Diagnosis of tuberculosis based on the detection of a cocktail of mycobacterial antigen 85B, ESAT-6 and cord factor by immuno-PCR

Attempts were made to enhance the sensitivity of immuno-PCR assay based on the detection of cocktail of mycobacterial antigen 85B (Rv1886c), ESAT-6 (Rv3875) and cord factor (trehalose 6,6'-dimycolate) in pulmonary and extrapulmonary TB patients. Detection of Ag85B was found to be superior to the detection of cocktail in TB patients.

Enhancement of Th1 immune responses to recombinant influenza nucleoprotein by Ribi adjuvant

A broad coverage influenza vaccine against multiple viral strains based on the viral nucleoprotein (NP) is a goal pursued by many laboratories. If the goal is to formulate the vaccine with recombinant NP it is essential to count on adjuvants capable of inducing cellular immunity. This work have studied the effect of the monophosphoryl lipid A and trehalose dimycolate, known as the Ribi Adjuvant System (RAS), in the immune response induced in mice immunized with recombinant NP. The NP was formulated with RAS and used to immunize BALB/c mice. Immunizations with NP-RAS increased the humoral and cellular immune responses compared to unadjuvanted NP. The predominant antibody isotype was IgG2a, suggesting the development of a Th1 response. Analysis of the cytokines from mice immunized with NP-RAS showed a significant increase in the production of IFN-g and a decreased production of IL-10 and IL-4 compared to controls without RAS. These results are similar to those usually obtained using Freund’s adjuvant, known to induce Th1 and CTL responses when co-administered with purified proteins, and suggest that a similar approach may be possible to enhance the performance of a T-cell vaccine containing NP.

MARCO, TLR2, and CD14 are required for macrophage cytokine responses to mycobacterial trehalose dimycolate and Mycobacterium tuberculosis

Virtually all of the elements of Mycobacterium tuberculosis (Mtb) pathogenesis, including pro-inflammatory cytokine production, granuloma formation, cachexia, and mortality, can be induced by its predominant cell wall glycolipid, trehalose 6,6′-dimycolate (TDM/cord factor). TDM mediates these potent inflammatory responses via interactions with macrophages both in vitro and in vivo in a myeloid differentiation factor 88 (MyD88)-dependent manner via phosphorylation of the mitogen activated protein kinases (MAPKs), implying involvement of toll-like receptors (TLRs). However, specific TLRs or binding receptors for TDM have yet to be identified. Herein, we demonstrate that the macrophage receptor with collagenous structure (MARCO), a class A scavenger receptor, is utilized preferentially to “tether” TDM to the macrophage and to activate the TLR2 signaling pathway. TDM-induced signaling, as measured by a nuclear factor-kappa B (NF-κB)-luciferase reporter assay, required MARCO in addition to TLR2 and CD14. MARCO was used preferentially over the highly homologous scavenger receptor class A (SRA), which required TLR2 and TLR4, as well as their respective accessory molecules, in order for a slight increase in NF-κB signaling to occur. Consistent with these observations, macrophages from MARCO^−/− or MARCO^−/−SRA^−/− mice are defective in activation of extracellular signal-related kinase 1/2 (ERK1/2) and subsequent pro-inflammatory cytokine production in response to TDM. These results show that MARCO-expressing macrophages secrete pro-inflammatory cytokines in response to TDM by cooperation between MARCO and TLR2/CD14, whereas other macrophage subtypes (e.g. bone marrow–derived) may rely somewhat less effectively on SRA, TLR2/CD14, and TLR4/MD2. Macrophages from MARCO^−/− mice also produce markedly lower levels of pro-inflammatory cytokines in response to infection with virulent Mtb. These observations identify the scavenger receptors as essential binding receptors for TDM, explain the differential response to TDM of various macrophage populations, which differ in their expression of the scavenger receptors, and identify MARCO as a novel component required for TLR signaling.

The causative agent of tuberculosis, Mycobacterium tuberculosis, has a lipid-rich cell wall that contains a high percentage of mycolic acids. These mycolic acids contribute to both the impermeable nature of the cell wall and to the immunostimulatory properties of the bacterium. Indeed, it has been known for over 50 years that trehalose 6,6′-dimycolate (TDM/cord factor) is the major immunogenic lipid of M. tuberculosis, which induces potent pro-inflammatory responses from macrophages, although the receptor has not been identified. We have demonstrated that the toll-like receptor (TLR) pathway is required for pro-inflammatory cytokine production in response to TDM; however, the TLRs alone, or in conjunction with known co-receptors, are not sufficient to induce a response. We demonstrate that the macrophage receptor MARCO, a scavenger receptor, is utilized preferentially to “tether” TDM to the macrophage and activate the TLR2 signaling pathway, and is used preferentially over the related SRA. Macrophages from MARCO^−/− mice are defective in activation of TDM-induced signaling and subsequent pro-inflammatory cytokine production in response to both TDM-coated beads and virulent M. tuberculosis. By identifying the macrophage receptors involved in initial recognition we can now explain variable responses to TDM between different macrophage populations (which differ in scavenger receptor expression), and have identified a novel co-receptor that may be involved in lipid presentation to TLRs.

Vaccination with recombinant Mycobacterium avium subsp. paratuberculosis proteins induces differential immune responses and protects calves against infection by oral challenge

We previously reported the in vitro cellular immune responses to recombinant antigens (rAgs) of Mycobacterium avium subsp. paratuberculosis (MAP). Here we report the differential immune responses and protective efficacy of four rAgs of MAP (85A, 85B, 85C, and superoxide dismutase (SOD)) used with two adjuvants (monophosphoryl lipid A (MPLA) containing synthetic trehalose dicorynomycolate, cell wall skeleton (MPLA) and bovine IL-12), against MAP challenge in calves. Group I was administered the four rAgs with MPLA and IL-12. Group II was administered the four rAgs and MPLA. Group III received MPLA and IL-12, and Group IV MPLA. rAgs induced significant lymphoproliferative responses in vaccinated animals (Groups I and II). All the rAgs induced significant IFN-gamma production from 11 to 23 wk after primary vaccination (APV), except for SOD. Significant increases were noted in CD3(+), CD4(+), CD8(+), CD21(+), CD25(+), and gammadelta(+) cells against all four rAgs in vaccinated animals. rAg-specific expression of IL-2, IL-12p40, IFN-gamma and TNF-alpha was significantly higher in the two vaccinated groups. Culture results found 4/8 animals in Group I, 3/8 animals in Group II, and 3/4 animals in Groups III and IV were positive for MAP in one or more tissues. Among the seven positive animals in Groups I and II, all but one had had <10CFU. Isolation was confined to one tissue in these animals, except in one animal in which MAP was isolated from two tissues. In the control groups (III and IV), MAP was cultured from up to five different tissues with >250CFU. Preliminary data from this study indicates that all four rAgs induced a good Th1 response and conferred protection against MAP infection in calves.

Mycobacterial glycolipid trehalose 6,6'-dimycolate-induced hypersensitive granulomas: contribution of CD4+ lymphocytes

The granulomatous response is a characteristic histological feature of Mycobacterium tuberculosis infection responsible for organism containment. The development of cell-mediated immunity is essential for protection against disease, as well as being required for maintenance of the sequestering granulomatous response. Trehalose 6,6'-dimycolate (TDM; cord factor), a glycolipid associated with the cell wall of mycobacteria, is implicated as a key immunogenic component in M. tuberculosis infection. Models of TDM-induced hypersensitive granulomatous response have similar pathologies to that of active tuberculosis infection. Prior immunization (sensitization) of mice with TDM results in exacerbated histological damage, inflammation and lymphocytic infiltration upon subsequent TDM challenge. Adoptive transfer experiments were performed to ascertain the cell phenotype governing this response; CD4(+) cells were identified as critical for development of related pathology. Mice receiving CD4(+) cells from donor TDM-immunized mice demonstrated significantly increased production of Th1-type cytokines IFN-gamma and IL-12 within the lung upon subsequent TDM challenge. Control groups receiving naïve CD4(+) cells, or CD8(+) or CD19(+) cells isolated from TDM-immunized donors, did not exhibit an exacerbated response. The identified CD4(+) cells isolated from TDM-immunized mice produced significant amounts of IFN-gamma and IL-2 when exposed to TDM-pulsed macrophages in vitro. These experiments provide further evidence for involvement of a cell-mediated response in TDM-induced granuloma formation, which mimics pathological damage elicited during M. tuberculosis infection.

Modulation of immune responses in mice to recombinant antigens from PE and PPE families of proteins of Mycobacterium tuberculosis by the Ribi adjuvant

Three proteins of PE and PPE families of Mycobacterium tuberculosis were evaluated for their ability to induce T cell responses in mice. To enhance immunity induced by protein immunization, we tested the efficacy of adjuvant Ribi (monophosphoryl lipid A+TDM), along with three proteins of the PE/PPE family. Balb/c mice were subcutaneously injected with recombinant proteins, encoded by Rv1818c, Rv3018c and Rv3812 genes of M. tuberculosis H37Rv, formulated with Ribi or IFA for comparative study. Sera from mice immunized with Ribi revealed an increase in the specific immunoglobulin G titers by twofold against Ribi than in mice immunized with IFA. Ribi also elicited stronger delayed-type hypersensitivity and cytotoxic T-lymphocyte activity against the recombinant proteins when compared with IFA. Antigen specific IgG subclass analysis showed that Ribi tends to facilitate IgG2a production, suggesting enhancement of predominant Th1 response which in turn may facilitate increased production of protective IFN-gamma. Furthermore, Ribi preparation increased the number of T cells secreting IFN-gamma. These results indicate that Ribi acts as an effective adjuvant for immune response to antigens of M. tuberculosis. For the first time, we demonstrate that Rv3018c, Rv1818c and Rv3812 proteins of PE/PPE family are T cell antigens with vaccine potential.

Molecular and supra-molecular structure related differences in toxicity and granulomatogenic activity of mycobacterial cord factor in mice

To establish the structure biological activity relationship of cord factor (trehalose 6,6'-dimycolate, TDM), we compared the molecular or supra-molecular structure of TDM micelles with toxicity, thymic atrophy and granulomatogenicity in lungs and spleen of BALB/c mice. According to the difference in the mycolyl subclass composition, TDM was divided into two groups, one possessing alpha-, methoxy- and keto-mycolates in M. tuberculosis H37Rv, M. bovis BCG and M. kansasii (group A) and the other having alpha-, keto- and wax ester-mycolates in M. avium serotype 4, M. phlei and M. flavescens (group B), although mycolic acid molecular species composition differed in each group considerably. Supra-molecular structure of TDM micelle differed species to species substantially and the micelle size of TDM from M. bovis BCG Connaught was the largest. The highest toxicity was shown with TDM from M. tuberculosis H37Rv which possessed the highest amount of alpha- (47.3%) and methoxy-mycolates (40.8%), while TDM from M. phlei having the low amount of alpha-mycolate (11.6%) showed almost no toxicity with the given doses. The thymic atrophy was observed with TDM from group A, but not with TDM from group B. On the other hand, TDM from group B showed massive lung granulomatogenic activity based on the histological observations and organ indices. Taken together, group A TDM showed a wide variety of micelle sizes and specific surface areas, high to low toxicity and marked to moderate granulomatogenicity, while group B TDM showed smaller sizes of micelles and larger specific surface areas, lower toxicity but higher granulomatogenicity in lungs. Existence of higher amount of longer chain alpha-mycolates in TDM appeared to be essential for high toxicity and thymic apoptotic activity, whereas TDM possessing wax ester-mycolate with smaller sized micelles seemed to be less toxic, but more granulomatogenic in lungs in mice. Thus, the mycolic acid subclass and molecular species composition of TDM affect critically the micelle forms, toxicity and granulomatogenicity in mice, while the relative abundances and carbon chain length of alpha-mycolate affected the toxicity in mice.

Adjuvant-enhanced antibody responses in the absence of toll-like receptor signaling

Innate immune signals mediated by Toll-like receptors (TLRs) have been thought to contribute considerably to the antibody-enhancing effects of vaccine adjuvants. However, we report here that mice deficient in the critical signaling components for TLR mount robust antibody responses to T cell-dependent antigen given in four typical adjuvants: alum, Freund's complete adjuvant, Freund's incomplete adjuvant, and monophosphoryl-lipid A/trehalose dicorynomycolate adjuvant. We conclude that TLR signaling does not account for the action of classical adjuvants and does not fully explain the action of a strong adjuvant containing a TLR ligand. This may have important implications in the use and development of vaccine adjuvants.

CD3+ cells transfer the hypersensitive granulomatous response to mycobacterial glycolipid trehalose 6,6′-dimycolate in mice

The granulomatous response is the characteristic histological feature ofMycobacterium tuberculosisinfection that is essential for organism containment. Trehalose 6,6-dimycolate (TDM), a cell-wall glycolipid present on most mycobacterial species, has been implicated in the pathogenesis ofM. tuberculosisinfection. TDM has potent immunoregulatory and inflammatory properties, and can be used to model granulomatous reactions that mimic, in part, pathology caused during active infection. This study examined the hypersensitive granulomatous response, focusing on cellular responses specific to TDM. Lungs from mice immunized with TDM emulsion demonstrated exacerbated histological damage, inflammation, and lymphocytic infiltration upon subsequent challenge with TDM. Splenocytes recovered from these mice demonstrated significant interferon (IFN)-γproduction during recall response to TDM, as well as increased production of proinflammatory mediators (tumour necrosis factor-α, interleukin-6 and macrophage inflammatory protein-1α). The exacerbated response could be adoptively transferred to naïve mice. Administration of non-adherent lymphocytes or purified CD3+cells from TDM-immunized mice led to increased inflammation, lymphocytic infiltration, and vascular endothelial cell damage upon challenge with TDM. Recipient mice that received immunized CD3+lymphocytes demonstrated significant increases in Th1-type cytokines and proinflammatory mediators in lung tissue following TDM challenge. When CD1d−/−mice were immunized with TDM, they failed to generate a specific IFN-γresponse, suggesting a role for this molecule in the generation of hypersensitivity. These experiments provide further evidence for the involvement of TDM-specific CD3+T cells in pathological damage elicited duringM. tuberculosisinfection.

Trans-cyclopropanation of mycolic acids on trehalose dimycolate suppresses Mycobacterium tuberculosis -induced inflammation and virulence

Recent studies have shown that fine structural modifications of Mycobacterium tuberculosis cell envelope lipids mediate host cell immune activation during infection. One such alteration in lipid structure is cis-cyclopropane modification of the mycolic acids on trehalose dimycolate (TDM) mediated by proximal cyclopropane synthase of alpha mycolates (pcaA), a proinflammatory lipid modification during early infection. Here we examine the pathogenetic role and immunomodulatory function of mycolic acid cyclopropane stereochemistry by characterizing an M. tuberculosis cyclopropane-mycolic acid synthase 2 (cmaA2) null mutant (Delta cmaA2) that lacks trans-cyclopropanation of mycolic acids. Although titers of WT and Delta cmaA2 organisms were identical during mouse infection, Delta cmaA2 bacteria were hypervirulent while inducing larger granulomas than WT M. tuberculosis. The hypervirulence of the Delta cmaA2 strain depended on host TNF-alpha and IFN-gamma. Loss of trans-cyclopropanation enhanced M. tuberculosis-induced macrophage inflammatory responses, a phenotype that was transferable with petroleum ether extractable lipids. Finally, purified TDM lacking trans-cyclopropane rings was 5-fold more potent in stimulating macrophages. These results establish cmaA2-dependent trans-cyclopropanation of TDM as a suppressor of M. tuberculosis-induced inflammation and virulence. In addition, cyclopropane stereochemistries on mycolic acids interact directly with host cells to both positively and negatively influence host innate immune activation.

Of mice, men, and elephants: Mycobacterium tuberculosis cell envelope lipids and pathogenesis

Mycolic acids and structures attached to them constitute a major part of the protective envelope of Mycobacterium tuberculosis, and for this reason, their role in tuberculosis pathogenesis has been extensively studied. In this issue of the JCI, Rao et al. examine the effect of trans-cyclopropanation of oxygenated mycolic acids attached to trehalose dimycolate (TDM) on the murine immune response to infection (see the related article beginning on page 1660). Surprisingly, they found that an M. tuberculosis mutant lacking trans-cyclopropane rings was hypervirulent in mice. The recent recognition of a hypervirulence phenotype in mice associated with laboratory and clinical M. tuberculosis strains with altered cell wall components has provided new insights into how M. tuberculosis may establish persistent infection. However, to date, characterization of these bioactive products in pathogenesis has been largely reductionistic; the relationship of their effects observed in mice to the persistent infection and tuberculosis caused by M. tuberculosis observed in humans remains obscure.

Pseudo-rationale design of efficient TB vaccines: Lesson from the mycobacterial 27-kDa lipoprotein

To develop or improve acellular vaccines against tuberculosis, scientists are in quest for the most efficient Th1 antigens. Immunization of mice with the M. tuberculosis 27-kDa antigen resulted in a strong Th1 immune response as indicated by serum analysis, splenocyte proliferation and cytokines secretion profile. Unexpectedly, mice immunized with 27-kDa turned out to be more susceptible to mycobacterial challenge as we found significant increase in the splenic cfu count compared to control groups. Moreover, the protection provided by BCG or other mycobacterial antigens was completely abolished once the 27-kDa antigen was added to the vaccine preparations. Further analysis of 27-kDa revealed that this lipoprotein is a B-cell mitogen, a feature that is known to be linked to enhanced virulence of the pathogen. However, by using the non-acylated form, 27DeltaSP, we excluded the involvement of the mitogenicity of 27-kDa in its deleterious effect. Currently, there is no explanation to the fact that the 27-kDa interferes with the protective immunity of other mycobacterial antigens; however, it is clear that 27-kDa need to be excluded from any future vaccine preparations. Indeed, we developed a multivalent vaccine that consists of six other mycobacterial antigens: 85B, 38-kDa, ESAT-6, CFP21, Mtb8.4 and 16-kDa. Immunization of mice with these antigens emulsified in Ribi adjuvant system and supplemented with recombinant IFN-gamma, resulted in strong Th1 immune response and a high protection level that was comparable to that of BCG.

Differences in serological responses to specific glycopeptidolipid-core and common lipid antigens in patients with pulmonary disease due to Mycobacterium tuberculosis and Mycobacterium avium complex

Disease due to the Mycobacterium avium complex (MAC) is one of the most important opportunistic pulmonary infections. Since the clinical features of MAC pulmonary disease and tuberculosis (TB) resemble each other, and the former is often difficult to treat with chemotherapy, early differential diagnosis is desirable. The humoral immune responses to both diseases were compared by a unique multiple-antigen ELISA using mycobacterial species-common and species-specific lipid antigens, including glycopeptidolipid (GPL)-core. The results were assessed for two patient groups hospitalized and diagnosed clinically as having TB or MAC pulmonary disease. Diverse IgG antibody responsiveness was demonstrated against five lipid antigens: (1) monoacyl phosphatidylinositol dimannoside (Ac-PIM2), (2) cord factor (trehalose 6,6'-dimycolate) (TDM-T) and (3) trehalose monomycolate from Mycobacterium bovis Bacillus Calmette-Guérin (BCG) (TMM-T), and (4) trehalose monomycolate (TMM-M) and (5) GPL-core from MAC. Anti-GPL-core IgG antibody was critical, and detected only in the primary and the secondary MAC diseases with high positivity, up to 88.4 %. However, IgG antibodies against Ac-PIM2, TDM-T and TMM-T were elevated in both TB and MAC patients. Anti-TMM-M IgG antibody was also elevated in MAC disease preferentially, with a positive rate of 89.9 %, and therefore, it was also useful for the diagnosis of the disease. IgG antibody levels were increased at the early stages of the disease and declined in parallel to the decrease of bacterial burden to near the normal healthy control level, when the anti-mycobacterial chemotherapy was completed successfully. Unexpectedly, about 25 % of hospitalized TB patient sera were anti-GPL-core IgG antibody positive, although the specificity of GPL-core was sufficiently high (95.8 % negative in healthy controls), suggesting that a considerable number of cases of latent co-infection with MAC may exist in TB patients. Taken together, the combination of multiple-antigen ELISA using mycobacterial lipids, including GPL-core and TMM-M, gives good discrimination between healthy controls and sera from patients with TB or MAC disease, although for accurate diagnosis of TB more specific antigen(s) are needed.

Macrophage scavenger receptor down-regulates mycobacterial cord factor-induced proinflammatory cytokine production by alveolar and hepatic macrophages

We aimed to reveal the regulatory function of macrophage scavenger receptor-A (MSR-A) in proinflammatory cytokine production by macrophages stimulated with mycobacterial cord factor (CF). By the culture with CF, MSR-A (+/+) alveolar macrophages and Kupffer cells produced TNF-alpha/MIP-1alpha in a time- and dose-dependent manner. However, the amounts of cytokines produced by them were much less compared to those produced by MSR-A (-/-) macrophages. Consistent with this, treatment of MSR-A (+/+) macrophages with anti-MSR-A antibody increased TNF-alpha production. Binding of CF to MSR-A was demonstrated by measuring the binding affinity. These results indicate that CF binds MSR-A, and MSR-A down-regulates TNF-alpha/MIP-1alpha production by activated macrophages, suggesting the role of this receptor in suppression of excessive inflammatory responses during mycobacterial infection.

Mycobacterium hsp65 DNA entrapped into TDM-loaded PLGA microspheres induces protection in mice against Leishmania (Leishmania) major infection

Heat shock proteins (HSPs) are highly conserved among different organisms. A mycobacterial HSP65 DNA vaccine was previously shown to have prophylactic and immunotherapeutic effects against Mycobacterium tuberculosis infection in mice. Here, BALB/c mice were immunized with mycobacterial DNA-hsp65 or with DNA-hsp65 and trehalose dymicolate (TDM), both carried by biodegradable microspheres (MHSP/TDM), and challenged with Leishmania (Leishmania) major. MHSP/TDM conferred protection against L. major infection, as indicated by a significant reduction of edema and parasite loads in infected tissues. Although high levels of interferon-gamma and low levels of interleukin (IL)-4 and IL-10 were detected in mice immunized with DNA-hsp65 or MHSP/TDM, only animals immunized with MHSP/TDM displayed a consistent Th1 immune response, i.e., significantly higher levels of anti-soluble Leishmania antigen (SLA) immunoglobulin G (IgG)2a and low anti-SLA IgG1 antibodies. These findings indicate that encapsulated MHSP/TDM is more immunogenic than naked hsp65 DNA, and has great potential to improve vaccine effectiveness against leishmaniasis and tuberculosis.

Diverse humoral immune responses and changes in IgG antibody levels against mycobacterial lipid antigens in active tuberculosis

Humoral immune responses of active TB patients against six mycobacterial lipid antigens [trehalose 6,6'-dimycolate (TDM) from Mycobacterium bovis BCG (TDM-T) and Mycobacterium avium complex (TDM-M), trehalose 6-monomycolate (TMM) from M. bovis BCG (TMM-T) and M. avium complex (TMM-M), triacyl (PL-2) and tetraacyl (PL-1) phosphatidylinositol dimannosides] were examined by ELISA. IgG antibodies of TB patients with active disease reacted against the six lipid antigens distinctively, but heterogeneously. If tests were combined and an overall positive was scored cumulatively when any one of the six tests was positive, a good discrimination between patient and normal subject was obtained. A positive result in any one of the six tests was obtained in 91.5% of all 924 hospitalized patients and 93.3% of 210 patients at their first visit to the outpatient clinic. The IgG antibody response differed considerably from patient to patient, and the response patterns were grouped into several types. IgG antibody levels paralleled the bacterial burden; however, the smear-negative (culture-positive) patient group also showed high positive rates and mean ELISA DeltaA values against the six lipid antigens. There were also marked differences in positive rate and mean DeltaA values between cavity-positive and -negative groups, the former being higher than the latter. After anti-TB chemotherapy was initiated, IgG antibody levels decreased dramatically, paralleling the decrease in the amount of excretion of bacteria. Since multiple-antigen ELISA using particular lipid antigens was highly sensitive, and IgG antibody levels vary greatly at different stages of the disease, this technique is applicable for early diagnosis of smear-negative (and -positive) active TB and the prognosis for completion of anti-TB chemotherapy.

Influence of the washing buffer composition on the sensitivity of an enzyme-linked immunosorbent assay using mycobacterial glycolipids as capture antigens

Immunogenic glycolipids from the cell wall of Mycobacterium tuberculosis are potential capture antigens in enzyme-linked immunosorbent assays (ELISAs) for the serodiagnostis of tuberculosis. Typically, washing steps in ELISAs are performed with buffers containing a detergent. However, Tween-20, the most commonly added detergent, was reported to be able to remove the coating of certain glycolipid antigens from microtitre wells. In order to determine the influence of the washing buffer composition on the results, we measured serum immunoglobulin G (IgG) against three mycobacterial glycolipids by ELISA, conducting three separate experiments with three different buffers: Tris-buffered saline (TBS), TBS plus 0.02% Tween-20 (TBS-Tween), or TBS plus 0.3% bovine serum albumin (TBS-BSA). The capture antigens applied were lipoarabinomannan with the basic arabinose-containing motif (AraLAM), the mannose-capped version of lipoarabinomannan (ManLAM), and trehalose-6,6'-dimycolate (cord factor). All ELISAs achieved acceptable specificities around 95%. The sensitivities, however, varied widely, depending upon the sort of washing buffer used. In 38 patients with sputum smear-positive pulmonary tuberculosis and control groups of 79 patients with non-tuberculosis lung disease and 92 healthy volunteers, the anti-cord factor ELISA achieved 100%, 31.6%, and 60.5% with TBS, TBS-Tween, and TBS-BSA, respectively. Corresponding sensitivity values for AraLAM were 39.5%, 26.3%, and 23.7%, and for ManLAM 94.7%, 65.8%, and 55.3%. We conclude that Tween-20 or BSA should be omitted from the washing buffer in ELISAs, when the capture antigen is of lipid nature.

Requisite role for complement C5 and the C5a receptor in granulomatous response to mycobacterial glycolipid trehalose 6,6'-dimycolate

The development of pulmonary granulomatous lesions during mycobacterial infection is a complex phenomenon, in part caused by responses elicited towards the surface glycolipid trehalose 6,6'-dimycolate (TDM; cord factor). The molecular mechanisms underlying granuloma formation following challenge with TDM are not yet completely understood. The present study defines pathologic differences in acute response to Mycobacterium tuberculosis TDM in C57BL/6 mice and mice lacking the C5a receptor (C5aR-/-). Mice were intravenously injected with TDM prepared in water-in-oil-in-water emulsion and examined for histologic response and changes in proinflammatory cytokines and chemokines in lung tissue. Control C5a receptor-sufficient mice demonstrated a granulomatous response that peaked between days 4 and 7. Increased production of macrophage inflammatory protein-1 alpha (MIP-1alpha), interleukin-1beta (IL-1beta) and CXC chemokine KC (CXCL1) correlated with development of granulomas, along with modest change in tumor necrosis factor-alpha (TNF-alpha). In contrast, the C5aR-/- mice revealed markedly exacerbated inflammatory response. The receptor-deficient mice also demonstrated a lack of coherent granulomatous response, with severe oedema present and instances of lymphocytic cuffing around pulmonary vessels. Lung weight index was increased in the C5aR-/- mice, correlating with increased MIP-1alpha, KC, IL-1beta and TNF-alpha over that identified in the congenic C5aR-sufficient controls. Correlate experiments performed in C5-deficient (B10.D2-H2d H2-T18c Hco/oSnJ) mice revealed similar results, leading to the conclusion that C5 plays a significant role in mediation of chemotactic and activation events that are the basis for maturation of granulomatous responses to TDM.

Mycobacterial glycolipid cord factor trehalose 6,6'-dimycolate causes a decrease in serum cortisol during the granulomatous response

Serum cortisol levels were evaluated in mice following intravenous administration of purified mycobacterial glycolipid trehalose 6,6'-dimycolate (TDM). C57BL/6 mice develop lung granulomas in response to TDM, while A/J mice are deficient in this process. Administration of TDM to C57BL/6 mice led to a rapid reduction in serum cortisol, concurrent with initiation of the granulomatous response and cytokine and chemokine mRNA induction. Cortisol levels were lowest on day 5 after TDM administration, but there was significant production of IL-6, TNF-alpha and IL-1beta messages. Granuloma formation and full immune responsiveness to TDM were only apparent upon a sufficient decrease in levels of systemic cortisol. Treatment of the C57BL/6 mice with hydrocortisone abolished inflammatory responses. Histologically nonresponding A/J mice exhibited higher constitutive serum cortisol and demonstrated different kinetics of cortisol reduction upon administration of TDM. A/J mice demonstrated hyperplastic morphology in the suprarenal gland with a high degree of vacuolization in the medullary region and activation of cells in the zona fasciculata and zona reticularis. The A/J mice were dysregulated with respect to cytokine responses thought to be necessary during granuloma formation. The high constitutive serum cortisol in the A/J mice may therefore contribute to pulmonary immunoresponsiveness and the establishment of an environment counterproductive to the initiation of granulomatous responses. The identification of a mycobacterial glycolipid able to influence serum cortisol levels is unique and is discussed in relation to immunopathology during tuberculosis disease.

Mycobacterial trehalose 6,6′-dimycolate preferentially induces type 1 helper T cell responses through signal transducer and activator of transcription 4 protein

Mycobacterium tuberculosis is an intracellular pathogen of tuberculosis and its pathogenicity is related to the ability to escape killing by ingested macrophages and induce delayed-type hypersensitivity (DTH). A major component of the cell wall of M. tuberculosis is trehalose 6,6'-dimycolate (TDM), which has been implicated as a pathogenetic factor. The expression of DTH and cell-mediated immunity is dependent on the macrophage-cytokine-type 1 helper T (Th1) lymphocyte axis. Cytokines, interleukin-12 (IL-12) and interferon-gamma (IFN-gamma), play a critical role in the process and IL-12-activated signal transducer and activator of transcription (STAT) 4 is required for the development of fully functional Th1 cells. To clarify host responses to mycobacterial TDM, we have analyzed footpad reaction, histopathology and cytokine profile of experimental granulomatous lesions using STAT4-deficient mice. In the present study, we have demonstrated that mycobacterial TDM selectively induces the Th1 response through the STAT4 signaling pathway, because mice lacking STAT4 protein significantly reduced to develop DTH, hypersensitivity granulomas, and Th1 cytokine responses, when compared to BALB/c mice. These results shed light on the molecular pathogenesis of mycobacterial disease. Taken together with previous studies, TDM is a pleiotropic molecule against the host and participates in the pathogenesis.

Evaluation of lipopolysaccharide and capsular polysaccharide as subunit vaccines against experimental melioidosis

Burkholderia pseudomallei is the causative agent of melioidosis, which is a major cause of morbidity and mortality in endemic regions. Currently there is no human vaccine against melioidosis. In this study, LPS or capsular polysaccharide was used to immunize BALB/c mice. The different polysaccharide antigens induced antibody responses. Mice vaccinated with LPS developed predominantly IgM and IgG3 responses. Contrastingly, mice vaccinated with capsular polysaccharide developed a predominantly IgG2b response. After immunization, mice were challenged by the intra-peritoneal route and an increased mean time to death was observed compared with unvaccinated controls. Immunization with LPS provided an optimal protective response. Mice challenged by the aerosol route showed a small increase in the mean time to death compared with the unvaccinated controls. The passive transfer of antigen from immunized into naïve mice provided protection against a subsequent challenge. This study is the first time antigens protective by active immunization have been identified and suggests that polysaccharides have potential as vaccine candidates against melioidosis.

Failure of CD1D-/-Mice to Elicit Hypersensitive Granulomas to Mycobacterial Cord Factor Trehalose 6,6′-Dimycolate

The present study defines pathologic differences in acute and hypersensitive responses to Mycobacterium tuberculosis glycolipid trehalose-6,6'-dimycolate (TDM, cord factor) in normal BALB/c mice and those deficient in group II CD1 molecule CD1d1. Mice immunized against TDM demonstrate hypersensitive responses, yet the mechanisms for TDM presentation remain elusive. Mice lacking CD1d (CD1D(-/-)) demonstrate dysregulated granulomatous response to TDM, compared with CD1D(+/-) heterozygous controls. Because CD1d-restricted T cells can regulate macrophage immune functions at mucosal surfaces, we hypothesized that CD1D(-/-) mice would show deficient TDM-induced hypersensitive pulmonary granulomatous response in which T cells play a central role. Control CD1D(+/+) mice sensitized and subsequently challenged with TDM demonstrated aggressive inflammation defined by monocytic lesions contained by CD3(+) lymphocytic cuffing. CD1D(-/-) mice demonstrated distinctly different pathologies, with edema present concurrent with extended, nonfocal mononuclear cell-based granulomatous reactions. Furthermore, CD1D(-/-) mice did not demonstrate destructive lesions, and CD3(+) lymphocytes were only loosely organized in proximity to reactive pathology. The CD1d-deficient mice demonstrated rapid increases in proinflammatory mRNAs, with significant differences in interferon-gamma (IFN-gamma) compared to the wild-type group. IFN-gamma, interleukin-6 (IL-6), and IL-12 proteins were significantly elevated in the CD1D(-/-) group compared with wild-type mice (p < 0.05) 2 days after TDM challenge. However, by 7 days postadministration, similar production for all cytokines and proinflammatory molecules examined was present in both groups of mice. These experiments provide evidence for a role for CD1d in mediation of pathology during hypersensitive responses to the mycobacterial glycolipid TDM.

The role of adjuvant on the regulatory effects of NK cells on B cell responses as revealed by a new model of NK cell deficiency

We have utilized a novel method to generate transgenic mice that are deficient in NK cells. The strategy entails introduction of the H and L chain genes encoding PK136, an antibody shown to be effective in the in vivo elimination of NK cells, into the mouse genome. Since the introduced H chain gene does not contain sequences encoding membrane exons, the transgenic Ig is not expressed on the cell surface, but is secreted by activated B cells. We show that these animals are chronically depleted of NK cells, but not B, T or NKT cells. Therefore, they are compromised in their ability to mediate NK-mediated cytotoxicity. In addition, the deficiency in NK cells reduces the level of switching to various downstream isotypes in response to T-independent type II antigens. However, this reduction is only apparent when antigens are injected in the presence of adjuvant. Since NKT cells are not depleted, the effect cannot be attributed to this subpopulation. These results help to resolve differences in previous findings regarding the role of NK cells in antibody responses.

Reduced cerebral infection of Neospora caninum-infected mice after vaccination with recombinant microneme protein NcMIC3 and ribi adjuvant

C57BL/6 mice were vaccinated with a bacterially expressed and purified polyhistidine-tagged full-length version of the microneme protein NcMIC3 (recNcMIC3) emulsified in Ribi Adjuvant System (RAS). Subsequently, they were challenged by intraperitoneal inoculation of 2 x 10(6) live Neospora caninum tachyzoites. As controls, groups of mice received phosphate-buffered saline (PBS)-RAS alone (adjuvant control) or were treated with PBS before infection (infection control). The protective effect of vaccination was assessed by Neospora-specific polymerase chain reaction (PCR), immunohistochemical investigation of brain tissue, and serological means (enzyme-linked immunosorbent assay). Assessment by PCR performed on DNA from different organs revealed that in all treatment groups parasite DNA could only be detected in brain tissue. According to the PCR results. the recNcMIC3 vaccine conferred protection to 75% of mice (n = 16 in 2 independent experiments), whereas application of PBS-RAS and of PBS alone resulted in protection of 12.5% and 0% of mice, respectively (n = 16 as above). Mice in the PBS-treated infection control group were affected by evident clinical signs of neosporosis starting on day 6 postinfection (p.i.). Conversely, none of the animals treated with either PBS-RAS or recNcMIC3 exhibited any symptoms until day 21 p.i. Immunohistochemical staining of paraffin-embedded brain tissue sections confirmed the protective effect of recNcMIC3 vaccination. Quantitative Neospora-specific real-time PCR revealed that infection intensities were lower in the brain tissues of recNcMIC3-vaccinated mice compared with PBS-RAS-treated adjuvant control mice. Serological analysis showed that the protective effect observed in recNcMIC3-vaccinated mice was associated with a Th2-type IgG1 antibody response directed against native NcMIC3 and a mixed IgG1-IgG2a antibody response directed against the recombinant antigen itself. Taken together, these results demonstrated that recombinant NcMIC3 vaccine confers a significant protectivity against experimentally induced cerebral neosporosis in mice.

Serodiagnosis of tuberculosis: comparison of immunoglobulin A (IgA) response to sulfolipid I with IgG and IgM responses to 2,3-diacyltrehalose, 2,3,6-triacyltrehalose, and cord factor antigens

Nonpeptidic antigens from the Mycobacterium tuberculosis cell wall are the focus of extensive studies to determine their potential role as protective antigens or serological markers of tuberculous disease. Regarding this latter role and using an enzyme-linked immunosorbent assay, we have made a comparative study of the immunoglobulin G (IgG), IgM, and IgA antibody responses to four trehalose-containing glycolipids purified from M. tuberculosis: diacyltrehaloses, triacyltrehaloses, cord factor, and sulfolipid I (SL-I). Sera from 92 tuberculosis patients (taken before starting antituberculosis treatment) and a wide group of control individuals (84 sera from healthy donors, including purified protein derivative-negative, -positive, healed, and vaccinated individuals, and 52 sera from nontuberculous pneumonia patients), all from Spain, were studied. The results indicated a significantly elevated IgG and IgA antibody response in tuberculosis patients, compared with controls, with all the antigens used. SL-I was the best antigen studied, showing test sensitivities and specificities for IgG of 81 and 77.6%, respectively, and of 66 and 87.5% for IgA. Using this antigen and combining IgA and IgG antibody detection, high test specificity was achieved (93.7%) with a sensitivity of 67.5%. Currently, it is widely accepted that it is not possible to achieve sensitivities above 80% in tuberculosis serodiagnosis when using one antigen alone. Thus, we conclude that SL-I, in combination with other antigenic molecules, could be a useful antigen for tuberculosis serodiagnosis.

Immunological properties of trehalose dimycolate (cord factor) and other mycolic acid-containing glycolipids--a review

Mycolic acids are characteristic fatty acids of Mycobacteria and are responsible for the wax-like consistence of these microorganisms. Decades of research revealed that mycolic acid-containing glycolipids, in particular trehalose-6,6'-dimycolate (TDM, cord factor) as their best-studied representative, exert a number of immunomodifying effects. They are able to stimulate innate, early adaptive and both humoral and cellular adaptive immunity. Most functions can be associated with their ability to induce a wide range of chemokines (MCP-1, MIP-1alpha, IL-8) and cytokines (e.g., IL-12, IFN-gamma, TNF-alpha, IL-4, IL-6, IL-10). This review tries to link well-known properties of mycolic acid-containing glycolipids, e.g., stimulation of cellular and humoral immunity, granuloma formation and anti-tumor activity, with recent findings in molecular immunology and to give an outlook on potential practical applications.

Influence of trehalose 6,6'-dimycolate (TDM) during mycobacterial infection of bone marrow macrophages

The relative role of surface lipids in the innate macrophage response to infection with mycobacteria remains unknown. Trehalose 6,6'-dimycolate (TDM), a major component of the mycobacterial cell wall, can elicit hypersensitive as well as T-cell-independent foreign body responses. The T-cell-independent contribution of TDM to the primary macrophage response to mycobacterial infection was investigated. Bone-marrow-derived macrophages isolated from C57BL/6 mice were infected with native Mycobacterium tuberculosis (MTB) or with MTB delipidated using petroleum ether extraction methods. The removal of surface lipids caused decreased bacterial survival in macrophages, but there was no loss of bacterial growth in broth culture. Bacterial survival within macrophages was restored upon reconstitution of the bacteria with purified TDM. The cytokine and chemokine parameters of the macrophage responses were also investigated. The amounts of IL-1beta, TNF-alpha, IL-6 and MIP-1alpha produced were significantly reduced following delipidation, but were restored upon reconstitution with TDM. The amount of IL-12 produced, but not the amount of IL-10 produced, was also significantly reduced upon macrophage infection with delipidated MTB. Furthermore, nitric oxide responses were not impaired upon infection with delipidated MTB, suggesting that intracellular survival and macrophage secretion of cytokines and chemokines are differentially controlled. These studies indicate that TDM is a major component contributing to the innate macrophage responses to MTB infection.

Priming and activation of mouse macrophages by trehalose 6,6'-dicorynomycolate vesicles from Corynebacterium glutamicum

Vesicles consisting of pure trehalose dicorynomycolate (TDCM), the corynebacterial analog of the most studied mycobacterial glycolipid 'cord factor', were isolated from Corynebacterium glutamicum cells by mild detergent treatment; these induced in vivo a macrophage priming similar to that obtained with mycobacterial-derived trehalose dimycolate. In vitro, both TDCM and bacterial lipopolysaccharide (LPS) induced in macrophages the production of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha), endotoxin tolerance, and were primed for an enhanced secondary NO response to LPS. Interferon-gamma pretreatment did not influence the LPS-induced TNF-alpha response, but considerably increased the TDCM-induced response.

Role of trehalose dimycolate in recruitment of cells and modulation of production of cytokines and NO in tuberculosis

Mice treated with viable Mycobacterium tuberculosis with no glycolipid trehalose dimycolate (TDM) on the outer cell wall (delipidated M. tuberculosis) by intraperitoneal or intratracheal inoculation presented an intense recruitment of polymorphonuclear cells into the peritoneal cavity and an acute inflammatory reaction in the lungs, respectively. In addition, lung lesions were resolved around the 32nd day after intratracheal inoculation. TDM-loaded biodegradable poly-DL-lactide-coglycolide microspheres as well as TDM-coated charcoal particles induced an intense inflammatory reaction. In addition, high levels of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), IL-12, IL-10, gamma interferon (IFN-gamma), and IL-4 production were detected in lung cells, and nitric oxide (NO) production was high in culture supernatants of bronchoalveolar lavage cells. These in vivo data were confirmed by in vitro experiments using peritoneal macrophages cultured in the presence of TDM adsorbed onto coverslips. High levels of IFN-gamma, IL-6, TNF-alpha, IL-12, IL-10, and NO were detected in the culture supernatants. Our results suggest that TDM contributes to persistence of infection through production of cytokines, which are important for the recruitment of inflammatory cells and maintenance of a granulomatous reaction. In addition, our findings are important for a better understanding of the immunostimulatory activity of TDM and its possible use as an adjuvant in experiments using DNA vaccine or gene therapy against tuberculosis.

Mycobacterial cord factor, but not sulfolipid, causes depletion of NKT cells and upregulation of CD1d1 on murine macrophages

Trehalose 6,6'-dimycolate (TDM, cord factor) has frequently been used as an adjuvant to stimulate antibody production. Although it also induces cellular immunity, detailed studies about the underlying events do not exist. To determine the kinetics of TDM-specific changes promoting a T helper 1 (Th1) response, we injected mice with TDM or 2,3,6,6'-tetraacyl trehalose 2'-sulfate (SL, sulfolipid), another mycobacterial trehalose-containing glycolipid without mycolic acid. TDM, but not SL, caused a strong increase in serum interferon-gamma (IFN-gamma) levels 2 days later, accompanied by expansion of natural killer (NK) cells. Subsequent TDM effects included depletion of normal-density CD4(+) NK1.1(+) TCRalpha/beta(intermediate) cells from day 7 on, upregulation of MHC class II and CD1d1 on macrophages (peaking on day 21), and an increased proportion of Th1 cells evident after 3 weeks. TDM, but not a similar glycolipid without mycolic acid, can therefore initiate a cascade of events starting with strong release of IFN-gamma and NK cell expansion, resulting in the appearance of macrophages activated for antigen presentation. Our data therefore provide the basis for optimized immunization schedules with TDM as the adjuvant component of a Th1 vaccine.

New diagnostic approach for ocular tuberculosis by ELISA using the cord factor as antigen

BACKGROUND/AIMS

Diagnosis of ocular tuberculosis is difficult, particularly the retinal vasculitis type, because most cases occur without concurrent active pulmonary tuberculosis. Recently, it has been reported that detection of antibodies against purified cord factor (trehalose-6,6'-dimycolate, TDM), the best studied, most antigenic, and most abundant cell wall component of tubercule bacilli, is very useful for rapid serodiagnosis of pulmonary tuberculosis. In this study, an attempt was made to evaluate whether the detection of anticord factor antibody is also useful for diagnosis of ocular tuberculosis and the necessity of antituberculous therapy for tuberculous retinochoroiditis was discussed.

METHODS

Cases consisted of 15 patients with uveitis and retinal vasculitis, nine patients with presumed ocular tuberculosis, three patients with sarcoidosis, and three patients with Behçet's disease. IgG antibodies against purified cord factor prepared from Mycobacterium tuberculosis H37Rv were detected by enzyme linked immunosorbent assay.

RESULTS

All cases of clinically presumed ocular tuberculosis were positive, whereas all of the cases of sarcoidosis or Behçet's disease were negative for anticord factor antibodies. When the anticord factor antibody titres were compared on the basis of the presence or absence of previous antituberculosis chemotherapy, the mean anticord factor antibody titre of the untreated group showed a tendency to be higher than in the treated group, but not significantly (p=0.07).

CONCLUSIONS

The detection of anticord factor antibody may be useful to support the diagnosis of ocular tuberculosis. Additionally, a positive result for anticord factor antibody may indicate that tubercule bacilli are present in some organ(s) of the patient even in the absence of active systemic disease.

Anti-cord factor (trehalose 6,6'dimycolate) IgG antibody in tuberculosis patients recognizes mycolic acid subclasses

The detection of anti-cord factor (trehalose 6,6'-dimycolate) IgG antibody in active (smear-and/or culture-positive) and inactive (smear-and culture-negative) tuberculosis patients is a useful serodiagnostic tool that can be used for early clinical diagnosis of the disease. We estimated the titers of anticord factor IgG antibody in the sera of tuberculosis patients, and compared them with those of Mycobacterium avium-infected patients. Most of the serum samples obtained from the tuberculosis patients were highly reactive against M. tuberculosis (MTB) cord factor isolated from M. tuberculosis H37Rv, a human-type mycobacterial strain, whereas they were less reactive against M. avium (MAC) cord factor. Similarly, most of the serum samples of the MAC-infected patients were highly reactive against MAC cord factor and less reactive against MTB cord factor. These results suggest that anti-cord factor IgG antibody recognizes the mycolic acid subclasses as an epitope which comprises cord factor, since MTB and MAC cord factor differ in mycolic acid subclasses and molecular species composition. To clarify the exact antigenic epitope in cord factor and to find out a more sensitive and specific diagnostic test antigen, we examined the reactivity of patients' sera to glycolipids containing trehalose (cord factor and sulfolipid) obtained from various mycobacterial species. Furthermore, the reactivity of human antisera to various mycolic acid subclasses (alpha-, methoxy and keto mycolic acids) of MTB cord factor was compared. We found that anti-cord factor IgG antibody in the sera of human tuberculosis patients most strikingly recognized methoxy mycolic acid in the cord factor of M. tuberculosis, whereas it recognized alpha- and keto mycolic acids weakly. Pre-absorption studies of antibody with MTB cord factor or methoxy mycolic acid methyl ester showed that anti-cord factor antibody was absorbed partially, but consistently. This is the first report describing that the specific subclass of mycolic acid from mycobacteria is antigenic in the humoral immune system of human tuberculosis infection.

Tumor necrosis factor is required for the priming of peritoneal macrophages by trehalose dimycolate

Trehalose dimycolate (TDM), a glycolipid present in the cell wall of Mycobacterium spp., is a powerful immunostimulant. We have developed an original model of macrophage activation where TDM is injected in vivo to prime peritoneal macrophages. These primed macrophages do not express inducible NO synthase (NOS II), however, they can be fully activated, i.e. induced to express NOS II and to develop a NOS II-dependent antiproliferative activity, following in vitro exposure to low concentrations of LPS. In a previous paper, we have shown that TDM-priming of mouse peritoneal macrophages is mediated by the sequential production of IL-12 and IFN-gamma. In the present paper, we investigated the role of TNF in the priming of macrophages by TDM. By semi-quantitative RT-PCR, we have shown that TDM injection induced transcription of TNF-alpha in peritoneal cells. TNF-mRNA levels peaked 5 hours after TDM injection and remained elevated for at least 32 hours. TNF expression was absolutely necessary for macrophage priming, as injection of an anti-TNF monoclonal antibody, 4 h before and 20 hours after TDM injection, prevented LPS-dependent activation of macrophages in vitro. This result was confirmed by the inability of TDM to prime macrophages from LT-alpha/TNF-alpha knockout (LT/TNFKO) mice. In addition, analysis of LT/TNFKO mice treated with TDM revealed that induction of the IL-12 transcript in their peritoneal cells and expression of a functional NADPH oxidase in macrophages are TNF-independent events.

Serodiagnosis of Hansen's disease/leprosy by enzyme-linked immunosorbent assay using cord factor (trehalose 6,6'-dimycolate) as an antigen

IgG and/or IgM antibodies against mycobacterial cord factor (trehalose 6,6'-dimycolate, TDM) in sera of 65 patients of Hansen's disease (21 cases with smear-positive and 44 cases with smear-negative) and 60 healthy individuals were tested by enzyme-linked immunosorbent assay (ELISA) with TDM purified from Mycobacterium tuberculosis H37Rv as an antigen. Of 65 patients with Hansen's disease, 58 cases (89.2%) had positive results (21 samples from 21 patients, 100% with acid-fast bacilli positive in the lesion, and 37 samples from 44 patients, 84.0% with acid-fast bacilli negative Hansen's disease diagnosed clinically). The sensitivity and specificity of anti-cord factor ELISA were higher than those of anti-phenolic glycolipid-I (PGL-I) agglutination test. Among the total, 34 patients were classified clinically into three types of the disease, lepromatous leprosy (LL), borderline lepromatous (BL) and borderline tuberculoid (BT). The antibody titer showed LL > BL > BT, indicating that the elevation of anti-cord factor antibody titers appeared to be parallel with the degree of humoral immune response against M. leprae. By using semisynthetic cord factor consisting of a single subclass of mycolic acid from M. tuberculosis, it was revealed that sera from patients with Hansen's disease were highly reactive against alpha-mycoloyl cord factor (alpha-TDM) and less reactive against methoxy mycoloyl TDM (methoxy TDM), differed from sera of tuberculosis patients, which were highly reactive against both methoxy and alpha-mycoloyl cord factor (alpha-TDM). Most of sera from patients with Hansen's disease were more reactive against TMM than TDM, differed from sera of tuberculosis patients which were highly reactive against TDM. ELISA using TDM as an antigen is simple, reproducible and useful for the rapid serodiagnosis of Hansen's disease, especially for smear-negative cases.

Production and partial characterization of antibody to cord factor (trehalose 6,6'-dimycolate) in mice

Antibody production against the trehalose 6,6'-dimycolate (TDM, cord factor) of Rhodococcus ruber, a non-pathogenic species of the Actinomycetales group, was investigated in mice by repeated intraperitoneal injection of TDM in water-in-oil-in-water micelles without carrier protein. The antigenic TDM was isolated and purified chromatographically from the chloroform-methanol extractable lipids of R. ruber. The hydrophobic moiety of this TDM was composed of two molecules of monoenoic or dienoic alpha-mycolic acids with a carbon chain length ranging from C44 to C48 centering at C46. To detect the antibody, an enzyme-linked immunosorbent assay (ELISA) system was employed using plastic plates coated with TDM. The antibody reacted against the TDM of R. ruber. The antibody was reactive in similar fashion against glycosyl monomycolates differing in the carbohydrate moiety, such as that of glucose mycolate (GM) and mannose mycolate (MM), obtained from R. ruber. Moreover, the antibody reacted against mycolic acid methyl ester itself when it was used as the antigen in ELISA, and trehalose did not absorb the antibody to TDM or inhibit the reaction. These results indicate that the epitope of TDM recognized by the antibody is mycolic acid, an extremely hydrophobic part of the molecule. Next, we prepared monoclonal anti-TDM antibody (moAb) in mice myeloma cells to examine its biological activities and the role of humoral immunity in mycobacterial infection. MoAb reacted against the TDM, glycosyl mycolate, and mycolic acid methyl ester in ELISA in the same manner as our polyclonal antibody did. The administration of moAb suppressed granuloma formation in the lungs, spleen, and liver induced by TDM and inhibited the production of interleukin-1 (IL-1) and chemotactic factor, which is reported to precede granuloma formation.

Production and partial characterization of anti-cord factor (trehalose-6,6'-dimycolate) IgG antibody in rabbits recognizing mycolic acid subclasses of Mycobacterium tuberculosis or Mycobacterium avium

An ELISA with cord factor (trehalose-6,6'-dimycolate) is useful for the serodiagnosis of tuberculosis. To clarify the exact antigenic epitope in cord factor, recognized by a rabbit anti-cord factor IgG antibody, and to ascertain the most sensitive and specific diagnostic test antigen, rabbits were immunized with two kinds of cord factors isolated from Mycobacterium tuberculosis or Mycobacterium avium and the reactivities of the sera were tested against cord factors or the component mycolic acid methyl esters by ELISA. The serum from rabbits immunized with M. tuberculosis cord factor was highly reactive against M. tuberculosis cord factor, but less reactive against M. avium cord factor. In contrast, the serum from rabbits immunized with M. avium cord factor was highly reactive against M. avium cord factor but less reactive against M. tuberculosis cord factor. Moreover, the serum from rabbits immunized with M. tuberculosis cord factor reacted against mycolic acid methyl esters, especially methoxy mycolic acid methyl ester. On the other hand, the serum from rabbits immunized with M. tuberculosis cord factor was less reactive against trehalose-6-monomycolate and not reactive against sulfolipid (2,3,6,6'-tetraacyl trehalose 2'-sulfate). From these results, it was concluded that the anti-cord factor IgG antibody, produced experimentally in rabbits, recognized the differences in the cord factor structures, i.e. the hydrophobic moiety rather than the carbohydrate moiety. It was also noted that the serum from rabbits immunized with M. tuberculosis cord factor was highly reactive against methoxy mycolic acid as an epitope. This paper is the first to describe how the anti-cord factor IgG antibody can recognize the mycolic acid subclasses, which differ according to the species of mycobacteria.

Analysis of the ability of five adjuvants to enhance immune responses to a chimeric plant virus displaying an HIV-1 peptide

The ability of five different adjuvants (alum, complete Freund's adjuvant, Quil A, AdjuPrime and Ribi) to stimulate humoral and T-cell mediated immune responses against a purified chimeric virus particle was investigated. Each adjuvant was administered subcutaneously to adult mice together with 10 microg of wildtype (wt) cowpea mosaic virus (CPMV) or a chimeric CPMV displaying the HIV-1 gp41 peptide, residues 731-752. All preparations elicited strong antibody responses to CPMV, but Quil A elicited the highest and most consistent responses to the HIV-1 peptide. This finding was reflected in both ELISA titres with immobilized peptide and in HIV-1-neutralizing antibody. In addition Quil A was also, the only adjuvant to stimulate an in vitro proliferative T-cell response. Surprisingly with all adjuvant formulations a predominately IgG2a anti-gp41 peptide response was observed, indicating a type 1 T-helper cell-like response. Furthermore, the efficiency of the CPMV display system was demonstrated by its ability to induce good levels of peptide specific antibody in the absence of any adjuvant.

Rapid serodiagnosis of Mycobacterium avium-intracellulare complex infection by ELISA with cord factor (trehalose 6, 6'-dimycolate), and serotyping using the glycopeptidolipid antigen

Mycobacterium avium-intracellulare complex (MAC) is one of the most important opportunistic pathogens, particularly in patients with acquired immunodeficiency syndrome (AIDS). The aim of this study was to determine whether an enzyme-linked immunosorbent assay (ELISA) using trehalose 6,6'-dimycolate (TDM) as an antigen can be used for the rapid serodiagnosis of MAC infection. We also identified MAC serotypes by ELISA using serotype-specific glycopeptidolipid (GPL) antigen. To confirm our findings, the thin-layer chromatographic (TLC) behavior of serotype-specific GPL of the strains isolated from MAC-infected patients was also tested. Forty patients infected with MAC and 30 healthy controls were tested. Thirty-two of the 40 MAC-infected patients had higher titers of serum antibodies against MAC TDM than against MTB TDM, while all 30 healthy control sera were unreactive to MAC TDM and MTB TDM. Results of the GPL ELISA indicated that 20 of the 40 MAC-infected patients' sera were reactive against serotype 4 GPL, 3 against serotype 8 GPL, and 1 against serotype 16 GPL. A TLC analysis of the GPL of the 40 MAC isolates showed that 16 strains were of serotype 4, 5 of serotype 8, and 2 of serotype 16. Results of the GPL ELISA were in good accord with those of the TLC analysis for most patients. Our findings suggest that ELISA using TDM is useful for rapid serodiagnosis of MAC infection, and that complementary ELISA testing using serotype-specific GPL gives additional detailed information concerning MAC serotypes.

Enzyme immunoassay to detect antituberculous glycolipid antigen (anti-TBGL antigen) antibodies in serum for diagnosis of tuberculosis

We report the development of an EIA specific for antituberculosis antibody in human serum for the clinical evaluation of tuberculosis. We developed a TLC immunostaining method to detect specific antigens for antibodies in the serum of patients with tuberculosis. The detected specific antigens, TDM and specific gylcolipid fraction, were individually purified from M. tuberculosis H37Rv by column chromatography. The two purified fractions were mixed and the mixture, termed TBGL antigen, was applied to an enzyme immunoassay suitable for the measurement of antituberculosis antibodies in serum. This EIA meets all the requirements of routine clinical assay in terms of sensitivity (detection limit: 0.125 U/ml), reproducibility (total CV : 3.3-6.0%), accuracy (recovery: 96-105%), simplicity and rapidity (< 2.5 h). Clinical validation of the assay was confirmed by the measurement of the anti-tuberculosis antibody in the serum of normal subjects and patients with pulmonary tuberculosis. The EIA tested in this study showed a high serodiagnostic discriminating power (90% sensitivity and 98% specificity).

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

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

[Serodiagnosis with trehalose-6,6'-dimycolate of pulmonary tuberculosis]

Enzyme-linked immunosorbent assay (ELISA) was used to examine serum antibody levels of mycobacterial antigen in 92 patients with active tuberculosis, 36 with cured tuberculosis, 45 with nontuberculous mycobacteriosis, and as 31 with other diseases. Glycolipid fraction containing mainly cord factor (trehalose-6,6'-mycolate) from Mycobacterium tuberculosis H37Rv were used as ELISA antigen. Overall positive rates of the ELISA tests in the patients with active pulmonary tuberculosis, those with nontuberculous mycobacteriosis, and those with other diseases were 67.4%, 75.6%, and 6.5%, respectively. Patients with tuberculosis and those with nontuberculous mycobacteriosis differed from the control group (p < 0.0001). Higher positive rates were correlated with bacterial loads (smear-positive vs smear-negative, p < 0.01) and with chest roenrgenographic findings (far advanced or other cavitary vs noncavitary, p < 0.01). Because 18 of 36 smear-negative patients (50%) had positive results, we believe that the ELISA test with this antigen can be useful for diagnosis of M. tuberculosis, especially in patients with smear-negative.

Studies of polymorphic DNA fingerprinting and lipid pattern of Mycobacterium tuberculosis patient isolates in Japan

Strain differentiation by DNA restriction fragment length polymorphism (RFLP) has been used mainly for the epidemiological purpose of Mycobacterium tuberculosis infection. In this study, we tried to connect the molecular and phenotypic characteristics of M. tuberculosis patient isolates by comparing the DNA fingerprints obtained by RFLP using IS6110 and lipid patterns using two-dimensional thin-layer chromatography (2-D TLC) with silica gel, since M. tuberculosis has a lipid-rich cell envelope which contributes to the virulence and immunomodulatory properties. We found that 66 isolates of M. tuberculosis from tuberculosis patients showed that the occurrence of IS6110 varied from 1 to 24 copies. The IS6110 patterns were highly variable among isolates. Fifty different RFLP patterns were observed, and 12 RFLP patterns were shared by two or more strains. By computerized analysis of the RFLP patterns of M. tuberculosis patient isolates, we found that 95% of the isolates fell into seven clusters, from A to G, with at least two isolates in each (> 30% similarity). Among the cellular lipids, the phospholipid composition did not differ by strain, whereas the glycolipid pattern differed markedly. Especially, the relative concentration of cord factor and sulfolipid, both of which were known as virulent factors, varied by strain. The fingerprints of some strains showed an association between the DNA and glycolipid patterns, even though some of the same DNA fingerprint strains showed differences in lipid patterns. Among the patient isolates, M. tuberculosis strain 249 possessed a specific glycolipid with 2-O-methyl-L-rhamnose and L-rhamnose, which is rarely found in other strains. This glycolipid showed serological activity against the sera of tuberculosis patients, even if the reactivity was not as strong as trehalose dimycolate. It also showed the inhibition of phagosome-lysosome fusion in macrophages, suggesting involvement with virulence. These results suggest that RFLP analysis using IS6110 is useful for clustering the human isolates of M. tuberculosis, however, for further strain differentiation on virulence, a lipid analysis provides more information.

[Serodiagnosis of tuberculosis by detection of antituberculous glycolipid antigen (TBGL antigen) antibodies in serum using enzyme-linked immunosorbent assay: clinical evaluation of anti-TBGL antibodies assay kit]

Kyowa Medex Co., Ltd. developed the kit for the sero-diagnosis of tuberculosis, which detects IgG antibodies against tuberculous glycolipids antigen containing cord factor (TBGL antigen) prepared from M. tuberculosis using the enzyme-linked immunosorbent assay technique. We evaluated the kit using clinical specimens and the results are as follows: 1) In total, 34 out of 39 cases (87.2%) with active pulmonary tuberculosis showed positive anti-TBGL antibody. 2) Patients with cavity, patients with extensive lesions and patients excreting large amount of acid fast bacilli tended to show high positivity rates. 3) The antibody titers increased in 7 out of 11 cases after starting the antituberculous chemotherapy. 4) The use of the antibody is unsuitable for the determination of the activity of tuberculosis since the antibody titers only slightly decreased even after chemotherapy for two years. 5) Two out of four nontuberculous mycobacteriosis cases showed high antibody titers 6) All three AIDS patients with tuberculosis showed low antibody titers. 7) The antibody was negative in almost all healthy controls showing a positive PPD skin test after vaccination with BCG, and it was therefore assumed that the antibody titer is not increased by BCG vaccination. 8) The antibody titers of the staff members working in the tuberculosis wards were not high compared with those of staff members working in the other wards.

The serum neutralizing antibody response in cattle to Fusobacterium necrophorum leukotoxoid and possible protection against experimentally induced hepatic abscesses

The serum antileukotoxin antibody response and protection against subsequent experimental challenge with Fusobacterium necrophorum were investigated in 30 steers vaccinated with crude F. necrophorum leukotoxoid. Culture supernatant of F. necrophorum, strain 25, containing leukotoxoid was concentrated. The steers were assigned randomly to six groups (n = 5): PBS control with Stimulon adjuvant; vaccinated with concentrated supernatant diluted to provide 2.5, 5.0, 10.0, or 20.0 ml with the water-soluble Stimulon adjuvant; and 5.0 ml with the Ribi oil-emulsion adjuvant. The steers were injected subcutaneously on days 0 and 21. Blood samples were collected at weekly intervals to monitor serum antileukotoxin antibody titres. On day 42, all the steers were challenged intraportally with F. necrophorum culture. Three weeks later (day 63), the steers were killed and necropsied for examination of their livers and assessment of protection. Steers vaccinated with crude leukotoxoid tended to have higher antileukotoxin titres than the controls, but the difference was not significant. Also, the antibody titre did not appear to be dose-dependent. In the control group, 3 out of 5 steers developed liver abscesses. The incidence of liver abscesses in steers vaccinated with Stimulon adjuvant was not dose related; however, only 8 of the 25 vaccinated steers developed abscesses. None of the steers vaccinated with the 5.0 ml dose with Ribi had any abscesses. Evidence for a relationship between antileukotoxin antibody and protection was shown by the lower titre in those steers that developed abscesses compared to those that did not. It was concluded that antileukotoxin antibody titres probably provided some degree of protection against experimentally induced liver abscesses, but further dose-titration studies using Ribi or possibly another more effective adjuvant will be needed to confirm this.

Detection of anti-cord factor antibodies in intestinal tuberculosis for its differential diagnosis from Crohn's disease and ulcerative colitis

We have developed a diagnostic method for pulmonary tuberculosis by detecting antibody to cord factor using enzyme-linked immunosorbent assay (ELISA). This study was to evaluate the usefulness of our method for a diagnosis of intestinal tuberculosis, and especially its ability to differentiate this disease from other inflammatory bowel diseases. Antibodies of the immunoglobulin G class against cord factor (trehalose-6,6'-dimycolate) from 27 patients with intestinal tuberculosis, 16 patients with Crohn's disease (CD), and 27 patients with ulcerative colitis (UC) were tested by ELISA with cord factor purified from Mycobacterium tuberculosis H37Rv as the antigen. Twenty-three of the 27 patients with intestinal tuberculosis (85%) showed elevated values distinct from healthy controls. None of the patients with CD showed an elevation of antibody titers. Of the 27 patients with UC, 26 (96%) did not show any anti-cord factor antibody elevation. We conclude that this method is simple and results are reproducible. The results of our study justify undertaking the detection of anti-cord factor antibodies to diagnose intestinal tuberculosis.

Evaluation of several adjuvants as alternatives to the use of Freund's adjuvant in rabbits

In three experiments we evaluated several types of adjuvants as an alternative to Freund's adjuvant (FA). In the first experiment three adjuvant preparations (a water-in-oil emulsion (Specol), a combination preparation of monophosphoryl lipid A + trehalose dimycolate + cell wall skeleton and a non-ionic block polymer surfactant (TiterMax)) were evaluated. The adjuvants were combined with three different types of weak immunogenic antigens (synthetic peptide, glycolipid and particulate antigen) and administered following the intramuscular and subcutaneous route. The evaluation was based on clinical, pathological and immunological parameters. The animals did not appear to be severely or chronically impaired by the experiment. After injection of the RIBI adjuvant, side effects of the same severity as with FA were induced, while low antibody titers were produced. TiterMax caused few side effects, while antibody responses were very low. In comparing Specol and FA, Specol had far fewer adverse effects than FA. However, Specol had immunostimulating properties of the same level as FA. In the second experiment, the effect of injected volume of FA on side effects and antibody titer was studied. Immunization of rabbits with a total of 0.5 ml FA at different sites does not seem to increase the immune response when compared with the immune response seen after injection of 0.5 ml FA at one site. However side effects were seen in all the animals. In the third experiment, the side effects following intradermal (i.d.) injection of the adjuvants were studied. After i.d. injection of FA or RIBI, undesirable effects were found. No side effects occurred after i.d. injection of Specol or TiterMax. From the studies it is concluded that Specol is an alternative to FA for hyperactivation of the immune response in rabbits.

Clinical evaluation of rapid serodiagnosis of pulmonary tuberculosis by ELISA with cord factor (trehalose-6,6'-dimycolate) as antigen purified from Mycobacterium tuberculosis

Immunoglobulin G (IgG) antibodies against purified cord factor (trehalose-6,6'-dimycolate) prepared from Mycobacterium tuberculosis H37Rv were determined by enzyme-linked immunosorbent assay (ELISA), and its diagnostic usefulness was evaluated. Serum specimens from 65 patients with active pulmonary tuberculosis, 58 patients with inactive pulmonary tuberculosis, 36 patients with diseases other than tuberculosis, and 66 healthy adults were examined. Patients with active pulmonary tuberculosis showed significantly higher titers of IgG antibodies against cord factor than did other groups (p < 0.001). The antibody titer greater than 0.29 in absorption difference (492 to 630 nm) of 160-times diluted serum was set as positive in ELISA. For patients with active and untreated pulmonary tuberculosis, the ELISA had a sensitivity of 81% and a specificity of 96%. From these results, it was concluded that the detection of IgG antibodies against cord factor is useful for serodiagnosis of active pulmonary tuberculosis. It was also indicated that the anticord factor antibody titers decline to the normal level as a result of antituberculosis chemotherapy.

Immunoadjuvant activity of a liposomal IL-6 formulation

The adjuvant effect of interleukin 6 (IL-6) entrapped in liposomes was evaluated using a 65 kDa heat shock protein as a model antigen. The secondary humoral immune response either to antigen alone, or incorporated into liposomes, and the effect of IL-6 entrapped in liposomes, on this response were studied in Balb/c mice. The adjuvanticity of these formulations was compared with that of potent adjuvants such as Ribi and dimethyldioctadecylammoniumbromide (DDA). The importance of IL-6 during adjuvant activity was supported by the observation that high serum IL-6 levels were induced in Balb/c mice by all members of a panel of adjuvants tested. Following incorporation into liposomes, IL-6 retained its full biological activity, as shown by its capacity to sustain growth of the IL-6-dependent B9 cell line. At antigen dosages where Ribi and DDA gave minimal or no secondary antibody titres, incorporation of antigen into liposomes resulted in measurable secondary antibody titres. Interestingly, this adjuvant activity was significantly enhanced when liposomes containing IL-6 were co-injected with the liposomal antigen formulation. These results illustrate the potential adjuvant properties of this formulation, which seem especially useful for vaccines containing weak or non-immunogenic antigens.

Inhibition of interleukin-6 release and T-cell proliferation by synthetic mirror pseudo cord factor analogues in human peripheral blood mononuclear cells

The effects of synthetic alkyl ((alkyl 6-deoxy-a-D-gluco-heptopyranosyluronate) 6-deoxy-a-D-gluco-heptopyranoside) uronates, a novel type of mirror pseudo cord factor, on the in vitro modulation of interleukin-6 production and T-cell proliferation in human peripheral blood mononuclear cells, were investigated. Synthetic mirror pseudo cord factors with alkyl chains ranging from C16 to C18 have very weak interleukin-6-inducing capacities and lack mitogenic activities for T-cell proliferation. However, they could inhibit IL-6 release induced by sonicated Bacillus Calmette-Guérin (S-BCG), bacterial endotoxin, and phytohaemagglutinin in a dose-dependent manner. Inhibition was observed not only with mononuclear cells but also with purified monocytes. Furthermore, these synthetic compounds could suppress T-lymphocyte proliferation stimulated by sonicated Mycobacterium tuberculosis H37Rv (S-H37Rv) antigens, S-BCG antigens, as well as by recombinant 65 kDa mycobacterial heat-shock protein. In contrast, these compounds failed to inhibit the phytohaemagglutinin-induced T-cell proliferation. We conclude that the inhibition of cytokine release and T-cell proliferation by synthetic mirror pseudo cord factors was due to direct blocking of the function and/or activity of monocytes or antigen-presenting cells.