 (p > 0.05), and IL-1β (p < 0.01) mRNAs and promoting the expression of IL-10 mRNA (L-GML: p > 0.05, H-GML: p < 0.05, respectively) in the superficial inguinal lymph nodes. Histopathological examination found mild congestion in the lung and inguinal lymph nodes of IPV, while the tissues (brain, lung, and inguinal lymph nodes) of L-GML and H-GML were the same as CON with no obvious lesions. The above results indicate that GML may improve the growth performance of weaned piglets and enhance the immunity of PRV-inactivated vaccine by increasing the levels of PRV gB antibody and immunoglobulin and regulating cytokine levels.

Regulation of Immune Homeostasis via Muramyl Peptides-Low Molecular Weight Bioregulators of Bacterial Origin

Metabolites and fragments of bacterial cells play an important role in the formation of immune homeostasis. Formed in the course of evolution, symbiotic relationships between microorganisms and a macroorganism are manifested, in particular, in the regulation of numerous physiological functions of the human body by the innate immunity receptors. Low molecular weight bioregulators of bacterial origin have recently attracted more and more attention as drugs in the prevention and composition of complex therapy for a wide range of diseases of bacterial and viral etiology. Signaling networks show cascades of causal relationships of deterministic phenomena that support the homeostasis of multicellular organisms at different levels. To create networks, data from numerous biomedical and clinical research databases were used to prepare expert systems for use in pharmacological and biomedical research with an emphasis on muramyl dipeptides. Muramyl peptides are the fragments of the cell wall of Gram-positive and Gram-negative bacteria. Binding of muramyl peptides with intracellular NOD2 receptors is crucial for an immune response on pathogens. Depending on the microenvironment and duration of action, muramyl peptides possess positive or negative regulation of inflammation. Other factors, such as genetic, pollutions, method of application and stress also contribute and should be taken into account. A system biology approach should be used in order to systemize all experimental data for rigorous analysis, with the aim of understanding intrinsic pathways of homeostasis, in order to define precise medicine therapy and drug design.

Immunomodulatory Lectin-like Peptides for Fish Erythrocytes-Targeting as Potential Antiviral Drug Delivery Platforms

One of the challenges of science in disease prevention is optimizing drug and vaccine delivery. Until now, many strategies have been employed in this sector, but most are quite complex and labile. To overcome these limitations, great efforts are directed to coupling drugs to carriers, either of natural or synthetic origin. Among the most studied cell carriers are antigen-presenting cells (APCs), however, red blood cells (RBCs) are positioned as attractive carriers in drug delivery due to their abundance and availability in the body. Furthermore, fish RBCs have a nucleus and have been shown to have a strong involvement in modulating the immune response. In this study, we evaluated the binding of three peptides to rainbow trout RBCs, two lectin-like peptides and another derived from Plasmodium falciparum membrane protein, in order to take advantage of this peptide-RBCs binding to generate tools to improve the specificity, efficacy, immunostimulatory effect, and safety of the antiviral therapeutic or prophylactic administration systems currently used.

Rational Vaccine Design in Times of Emerging Diseases: The Critical Choices of Immunological Correlates of Protection, Vaccine Antigen and Immunomodulation

Vaccines are the most effective medical intervention due to their continual success in preventing infections and improving mortality worldwide. Early vaccines were developed empirically however, rational design of vaccines can allow us to optimise their efficacy, by tailoring the immune response. Establishing the immune correlates of protection greatly informs the rational design of vaccines. This facilitates the selection of the best vaccine antigens and the most appropriate vaccine adjuvant to generate optimal memory immune T cell and B cell responses. This review outlines the range of vaccine types that are currently authorised and those under development. We outline the optimal immunological correlates of protection that can be targeted. Finally we review approaches to rational antigen selection and rational vaccine adjuvant design. Harnessing current knowledge on protective immune responses in combination with critical vaccine components is imperative to the prevention of future life-threatening diseases.

Translation of peptidoglycan metabolites into immunotherapeutics

The discovery of defined peptidoglycan metabolites that activate host immunity and their specific receptors has revealed fundamental insights into host-microbe recognition and afforded new opportunities for therapeutic development against infection and cancer. In this review, we summarise the discovery of two key peptidoglycan metabolites, γ-d-glutamyl-meso-diaminopimelic acid (iE-DAP) and muramyl dipeptide and their respective receptors, Nod1 and Nod2, and review progress towards translating these findings into therapeutic agents. Notably, synthetic derivatives of peptidoglycan metabolites have already yielded approved drugs for chemotherapy-induced leukopenia and paediatric osteosarcoma; however, the broad effects of peptidoglycan metabolites on host immunity suggest additional translational opportunities for new therapeutics towards other cancers, microbial infections and inflammatory diseases.

Synthesis and immunopotentiating activity of novel isoxazoline functionalized coumarins

A novel series (13) of isoxazoline functionalized coumarins was synthesized through 1,3-dipolar cyclization of nitrile oxides with Allylated coumarins. Synthesis of effective and target selective immunostimulators through conjugation of diversely substituted isoxazolines and 7-hydroxycoumarins is the focus of the present article. The proposed synthetic scheme was observed to be highly regiospecific yielding attempted conjugates in good yield (>90%). Kinetic resolution of the racemates was carried out by employing lipase B from Candida antarctica (CALB). The synthesized compounds were screened in vitro and in vivo for their biological activities viz. toxicity and impact on splenocyte proliferation (T- and B-cell proliferation), antibody production (HA titre), delayed-type hypersensitivity reaction (DTH), T-cell subtypes (CD4 and CD8), cytokine production (IL-2, IFN-γ, and IL-4) and NO (macrophage) production. Our results establish that isoxazoline functionalized coumarins exhibit excellent immune potentiating activity especially compounds 2, 4 and 8 whose activity is more than that of Levimasole as standard. The structure activity relations are explained in light of the structural/functional aspects of tested compounds. To the best of our knowledge the presented work is first of its kind and is presaged to prove very useful for the design and synthesis of bis-heterocycle based novel, therapeutically selective and effective immunopotentiators.

Animal Models for the Study of Rodent-Borne Hemorrhagic Fever Viruses: Arenaviruses and Hantaviruses

Human pathogenic hantaviruses and arenaviruses are maintained in nature by persistent infection of rodent carrier populations. Several members of these virus groups can cause significant disease in humans that is generically termed viral hemorrhagic fever (HF) and is characterized as a febrile illness with an increased propensity to cause acute inflammation. Human interaction with rodent carrier populations leads to infection. Arenaviruses are also viewed as potential biological weapons threat agents. There is an increased interest in studying these viruses in animal models to gain a deeper understating not only of viral pathogenesis, but also for the evaluation of medical countermeasures (MCM) to mitigate disease threats. In this review, we examine current knowledge regarding animal models employed in the study of these viruses. We include analysis of infection models in natural reservoirs and also discuss the impact of strain heterogeneity on the susceptibility of animals to infection. This information should provide a comprehensive reference for those interested in the study of arenaviruses and hantaviruses not only for MCM development but also in the study of viral pathogenesis and the biology of these viruses in their natural reservoirs.

Adamantoylated biologically active small peptides and glycopeptides structurally related to the bacterial peptidoglycan

A large number of novel synthetic compounds representing smaller parts of original peptidoglycan molecules have been synthesized and found to possess versatile biological activity, particularly immunomodulating properties. A series of compounds containing the adamantyl residues coupled to peptides and glycopeptides characteristic for bacterial peptidoglycan was described. The new adamantylpeptides and adamantylglycopeptides were prepared starting from N-protected racemic adamantylglycine and dipeptide L-Ala-D-isoglutamine. The adamantyl glycopeptides were obtained by coupling the adamantyltripeptides with alpha-D-mannose moiety through spacer molecule of fixed chirality. Since the starting material was D,L-(adamantyl-glycine) the condensation products with the dipeptide were mixtures of diastereoisomers. The obtained diastereoisomers were separated, characterized, and tested for immunostimulating activity. An HPLC method for purity testing was developed and adapted for the particular compounds.

Influence of mannosylation on immunostimulating activity of adamant-1-yl tripeptide

The mannosylated derivative of adamant-1-yl tripeptide (D-(Ad-1-yl)Gly-L-Ala-D-isoGln) was prepared to study the effects of mannosylation on adjuvant (immunostimulating) activity. Mannosylated adamant-1-yl tripeptide (Man-OCH(2) CH(Me)CO-D-(Ad-1-yl)Gly-L-Ala-D-isoGln) is a non-pyrogenic, H(2) O-soluble, and non-toxic compound. Adjuvant activity of mannosylated adamantyl tripeptide was tested in the mouse model with ovalbumin as an antigen and in comparison to the parent tripeptide and peptidoglycan monomer (PGM, β-D-GlcNAc-(1→4)-D-MurNAc-L-Ala-D-isoGln-mesoDAP(εNH(2) )-D-Ala-D-Ala), a well-known effective adjuvant. The mannosylation of adamantyl tripeptide caused the amplification of its immunostimulating activity in such a way that it was comparable to that of PGM.

Synthesis and immunostimulating properties of novel adamant-1-yl tripeptides

The aim of this work was to prepare L- and D-(adamant-1-yl)-Gly-L-Ala-D-isoGln peptides in order to study their adjuvant (immunostimulating) activities. Adjuvant activity of adamant-1-yl tripeptides was tested in the mouse model using ovalbumin as an antigen and in comparison to the peptidoglycan monomer (PGM; β-D-GlcNAc-(1→4)-D-MurNAc-L-Ala-D-isoGln-mesoDAP(εNH(2) )-D-Ala-D-Ala) and structurally related adamant-2-yl tripeptides.

Fusion with extracellular domain of cytotoxic T-lymphocyte-associated-antigen 4 leads to enhancement of immunogenicity of Hantaan virus DNA vaccines in C57BL/6 mice

BACKGROUND

Hantaan virus (HTNV) is the causative agent of the most severe form of a rodent-borne disease known as hemorrhagic fever with renal syndrome (HFRS). A safe and effective HTNV vaccine is needed. Vaccination with DNA constructs expressing fused antigen with bioactive factors, has shown promising improvement of immunogenicity for viral agents in animal models, but the effect of fusion strategy on HTNV DNA vaccine has not been investigated.

RESULTS

DNA plasmids encoding the HTNV nucleocapsid protein (N) and glycoprotein (Gn and Gc) in fusion to the extracellular domain of cytotoxic T-lymphocyte-associated-antigen 4 (eCTLA-4) targeting to antigen presenting cells (APCs) were constructed. Intramuscular immunization of mice with plasmids expressing eCTLA-4-HTNV-N/GP fusion proteins leads to a significant enhancement of the specific antibody response as well as cytotoxic T-lymphocyte (CTL) response in C57BL/6 mice. Moreover, this effect could be further augmented when co-administered with CpG motifs.

CONCLUSIONS

Modification of viral antigen in fusion to bioactive factor will be promising to confer efficient antigen presentation and improve the potency of DNA vaccine in mice.

Muropeptides trigger distinct activation profiles in macrophages and dendritic cells

Bacterial peptidoglycan and its muropeptide derivatives potently activate mammalian innate immune system and are promising immunomodulators and vaccine adjuvants. However, their effects on human antigen-presenting cells, such as dendritic cells (DCs) and Mphi, are not fully understood. Lysozyme treatment of PG from Salmonella typhi yielded three muropeptides, GlcNAc-MurNAc-L-Ala-D-isoGlu-meso-DAP (GM-3P), GlcNAc-MurNAc-L-Ala-D-isoGlu-meso-DAP-D-Ala (GM-4P), and a dimer (GM-4P)(2), in which two GM-4P monomers are linked through their peptidic moieties. All three muropeptides induced TNF-alpha and IL-6 production by Mphi (GM-3P>GM-4P>>(GM-4P)(2)), but failed to trigger TNF-alpha, IL-6 and IL-12p70 production by immature DCs. At the same time, muropeptide-stimulated DCs abundantly produced inflammatory chemokines IL-8, MIP-1 alpha and MIP-1 beta, as well as displayed signs of phenotypic and functional maturation. Thus, muropeptide-dependent pro-inflammatory cytokine production is repressed in DCs. While this defect may be partly compensated in vivo by muropeptide-activated Mphi, neither Mphi nor DCs produce Th1- or Th17-polarizing cytokines upon muropeptide stimulation, which may contribute to the preferential induction of Th2 responses by muropeptides and should be taken into account when designing muropeptide-based immunomodulators and adjuvants.

Comparative study of structurally related peptidoglycan monomer and muramyl dipeptide on humoral IgG immune response to ovalbumin in mouse

Structurally related peptidoglycan monomer (PGM) and muramyl dipeptide (MDP) differ in several aspects of biological activity but have in common immunostimulating properties. Comparative study of the effects of these adjuvants on humoral IgG immune response specific for protein antigen ovalbumin (OVA) was carried out in two inbred mouse strains, CBA and NIH/OlaHsd, and their ability to modulate the bias of immune response towards Th1/Th2 was evaluated. MDP had better adjuvant activity at some points than PGM, whereas both adjuvants stimulated Th2-biased immune response specific for OVA. In comparison to Complete Freund's adjuvant (CFA), as a golden standard of adjuvant action, both PGM and MDP exhibited considerably lower activity. Addition of PGM to Incomplete Freund's adjuvant (IFA) on humoral immune response was studied also, and the effect of such adjuvant formulation was compared to the effect of CFA. While CFA induced the switch towards Th1-biased immune response, the addition of PGM into IFA did have no impact on modulating the immune response towards more pronounced Th2-type of immune response, defined by IFA itself.

Comparative immunomodulatory properties of a chitosan-MDP adjuvant combination following intranasal or intramuscular immunisation

As the precise functions of adjuvants become clearer, opportunities are presented in their complementary use for the induction of tailored immune responses to subunit vaccines. Here we comparatively investigate the immunological outcome following intranasal or intramuscular immunisation with Helicobacter pylori urease admixed to a chitosan and muramyl di-peptide (MDP) combination. MDP appeared to limit the antigenicity of rUre by either administration route. Nasal administration of the combined adjuvant formulation resulted in an up-regulation of type I recall responses in splenocytes as opposed to adjuvantisation with chitosan alone. In contrast, intramuscular immunisation appeared to limit the responsiveness to the antigen when adjuvanted with chitosan and even more so when chitosan was combined with MDP, suggesting that the mechanism of adjuvantisation and adjuvant synergy differed depending on the immunisation route. Recognising the benefit of improved delivery of MDP intranasally due to the specific physiological effects of chitosan, we discuss the impact of the newly identified pathogen associated molecular pattern (PAMP) role of MDP with respect to the adjuvanticity of proposed chemical variants of this peptide adjuvant.

Adjuvant synergy: The effects of nasal coadministration of adjuvants

Modern peptide and protein subunit vaccines suffer from poor immunogenicity and require the use of adjuvants. However, none of the currently licensed adjuvants can elicit cell-mediated immunity or are suitable for mucosal immunization. In this study we explored the immunological effect of nasal co-administration of adjuvants with distinct functions: cholera toxin subunit B, a potent mucosal adjuvant that induces strong humoral responses, muramy di-peptide (MDP), an adjuvant known to elicit cell mediated immunity but rarely used nasally, and chitosan, an adjuvant that achieves specific physiological effects on mucosal membranes that improve antigen uptake. Groups of five female BALB/c mice received on days 1 and 56 nasal instillations of the recombinant Helicobacter pylori antigen urease admixed to single or multiple adjuvant combinations. Serum IgG kinetics were followed over 24 weeks. At the conclusion of the experiment, local antibody responses were determined and antigen-specific recall responses in splenocyte cultures were assayed for proliferation and cytokine production. The combination of adjuvants was shown to further contribute to the increased antigenicity of recombinant H. pylori urease. The data presented here outline and support facilitation of increased immunomodulation by an adjuvant previously defined as an effective mucosal adjuvant (chitosan) for another adjuvant (MDP) that is not normally effective via this route.

Lipid and carbohydrate based adjuvant/carriers in immunology

This review discusses various issues regarding vaccines; what are they and how they work, safety aspects, the role of adjuvants and carriers in vaccination, synthetic peptides as immunogens, and new technologies for vaccine development and delivery including the identification of novel adjuvants for mucosal vaccine delivery. There has been a recent increase of interest in the use of lipids and carbohydrates as adjuvants, and so a particular emphasis is placed on adjuvants derived from lipids or carbohydrates, or from both.

Hantavirus infections and their prevention

Hantaviruses are rodent-borne bunyaviruses which cause haemorrhagic fever with renal syndrome and Hantavirus pulmonary syndrome in humans. This review covers the host interactions of the viruses, including the rodent reservoirs, the clinical outcome of human infections as well as the pathogenesis and laboratory diagnosis of infections. The current stage in prophylaxis and therapy of hantaviral diseases is described and different approaches in vaccine development are discussed.

Cellular and humoral adjuvant activity of lectins isolated from Korean mistletoe (Viscum album colaratum)

The adjuvant effect of lectins (KML-C) isolated from Korean mistletoe (Viscum album coloratum) on induction of humoral and cellular immune responses against keyhole limpet hemocyanine (KLH) was examined. When mice were immunized subcutaneously (s.c.) with KLH (20 micrograms/mouse) admixed with or without 50 ng/mouse of KML-C (KLH + KML-C), mice immunized with KLH + KML-C showed significantly higher antibody titers against KLH than those immunized with KLH alone, showing the highest titer 5 weeks after immunization. Furthermore, boost immunization with KLH + KML-C at 2-week interval elicited much higher activity than single immunization to enhance antibody responses against KLH. The assay for determining isotypes of antibodies revealed that KML-C augmented KLH-specific antibody titers of IgG1, IgG2a and IgG2b. The culture supernatants obtained from the splenocytes of mice treated with KLH + KML-C also showed a higher level of both KLH-specific Th-1 (IL-2 and IFN-gamma) and Th-2 type cytokine (IL-4). In an in vitro analysis of T lymphocyte proliferation to KLH on week 4, the splenocytes of mice treated with KLH + KML-C showed a significantly higher proliferating activity than those treated with KLH alone. In addition, mice immunized twice with KLH + KML-C and followed by intrafootpad (i.f.) injection of KLH (50 micrograms/site) 14 weeks after the primary immunization induced a higher delayed-type hypersensitivity (DTH) reaction than mice treated with KLH alone. These results suggest that KML-C is a potent immunoadjuvant to enhance cellular and humoral immune responses.

Molecular cloning and high-level expression of G2 protein of hantaan (HTN) virus 76-118 strain in the yeast Pichia pastoris KM71

Hantaan viral G2 envelope gene, which is known to be one of major antigens and induce neutralizing antibodies, was cloned into expression vector pHIL-S1 which consists of AOX1 promoter, PHO1 signal sequence, HIS4 gene and other components. The recombined plasmid was transformed into methylotropic yeast, Pichia pastoris of KM71 and recombinant strains harboring multi-copy of G2 gene were selected. Expression of the cloned G2 gene was confirmed with Western blot analysis using anti-sera of guinea pig immunized with the carboxyl terminal region of G2 protein expressed in Escherichia coli. The expression of G2 gene from the recombinant strain was tightly repressed by dextrose and effectively induced by methanol, an inducer of AOX1 promoter. The highest expression level was observed from 1 day after induction and maintained at the same level for up to 4 days.

Comparative study of the effects of peptidoglycan monomer and structurally related adamantyltripeptides on humoral immune response to ovalbumin in the mouse

Peptidoglycan monomer, GlcNAc-MurNAc-L-Ala-D-isoGln-mesoDAP(omega NH2)-D-Ala-D-Ala (PGM) originating from Brevibacterium divaricatum and synthetic adamantyltripeptides, diastereoisomers of D,L-(adamant-2-yl)-Gly-L-Ala-D-isoGln (AdTP1 and AdTP2) exhibit immunomodulating activity. An experimental model in the mouse has been established with suboptimal amounts of ovalbumin (OVA) as the immunogen, and parallel testing of adjuvant activity of these three immunomodulators was carried out in Balb/c, C57B16 or CBA mice. Tested compounds (100 or 200 micrograms/mouse) mixed with OVA in saline (50 micrograms/mouse) were administered s.c. Anti-OVA was assayed by ELISA in the sera of mice taken 7 days after the boosters (given on days 14 and 28). The treatment with PGM and one of the diastereoisomers, AdTP2, resulted in significantly higher increase in anti-OVA IgG levels (stimulation index up to 46) with respect to controls and groups treated with AdTP1. The effect of AdTP2 treatment was comparable to that of PGM in most experiments after the first booster, but after the second booster PGM exhibited markedly better effect. PGM and AdTP2 also induced markedly higher levels of IgG1 and IgG2 anti-OVA subclasses than detected in controls and AdTP1 treated mice, indicating that these two immunomodulators might upregulate both Th1-like and Th2-like immune responses.

Enhancing activity of mycobacterial cell-derived adjuvants on immunogenicity of recombinant human hepatitis B virus vaccine

In a previous study, we demonstrated that a lipophilic derivative of muramyl dipeptide [MDP-Lys(L18)] augmented antibody response to recombinant human hepatitis B surface antigen (rhHBsAg) when it was co-immunized with rhHBsAg solubilized in PBS. Here, we examined adjuvant activity of two bacterial cell-derived adjuvants such as Bacillus Calmette-Guérin cell wall skeleton (BCG-CWS) and trehalose-6,6'-dimycolate (TDM), to enhance immunogenicity of rhHBsAg, comparing their activity with that of MDP-Lys(L18). In an animal model where mice were immunized subcutaneously (s.c.) with rhHBsAg (25 micrograms/mouse) admixed with 100 micrograms/mouse of BCG-CWS (Vac/BCG-CWS) or 50 micrograms/mouse of TDM (Vac/TDM) in o/w emulsion formulation, both mice immunized with Vac/BCG-CWS and Vac/TDM showed higher antibody titres to HB antigen than those of mice immunized with the recombinant vaccine alone. The activity of BCG-CWS and TDM to enhance antibody induction seemed to be almost the same with that of MDP-Lys(L18). Furthermore, the enhanced antibody response raised by these adjuvants was shown to be due to high titres of HB antigen-specific IgG1. In addition, the activity of these three adjuvants to enhance antibody response was shown to be higher than that of the present clinical vaccine, aluminium hydroxide-attached rhHBsAg (rhHBsAg-alum). In an analysis of delayed-type hypersensitivity (DTH) reaction where mice were immunized with rhHBsAg admixed with or without each adjuvant in o/w emulsion and followed by intrafootpad (i.f.) injection of rhHBsAg 4 weeks after immunization, mice immunized with Vac/BCG-CWS and Vac/TDM as well as Vac/MDP-Lys(L18) showed a significant increment of swelling reaction. These results suggest that BCG-CWS, TDM and MDP-Lys(L18) are potential adjuvants to enhance the immunogenicity of rhHBsAg to induce humoral and cellular responses.