Cell wall skeleton of Mycobacterium bovis BCG enhances the vaccine potential of antigen 85B against tuberculosis by inducing Th1 and Th17 responses

A safe and effective adjuvant is necessary to induce reliable protective efficacy of the protein-based vaccines against tuberculosis (TB). Mycobacterial components, such as synthetic cord factor and arabinogalactan, have been used as one of the adjuvant components. Mycobacterium bovis bacillus Calmette- Guérin cell-wall skeleton (BCG-CWS) has been used as an effective immune-stimulator. However, it is not proven whether BCG-CWS can be an effective adjuvant for the subunit protein vaccine of TB. In this study, we demonstrated that the BCG-CWS effectively coupled with Ag85B and enhanced the conjugated Ag85B activity on the maturation of dendritic cells (DCs). Ag85B-BCG-CWS-matured DCs induced significant Th1 and Th17 responses when compared to BCG-CWS or Ag85B alone. In addition, significant Ag85B-specific Th1 and Th17 responses were induced in Ag85B-BCG-CWS-immunized mice before infection with M. tuberculosis and maintained after infection. Moreover, Ag85B-BCG-CWS showed significant protective effect comparable to live BCG at 6 weeks after infection and maintained its protective efficacy at 32 weeks post-challenge, whereas live BCG did not. These results suggest that the BCG-CWS may be an effective adjuvant candidate for a protein-based vaccine against TB.

Mycobacterial cell-wall skeleton as a universal vaccine vehicle for antigen conjugation

Mycobacterial cell-wall skeleton (CWS) is an immunoactive and biodegradable particulate adjuvant and has been used for immunotherapy in patients with cancer. The CWS of Mycobacterium bovis bacillus Calmette-Guérin (BCG-CWS) was studied as a universal vaccine vehicle for antigen conjugation, to develop potentially effective and safe vaccines. Here, we describe experiments in which protein antigens, such as keyhole limpet haemocyanin (KLH), ovalbumin (OVA) and bovine serum albumin (BSA) were highly efficiently coupled to 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide (EDC/NHS)-activated carboxyl groups of BCG-CWS, and tested the immunogenicity of OVA-conjugated BCG-CWS vaccine. We found that a strong immune response was induced in mice immunised with OVA-conjugated BCG-CWS, which was similar to the enhancement of the immune responses in mice immunised with OVA and complete Freund's adjuvant. Covalent conjugation of OVA to BCG-CWS was essential for Th1-skewed immune responses, with prominent expression of IFN-γ. Furthermore, antigen-conjugated BCG-CWS vaccine is simple to manufacture, safe, and easy to use. Our results suggest that mycobacterial CWS as a universal vaccine vehicle for conjugation of a wide variety of antigens constitutes a breakthrough for development of the most promising vaccines for infections, allergic diseases, and cancer.

Bacillus calmette-guerin cell wall cytoskeleton enhances colon cancer radiosensitivity through autophagy

The cell wall skeleton of Mycobacterium bovis Bacillus Calmette-Guerin (BCG/CWS) is an effective antitumor immunotherapy agent. Here, we demonstrate that BCG/CWS has a radiosensitizing effect on colon cancer cells through the induction of autophagic cell death. Exposure of HCT116 colon cancer cells to BCG/CWS before ionizing radiation (IR) resulted in increased cell death in a caspase-independent manner. Treatment with BCG/CWS plus IR resulted in the induction of autophagy in colon cancer cells. Either the autophagy inhibitor 3-methyladenine or knockdown of beclin 1 or Atg7 significantly reduced tumor cell death induced by BCG/CWS plus IR, whereas the caspase inhibitor z-VAD-fmk failed to do so. BCG/CWS plus IR-mediated autophagy and cell death was mediated predominantly by the generation of reactive oxygen species (ROS). The c-Jun NH(2)-terminal kinase pathway functioned upstream of ROS generation in the induction of autophagy and cell death in HCT116 cells after co-treatment with BCG/CWS and IR. Furthermore, toll-like receptor (TLR) 2, and in part, TLR4, were responsible for BCG/CWS-induced radiosensitization. In vivo studies revealed that BCG/CWS-mediated radiosensitization of HCT116 xenograft growth is accompanied predominantly by autophagy. Our data suggest that BCG/CWS in combination with IR is a promising therapeutic strategy for enhancing radiation therapy in colon cancer cells through the induction of autophagy.

Mycobacterium tuberculosis HBHA protein reacts strongly with the serum immunoglobulin M of tuberculosis patients

Identification and characterization of serologically active mycobacterial antigens are prerequisites for the development of diagnostic reagents. We examined the humoral immune responses of active tuberculosis (TB) patients against Triton-soluble proteins extracted from Mycobacterium tuberculosis by immunoblotting. A 29-kDa protein reacted with immunoglobulin M (IgM) in the pooled sera of the patients, and its N-terminal amino acid sequence matched that of the heparin-binding hemagglutinin (HBHA). Recombinant full-length HBHA was expressed in Escherichia coli (rEC-HBHA) and M. smegmatis (rMS-HBHA). In immunoblot analysis, the IgM antibodies of the TB patients reacted strongly with rMS-HBHA but not with rEC-HBHA, whereas the IgG antibodies of these patients reacted weakly with both recombinant HBHA proteins. In enzyme-linked immunosorbent assay analysis using rMS-HBHA and 85B as antigens, the mean levels and sensitivities of the anti-HBHA IgM antibodies of the TB patients were significantly higher than those of the anti-antigen 85B IgM antibodies, while the IgG antibodies showed the opposite results. Of interest in this respect, the pooled sera from the TB patients that contained anti-HBHA IgM antibodies neutralized the entry of M. tuberculosis into epithelial cells. These findings suggest that IgM antibody to HBHA may play a role in protection against extrapulmonary dissemination.

Protein kinase C zeta plays an essential role for Mycobacterium tuberculosis-induced extracellular signal-regulated kinase 1/2 activation in monocytes/macrophages via Toll-like receptor 2

This study characterized the upstream signalling molecules involved in extracellular signal-regulated kinase (ERK) 1/2 activation and determined their effects on differential tumour necrosis factor (TNF)-alpha expression by monocytes/macrophages infected with virulent or avirulent mycobacteria. The avirulent Mycobacterium tuberculosis (MTB) strain H37Ra (MTBRa) induced higher levels of activation of ERK 1/2 and the upstream MAPK kinase (MEK)1 and, subsequently, higher levels of TNF-alpha expression in human primary monocytes and monocyte-derived macrophages, as compared with MTB strain H37Rv (MTBRv). The MTB-induced activation of ERK 1/2 was not dependent on Ras or Raf. However, inhibition of the activity of atypical protein kinase C (PKC) zeta decreased the in vitro phosphorylation of MEK, ERK 1/2 activation and subsequent TNF-alpha induction caused by MTBRv or MTBRa. Toll-like receptor (TLR) 2 was found to play a major role in MTB-induced TNF-alpha expression and PKCzeta phosphorylation. Co-immunoprecipitation experiments showed that PKCzeta interacts physically with TLR2 after MTB stimulation. Moreover, PKCzeta phosphorylation was increased more in macrophages following MTBRa, versus MTBRv, infection. This is the first demonstration that PKCzeta interacts with TLR2 to play an essential role in MTB-induced ERK 1/2 activation and subsequent TNF-alpha expression in monocytes/macrophages.

Role of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase pathways in the secretion of tumor necrosis factor-alpha and interleukin-10 by the PPD antigen of Mycobacterium tuberculosis

Here we investigated the role of the phosphatidylinositol 3-kinase (PI 3-K) and mitogen-activated protein kinase (MAPK) pathways in the secretion of tumor necrosis factor (TNF)-alpha and interleukin (IL)-10 in human primary monocytes after stimulation with the PPD antigen of Mycobacterium tuberculosis. MAPK [extracellular signal-regulated kinase (ERK) 1/2 and p38] and Akt are rapidly phosphorylated in human monocytes stimulated with PPD. We found that the PI 3-K-Akt pathway stimulated by PPD is essential for both IL-10 and TNF-alpha production, although the inhibition of IL-10 production was more pronounced. The analysis of cytokine production using specific inhibitors of the MAPK pathway revealed that both p38 and ERK activation are essential for PPD-induced TNF-alpha production, whereas p38, but not ERK, activation is essential for IL-10 secretion. The inhibition of PI 3-K did not significantly activate p38 MAPK or ERK 1/2 in PPD-stimulated human monocytes. Further, the Src inhibitor PP2 inhibited the release of TNF-alpha but enhanced IL-10 release, suggesting the differential regulation of Src kinase in upstream signaling. Collectively, these data suggest that the PI 3-K and MAPK pathways play a central role in the regulation of both pro- and anti-inflammatory cytokines by the PPD antigen of M. tuberculosis.

Intracellular network of phosphatidylinositol 3-kinase, mammalian target of the rapamycin/70 kDa ribosomal S6 kinase 1, and mitogen-activated protein kinases pathways for regulating mycobacteria-induced IL-23 expression in human macrophages

We previously demonstrated that Mycobacterium tuberculosis (M. tbc)-induced interleukin (IL)-12 expression is negatively regulated by the phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated kinase (ERK) 1/2 pathways in human monocyte-derived macrophages (MDMs). To extend these studies, we examined the nature of the involvement of toll-like receptors (TLRs) and intracellular signalling pathways downstream from PI3K in M. tbc-induced IL-23 expression in human MDMs. M. tbc-induced Akt activation and IL-23 expression were essentially dependent on TLR2. Blockade of the mammalian targets of rapamycin (mTOR)/70 kDa ribosomal S6 kinase 1 (S6K1) pathway by the specific inhibitor rapamycin greatly enhanced M. tbc-induced IL-12/IL-23 p40 (p40) and IL-23 p19 (p19) mRNA and IL-23 protein expression. In sharp contrast, p38 mitogen-activated protein kinase (MAPK) inhibition abrogated the p40 and p19 mRNA and IL-23 protein expression induced by M. tbc. Furthermore, the inhibition of PI3K-Akt, but not ERK 1/2 pathway, attenuated M. tbc-induced S6K1 phosphorylation, whereas PI3K inhibition enhanced p38 phosphorylation and apoptosis signal-regulating kinase 1 activity during exposure to M. tbc. Although the negative or positive regulation of IL-23 was not reversed by neutralization of IL-10, it was significantly modulated by blocking TLR2. Collectively, these findings provide new insight into the homeostatic mechanism controlling type 1 immune responses during mycobacterial infection involving the intracellular network of PI3K, S6K1, ERK 1/2 and p38 MAPK pathways in a TLR2-dependent manner.

The mycobacterial 38-kilodalton glycolipoprotein antigen activates the mitogen-activated protein kinase pathway and release of proinflammatory cytokines through Toll-like receptors 2 and 4 in human monocytes

Although the 38-kDa glycolipoprotein of Mycobacterium tuberculosis H37Rv is known to evoke prominent cellular and humoral immune responses in human tuberculosis (TB), little information is known about intracellular regulatory mechanisms involved in 38-kDa antigen (Ag)-induced host responses. In this study, we found that purified 38-kDa glycolipoprotein activates mitogen-activated protein kinases (MAPKs; extracellular signal-regulated kinase 1/2 [ERK1/2] and p38) and induces tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) in human monocytes. When the 38-kDa Ag was applied to monocytes from TB patients and healthy controls, the activation of ERK1/2 and p38 MAPK and the subsequent cytokine secretion were greater in the monocytes from the active pulmonary TB patients than in monocytes from the healthy controls. Additionally, neutralizing antibodies for Toll-like receptor 2 (TLR2) or TLR4 significantly reduced the ERK1/2 and p38 activation induced by the 38-kDa protein when the antibodies were applied to HEK293 cells overexpressing TLR2 or TLR4 as well as human primary monocytes. Furthermore, the inhibition of TLR2 significantly, and that of TLR4 partially, decreased the 38-kDa Ag-induced secretion of TNF-alpha and IL-6 in human monocytes. The intact protein moieties of the 38-kDa protein were responsible for biologic activities by this Ag. These data collectively demonstrate that the 38-kDa glycolipoprotein, acting through both TLR2 and TLR4, induces the activation of the ERK1/2 and p38 MAPK pathways, which in turn play an essential role in TNF-alpha and IL-6 expression during mycobacterial infection.

Identification of the new T-cell-stimulating antigens from Mycobacterium tuberculosis culture filtrate

The proteins secreted by Mycobacterium tuberculosis are an important target for vaccine development. To identify the antigens from M. tuberculosis culture filtrate (CF) that strongly stimulate T-cells, the CF was fractionated by ion-exchange chromatography and then non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis with mini-whole gel elution. Each fraction was screened for its ability to induce interferon-gamma (IFN-gamma) production in peripheral blood mononuclear cells isolated from healthy tuberculin reactors. The protein bands that strongly induced IFN-gamma production were subjected to N-terminal sequencing. Two new proteins, a 17-kDa protein (Rv0164, MTSP17) and an 11-kDa (Rv3204, MTSP11) protein, were identified. The recombinant MTSP17 (rMTSP17) and rMTSP11 induced significant production of IFN-gamma and interleukin (IL)-12p40 in peripheral blood mononuclear cells from healthy tuberculin reactors. Interestingly, IL-12p40 production in response to rMTSP11 was significantly higher than that in response to rMTSP17 or the three components of the antigen 85 complex. These results suggest that MTSP11 antigen should be further evaluated as a component of a subunit vaccine.

Interleukin-8 is differentially expressed by human-derived monocytic cell line U937 infected with Mycobacterium tuberculosis H37Rv and Mycobacterium marinum

Although Mycobacterium marinum is closely related to Mycobacterium tuberculosis H37Rv genomically, the clinical outcome in humans is quite different for M. marinum and M. tuberculosis infections. We investigated possible factors in the host macrophages for determining differential pathological responses to M. tuberculosis and M. marinum using an in vitro model of mycobacterial infection. Using suppression-subtractive hybridization, we identified 12 differentially expressed genes in the human monocytic cell line U937 infected with M. tuberculosis and M. marinum. Of those genes, the most frequently recovered transcript encoded interleukin-8 (IL-8). Northern hybridization revealed that IL-8 mRNA was highly upregulated in M. tuberculosis-infected U937 cells compared with M. marinum-infected cells. In addition, enzyme-linked immunosorbent assay showed that IL-8 protein secretion was significantly elevated in M. tuberculosis-infected U937 cells, human primary monocytes, and monocyte-derived macrophages compared with that in M. marinum-infected cells. The depressed IL-8 expression was unique in M. marinum-infected cells compared with cells infected with other strains of mycobacteria, including M. tuberculosis H37Ra, Mycobacterium bovis BCG, or Mycobacterium smegmatis. When the expression of NF-kappaB was assessed in mycobacterium-infected U937 cells, IkappaBalpha proteins were significantly degraded in M. tuberculosis-infected cells compared with M. marinum-infected cells. Collectively, these results suggest that differential IL-8 expression in human macrophages infected with M. tuberculosis and M. marinum may be critically associated with distinct host responses in tuberculosis. Additionally, our data indicate that differential signal transduction pathways may underlie the distinct patterns of IL-8 secretion in cells infected by the two mycobacteria.

Role of mitogen-activated protein kinase pathways in the production of tumor necrosis factor-alpha, interleukin-10, and monocyte chemotactic protein-1 by Mycobacterium tuberculosis H37Rv-infected human monocytes

The role of mitogen-activated protein kinase (MAPK) pathways in the secretion of tumor necrosis factor (TNF)-alpha, interleukin (IL)-10, IL-8, and monocyte chemotactic protein-1 (MCP-1) was investigated in human monocytes that were infected with Mycobacterium tuberculosis H37Rv. Analysis of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 kinase showed rapid phosphorylation of both subfamilies in response to M. tuberculosis H37Rv. Using highly specific inhibitors of p38 (SB203580) and of MAPK kinase-1 (U0126 and PD98059), we found that both p38 and ERK were essential for M. tuberculosis H37Rv-induced TNF-alpha production, whereas activation of the p38 pathway, but not that of ERK, was essential for M. tuberculosis H37Rv-induced IL-10 production. Interestingly, the ERK pathway, but not that of p38, was critical for MCP-1 secretion from human monocytes that were infected with M. tuberculosis H37Rv. However, IL-8 secretion was not regulated by ERK1/2 or p38 MAPK. Collectively, these results suggest that induction of the MAPK pathway is required for the expression of TNF-alpha, IL-10, and MCP-1 by human monocytes during M. tuberculosis H37Rv infection.

Depressed interleukin-12 production by peripheral blood mononuclear cells after in vitro stimulation with the 30-kDa antigen in recurrent pulmonary tuberculosis patients

Some patients develop recurrent tuberculosis (R-TB), even after successfully completing initial anti-tubercular treatment. Although R-TB may be caused by relapse or exogenous reinfection, little is known about the underlying host responses associated with R-TB. This study investigated the profile of cytokines [interferon (IFN)-gamma, interleukin (IL)-12, tumor necrosis factor (TNF)-alpha, IL-6, and IL-10] present in peripheral blood mononuclear cells (PBMCs) of 17 R-TB patients after stimulation with the 30-kDa antigen (Ag) or purified protein derivative (PPD) Ag of Mycobacterium tuberculosis. These data were compared with data obtained from 15 patients with newly diagnosed pulmonary TB (N-TB), 22 patients with treatment failure (TF-TB), and 19 healthy tuberculin reactors (HTR). N-TB and R-TB patients were enrolled in this study within 1 month of beginning anti-tubercular chemotherapy. ELISA results showed that IFN-gamma production following stimulation with the 30-kDa Ag was significantly lower in each group of TB patients than in the HTR controls. In addition, patients with R-TB showed the most significant IL-12 depression among the subject groups after in vitro stimulation with either Ag. Furthermore, a significant decrease in TNF-alpha and IL-10 levels was observed in R-TB patients relative to N-TB patients. However, there was no statistical difference in TNF-alpha and IL-10 production between R-TB patients, TF-TB patients, and HTR controls. Our findings suggest that the underlying mechanisms of cytokine regulation might differ between N-TB and R-TB patients, and that decreased IL-12 production in response to the 30-kDa or PPD Ag might be involved in the immunopathogenesis of human R-TB.

Depressed interleukin-12 (IL-12), but not IL-18, production in response to a 30- or 32-kilodalton mycobacterial antigen in patients with active pulmonary tuberculosis

The secreted 30-kDa antigen (Ag) of Mycobacterium tuberculosis directly stimulates Th1-type protective cytokine responses in healthy tuberculin reactors but not in patients with active tuberculosis (TB). To examine the cytokine profiles attributable to Th1 suppression associated with active TB, interleukin-12 (IL-12), IL-18, and IL-10 production in response to a 30- or 32-kDa Ag in 16 patients with active pulmonary TB and 24 healthy controls was investigated by enzyme-linked immunosorbent assay. In TB patients, production of IL-12 p40, as well as gamma interferon (IFN-gamma), by 30- or 32-kDa Ag-stimulated peripheral blood mononuclear cells (PBMC) was significantly decreased compared with that in healthy tuberculin reactors. There were no significant differences in IL-18 production between patients and controls early during stimulation (16 h). However, PBMC from patients showed significantly enhanced IL-18 proteins after 96 h of stimulation. Similarly, higher IL-10 production was observed in the TB patients than in healthy tuberculin reactors. After 2 months of anti-TB therapy, the mean IFN-gamma and IL-12 p40 production and the mean blastogenic responses were significantly increased in PBMC in the 10 TB patients who were followed up. Our findings provide evidence that depressed IL-12 in response to the 30- or 32-kDa Ag is involved in the immunopathogenesis of human active pulmonary TB.

Dysregulated production of interferon-gamma, interleukin-4 and interleukin-6 in early tuberculosis patients in response to antigen 85B of Mycobacterium tuberculosis

Both interferon-gamma (IFN-gamma) and interleukin (IL)-4 expression in T cells and IL-6 expression in cells of the monocyte/macrophage lineage were monitored using antigen 85B (Ag85B) protein and purified protein derivative (PPD) antigen in the early stages of tuberculosis (TB). We showed that the levels of cell-associated IFN-gamma and IL-4 (mRNA and intracellular cytokine) in Ag85B-stimulated T cells were significantly depressed in TB patients compared with those in healthy tuberculin reactors. On the other hand, the capacity of peripheral blood mononuclear cells (PBMC) to produce IL-6 spontaneously ex vivo was enhanced in patients (P < 0. 001), but their corresponding capacities to respond to Ag85B were not significantly different from those of normal donors. After 2 months of antituberculosis therapy, the mean blastogenic responses of Ag85B-stimulated PBMC from seven TB patients were increased 6. 1-fold (P = 0.011). Furthermore, the proportions of both IFN-gamma- (P < 0.01) and IL-4- (P = 0.05) producing T cells were significantly increased. However, those of IL-6-producing cells were diminished in response to Ag85B (P = 0.05). Our results suggest that there may be an altered regulation of IFN-gamma, IL-4 and IL-6 to Ag85B in the early stages of TB.

Isolation and partial characterisation of the Triton X-100 solubilised protein antigen from Mycobacterium tuberculosis

This report describes extraction of a new native antigen fraction from Mycobacterium tuberculosis without massive degradation of proteins by Triton X-100. The Triton X-100 solubilised protein (TSP) antigen showed a characteristic antigen profile and reproducible extraction pattern. To characterise the nature of their composition, the TSP antigen was fractionated by Triton X-114 phase partitioning. The TSP antigen contained a variety of lipids and glycoconjugates as well as diverse proteins. Most proteins were partitioned into the aqueous phase during phase fractionation, whereas non-protein molecules and lipoproteins were recovered in the detergent phase. The lymphoproliferative responses to the TSP aqueous fraction in healthy tuberculin reactors were significantly higher than those to the purified protein derivative (PPD) and unfractionated TSP. In contrast, the antibody responses to TSP aqueous fraction in tuberculosis patients showed weak reactivity. This study suggests that the TSP aqueous fraction can be used as a T-cell antigen associated with protective immunity against tuberculosis.

Site-directed mutagenesis of tryptophan residues to conserved hydrophobic residues inhibits the processing of human KB cell folate receptor

We are interested in identifying the ligand binding site of the human folate receptor (hFR). Previous reports have suggested a role of tryptophan(W) residues in ligand binding. We used site-directed mutagenesis to change the conserved W residues in positions 86, 116, 142, 143, 156, 160, and 193 of the hFR to either leucine(L) or phenylalanine(F) to examine the role of these W residues in hFR function. Although all W to L changes except W86L produced unstable proteins, W to F changes were tolerated. Based on total folate binding and transport studies, Chinese hamster ovary (CHO) cells transfected with W86L, W116F, and W143F expressed high levels of functional hFR, equivalent to cells transfected with wt hFR. CHO cells transfected with W142F, W156F, W160F, and W193F expressed low or undetectable levels of functional hFR although mRNA was present. Of these four mutants, only W142F expressed easily detectable immunoprecipitable protein but it was not fully glycosylated. Since glycosylation may affect the ability of hFR to bind folate, we expressed W142F in Xenopus oocytes which glycosylate the mutant and wild type proteins to the same apparent extent. In oocytes, the stoichiometry of folate binding was identical between the fully processed mutant protein and the wild type hFR. These results indicate that in CHO cells three of the seven W mutations (W86L, W116F, and W143F) function normally, whereas four of the seven W mutations (W142F, W156F, W160F, and W193F) produce unstable or abnormally processed protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Stable transfectants of human MCF-7 breast cancer cells with increased levels of the human folate receptor exhibit an increased sensitivity to antifolates

A major problem in cancer therapy is tumor drug resistance such as is found with antifolates (e.g., methotrexate [MTX]). We are specifically interested in the role of the human folate receptor (hFR) in MTX resistance. To investigate whether transfection of hFR results in increased MTX uptake and increased drug sensitivity, human mammary carcinoma (MCF-7) cells and Chinese hamster ovary cells (CHO) (cells which do not express detectable levels of hFR) were transfected with hFR cDNA. Stable human mammary carcinoma and Chinese hamster ovary transfectants expressing high levels of hFR were selected for further analysis. Transfected cells which express increased levels of hFR grow more rapidly than mock transfected or wild type cells in media containing physiologic concentrations of folates. The hFR expressed by these cells is sorted to the plasma membrane and is functional as determined by cell surface binding of a radiolabeled folic acid derivative and by internalization of [3H]methotrexate. The stable transfectants that express increased levels of hFR are also more sensitive to MTX in physiologic concentrations of folates. We conclude that increased expression of hFR by human mammary carcinoma and Chinese hamster ovary cells cultured under these conditions results in an enhanced growth rate, increased folic acid binding, and increased MTX uptake and cytotoxicity.

Monoclonal antibodies against beta-antigen of Mycobacterium tuberculosis and their interspecies reactivities

Beta-antigen is one of the major proteins of Mycobacterium tuberculosis. We purified this antigen from the unheated culture filtrate of Mycobacterium tuberculosis Aoyama B and obtained nine monoclonal antibodies against the beta-antigen. Nine monoclonal antibodies were divided into two groups according to their patterns on Western blotting. The result indicated the existence of two or more determinant groups against these monoclonal antibodies on the beta-antigen molecule. The interspecies reactivity of monoclonal antibodies among twenty-one species of Mycobacteria was also examined by dot blotting analysis. Two monoclonal antibodies, designated 4G5E10 and 5F3F2, showed a specificity restricted to the Mycobacterium tuberculosis complex, could be used for serodiagnosis of Mycobacterium tuberculosis infection.