BCG-primed Mice Research Articles

Immunogenicity and protective efficacy of heterologous prime-boost regimens with mycobacterial vaccines and recombinant adenovirus- and poxvirus-vectored vaccines against murine tuberculosis

To evaluate regimens using bacillus Calmette-Guérin (BCG) or recombinant BCG (rBCG) overexpressing Ag85B for priming, followed by boosting with a modified vaccinia virus Ankara strain (MVA) and/or adenovirus vector (AD) expressing an Ag85B-ESAT6 fusion protein. Cellular and humoral immune responses were determined after subcutaneous vaccination, which was employed to trigger systemic immunity against intravenous infection in a mouse model of tuberculosis (TB). Bacterial loads and lung histology were evaluated. The relative IgG2a and IgG1 antibody levels indicated that the viral-vectored vaccines generated a T-helper type 1 (Th1)-biased response after two doses of viral boost vaccinations. Boosting BCG-primed mice with viral vaccines induced a Th1 immune response that included both CD4 and CD8 T-cells generating antigen-specific interferon-gamma (IFN-γ) and CD8 T cytotoxic activity. Only mice vaccinated with two different viral boosters after BCG priming exhibited a significant reduction in bacterial burden in the lung after challenge. Histology examinations confirmed the attenuation of lung damage and more compact granulomas. After mycobacteria priming, boosting with AD85B-E6 followed by MVA85B-E6 afforded better protection than the reverse order of administration of the viral vectors. This study demonstrates the potential of multiple heterologous viral booster vaccines, although the exact correlates of protection and optimal regimens should be further investigated for the rational design of future vaccine strategies.

Recombinant HBHA Boosting Effect on BCG-Induced Immunity againstMycobacterium tuberculosisInfection

Heterologous prime-boost regimens are effective strategies to promote long-term memory and strong cellular Th1 responses to Mycobacterium tuberculosis, when BCG is used in the priming step. Subcutaneous or intranasal boosting of BCG-vaccinated newborn mice with native heparin-binding haemagglutinin (nHBHA) significantly enhances protection against M. tuberculosis. However, nHBHA is characterized by a complex methylation pattern in its C-terminal domain, which is important for protective immunogenicity in primary vaccination. In this study we addressed the question whether boosting with recombinant, non-methylated HBHA (rHBHA) produced in Escherichia coli may enhance protection of BCG-primed newborn mice. We found that while subcutaneous rHBHA boosting enhanced protection of BCG-primed mice against intranasal M. tuberculosis infection both in spleen and lungs, enhanced protection against aerosol infection was only seen in the spleen (0.72 logs; P < 0.05) but not in the lungs. Thus, in BCG-primed mice the methylation of the C-terminal domain of HBHA is dispensable for the induction of enhanced protection in the lungs against intranasal but not aerosol infection, whereas it enhances protection in the spleen in both challenge models. This report thus provides evidence that rHBHA may be considered as a booster vaccine against disseminated tuberculosis.

In vivo hepatoprotective activity of the aqueous extract of Artemisia absinthium L. against chemically and immunologically induced liver injuries in mice

Aim of the study This study aimed to evaluate in vivo hepatoprotective activity of the aqueous extract of Artemisia absinthium L. (AEAA), which has been used for the treatment of liver disorders in Traditional Uighur Medicine. Materials and methods Qualitative and quantitative phytochemical analysis of the AEAA was performed by means of thin layer chromatography and spectrophometric assays. Aqueous extract (50, 100 or 200 mg/kg body weight/day) was administered orally to experimental mice. Liver injury was induced chemically, by a single CCl 4 administration (0.1% in olive oil, 10 ml/kg, i.v.), or immunologically, by injection of endotoxin (LPS, 10 μg, i.v.) in BCG-primed mice. The levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) in mouse sera, as well as superoxide dismutase (SOD), glutathione peroxidase (GPx) and malondialdehyde (MDA) in mouse liver tissues were measured. The biochemical observations were supplemented by histopathological examination. Results Obtained results demonstrated that the pretreatment with AEAA significantly ( P < 0.001) and dose-dependently prevented chemically or immunologically induced increase in serum levels of hepatic enzymes. Furthermore, AEAA significantly ( P < 0.05) reduced the lipid peroxidation in the liver tissue and restored activities of defense antioxidant enzymes SOD and GPx towards normal levels. In the BCG/LPS model, increase of the levels of important pro-inflammatory mediators TNF-α and IL-1 was significantly ( P < 0.01) suppressed by AEAA pretreatment. Histopathology of the liver tissue showed that AEAA attenuated the hepatocellular necrosis and led to reduction of inflammatory cells infiltration. Phytochemical analyses revealed the presence of sesquiterpene lactones, flavonoids, phenolic acids and tannins in the AEAA. Conclusions The results of this study strongly indicate the protective efect of AEAA against acute liver injury which may be attributed to its antioxidative and/or immunomodulatory activity, and thereby scientifically support its traditional use.

Boosting with mycobacterial heparin-binding haemagglutinin enhances protection of Mycobacterium bovis BCG-vaccinated newborn mice against M. tuberculosis

Heterologous prime-boost regimens are a valuable strategy to improve the generation of effector-memory T cell responses against intracellular pathogens. In this study we show that newborn mice vaccinated with bacillus Calmette-Guérin (BCG) and boosted with heparin-binding haemagglutinin (HBHA) had enhanced protective immunity against intranasal or aerosol Mycobacterium tuberculosis challenge over non-boosted mice, as evidenced by a considerable reduction of mycobacterial load in spleen and lung. The route of HBHA delivery had a differential impact on cytokine and antibody production in BCG-primed mice. The prime-boost regimen induced not only HBHA-specific IFN-γ, but also other cytokines, such as IL-12 and TGF-β, which may be associated with the generation of lung Th1 effector-memory lymphocytes, responsible for the enhanced protection against M. tuberculosis challenge.

Analysis of binding site for the novel small-molecule TLR4 signal transduction inhibitor TAK-242 and its therapeutic effect on mouse sepsis model.

TAK-242, a novel synthetic small-molecule, suppresses production of multiple cytokines by inhibiting Toll-like receptor (TLR) 4 signalling. In this study, we investigated the target molecule of TAK-242 and examined its therapeutic effect in a mouse sepsis model. Binding assay with [(3)H]-TAK-242 and nuclear factor-kappaB reporter assay were used to identify the target molecule and binding site of TAK-242. Bacillus calmette guerin (BCG)-primed mouse sepsis model using live Escherichia coli was used to estimate the efficacy of TAK-242 in sepsis. TAK-242 strongly bound to TLR4, but binding to TLR2, 3, 5, 9, TLR-related adaptor molecules and MD-2 was either not observed or marginal. Mutational analysis using TLR4 mutants indicated that TAK-242 inhibits TLR4 signalling by binding to Cys747 in the intracellular domain of TLR4. TAK-242 inhibited MyD88-independent pathway as well as MyD88-dependent pathway and its inhibitory effect was largely unaffected by lipopolysaccharide (LPS) concentration and types of TLR4 ligands. TAK-242 had no effect on the LPS-induced conformational change of TLR4-MD-2 and TLR4 homodimerization. In mouse sepsis model, although TAK-242 alone did not affect bacterial counts in blood, if co-administered with ceftazidime it inhibited the increases in serum cytokine levels and improved survival of mice. TAK-242 suppressed TLR4 signalling by binding directly to a specific amino acid Cys747 in the intracellular domain of TLR4. When co-administered with antibiotics, TAK-242 showed potent therapeutic effects in an E. coli-induced sepsis model using BCG-primed mice. Thus, TAK-242 may be a promising therapeutic agent for sepsis.

Antigen-dependent in vitro culture of protective T cells from BCG-primed mice.

Induction of protective immunity against pathogenic mycobacteria depends on vaccination with live organisms such as Bacille Calmette-Guérin (BCG). However, it is not known how many and which antigens are involved in the protective host response. In this study, we developed a system of antigen-dependent in vitro culture which is suitable for the analysis of protective subunits, presented in a soluble form. Spleen cells from Mycobacterium bovis BCG-immune mice, enriched for T cells and depleted of adherent cells on a column of G-10 Sephadex, were cultured for periods varying between 3 and 14 days before transfer and challenge with M. tuberculosis in irradiated hosts. Following 10 days in culture, immune T cells sustained their capacity to transfer protection to tuberculous infection when incubated in the presence of either live BCG or a soluble extract from M. tuberculosis, but lost this ability when cultured in the absence of antigen, or in the presence of the polyclonal mitogen concanavalin A. One immunodominant antigen, represented by the recombinant 38-kD antigen, failed to sustain the adoptive protection, despite pronounced stimulation of lymphoproliferation in culture. Antigenic in vitro stimulation of protective T cells was accompanied by enhanced responsiveness to exogenous IL-2. The experimental system described may be generally suitable to test in vitro the protective potentials of soluble molecular subunits of mycobacteria.

Mycophenolate mofetil prevents lethal acute liver failure in mice induced by bacille Calmette‐Guérin and lipopolysaccharide

To investigate the effect of mycophenolate mofetil (MMF) on acute liver injury induced by bacille Calmette-Guérin (BCG) and lipopolysaccharide (LPS). Acute liver failure was induced in male Kunming strain mice by injecting the animals with BCG 2.5 mg per mouse, and LPS 10 microg per mouse 10 days later. The mice in the treatment groups were given MMF 2 h before, simultaneous with, or 2 h after administration of LPS, and the mice in the control group were given the same dose of saline. The 24-h survival rate, serum alanine aminotransferase (ALT), and aspartate aminotransferase (AST) levels were compared. Serum levels of tumor necrosis factor alpha (TNF-alpha), interferon gamma (IFN-gamma), and interleukin 6 (IL-6) were measured and the expressions of TNF-alpha, IFN-gamma, and IL-6 mRNA in the liver tissue were determined by reverse transcription-polymerase chain reaction (RT-PCR). Concanavalin A (Con A)-induced splenocyte proliferation were determined by methods of methyl thiazolyl tetrazolium. Injecting a small dose of LPS into BCG-primed mice caused a lethal hepatic injury mimicking acute hepatitis, from which 16 of the 20 mice died within 24 h (20% survival rate). Massive necrosis of parenchymal hepatocytes with marked inflammatory cell infiltration was observed by histological examination. In parallel, serum ALT and TNF-alpha, IFN-gamma, and IL-6 levels were increased. Expression of TNF-alpha, IFN-gamma, and IL-6 mRNA in the liver were significantly increased also. Treatment with MMF markedly reduced the death rate in a dose-dependent manner. It reached its maximal effect at the dosage of 150 mg per kg of body weight when pretreated 2 h before LPS injection, with improvement of histological feather and survival rate (84.2%, 16/19). MMF significantly inhibited serum levels of TNF-alpha, IFN-gamma, and IL-6, and significantly reduced TNF-alpha, IFN-gamma, and IL-6 expression in the liver, which increased after BCG and LPS injection. Moreover, splenocyte proliferation response induced by Con A was also inhibited by MMF treatment. Treatment with MMF has a protective effect on endotoxin-induced fatal liver failure by regulating the production of inflammatory cytokines and T-cell proliferation.

Involvement of Up-Regulated CXC Chemokine Ligand 16/Scavenger Receptor That Binds Phosphatidylserine and Oxidized Lipoprotein in Endotoxin-Induced Lethal Liver Injury via Regulation of T-Cell Recruitment and Adhesion

A murine model of endotoxin-induced lethal liver injury induced by Mycobacterium bovis BCG plus lipopolysaccharide (LPS) has been widely accepted and used. It has been reported that T cells play an important role in the pathogenesis of liver damage in this model. However, the precise mechanisms involved in regulation of the trafficking of effector T cells need to be elucidated. In the present study, we first reported that CXCL16/SR-PSOX (CXC chemokine ligand 16/scavenger receptor that binds phosphatidylserine and oxidized lipoprotein), a chemokine containing both membrane-anchored and soluble forms, was strongly up-regulated and predominantly distributed in the vascular endothelium in the injured liver tissue in the model. The secretory and membrane-anchored CXCL16/SR-PSOX functioned as a chemokine and an adhesive molecule, respectively, to attract T cells to a tumor necrosis factor alpha-activated endothelial cell line (SVEC) in vitro. To further identify the pathophysiological roles of CXCL16/SR-PSOX in the liver injury, the anti-CXCL16 antibody was administered to the BCG-primed mice before LPS challenge in vivo. Significant protection effects were observed with 70% of mice regarding lethality, the massive necrosis in the liver was reduced, and the intrahepatic infiltrating T cells were significantly inhibited. Taken together, these findings strongly suggest that functional CXCL16/SR-PSOX, as both a chemokine and an adhesion molecule, may be involved in the pathogenesis of the endotoxin-induced lethal liver injury via recruitment and adhesion of activated T cells to the vascular endothelium.

Overexpression of Interleukin-15 increases susceptibility to lipopolysaccharide-induced liver injury in mice primed with Mycobacterium bovis bacillus Calmette-Guerin.

Mice primed with Mycobacterium bovis bacillus Calmette-Guérin (BCG) are highly sensitive to lipopolysaccharide (LPS)-induced liver injury and lethality. We found that interleukin-15 (IL-15) transgenic (Tg) mice primed with BCG were more susceptible to LPS-induced liver injury than non-Tg mice. The numbers of CD44+ CD8+ T cells expressing intracellular gamma interferon (IFN-gamma) significantly increased in the livers of BCG-primed IL-15 Tg mice after LPS injection, and the depletion of CD8+ T cells from BCG-primed IL-15 Tg mice completely abolished the susceptibility to LPS-induced lethality. Liver T cells from BCG-primed IL-15 Tg mice produced IFN-gamma in vitro in response to LPS, which was inhibited by the addition of anti-IL-12 monoclonal antibody (MAb). In vivo treatment with anti-IL-12 MAb inhibited the appearance of CD44+ CD8+ T cells expressing intracellular IFN-gamma after LPS injection. These results suggest that the overexpression of IL-15 increases susceptibility to LPS-induced liver injury in BCG-primed mice via bystander activation of CD8+ T cells.

Suppression of murine endotoxin response by E5531, a novel synthetic lipid A antagonist.

As a consequence of blood-borne bacterial sepsis, endotoxin or lipopolysaccharide (LPS) from the cell walls of gram-negative bacteria can trigger an acute inflammatory response, leading to a series of pathological events and often resulting in death. To block this inflammatory response to endotoxin, a novel lipid A analogue, E5531, was designed and synthesized as an LPS antagonist, and its biological properties were examined in vitro and in vivo. In murine peritoneal macrophages, E5531 inhibited the release of tumor necrosis factor alpha (TNF-alpha) by Escherichia coli LPS with a 50% inhibitory concentration (IC50) of 2.2 nM, while E5531 elicited no significant increases in TNF-alpha on its own. In support of a mechanism consistent with antagonism of binding to a cell surface receptor for LPS, E5531 inhibited equilibrium binding of radioiodinated LPS ([125I]2-(r-azidosalicylamido)-1, 3'-dithiopropionate-LPS) to mouse macrophages with an IC50 of 0.50 microM. E5531 inhibited LPS-induced increases in TNF-alpha in vivo when it was coinjected with LPS into C57BL/6 mice primed with Mycobacterium bovis bacillus Calmette-Guérin (BCG). In this model, the efficacy of E5531 was inversely correlated to the LPS challenge dose, consistent with a competitive antagonist-like mechanism of action. Blockade of the inflammatory response by E5531 could further be demonstrated in other in vivo models: E5531 protected BCG-primed mice from LPS-induced lethality in a dose-dependent manner and suppressed LPS-induced hepatic injury in Propionibacterium acnes-primed or galactosamine-sensitized mice. These results argue that the novel synthetic lipid A analogue E5531 can antagonize the action of LPS in in vitro and suppress the pathological effects of LPS in vivo in mice.

A lipid A analog inhibits LPS-induced cytokine expression and improves survival in endotoxemic mice.

It has recently been shown that inactive disaccharidic analogs of lipid A, an essential structure of lipopolysaccharide (LPS), may act as LPS antagonists which would be effective against septic shock induced by gram-negative bacteria endotoxin. In the present study we examined the inhibitory effect of DY-9973, a synthetic monosaccharidic lipid A analog, on LPS-induced cytokine expression in macrophages and lethal toxicity in mice. DY-9973 inhibited TNF-alpha production induced by LPS in human monocytes and monoblastic U937 cells. Expression of cytokine mRNAs such as TNF-alpha and IL-1 beta induced by LPS was inhibited by treatment with DY-9973 in U937 cells. Meanwhile, DY-9973 did not inhibit IL-1 beta-induced TNF-alpha production in U937 cells. TNF-alpha production induced by LPS or IL-1 beta was similarly inhibited by treatment with herbimycin, a tyrosine kinase inhibitor. Pretreatment with DY-9973 inhibited the elevation of serum TNF-alpha activity induced by the injection of LPS and reduced the lethal toxicity of LPS in BCG-primed mice. These results suggest that monosaccharidic lipid A analog such as DY-9973 can inhibit LPS-induced activation of macrophages and that it reduces lethal toxicity of LPS.

Specificity of antibodies raised against a specific phosphoromonothioate oligonucleotide sequence

The phosphoromonothioate oligonucleotide HPV (human papilloma virus) sequence (monothioate HPV) 5′-TTG, CTT,CCA,TCT,TCC,TCG,TC-3′ was photocoupled via three different sites (the 5′-end, the 3′-end and the midpoint) to PPD (purified protein derivative) and OA (ovalbumin), and the three types of conjugates (5′-HPV/carrier, 3′-HPV/carrier and midpoint-HPV/carrier) were used for the immunization of mice. Furthermore, a group of mice were immunized with the HPV sequence alone. No detectable antibody response against the monothioate HPV oligonucleotide was seen in mice receiving only the unconjugated monothioate HPV sequence. The OA-coupled monothioate HPV sequence also failed to elicit a detectable antibody response against the monothioate HPV oligonucleotide. However the PPD-conjugated monothioate HPV sequences induced a significant anti-monothioate HPV antibody response in BCG (bacille Calmette Guérin)-primed mice, a result that must be ascribed to the effect of using PPD as a carrier in BCG-primed mice. The antisera from all groups were tested on plates coated with the corresponding OA conjugates. By far the strongest response was obtained in mice receiving the HPV sequence coupled at the midpoint position. Further, all three groups of antisera obtained by immunizing with the different PPD conjugates were tested on microtiter plates coated with one of the three different OA conjugates. The antisera differed in their response depending on which OA conjugate was used for coating of the plate. Again, the midpoint-HPV/PPD antiserum showed the highest response, and this conjugate apparently represents the most efficient immunogen. Results from inhibition experiments with various relevant analogs of the monothioate HPV sequence showed that the three antiserum pools contained antibodies predominantly directed against the conformation of the monothioate backbone structure, but that at least a subpopulation of the antibodies recognized structures, which depended on the specific HPV base sequence.

Interleukin‐12 is required for interferon‐γ production and lethality in lipopolysaccharide‐induced shock in mice

Several cytokines, in particular tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), have been shown to be responsible for pathological reactions which may lead to shock and death observed in infection with Gram-negative bacteria and in response to endotoxins (lipopolysaccharides, LPS). Priming of mice with the avirulent Bacille Calmette Guérin (BCG) vaccine strain of Mycobacterium bovis increases the sensitivity of mice to the lethal effect of LPS and results in an efficient priming for cytokine production. In response to low doses (1 microgram/mouse) of LPS, BCG-primed mice produce interleukin-12 (IL-12) which controls IFN-gamma production, as demonstrated by the ability of neutralizing anti-IL-12 antibodies to suppress IFN-gamma production. However, the concentration of the biologically active IL-12 p70 heterodimer is similar in the serum of both BCG-primed or unprimed mice, reaching levels of 1-3 ng/ml at 3-6 h after LPS injection, whereas IFN-gamma production was observed only in BCG-primed mice. The priming effect of BCG on IFN-gamma production appears to be mostly due to its ability to increase TNF-alpha production, which acts as cofactor with LPS-induced IL-12 in inducing IFN-gamma production, as shown by the ability of injection of TNF-alpha and LPS (1 microgram/mouse), but not LPS alone, to induce IFN-gamma production. However, in addition to TNF-alpha, other LPS-induced cofactor(s) are required in cooperation with IL-12 to induce optimal IFN-gamma production, because co-injection of TNF-alpha and IL-12, sufficient to induce serum concentrations of both cytokines higher and more persistent than those obtained by injection of LPS, was not sufficient to induce IFN-gamma production in vivo. Neutralizing anti-IL-12 antibodies, in addition to inhibiting the in vivo LPS-induced IFN-gamma production, also completely protect BCG-primed mice injected with up to 10 micrograms of LPS from shock-induced death. Thus, IL-12 is required for IFN-gamma production and lethality in an endotoxic shock model in mice.

Mycobacterium bovis BCG priming induces a strong potentiation of the antibody response induced by recombinant BCG expressing a foreign antigen.

Several recent studies have demonstrated that strong cellular or humoral immune responses can be induced against foreign antigens expressed by recombinant Mycobacterium bovis BCG. It has therefore been suggested that BCG could represent one of the best candidate vectors for live recombinant vaccines. However, a large percentage of the human population has been immunized by BCG, and this priming could modify the immune response to future recombinant BCG vaccines. In the present study, we have therefore compared the immune responses induced in naive and BCG-primed mice by two recombinant BCG vaccines expressing either beta-galactosidase or human immunodeficiency virus type 1 Nef antigens. Our results demonstrated that BCG priming limits the growth of recombinant BCG in mouse spleen or lymph nodes. This reduction in BCG growth was associated with decreased proliferative responses against Nef or beta-galactosidase antigens. This suppression, however, never exceeded 50%. Interestingly, in contrast to these reduced T-cell responses, BCG-primed mice developed high levels of anti-beta-galactosidase antibodies after immunization with recombinant BCG expressing this antigen. This stimulation of antibody responses was not due to polyclonal stimulation or to a nonspecific adjuvant effect of BCG. The isotypic patterns of anti-beta-galactosidase antibody responses induced by the recombinant BCG were similar in naive and BCG-primed mice. These results indicate that priming with BCG will not be a limitation for the use of recombinant BCG vaccines in humans.

Endogenous production of tumor necrosis factor in normal mice orally treated with deodan — A preparation from Lactobacillus bulgaricus “LB51”

The ability of orally administered Deodan, a product from the cell wall of Lactobacillus bulgaricus strain ″I. Bogdanov patent strain tumoronecroticane B51″ ATCC #21815, shortly called “LB51”, to induce endogenous tumor necrosis factor-alpha (TNFα) production in normal mice was evaluated. The priming and triggering activities of the preparation were investigated in combination with lipopolysaccharide (LPS) and live BCG vaccine. Deodan was applied at a dose of 150 mg/kg and various treatment schedules were employed. The serum levels of TNFα in treated mice were quantified by ELISA. Oral administration of Deodan at a dose of 150 mg/kg for 1, 3, 10 or 20 consecutive days only enhanced serum TNFα levels in treated mice. Maximal TNFα levels were reached 6 h after the last application of Deodan. Deodan was effective in priming TNFα in mice triggered intravenously (i.v.) with LPS. Deodan triggered the production of TNFα in BCG-primed mice. The preparation, however, was not an effective trigger of mice primed intradermally (i.d.) with 1 μg/ mouse LPS. These findings suggest that Deodan is both a primer and trigger of endogenous TNFα. The advantages of treatment of neoplastic disease with agents which induce endogenous TNFα is discussed.

Induction of polyclonal antibodies to the S1 subunit of pertussis toxin by synthetic peptides coupled to PPD: Effect of conjugation method, adjuvant, priming and animal species

Two peptides, designated L and K, covering a sequence near the NH-terminal end of the S1 subunit of pertussis toxin (PT) were conjugated to the PPD (purified protein derivative) of M. tuberculosis by either glutaraldehyde (GLUT) or succinimidyl 4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC) and N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) and injected into groups of mice and guinea pigs. Initially, the effect of priming the animals with BCG vaccine and the use of aluminium hydroxide as adjuvant for the anti-peptide antibody response was studied. The group of BCG-primed mice immunized with adsorbed peptide conjugates showed the highest anti-peptide conjugate antibody response. Based on this finding, groups of BCG-primed mice were immunized four times with either adsorbed peptide L-GLUT, peptide L-SMCC/SPDP or peptide K-SMCC/SPDP conjugates and the fine peptide specificity as well as the PT and S1 cross-reactivity was investigated in ELISA. Mice immunized with peptide L-GLUT showed a significant antibody response to the homologous conjugate, only, whereas the group injected with the peptide L-SMCC/SPDP conjugate gave a significant response to both peptide K and L conjugated by the SMCC-SPDP method. Likewise, mice immunized with the peptide K-SMCC/SPDP conjugate reacted with the homologous and peptide L-SMCC/SPDP conjugate, although only the response to the former conjugate was significantly greater than the response to PPD. All groups showed a strong anti-PPD response. The anti-PT/S1 cross-reactivity of the antisera varied considerably within each group but was found to be highest in the peptide L-GLUT-immunized animals. The results of the present study not only stress the importance of BCG priming and use of aluminium hydroxide adjuvants for the immunogenicity of the peptides in question but also point to the specificity of the conjugation methods employed as low cross-reactivity between the anti-peptide L-GLUT and L-SMCC/SPDP antisera was noted. Moreover, it appeared that the choice of conjugation method may have an effect on the ability of the peptide conjugates to induce an antibody response cross-reacting with the native protein.

Mycobacterial heat‐shock proteins as carrier molecules

We have previously shown that the priming of mice with live Mycobacterium tuberculosis var. bovis (Bacillus Calmette-Guérin, BCG) and immunization with the repetitive malaria synthetic peptide (NANP)40 conjugated to purified protein derivative (PPD), led to the induction of high and long-lasting titers of anti-peptide IgG antibodies, overcoming the requirement of adjuvants and the genetic restriction of the antibody response to the peptide (Lussow et al., Proc. Natl. Acad. Sci. USA 1990. 87:2960). This initial work led us to the following observations. BCG had to be live for priming to lead to the induction of anti-peptide antibodies. Surprisingly, priming with other living microorganisms which chronically infect the macrophage (e.g. Salmonella typhimurium and Leishmania major) also induced anti-peptide antibodies in mice immunized with PPD-(NANP)40 conjugate. It was, thus, hypothesized that molecules expressed during active infection and also known to be highly conserved between species, namely the heat-shock proteins (hsp), could mediate the T cell sensitization required for the production of anti-peptide antibodies. In fact, when the PPD protion of the conjugate was replaced by a highly purified recombinant protein corresponding to the 65-kDa (GroEL-type) hsp of M. bovis, this resulted in the production of anti-(NANP) IgG antibodies in BCG-primed mice, irrespective of the major histocompatibility complex-controlled responsiveness to the (NANP) sequence itself. Further, similar induction of anti-peptide antibody response was also obtained with a recombinant 70-kDa (DnaK-type) hsp of M. tuberculosis, but not with a small molecular mass (18 kDa) of M. leprae. Finally, an adjuvant-free carrier effect for anti-peptide IgG antibody production in BCG-primed mice, was also exerted by the GroEL hsp of Escherichia coli. This finding that hsp can act as carrier molecules without requiring conventional adjuvants is of potential importance in the development of vaccine strategies.

Effects ofE. Coli0111.B4 Lipopolysaccharide on Spin-Labelled Murine Macrophage and Hepatocyte Membranes

Macrophages and hepatocytes from normal and BCG-primed mice have been spin-labelled in their membranes with 5- and 16-doxyl stearic acid. Incubation of spin-labelled cells from BCG-primed animals with lipopolysaccharide from E. coli 0111.B4 produced a detectable and transient disturbance in the cell membranes as reflected by an increase in the order parameter measured from the electron spin resonance spectra of 5-doxyl-stearate. This membrane disturbance was maximal at 3-4 hours of incubation and was only detected with cells from mice primed with BCG. Spectra obtained from the 16-doxyl-stearate-labelled cells showed no change in order parameter on incubation with lipopolysaccharide.

The augmentation of tumor-specific immunity using haptenic muramyl dipeptide (MDP) derivatives. III. Eradication of disseminated murine chronic leukemia cells by utilizing MDP hapten-reactive helper T-cell activity.

A previous paper has demonstrated that enhanced tumor-specific immunity could be induced by priming mice with Bacillus Calmette Guerin (BCG) and subsequently immunizing them with syngeneic tumor cells modified with BCG-cross-reactive muramyl dipeptide (MDP) hapten. The present study establishes a tumor-specific immunotherapy protocol for a murine chronic leukemia based on the above T-T cell collaboration between antitumor effector T cells and anti-MDP hapten helper T cells induced by BCG priming. BALB/c mice which had been primed to BCG were injected intravenously (i.v.) with viable, syngeneic BCL1 leukemia cells. One week later, these mice were immunized intraperitoneally (i.p.) with unmodified or MDP hapten-modified, 10,000 R X-irradiated BCL1 cells, followed by 4 booster immunizations at 5-day intervals. The administration of unmodified BCL1 tumor cells into BCG-primed mice failed to prevent them from tumor death due to the persistent growth of preinjected BCL1 cells. In contrast, the immunization of BCG-primed, BCL1 leukemia-cell-bearing mice with MDP-modified BCL1 cells resulted in a high growth inhibition of leukemia cells and protection of these mice from death by leukemia. It was also revealed that potent tumor-specific, T-cell-mediated immunity was generated in mice which survived in this immunotherapy model. Thus, these results indicate that administration of MDP hapten-modified, syngeneic leukemia cells into leukemia-bearing mice which have been primed with BCG results in potent tumor-specific, T-cell-mediated immunity attributable to preventing the growth of disseminated leukemic cells.

Studies on the recovery from tolerance to tumor antigens. II. Accelerated recovery of tumor-specific effector T cells in tolerant mice by applying T-T cell interaction mechanism.

C3H/He mice were injected i.v. with heavily X-irradiated syngeneic X5563 tumor cells three times at 4-day intervals. This regimen resulted in the abrogation of the potential to generate X5563 tumor-specific T cell-mediated immunity as induced by i.d. inoculation of viable X5563 tumor cells followed by surgical resection of the tumor, representing the tolerance induction. Although such a tumor-specific tolerant state was long-lasting, the recovery of anti-X5563 effector T cell responses was observed when the above ordinary immunization procedure was performed 6 months after the tolerance induction. The present study investigated whether the recovery from the tolerance can be accelerated by applying a helper-effector T-T cell interaction model in which enhanced anti-X5563 immunity is obtained by priming mice with BCG and by immunizing X5563 tumor cells modified with BCG cross-reactive MDP hapten (designated as L4-MDP) in the presence of anti-L4-MDP helper T cells preinduced with BCG. The results demonstrated that BCG-primed mice which received the tolerance regimen failed to generate anti-X5563 immunity when the ordinary immunization was performed 2 or 3 months after the tolerance induction. In contrast, the immunization of BCG-primed and X5563-tolerant mice with L4-MDP-coupled X5563 tumor cells at comparable timing to that of the ordinary immunization were capable of generating potent X5563-specific in vivo protective T cell-mediated immunity. As control groups, BCG-primed or unprimed tolerant mice did not develop anti-X5563 immunity when immunized with L4-MDP-uncoupled or L4-MDP-coupled tumor cells, respectively. These results indicate that immunization of BCG-primed, tumor-tolerant mice with L4-MDP-modified tumor cells results in accelerated recovery from the tumor tolerance.