Evaluation of immunological adjuvant activities of saponin rich fraction from the fruits of Asparagus adscendens Roxb. with less adverse reactions

The hemolytic activity, in vitro as well as in vivo toxicity, and immunomodulatory potential of saponins-rich fraction of Asparagus adscendens Roxb. fruit (AA-SRF) have been assessed in this study in order to explore AA-SRF as an alternative safer adjuvant to standard Quil-A saponin. The AA-SRF showed lower hemolytic activity (HD₅₀ = 301.01 ± 1.63 µg/ml) than Quil-A (HD₅₀ = 17.15 ± 2.12 µg/ml). The sulforhodamine B assay also revealed that AA-SRF was less toxic to VERO cells (IC₅₀≥200 ± 4.32 µg/ml) than Quil-A (IC₅₀ = 60 ± 2.78 µg/ml). The AA-SRF did not lead to mortality in mice up to 1.6 mg and was much safer than Quil-A for in vivo use. Conversely, mice were subcutaneously immunized with OVA 100 μg alone or along with Alum (200 μg) or Quil-A (10 μg) or AA-SRF (50 μg/100 μg/200 μg) on days 0 and 14. The AA-SRF at 100 μg dose best supported the LPS/Con A primed splenocyte proliferation activity, elevated the serum OVA-specific total IgG antibody, IL-12, CD4 titer and upsurged CD3/CD19 expression in spleen as well as lymph node sections which in turn advocated its adjuvant potential. Thus, AA-SRF can be further studied for use as a safe alternative adjuvant in vaccines.

A two-dose optimum for recombinant S1 protein-based COVID-19 vaccination

BACKGROUND

Recombinant protein subunit vaccination is considered to be a safe, fast and reliable technique when combating emerging and re-emerging diseases such as coronavirus disease 2019 (COVID-19). Typically, such subunit vaccines require the addition of adjuvants to attain adequate immunogenicity. AS01, which contains adjuvants MPL and saponin QS21, is a liposome-based vaccine adjuvant system that is one of the leading candidates. However, the adjuvant effect of AS01 in COVID-19 vaccines is not well described yet.

METHODS

In this study, we utilized a mixture of AS01 as the adjuvant for an S1 protein-based COVID-19 vaccine.

RESULTS

The adjuvanted vaccine induced robust immunoglobulin G (IgG) binding antibody and virus-neutralizing antibody responses. Importantly, two doses induced similar levels of IgG binding antibody and neutralizing antibody responses compared with three doses and the antibody responses weakened only slightly over time up to six weeks after immunization.

CONCLUSION

These results suggested that two doses may be enough for a clinical vaccine strategy design using MPL & QS21 adjuvanted recombinant protein, especially in consideration of the limited production capacity of COVID-19 vaccine in a public health emergency.

Fab and Fc contribute to maximal protection against SARS-CoV-2 following NVX-CoV2373 subunit vaccine with Matrix-M vaccination

Recently approved vaccines have shown remarkable efficacy in limiting SARS-CoV-2-associated disease. However, with the variety of vaccines, immunization strategies, and waning antibody titers, defining the correlates of immunity across a spectrum of antibody titers is urgently required. Thus, we profiled the humoral immune response in a cohort of non-human primates immunized with a recombinant SARS-CoV-2 spike glycoprotein (NVX-CoV2373) at two doses, administered as a single- or two-dose regimen. Both antigen dose and boosting significantly altered neutralization titers and Fc-effector profiles, driving unique vaccine-induced antibody fingerprints. Combined differences in antibody effector functions and neutralization were associated with distinct levels of protection in the upper and lower respiratory tract. Moreover, NVX-CoV2373 elicited antibodies that functionally targeted emerging SARS-CoV-2 variants. Collectively, the data presented here suggest that a single dose may prevent disease via combined Fc/Fab functions but that two doses may be essential to block further transmission of SARS-CoV-2 and emerging variants.

Exploring the possible use of saponin adjuvants in COVID-19 vaccine

There is an urgent need for a safe, efficacious, and cost-effective vaccine for the coronavirus disease 2019 (COVID-19) pandemic caused by novel coronavirus strain, severe acute respiratory syndrome-2 (SARS-CoV-2). The protective immunity of certain types of vaccines can be enhanced by the addition of adjuvants. Many diverse classes of compounds have been identified as adjuvants, including mineral salts, microbial products, emulsions, saponins, cytokines, polymers, microparticles, and liposomes. Several saponins have been shown to stimulate both the Th1-type immune response and the production of cytotoxic T lymphocytes against endogenous antigens, making them very useful for subunit vaccines, especially those for intracellular pathogens. In this review, we discuss the structural characteristics, mechanisms of action, structure-activity relationship of saponins, biological activities, and use of saponins in various viral vaccines and their applicability to a SARS-CoV-2 vaccine.

Convenient synthesis of the immunogenic glycolipid BbGL1

A simple and efficient method to synthesize the immunogenic glycolipid BbGL1 is introduced. Two simple steps were required to obtain the desired product in good yield. First, a highly efficient glycosylation of cholesterol using galactosyl trichloroacetimidate as a donor was performed to produce cholesteryl-β-d-galactoside. Finally, an efficient palmitoylation on the C6-OH of the galactose of the synthesized saponin using sym-collidine and acyl chloride under microwave heating that produced BbGL1 in good yield. The procedure is a convenient and cheaper alternative to the reported procedures allowing a rapid preparation of multiple analogs and conjugates.

Vaccination with a CD4+ and CD8+ T-cell epitopes-based recombinant chimeric protein derived from Leishmania infantum proteins confers protective immunity against visceral leishmaniasis

Vaccination seems to be the best approach to control visceral leishmaniasis (VL). Resistance against infection is based on the development of a Th1 immune response characterized by the production of interferons-γ (IFN-γ), interleukin-12 (IL-12), granulocyte-macrophage-colony-stimulating factor (GM-CSF), and tumor necrosis factor-α (TNF-α), among others. A number of antigens have been tested as potential targets against the disease; few of them are able to stimulate human immune cells. In the present study, 1 prediction of MHC class I and II molecules-specific epitopes in the amino acid sequences of 3 Leishmania proteins: 1 hypothetical, prohibitin, and small glutamine-rich tetratricopeptide repeat-containing proteins, was performed using bioinformatics tools, and a T-cell epitopes-based recombinant chimeric protein was constructed, synthetized and purified to be evaluated in invitro and in vivo experiments. The purified protein was tested regarding its immunogenicity in peripheral blood mononuclear cells (PBMCs) from healthy subjects and VL patients, as well as to its immunogenicity and protective efficacy in a murine model against Leishmania infantum infection. Results showed a Th1 response based on high IFN-γ and low IL-10 levels derived from in chimera-stimulated PBMCs in both healthy subjects and VL patients. In addition, chimera and/or saponin-immunized mice presented significantly lower parasite burden in distinct evaluated organs, when compared to the controls, besides higher levels of IFN-γ, IL-2, IL-12, and GM-CSF, and an IgG2a isotype-based humoral response. In addition, the CD4⁺ and CD8⁺ T-cell subtypes contributed to IFN-γ production in the protected animals. The results showed the immunogenicity in human cells and the protective efficacy against L. infantum in a murine model, and well indicate that this recombinant chimera can be considered as a promising strategy to be used against human disease.

Immunomodulatory activities of pixatimod: emerging nonclinical and clinical data, and its potential utility in combination with PD-1 inhibitors

BACKGROUND

Pixatimod (PG545) is a novel clinical-stage immunomodulatory agent capable of inhibiting the infiltration of tumor-associated macrophages (TAMs) yet also stimulate dendritic cells (DCs), leading to activation of natural killer (NK) cells. Preclinically, pixatimod inhibits heparanase (HPSE) which may be associated with its inhibitory effect on TAMs whereas its immunostimulatory activity on DCs is through the MyD88-dependent TLR9 pathway. Pixatimod recently completed a Phase Ia monotherapy trial in advanced cancer patients.

METHODS

To characterize the safety of pixatimod administered by intravenous (IV) infusion, a one month toxicology study was conducted to support a Phase Ia monotherapy clinical trial. The relative exposure (AUC) of pixatimod across relevant species was determined and the influence of route of administration on the immunomodulatory activity was also evaluated. Finally, the potential utility of pixatimod in combination with PD-1 inhibition was also investigated using the syngeneic 4T1.2 breast cancer model.

RESULTS

The nonclinical safety profile revealed that the main toxicities associated with pixatimod are elevated cholesterol, triglycerides, APTT, decreased platelets and other changes symptomatic of modulating the immune system such as pyrexia, changes in WBC subsets, inflammatory changes in liver, spleen and kidney. Though adverse events such as fever, elevated cholesterol and triglycerides were reported in the Phase Ia trial, none were considered dose limiting toxicities and the compound was well tolerated up to 100 mg via IV infusion. Exposure (AUC) up to 100 mg was considered proportional with some accumulation upon repeated dosing, a phenomenon also noted in the toxicology study. The immunomodulatory activity of pixatimod was independent of the route of administration and it enhanced the effectiveness of PD-1 inhibition in a poorly immunogenic tumor model.

CONCLUSIONS

Pixatimod modulates innate immune cells but also enhances T cell infiltration in combination with anti-PD-1 therapy. The safety and PK profile of the compound supports its ongoing development in a Phase Ib study for advanced cancer/pancreatic adenocarcinoma with the checkpoint inhibitor nivolumab (Opdivo®).

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02042781 . First posted: 23 January, 2014 - Retrospectively registered.

Safety and immunogenicity of heterologous prime-boost immunization with viral-vectored malaria vaccines adjuvanted with Matrix-M™

The use of viral vectors in heterologous prime-boost regimens to induce potent T cell responses in addition to humoral immunity is a promising vaccination strategy in the fight against malaria. We conducted an open-label, first-in-human, controlled Phase I study evaluating the safety and immunogenicity of Matrix-M adjuvanted vaccination with a chimpanzee adenovirus serotype 63 (ChAd63) prime followed by a modified vaccinia Ankara (MVA) boost eight weeks later, both encoding the malaria ME-TRAP antigenic sequence (a multiple epitope string fused to thrombospondin-related adhesion protein). Twenty-two healthy adults were vaccinated intramuscularly with either ChAd63-MVA ME-TRAP alone (n=6) or adjuvanted with 25μg (n=8) or 50μg (n=8) Matrix-M. Vaccinations appeared to be safe and generally well tolerated, with the majority of local and systemic adverse events being mild in nature. The addition of Matrix-M to the vaccine did not increase local reactogenicity; however, systemic adverse events were reported more frequently by volunteers who received adjuvanted vaccine in comparison to the control group. T cell ELISpot responses peaked at 7-days post boost vaccination with MVA ME-TRAP in all three groups. TRAP-specific IgG responses were highest at 28-days post boost with MVA ME-TRAP in all three groups. There were no differences in cellular and humoral immunogenicity at any of the time points between the control group and the adjuvanted groups. We demonstrate that Matrix-M can be safely used in combination with ChAd63-MVA ME-TRAP heterologous prime-boost immunization without any reduction in cellular or humoral immunogenicity. Clinical Trials Registration NCT01669512.

Development of an Enzyme-Linked Immunosorbent Assay and Immunoaffinity Column Chromatography for Saikosaponin d Using an Anti-Saikosaponin d Monoclonal Antibody

This work developed a novel immunochemical approach for the quality control of saikosaponin d using an enzyme-linked immunosorbent assay. Splenocytes from mice immunized with the saikosaponin d-bovine serum albumin conjugate were fused with the hypoxanthine-aminopterin-thymidine-sensitive mouse myeloma SP2/0 cell line, and a hybridoma secreting monoclonal antibody against saikosaponin d was successfully obtained. The prepared anti-saikosaponin d monoclonal antibody 1E7F3 has a novel characteristic, showing weak reactivity with compounds that are structurally related to saikosaponin d. Using monoclonal antibody 1E7F3, a specific and reliable enzyme-linked immunosorbent assay was developed to detect saikosaponin d. The system shows a full measurement range from 156.25 to 5000.00 ng × mL(-1). Both intra-assay and inter-assay repeatability and precision were achieved, with relative standard deviations lower than 10.00%. The recovery rates ranged from 92.36% to 101.00%, meeting the requirements for biological samples. There was a good correlation between the enzyme-linked immunosorbent assay and high-performance liquid chromatography analyses of saikosaponin d, and the saikosaponin d levels in formulated Chinese medicines were successfully determined. Furthermore, immunoaffinity column chromatography was established using this anti-saikosaponin d monoclonal antibody, and the elution profile of saikosaponin d was detected by a Bio-Rad QuadTec UV/Vis detector at 203 nm. The results demonstrate that we generated a reliable and more efficient assay system for measuring saikosaponin d and provide a potential approach for purifying and separating saikosaponin d.

Low-dose cyclophosphamide enhances antigen-specific CD4(+) T cell responses to NY-ESO-1/ISCOMATRIX™ vaccine in patients with advanced melanoma

Clinical outcomes from cancer vaccine trials in patients with advanced melanoma have so far been disappointing. This appears at least partially due to a state of immunosuppression in these patients induced by an expansion of regulatory cell populations including regulatory T cells (Tregs). We have previously demonstrated potent immunogenicity of the NY-ESO-1/ISCOMATRIX™ vaccine in patients with resected melanoma (study LUD99-08); however, the same vaccine induced only a few vaccine antigen-specific immune responses in patients with advanced disease (study LUD2002-013). Pre-clinical models suggest that the alkylating agent cyclophosphamide can enhance immune responses by depleting Tregs. Therefore, we have enrolled a second cohort of patients with advanced melanoma in the clinical trial LUD2002-013 to investigate whether pre-treatment with cyclophosphamide could improve the immunogenicity of the NY-ESO-1/ISCOMATRIX™ vaccine. The combination treatment led to a significant increase in vaccine-induced NY-ESO-1-specific CD4(+) T cell responses compared with the first trial cohort treated with vaccine alone. We could not detect a significant decline in regulatory T cells in peripheral blood of patients 14 days after cyclophosphamide administration, although a decline at an earlier time point cannot be excluded. Our observations support the inclusion of cyclophosphamide in combination trials with vaccines and other immune-modulatory agents.

Oral immunization of haemaggulutinin H5 expressed in plant endoplasmic reticulum with adjuvant saponin protects mice against highly pathogenic avian influenza A virus infection

Pandemics in poultry caused by the highly pathogenic avian influenza (HPAI) A virus occur too frequently globally, and there is growing concern about the HPAI A virus due to the possibility of a pandemic among humans. Thus, it is important to develop a vaccine against HPAI suitable for both humans and animals. Various approaches are underway to develop such vaccines. In particular, an edible vaccine would be a convenient way to vaccinate poultry because of the behaviour of the animals. However, an edible vaccine is still not available. In this study, we developed a strategy of effective vaccination of mice by the oral administration of transgenic Arabidopsis plants (HA-TG) expressing haemagglutinin (HA) in the endoplasmic reticulum (ER). Expression of HA in the ER resulted in its high-level accumulation, N-glycosylation, protection from proteolytic degradation and long-term stability. Oral administration of HA-TG with saponin elicited high levels of HA-specific systemic IgG and mucosal IgA responses in mice, which resulted in protection against a lethal influenza virus infection with attenuated inflammatory symptoms. Based on these results, we propose that oral administration of freeze-dried leaf powders from transgenic plants expressing HA in the ER together with saponin is an attractive strategy for vaccination against influenza A virus.

Evaluation of mucosal and systemic immune responses elicited by GPI-0100- adjuvanted influenza vaccine delivered by different immunization strategies

Vaccines for protection against respiratory infections should optimally induce a mucosal immune response in the respiratory tract in addition to a systemic immune response. However, current parenteral immunization modalities generally fail to induce mucosal immunity, while mucosal vaccine delivery often results in poor systemic immunity. In order to find an immunization strategy which satisfies the need for induction of both mucosal and systemic immunity, we compared local and systemic immune responses elicited by two mucosal immunizations, given either by the intranasal (IN) or the intrapulmonary (IPL) route, with responses elicited by a mucosal prime followed by a systemic boost immunization. The study was conducted in BALB/c mice and the vaccine formulation was an influenza subunit vaccine supplemented with GPI-0100, a saponin-derived adjuvant. While optimal mucosal antibody titers were obtained after two intrapulmonary vaccinations, optimal systemic antibody responses were achieved by intranasal prime followed by intramuscular boost. The latter strategy also resulted in the best T cell response, yet, it was ineffective in inducing nose or lung IgA. Successful induction of secretory IgA, IgG and T cell responses was only achieved with prime-boost strategies involving intrapulmonary immunization and was optimal when both immunizations were given via the intrapulmonary route. Our results underline that immunization via the lungs is particularly effective for priming as well as boosting of local and systemic immune responses.

Performance of LBSap vaccine after intradermal challenge with L. infantum and saliva of Lu. longipalpis: immunogenicity and parasitological evaluation

In the last decade, the search for new vaccines against canine visceral leishmaniasis has intensified. However, the pattern related to immune protection during long periods after experimental infection in vaccine trials is still not fully understood. Herein, we investigated the immunogenicity and parasitological levels after intradermal challenge with Leishmania infantum plus salivary gland extract in dogs immunized with a vaccine composed of L. braziliensis antigens plus saponin as an adjuvant (LBSap vaccine). The LBSap vaccine elicited higher levels of total anti-Leishmania IgG as well as both IgG1 and IgG2. Furthermore, dogs vaccinated had increased levels of lymphocytes, particularly circulating B cells (CD21(+)) and both CD4(+) and CD8(+) T lymphocytes. LBSap also elicited an intense in vitro cell proliferation associated with higher levels of CD4(+) T lymphocytes specific for vaccine soluble antigen and soluble lysate of L. infantum antigen even 885 days after experimental challenge. Furthermore, LBSap vaccinated dogs presented high IFN-γ and low IL-10 and TGF-β1 expression in spleen with significant reduction of parasite load in this tissue. Overall, our results validate the potential of LBSap vaccine to protect against L. infantum experimental infection and strongly support further evaluation of efficiency of LBSap against CVL in natural infection conditions.

Immunoadjuvant activity, toxicity assays, and determination by UPLC/Q-TOF-MS of triterpenic saponins from Chenopodium quinoa seeds

The adjuvant activity of Chenopodium quinoa (quinoa) saponins on the humoral and cellular immune responses of mice subcutaneously immunized with ovalbumin (OVA) was evaluated. Two quinoa saponin fractions were obtained, FQ70 and FQ90, and 10 saponins were determined by UPLC/Q-TOF-MS. Mice were immunized subcutaneously with OVA alone or adjuvanted with Quil A (adjuvant control), FQ70, or FQ90. FQ70 and FQ90 significantly enhanced the amount of anti-OVA-specific antibodies in serum (IgG, IgG1, and IgG2b) in immunized mice. The adjuvant effect of FQ70 was significantly greater than that of FQ90. However, delayed type hypersensitivity responses were higher in mice immunized with OVA adjuvanted with FQ90 than mice treated with FQ70. Concanavalin A (Con A)-, lipopolysaccharide-, and OVA-stimulated splenocyte proliferation were measured, and FQ90 significantly enhanced the Con A-induced splenocyte proliferation. The results suggested that the two quinoa saponin fractions enhanced significantly the production of humoral and cellular immune responses to OVA in mice.

[Enhancing the immunogenic activity of influvac vaccine in the use of adjuvant TI complexes modified by echinochrome A]

The self-assembly of marine macrophyte glycolipids, holothurian saponin, and cholesterol gave rise to nanoscale morphological structures called tubular immunostimulating (TI) complexes. Whether the latter could be used on the basis of vaccine preparations containing the influenza virus subunit antigens was studied. There was an obvious increase in the immunogenicity of influenza virus hemagglutinin when the experimental animals were immunized with this antigen as part of TI complexes. It was shown that the adjuvant activity of the TI complex to influenza virus hemagglutinin could be enhanced by adding the known antioxidant echinochrome A from a sand-dollar (Echinarachnius parma) to the matrix of the TI complex.

Nanopatch targeted delivery of both antigen and adjuvant to skin synergistically drives enhanced antibody responses

Many vaccines make use of an adjuvant to achieve stronger immune responses. Alternatively, potent immune responses have also been generated by replacing the standard needle and syringe (which places vaccine into muscle) with devices that deliver vaccine antigen to the skin's abundant immune cell population. However it is not known if the co-delivery of antigen plus adjuvant directly to thousands of skin immune cells generates a synergistic improvement of immune responses. In this paper, we investigate this idea, by testing if Nanopatch delivery of vaccine - both the antigen and the adjuvant - enhances immunogenicity, compared to intramuscular injection. As a test-case, we selected a commercial influenza vaccine as the antigen (Fluvax 2008®) and the saponin Quil-A as the adjuvant. We found, after vaccinating mice, that anti-influenza IgG antibody and haemagglutinin inhibition assay titre response induced by the Nanopatch (with delivered dose of 6.5ng of vaccine and 1.4μg of Quil-A) were equivalent to that of the conventional intramuscular injection using needle and syringe (6000ng of vaccine injected without adjuvant). Furthermore, a similar level of antigen dose sparing (up to 900 fold) - with equivalent haemagglutinin inhibition assay titre responses - was also achieved by delivering both antigen and adjuvant (1.4μg of Quil-A) to skin (using Nanopatches) instead of muscle (intramuscular injection). Collectively, the unprecedented 900 fold antigen dose sparing demonstrates the synergistic improvement to vaccines by co-delivery of both antigen and adjuvant directly to skin immune cells. Successfully extending these findings to humans with a practical delivery device - like the Nanopatch - could have a huge impact on improving vaccines.

Immunoediting and persistence of antigen-specific immunity in patients who have previously been vaccinated with NY-ESO-1 protein formulated in ISCOMATRIX™

BACKGROUND

NY-ESO-1 protein formulated in ISCOMATRIX™ results in CD4+, CD8+ T cell and antibody-mediated immunity. We evaluated persistence of immunity, relapse-free survival and tumour antigen expression upon relapse in patients vaccinated in an earlier trial.

METHODS

Immunity was measured in 28 patients with resected NY-ESO-1-expressing tumours (melanoma 25, breast 3) 252-1,155 days (median = 681) after vaccination. In the earlier vaccination, trial patients received NY-ESO-1 with ISCOMATRIX™ adjuvant at three protein doses 10 μg, 30 μg or 100 μg (n = 14); 100 μg NY-ESO-1 protein (n = 8) or placebo (n = 6), together with 1 μg of intradermal (ID) NY-ESO-1 protein twice for DTH skin testing. Immune responses assessed in the current study included antibody titres, circulating NY-ESO-1-specific T cells and DTH reactivity 2 days after DTH skin testing with NY-ESO-1 protein (1 μg) or peptides (10 μg). Relapse-free survival was determined for 42 melanoma patients. On relapse NY-ESO-1 and HLA, class I was assessed by immunohistochemistry in 17.

RESULTS

Persisting anti-NY-ESO-1 immunity was detected in 10/14 recipients who had previously received vaccine with ISCOMATRIX™ adjuvant. In contrast, immunity only persisted in 3/14 who received 100 μg un-adjuvanted NY-ESO-1 protein (3/8) or 2 μg DTH protein (0/6) P = 0.02. Hence, persisting NY-ESO-1 immunity was associated with prior adjuvant. Tumour NY-ESO-1 or HLA class I was downregulated in participants who relapsed suggesting immunoediting had occurred.

CONCLUSION

Immunoediting suggests that a signal of anti-tumour activity was observed in high-risk resected melanoma patients vaccinated with NY-ESO-1/ISCOMATRIX™. This was associated with measurable persisting immunity in the majority of vaccinated subjects tested. A prospective randomised trial has been undertaken to confirm these results.

An enzyme-linked immunosorbant assay using monoclonal antibody against bacoside A₃ for determination of jujubogenin glycosides in Bacopa monnieri (L.) Wettst

INTRODUCTION

In Ayurvedic medicines, Bacopa monnieri (L.) Wettst. (brahmi) is known as a medicinal plant used for memory enhancement. Its active compounds are classified as pseudojujubogenin and jujubogenin glycosides. Owing to the lack of chromophore in the saponin glycoside structures, HPLC-UV-vis gives low sensitivity for determination of such compounds. In the case of the detection of small amounts of saponin glycosides, immunological assay could be a suitable method.

OBJECTIVE

To develop and validate a sensitive enzyme-linked immunosorbant assay (ELISA) using monoclonal antibody (MAb) against bacoside A₃, the major jujubogenin glycoside found in brahmi.

METHODOLOGY

An immunogen was prepared by conjugating bacoside A₃ with a bovine serum albumin (BSA). To determine its immunogenicity, the ratio of hapten in bacoside A₃-BSA conjugate was determined by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS). After immunisation in mice, hybridomas secreting MAbs against bacoside A₃ were produced by fusing the immunised splenocytes with SP2/0- Ag14 myeloma cells. The antibody was raised specifically against jujubogenin glycosides. The ELISA using anti-bacoside A₃ MAb was developed.

RESULTS

Bacoside A₃ in the range of 3.05-97.70 ng mL⁻¹ could be detected by ELISA using anti-bacoside A₃ MAb. The assay showed a detection limit of 0.48 ng mL⁻¹ (0.517 nm). The validation study showed that the method was precise, accurate and sensitive. Interestingly, the MAb showed cross-reactivity with the other jujubogenin glycosides, bacopaside X and IV. However, it did not show cross-reactivity with any of pseudojujubogenin glycosides.

CONCLUSION

The study demonstrated that ELISA using anti-bacoside A₃ MAb can be used for determination of total jujubogenin glycosides in brahmi.

The known immunologically active components of Astragalus account for only a small proportion of the immunological adjuvant activity when combined with conjugate vaccines

The 95 % ethanol extract of Astragalus has been demonstrated to have potent activity as an immunological adjuvant when administered with vaccines of various types. We endeavor here to identify the components of this extract that are responsible for this adjuvant activity. Mice were immunized with KLH conjugated to cancer carbohydrate antigens globo H and GD3 and cancer peptide antigen MUC1 combined with different Astragalus fractions or with commercially available Astragalus saponins and flavonoids. The antibody responses against cancer antigens and KLH were quantitated in ELISA assays, and toxicity was calculated by weight loss. Astragalosides II and IV were the most active components, but the toxicity of these two differed dramatically. Astragaloside II was the most toxic Astragalus component with 5-10 % weight loss at a dose of 500 µg while astragaloside IV showed no weight loss at all at this dose, suggesting that astragaloside IV might be utilized as an immunological adjuvant in future studies. Several flavonoids also had significant adjuvant activity. However, when the activities of these known immunologically active components of Astragalus (and of endotoxin) are calculated based on the extent of their presence in the 95 % ethanol extract, they provide only a small proportion of the immunological activity. This raises the possibility that additional uniquely active components of Astragalus may contribute to adjuvant activity, or that the adjuvant activity of Astragalus is greater than the activity of the sum of its parts.

Preclinical evaluation of the synthetic adjuvant SQS-21 and its constituent isomeric saponins

The saponin fraction QS-21 from Quillaja saponaria has been demonstrated to be a potent immunological adjuvant when mixed with keyhole limpet hemocyanin conjugate vaccines, as well as with other classes of subunit antigen vaccines. QS-21 adjuvant is composed of two isomers that include the apiose and xylose forms in a ratio of 65:35, respectively. The chemical syntheses of these two isomers in pure form have recently been disclosed. Herein we describe detailed in vivo immunological evaluations of these synthetic QS-21 isomeric constituents, employing the GD3-KLH melanoma antigen. With this vaccine construct, high antibody titers against GD3 ganglioside and KLH were elicited when GD3-KLH was co-administered with adjuvant, either as the individual separate synthetic QS-21 isomers (SQS-21-Api or SQS-21-Xyl), or as its reconstituted 65:35 isomeric mixture (SQS-21). These antibody titer levels were comparable to that elicited by vaccinations employing naturally derived QS-21 (PQS-21). Moreover, toxicities of the synthetic saponin adjuvants were also found to be comparable to that of naturally derived PQS-21. These findings demonstrate unequivocally that the adjuvant activity of QS-21 resides in these two principal isomeric forms, and not in trace contaminants within the natural extracts. This lays the foundation for future exploration of structure-function correlations to enable the discovery of novel saponins with increased potency, enhanced stability, and attenuated toxicity.

Design and synthesis of potent Quillaja saponin vaccine adjuvants

The success of antitumor and antiviral vaccines often requires the use of an adjuvant, a substance that significantly enhances the immune response to a coadministered antigen. Only a handful of adjuvants have both sufficient potency and acceptable toxicity for clinical investigation. One promising adjuvant is QS-21, a saponin natural product that is the immunopotentiator of choice in many cancer and infectious disease vaccine clinical trials. However, the therapeutic promise of QS-21 adjuvant is curtailed by several factors, including its scarcity, difficulty in purification to homogeneity, dose-limiting toxicity, and chemical instability. Here, we report the design, synthesis, and evaluation of chemically stable synthetic saponins. These novel, amide-modified, non-natural substances exhibit immunopotentiating effects in vivo that rival or exceed that of QS-21 in evaluations with the GD3-KLH melanoma conjugate vaccine. The highly convergent synthetic preparation of these novel saponins establishes new avenues for discovering improved molecular adjuvants for specifically tailored vaccine therapies.

[Immunoregulatory effects of periplocin from Cortex Periplocae in tumor-bearing mice]

AIM

To investigate the immune mechanisms for Periplocin from Cortex Periplocae (CPP) in tumor-bearing mice.

METHODS

H(22) tumor-bearing model BALB/c mice were applied to evaluated in vivo immunoregulatory effect of CPP. The influence of different dose CPP (0.25, 0.50 and 1.00 mg/kg) on immune organs in tumor-bearing mice were observed. T cell subsets of mice spleen were detected by flow cytometry. MTT assay was used to determine the influence of CPP on lymphocyte proliferation of mice spleen stimulated by ConA. The levels of TNF-alpha, IL-2 and IL-12 in serum from mice were detected by means of ELISA.

RESULTS

Thymus index and spleen index of H(22) tumor-bearing model control mice became less than that of normal mice (P<0.05). Compared to both model and normal control groups, thymus index and spleen index of H(22) tumor-bearing mice treated with CPP increased obviously (P<0.05). CPP had no influence on the number of CD8(+) T cells, but up-regulated markedly the number of CD3(+), CD4(+) T cells and the ratio of CD4(+)/CD8(+) in tumor-bearing mice. In CPP-treated mice, the percentage of CD3(+), CD4(+) T cells were not different from normal mice (P<0.05), the ratio of CD4(+)/CD8(+) was higher than that of normal mice (P<0.05). CPP enhanced obviously lymphocyte proliferation of mice spleen induced by ConA, the SI scores were even higher than that of normal mice. The levels of TNF-alpha, IL-2 and IL-12 in serum from CPP-treated mice, increased significantly compared to model control group (P<0.05) in a dose-dependent manner, were similar to or higher than that of normal mice.

CONCLUSION

CPP protected immune organs of tumor-bearing mice, increased obviously the percentage of CD4(+) and CD4(+)/CD8(+) among the T cell line, and enhanced lymphocyte proliferation of mice spleen significantly, stimulated the production of TNF-alpha, IL-2 and IL-12. The results suggested that CPP possessed potent immunoregulatory effect.

From Plasmids to Protection: A Review of DNA Vaccines Against Infectious Diseases

The field of DNA vaccine development began over 16 years ago with the observation that plasmid DNA could be injected into and expressed in vivo and drive adaptive immune responses. Since then, there has been great interest in developing this technology to create a new generation of vaccines with the ability to elicit both humoral and cellular immune responses from an inherently innocuous injection. However, DNA vaccines have yet to proceed past phase I/II clinical trials in humans--primarily due to a desire to induce more potent immune responses. This review will examine how DNA vaccines function to induce an immune response and how this information might be useful in future vaccine design.

Immune modulation by adjuvants combined with diphtheria toxoid administered topically in BALB/c mice after microneedle array pretreatment

Purpose

In this study, modulation of the immune response against diphtheria toxoid (DT) by various adjuvants in transcutaneous immunization (TCI) with microneedle array pretreatment was investigated.

Methods

TCI was performed on BALB/c mice with or without microneedle array pretreatment using DT as a model antigen co-administrated with lipopolysaccharide (LPS), Quil A, CpG oligo deoxynucleotide (CpG) or cholera toxin (CT) as adjuvant. The immunogenicity was evaluated by measuring serum IgG subtype titers and neutralizing antibody titers.

Results

TCI with microneedle array pretreatment resulted in a 1,000-fold increase of DT-specific serum IgG levels as compared to TCI. The immune response was further improved by co-administration of adjuvants, showing a progressive increase in serum IgG titers when adjuvanted with LPS, Quil A, CpG and CT. IgG titers of the CT-adjuvanted group reached levels comparable to those obtained after DT-alum subcutaneous injection. The IgG1/IgG2a ratio of DT-specific antibodies decreased in the following sequence: plain DT, Quil A, CT and CpG, suggesting that the immune response was skewed towards the Th1 direction.

Conclusions

The potency and the quality of the immune response against DT administered by microneedle array mediated TCI can be modulated by co-administration of adjuvants.

Immunogenicity assay of the Leishmune vaccine against canine visceral leishmaniasis in Brazil

Leishmune is the industrialized version of the FML-saponin vaccine which has been shown to develop 92-95% protection in vaccinated dogs and 76-80% vaccine efficacy against field canine visceral leishmaniasis (CVL) in Brazil. Leishmune has been proven to be safe and tolerable and a transmission-blocking vaccine which renders vaccinated dogs non-infectious to sand fly vectors. In the present investigation, 550 healthy seronegative dogs of endemic and epidemic areas of Brazil were monitored for Leishmune-induced immunogenicity during a 2-year trial. Another group of 588 untreated exposed dogs was also studied in parallel. Both groups were seronegative on day 0. The strong immunogenicity induced by Leishmune vaccine was demonstrated by the 98% of FML-seroconversion, increase in absorbencies, the 82.7% DTH positive reactions and increase in skin test size diameters, the average increase in CD8+ total lymphocytes population in blood (27.1%), expected for QS21 saponin-containing vaccine, the sustained proportions of CD4+ T cells, and the average increased proportions of CD21+ B lymphocytes (42.3%). The Leishmune-induced protection against CVL is demonstrated by the results: 98.8% asymptomatic dogs (at the end of first year) and 99% healthy survivors (at the end of the second year) among vaccinated dogs, compared to the 79.4% asymptomatic and 61% survivor dogs (p<0.001) monitored in the untreated exposed cohort. In spite of the low vaccine coverage, it was possible to detect a 66.1% (p<0.005) reduction in Belo Horizonte and an 80.2% (p<0.005) reduction in Araçatuba of the incidence of CVL among vaccinated dogs, when compared to the global incidence of CVL of each town, respectively. Our preliminary results support the potential use of Leishmune to prevent CVL epidemics.

Immunogenicity of lipid sustained release implants containing imiquimod, alpha-galactosylceramide, or Quil-A

The aim of this study was to investigate and compare the immunogenicity of liposome-forming, sustained release lipid implants containing either an alpha-galactosylceramide (alpha-GalCer) analogue, imiquimod or Quil-A (QA) as adjuvants. Ovalbumin (OVA) was used as a model antigen. Groups of C57Bl/6 mice were subcutaneously immunised with lipid implants containing one of the adjuvants, or inoculated with OVA in alum. The expansion of CD8+ and CD4+ transgenic T cells was analysed to assess the ability of these implants to stimulate cell-mediated immunity. In addition, the production of OVA-specific IgG antibodies was determined. QA-containing lipid implants were more efficient in the stimulation of CD8+ T cells and IgG antibodies than the two immunomodulators alpha-GalCer and imiquimod. These results suggest that, using this immunisationprotocol and dose of immunomodulators, QA was superior to imiquimod and alpha-GalCer.

Haemolytic activities and adjuvant effect of Anemone raddeana saponins (ARS) on the immune responses to ovalbumin in mice

In this study, saponins (ARS) extracted from the rhizoma of Anemone raddeana were evaluated for their haemolytic activities and its potential ability as adjuvant on the cellular and humoral immune responses of ICR mice against ovalbumin. The haemolytic activity of ARS was determined using 0.5% rabbit red blood cell. ARS showed a slight haemolytic effect, with its haemolytic percents being 16.50 and 3.56% at the concentrations of 500 and 250 microg/ml, respectively. ICR mice were immunized subcutaneously with OVA 100 microg alone or with OVA 100 mug dissolved in saline containing Alum (200 microg), QuilA (10 and 20 microg) or ARS (50, 100 or 200 microg) on Days 1 and 15. Two weeks later (Day 28), concanavalin A (Con A)-, lipopolysaccharide (LPS)- and OVA-stimulated splenocyte proliferation and OVA-specific antibodies in serum were measured. ARS significantly enhanced the Con A-, LPS-, and OVA-induced splenocyte proliferation in the OVA-immunized mice especially at a dose of 100 microg (P<0.01 or P<0.05). The OVA-specific IgG, IgG1 and IgG2b antibody levels in serum were also significantly enhanced by ARS compared with OVA control group (P<0.01 or P<0.05). Moreover, no significant differences (P>0.05) were observed between enhancing effect of ARS and QuilA on the OVA-specific IgG2b antibody responses to OVA in mice. The results suggest that ARS showed a slight haemolytic effect and enhanced significantly a specific antibody and cellular response against OVA in mice.

Determination of pseudojujubogenin glycosides from Brahmi based on immunoassay using a monoclonal antibody against bacopaside I

Bacopa monnieri (L.) Wettst. (Brahmi) is an Ayurvedic medicinal plant used for centuries as a memory enhancer. Dammarane-type triterpenoid saponins classified as pseudojujubogenin and jujubogenin glycosides are reported as the active components in this plant. In this study, the monoclonal antibody (MAb) against bacopaside I, a major pseudojujubogenin glycoside found in Brahmi, was produced and characterised. Bacopaside I was conjugated with bovine albumin serum to prepare an immunogen. Hybridomas secreting a monoclonal antibody against bacopaside I was produced by fusing splenocytes from an immunised mouse and SP2/0-Ag14 myeloma cells. The results showed that the antibodies were raised specifically against pseudojujubonin glycosides. An enzyme-linked immunosorbant assay (ELISA) using anti-bacopaside I MAb was performed in the range of 1.95-62.5 ng/mL of bacopaside I, with a limit of detection of 0.5 ng/mL. The method was validated and the practical use of the ELISA for analysing saponin glycosides from Brahmi was demonstrated.

Immunization of high-risk breast cancer patients with clustered sTn-KLH conjugate plus the immunologic adjuvant QS-21

PURPOSE

To determine the clinical toxicities and antibody response against sTn and tumor cells expressing sTn following immunization of high-risk breast cancer patients with clustered sTn-KLH [sTn(c)-KLH] conjugate plus QS-21.

EXPERIMENTAL DESIGN

Twenty-seven patients with no evidence of disease and with a history of either stage IV no evidence of disease, rising tumor markers, stage II (>or=4 positive axillary nodes), or stage III disease received a total of five injections each during weeks 1, 2, 3, 7, and 19. Immunizations consisted of sTn(c)-KLH conjugate containing 30, 10, 3, or 1 microg sTn(c) plus 100 microg QS-21. Induction of IgM and IgG antibodies against synthetic sTn(c) and natural sTn on ovine submaxillary mucin were measured before and after therapy. Fluorescence-activated cell sorting analyses assessed reactivity of antibodies to LSC and MCF-7 tumor cells.

RESULTS

The most common toxicities were transient local skin reactions at the injection site and mild flu-like symptoms. All patients developed significant IgM and IgG antibody titers against sTn(c). Antibody titers against ovine submaxillary mucin were usually of lower titers. IgM reactivity with LSC tumor cells was observed in 21 patients and with MCF-7 cells in 13 patients. There was minimal IgG reactivity with LSC cells.

CONCLUSION

Immunization with sTn(c)-KLH conjugate plus QS-21 is well tolerated and immunogenic in high-risk breast cancer patients. Future trials will incorporate sTn(c) as a component of a multiple antigen vaccine.

Vaccination against murine toxoplasmosis using recombinant Toxoplasma gondii SAG3 antigen alone or in combination with Quil A

PURPOSE

Surface antigen 3 (SAG3) of Toxoplasma gondii is very similar in structure to the major surface antigen 1 (SAG1). Although numerous studies have supported the importance of SAG1 in protection against T. gondii infection, few reports exist on SAG3.

MATERIALS AND METHODS

Glutathione-S-transferase (GST)-fused SAG3 of T. gondii (rSAG3) were immunized into BALB/c mice alone or in combination with Quil A (rSAG3/Quil A), and then evaluated the protective immunity in vivo and in vitro against murine toxoplasmosis.

RESULTS

Immunization with rSAG3 or rSAG3/Quil A resulted in significantly more survival days and fewer brain cysts after challenge with T. gondii compared to an infected control group. Mice immunized with rSAG3 alone or in combination with Quil A produced significantly more specific IgG2a antibody, whereas specific IgG1 antibody titers did not increase. The percentage of CD8+ T cells, IFN-gamma mRNA expression, and nitric oxide production significantly increased in rSAG3- and rSAG3/Quil A-immunized mice.

CONCLUSION

These results indicate that vaccination with Toxoplasma rSAG3 results in partial protective immunity against T. gondii infection through induction of a Th1-type immune response, and that protective immunity is accelerated by the modulating effects of Quil A.

Immunization of Rhesus monkeys with a SialylTn-mAb17-1A conjugate vaccine co-formulated with QS-21 induces a temporary systemic cytokine release and NK cytotoxicity against tumor cells

Tumor-associated antigens resulting from aberrant glycosylation, such as the SialylTn carbohydrate antigen, are frequently over-expressed on cancer cells and provide potential targets for cancer vaccination. Immunization of Rhesus monkeys with SialylTn coupled to a highly immunogenic carrier molecule and formulated on aluminum hydroxide induced a strong immune response against the carrier protein but only a moderate IgM immune response against the SialylTn carbohydrate antigen. Co-formulation with QS-21 adjuvant dramatically enhanced the anti-SialylTn immune response and resulted in a SialylTn-specific IgG switch. The kinetics of the carbohydrate-specific IgG response correlated with a temporary release of cytokines such as IFNgamma, IL-2, IL-1beta, TNFalpha and GM-CSF which was measurable in the immune serum by xMAP Multiplex technology. Furthermore, tumor cell killing by activated natural killer cells was induced. These data demonstrate that immunization with a tumor-associated carbohydrate antigen in a highly immunogenic formulation results in a temporary release of type 1 cytokines which may be required for the induction of a specific IgG immune response against the carbohydrate antigen as well as for activation of effector cells against tumor cells.

Phase I dose escalation safety and immunogenicity trial of Plasmodium falciparum apical membrane protein (AMA-1) FMP2.1, adjuvanted with AS02A, in malaria-naïve adults at the Walter Reed Army Institute of Research

We report the first safety and immunogenicity trial of the Plasmodium falciparum vaccine candidate FMP2.1/AS02A, a recombinant E. coli-expressed protein based upon the apical membrane antigen-1 (AMA-1) of the 3D7 clone formulated with the AS02A adjuvant. We conducted an open-label, staggered-start, dose-escalating Phase I trial in 23 malaria-naïve volunteers who received 8, 20 or 40microg of FMP2.1 in a fixed volume of 0.5mL of AS02A on a 0, 1, and 2 month schedule. Nineteen of 23 volunteers received all three scheduled immunizations. The most frequent solicited local and systemic adverse events associated with immunization were injection site pain (68%) and headache (29%). There were no significant laboratory abnormalities or vaccine-related serious adverse events. All volunteers seroconverted after second immunization as determined by ELISA. Immune sera recognized sporozoites and merozoites by immunofluorescence assay (IFA), and exhibited both growth inhibition and processing inhibition activity against homologous (3D7) asexual stage parasites. Post-immunization, peripheral blood mononuculear cells exhibited FMP2.1-specific lymphoproliferation and IFN-gamma and IL-5 ELISPOT assay responses. This is the first PfAMA-1-based vaccine shown to elicit both potent humoral and cellular immunity in humans. Encouraged by the potential of FMP1/AS02A to target host immunity against PfAMA-1 that is known to be expressed by sporozoite, hepatic and erythrocytic stages, we have initiated field trials of FMP2.1/AS02A in an endemic population in the Republic of Mali.

Therapeutic drug monitoring of digoxin: impact of endogenous and exogenous digoxin-like immunoreactive substances

Digoxin is a cardioactive drug with a narrow therapeutic range. Therapeutic drug monitoring is essential in clinical practice for efficacy as well as to avoid digoxin toxicity. Immunoassays are commonly used in clinical laboratories for determination of serum or plasma digoxin concentrations. Unfortunately, digoxin immunoassays are affected by both endogenous and exogenous compounds. Endogenous compounds are termed 'digoxin-like immunoreactive substances' (DLIS), which are found in elevated concentrations in volume-expanded patients. Exogenous compounds that interfere with digoxin assays are various drugs such as spironolactone, potassium canrenoate as well as Digibind (Fab fragment of antidigoxin antibody), which is used in treating life-threatening digoxin overdose. Moreover, various Chinese medicines such as Chan Su, Lu-Shen Wan and oleander-containing herbal preparations also interfere with serum digoxin measurements by immunoassays. Monitoring unbound (free) digoxin concentration may under certain circumstances eliminate such interferences. Clinicians should be aware of limitations of therapeutic drug monitoring of digoxin using immunoassays.

A model of experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice for the characterisation of intervention therapies

Multiple sclerosis (MS) and its different forms are studied in the animal model experimental autoimmune encephalomyelitis (EAE). Relapsing-remitting MS, the most common form of the disease can be induced in mice where clinical symptoms fluctuate in severity over time. However, the animal model does not experience periods of recovery where clinical signs are absent, unlike the human disease. We have developed a novel model of relapsing-remitting EAE in C57BL/6 mice immunised with myelin oligodendrocyte glycoprotein (MOG) peptide and Quil A as adjuvant. These animals have relapses that are followed by periods of recovery, during which time the animals do not exhibit illness. Furthermore, administration of the PPARgamma agonist pioglitazone prior to a predicted relapse prevents the expected development of symptoms in a dose-dependent fashion. Immune cell infiltration into white matter of the CNS and decreased production of inflammatory cytokine IFN-gamma in treated animals were also observed. Our model will be a valuable tool in assessing intervention therapies for RR-MS sufferers.

Priming with an adenovirus 35-circumsporozoite protein (CS) vaccine followed by RTS,S/AS01B boosting significantly improves immunogenicity to Plasmodium falciparum CS compared to that with either malaria vaccine alone

The RTS,S/AS02A protein-based vaccine consistently demonstrates significant protection against infection with Plasmodium falciparum malaria and also against clinical malaria and severe disease in children in areas of endemicity. Here we demonstrate with rhesus macaques that priming with a replication-defective human adenovirus serotype 35 (Ad35) vector encoding circumsporozoite protein (CS) (Ad35.CS), followed by boosting with RTS,S in an improved MPL- and QS21-based adjuvant formulation, AS01B, maintains antibody responses and dramatically increases levels of T cells producing gamma interferon and other Th1 cytokines in response to CS peptides. The increased T-cell responses induced by the combination of Ad35.CS and RTS,S/AS01B are sustained for at least 6 months postvaccination and may translate to improved and more durable protection against P. falciparum infection in humans.

Adjuvant-enhanced antibody responses to recombinant proteins correlates with protection of mice and monkeys to orthopoxvirus challenges

Recombinant proteins are being evaluated as smallpox and monkeypox vaccines because of their perceived safety compared to live vaccinia virus. Previously, we demonstrated that three or more injections of a Ribi-type adjuvant with a combination of three proteins from the outer membranes of intracellular (L1 protein) and extracellular (A33 and B5 proteins) forms of vaccinia virus protected mice against a lethal intranasal challenge with vaccinia virus. Here, we compared several adjuvants and found that QS-21 and to a lesser extent alum + CpG oligodeoxynucleotides accelerated and enhanced neutralizing antibody responses to a mixture of L1 and A33 proteins, provided the highest ratio of IgG2a to IgG1 isotype response, and protected mice against disease and death after only two immunizations 3 weeks apart. In addition, monkeys immunized with recombinant vaccinia virus proteins and QS-21 developed neutralizing antibody to monkeypox virus and had reduced virus load, skin lesions, and morbidity compared to the non-immunized group following monkeypox virus challenge.

Phase 1 randomized double-blind safety and immunogenicity trial of Plasmodium falciparum malaria merozoite surface protein FMP1 vaccine, adjuvanted with AS02A, in adults in western Kenya

We report the first trial of candidate malaria vaccine antigen FMP1, a 42kDa fragment from the C-terminus of merozoite surface protein-1 (MSP-1) from the 3D7 strain of Plasmodium falciparum, in an endemic area. Forty adult male and female residents of western Kenya were enrolled to receive 3 doses of either FMP1/AS02A or Imovax rabies vaccine by intra-deltoid injection on a 0, 1, 2 month schedule. Thirty-seven volunteers received all three immunizations and 38 completed the 12-month evaluation period. Slightly more recipients of the FMP1/AS02A vaccine experienced any instance of pain at 24 h post-immunization than in the Imovax group (95% versus 65%), but otherwise the two vaccines were equally safe and well-tolerated. Baseline antibody levels were high in both groups and were boosted in the FMP1/AS02A group. Longitudinal models revealed a highly significant difference between groups for both the average post-baseline antibody responses to MSP-1(42) (F1,335=13.16; P<0.001) and the Day 90 responses to MSP-1(42) (F1,335=16.69; P<0.001). The FMP1/AS02A vaccine is safe and immunogenic in adults and should progress to safety testing in children at greatest risk of malaria.

Evaluation of immunogenicity and efficacy of combined DNA and adjuvanted protein vaccination in a human immunodeficiency virus type 1/murine leukemia virus pseudotype challenge model

A DNA plasmid encoding human immunodeficiency virus type 1 (HIV-1) env, nef and tat genes was used in mice in a prime-boost immunization regimen with the corresponding recombinant proteins. The genetic immunogen was delivered with a gene gun and the proteins were injected intramuscularly together with the adjuvant AS02A. Immunizations were followed by experimental challenge with pseudotyped HIV-1 subtype A or B virus. In an initial experiment in which animals were challenged four weeks after the final immunization, all single modality and prime-boost vaccinations resulted in a significant level of protection as compared to control animals. There was a trend for DNA-alone immunization yielding the highest protection. In a subsequent study, a late challenge was performed 19 weeks after the final immunization. All groups having received the DNA vaccine, either alone or in combination with adjuvanted protein, exhibited strong protection against HIV replication. The subtype-specific protection against the experimental HIV challenge was significantly stronger than the cross-protection. Cellular and humoral immune responses were assessed during immunization and after challenge, but without clear correlation to protection against HIV replication. The data suggest that either DNA or protein antigens alone provide partial protection against an HIV-1/MuLV challenge and that DNA immunization is essential for achieving very high levels of efficacy in this murine HIV-1 challenge model. While prime-boost combinations were more immunogenic than DNA alone, they did not appear to provide any further enhancement over DNA vaccine mediated efficacy. The DNA immunogen might prime low levels of CD8+ T cells responsible for virus clearance or possibly a yet unidentified mechanism of protection.

An enzyme-linked immunosorbant assay using polyclonal antibodies against bacopaside I

Bacopa monnieri (L.) Wettst. (Brahmi) is a medicinal plant used as a memory enhancer in Ayurvedic medicines. Its active components are triterpenoid glycosides namely pseudojujubogenin and jujubogenin glycosides. In order to analyze these saponin glycosides, an enzyme-linked immunosorbant assay (ELISA) was developed using polyclonal antibodies against bacopaside I, one of the pseudojujubogenin glycosides found in the plant. Bacopaside I was conjugated with a bovine albumin serum (BSA) to prepare an immunogen. The bacopaside I-BSA conjugate was immunized to a rabbit for producing polyclonal antibodies (PAbs). The results showed that the antibodies were raised specifically against pseudojujubogenin glycosides. An ELISA using anti-bacopaside I PAbs was performed in the range of 1.95-62.5 ng mL(-1) of bacopaside I and the limit of detection was 0.1 ng mL(-1). The method was validated and the applicability of the ELISA for analyzing saponin glycosides from Brahmi was demonstrated.

Immune response in rhesus macaques after mixed modality immunisations with DNA, recombinant adenovirus and recombinant gp120 from human immunodeficiency virus type 1

The establishment of effective regimens for a vaccine against human immunodeficiency virus type 1 (HIV-1) is urgently needed. In the present study we have produced HIV-1 gp120 from a vaccine-relevant primary R5 isolate in recombinant vaccinia (rVV)-infected Vero cells. We have investigated the effect of boosting with this protein in mixed modality immunisations of rhesus macaques following different immunisation. As reported earlier, animals were primed with codon-optimised HIV-1(BX08)env DNA delivered as plasmid or as replication-deficient recombinant human adenovirus type 5 (rAd5), which both induced specific antibody and cellular immune responses (1). Boosting with rAd5 temporarily had increased the anti-gp120 antibody titres approximately 1 log (rAd5+rAd5) or 3 log (DNA+rAd5) (1). However, secondary rAd5 boosting showed less effect due to the induced vector-specific immunity. To further boost the antibody response, the rgp120(BX08) was injected with Quadri A saponin adjuvant. The protein boosting resulted in a 1-2 log antibody increase and also boosting of the cell-mediated immune response. Neutralising antibodies to the heterologous HIV-1(MN) were detected; however, neutralising antibodies to the primary HIV-1(Bx08) isolate were seen only transiently after rAd5 but not the rgp120 immunisation. It is concluded that the rgp120(Bx08) reagent from rVV-infected Vero cells is functional and immunogenic in macaques, inducing both antibody and cellular immunity. The rgp120(Bx08) is a relevant model antigen that may be used to boost antibody and cellular immunity in mixed modality vaccine regimens against HIV-1 in higher animals.

Natural killer T cells recognize diacylglycerol antigens from pathogenic bacteria

Natural killer T (NKT) cells recognize glycosphingolipids presented by CD1d molecules and have been linked to defense against microbial infections. Previously defined foreign glycosphingolipids recognized by NKT cells are uniquely found in nonpathogenic sphingomonas bacteria. Here we show that mouse and human NKT cells also recognized glycolipids, specifically a diacylglycerol, from Borrelia burgdorferi, which causes Lyme disease. The B. burgdorferi-derived, glycolipid-induced NKT cell proliferation and cytokine production and the antigenic potency of this glycolipid was dependent on acyl chain length and saturation. These data indicate that NKT cells recognize categories of glycolipids beyond those in sphingomonas and suggest that NKT cell responses driven by T cell receptor-mediated glycolipid recognition may provide protection against diverse pathogens.

Phase 1 safety and immunogenicity trial of malaria vaccine RTS,S/AS02A in adults in a hyperendemic region of western Kenya

We conducted a phase 1 trial of candidate malaria vaccine RTS,S/AS02A in western Kenya to determine its safety and immunogenicity in healthy adults in an area hyperendemic for malaria. Twenty adults were enrolled and received RTS,S/AS02A (50 microg of RTS,S in 0.5 mL of AS02A) by intramuscular injection on a 0-, 28-, and 178-day schedule. All 60 scheduled immunizations were given, and 18 of 20 volunteers completed the last study visit on day 210. The vaccine was safe and well-tolerated. There were no vaccine-related severe adverse events. The most common solicited adverse events associated with immunization were injection site pain and headache. The geometric mean concentration of antibodies to circumsporozoite protein was 1.9 microg/mL at baseline and it increased 2-4 weeks after each dose to 16, 17.8, and 36.6 microg/mL, respectively. These safety and immunogenicity data from adults in hyperendemic Kenya are comparable to data reported earlier from two trials in west African adults in hypo-endemic and meso-endemic areas of The Gambia. We conclude that in this small study, RTS,S/AS02A is safe and similarly immunogenic in malaria-exposed African adults of different ethnicity in different transmission settings.

Immunogenicity of Liposomes Containing Lipid Core Peptides and the Adjuvant Quil A

PURPOSE

The purpose of this study was to investigate the immunogenicity of liposomes containing mannosylated lipid core peptide (manLCP) constructs, both in vitro and in vivo, with or without the addition of the immune stimulating adjuvant Quil A.

METHODS

Mouse bone marrow dendritic cells (BMDC) were cultured with liposome formulations for 48 h, and the resulting level of BMDC activation was determined by flow cytometry. BMDC pulsed with liposome formulations were incubated with 5,6-carboxyfluoroscein diacetate succinimidyl ester-labeled T cells for 72 h and the resulting T cell proliferation was determined by flow cytometry. To investigate the immunogenicity of formulations in vivo, groups of C57Bl/6J mice were immunized by subcutaneous injection, and the resulting antigen-specific cytotoxic and protective immune responses toward tumor challenge evaluated.

RESULTS

Despite being unable to demonstrate the activation of BMDC, BMDC pulsed with liposomes containing manLCP constructs were able to stimulate the proliferation of naïve T cells in vitro. However, in vivo only liposomes containing both manLCP and Quil A were able to stimulate a strong antigen-specific cytotoxic immune response. Liposomes containing manLCP and Quil A within the same particle were able to protect against the growth of tumor cells to a similar level as if the antigen was administered in alum with CD4 help.

CONCLUSION

ManLCPs administered in liposomes are able to stimulate strong cytotoxic and protective immune responses if Quil A is also incorporated as an adjuvant.

Immunogenicity of a recombinant protein containing the Plasmodium vivax vaccine candidate MSP1(19) and two human CD4+ T-cell epitopes administered to non-human primates (Callithrix jacchus jacchus)

One of the most promising vaccine candidates against the erythrocytic forms of malaria is the 19 kDa C-terminal region of the merozoite surface protein 1 (MSP1(19)). As part of our studies aimed at the development of a Plasmodium vivax malaria vaccine, we characterized the immunogenic properties of a new bacterial recombinant protein containing the P. vivax MSP1(19) and two helper T-cell epitopes, the synthetic universal pan allelic DR epitope (PADRE) and a new internal MSP1 P. vivax epitope (DYDVVYLKPLAGMYK). We found that the recognition of His6MSP1(19)-DYDVVYLKPLAGMYK-PADRE was as good as the recognition of His6MSP1(19) indicating that the presence of the T-cell epitopes PADRE and DYDVVYLKPLAGMYK did not modify the MSP1(19) epitopes recognized by human IgG. The recombinant protein His6MSP1(19)-DYDVVYLKPLAGMYK-PADRE proved to be highly immunogenic in marmosets (Callithrix jacchus jacchus) when administered in incomplete Freund's adjuvant. However, when administered in other adjuvant formulations such as Quil A, CpG ODN 2006 or MPL/TDM, antibody titers to MSP1(19) were significantly lower. Among these three adjuvants, Quil A proved to be the most efficient one generating antibody titers significantly higher than the others. These results indicated that under the circumstances evaluated, adjuvants were key for the immunogenicity of the recombinant protein His6MSP1(19)-DYDVVYLKPLAGMYK-PADRE.

Evaluation of the Mtb72F polyprotein vaccine in a rabbit model of tuberculous meningitis

Using a rabbit model of tuberculous meningitis, we evaluated the protective efficacy of vaccination with the recombinant polyprotein Mtb72F, which is formulated in two alternative adjuvants, AS02A and AS01B, and compared this to vaccination with Mycobacterium bovis bacillus Calmette-Guérin (BCG) alone or as a BCG prime/Mtb72F-boost regimen. Vaccination with Mtb72F formulated in AS02A (Mtb72F+AS02A) or Mtb72F formulated in AS01B (Mtb72F+AS01B) was protective against central nervous system (CNS) challenge with Mycobacterium tuberculosis H37Rv to an extent comparable to that of vaccination with BCG. Similar accelerated clearances of bacilli from the cerebrospinal fluid, reduced leukocytosis, and less pathology of the brain and lungs were noted. Weight loss of infected rabbits was less extensive for Mtb72F+AS02A-vaccinated rabbits. In addition, protection against M. tuberculosis H37Rv CNS infection afforded by BCG/Mtb72F in a prime-boost strategy was similar to that by BCG alone. Interestingly, Mtb72F+AS01B induced better protection against leukocytosis and weight loss, suggesting that the polyprotein in this adjuvant may boost immunity without exacerbating inflammation in previously BCG-vaccinated individuals.

CpG oligonucleotides enhance the tumor antigen-specific immune response of an anti-idiotype antibody-based vaccine strategy in CEA transgenic mice

A murine monoclonal anti-idiotype (Id) antibody, 3H1 has been developed and characterized previously. Anti-Id 3H1 mimics a specific epitope of carcinoembryonic antigen (CEA) and can be used as a surrogate antigen for CEA. 3H1 induced anti-CEA immunity in different species of animals as well as humans and showed promise as a potential vaccine candidate in phase I/II clinical trials for colon cancer patients. One area of interest to us has been the development of new immune adjuvants that may augment the potency of 3H1 as a tumor vaccine. Oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODN) are potent immunostimulatory agents capable of enhancing the Ag-specific Th1 response when used as immune adjuvants. In this study, we have evaluated the efficacy of 3H1 as a tumor vaccine when admixed with a select CpG ODN 1826 in transgenic mice that express human CEA. The vaccine potential of 3H1 was also assessed in the presence of another widely used adjuvant, QS-21. 3H1 coupled to keyhole limpet hemocyanin (KLH) and mixed with Freund's adjuvant (FA) was used as a gold standard in this system. 3H1 vaccination with different adjuvants induced both humoral and cellular anti-3H1, as well as anti-CEA immunity in CEA transgenic mice. The immune sera could lyse CEA-transfected murine colon carcinoma cells, C15 effectively in an antibody-dependent cellular cytotoxicity assay. The anti-CEA antibody responses were somewhat comparable in each adjuvant-treated group of mice, whereas cellular immune responses were significantly greater when CpG was used as an adjuvant. Splenocytes obtained from 3H1-CpG-immunized mice showed an increased proliferative CD4(+) Th1-type T-cell response when stimulated in vitro with 3H1 or CEA and secreted elevated levels of Th1 cytokines (IL-2, IFN-gamma). This vaccine also induced MHC class I antigen-restricted CD8(+) T-cell responses. In a solid tumor model, C15 tumor growth was significantly inhibited by 3H1 vaccinations. In 3H1-CpG-vaccinated mice, the duration of survival was, however, longer compared to the 3H1-QS21-vaccinated mice. These findings suggest that 3H1-CpG vaccinations can break peripheral tolerance to CEA and induce protective antitumor immunity in this murine model transgenic for human CEA.

Local immune responses following nasal delivery of an adjuvanted influenza vaccine

A key barrier to producing effective nasal immunisations is the low efficiency of uptake of vaccines across the nasal mucosa. Using a recently developed cannulation system, we examined the antibody response induced by nasal immunisation with an ISCOMATRIX influenza vaccine. This showed for the first time, that following nasal vaccination, specific antibodies enter the circulation of primed animals via the draining lymphatics as a wave that peaks approximately 5-6 days after vaccination. These antibodies included some of the IgA isotype and possessed functional haemagglutination inhibition activity. These responses, though small, were induced using a very simple delivery system, emphasising the applicability of this cannulation model for evaluation of excipients and adjuvants aimed at improving intranasal vaccine efficacy.