Regulation of the yeast Yap1p nuclear export signal is mediated by redox signal-induced reversible disulfide bond formation

Yap1p, a crucial transcription factor in the oxidative stress response of Saccharomyces cerevisiae, is transported in and out of the nucleus under nonstress conditions. The nuclear export step is specifically inhibited by H(2)O(2) or the thiol oxidant diamide, resulting in Yap1p nuclear accumulation and induction of transcription of its target genes. Here we provide evidence for sensing of H(2)O(2) and diamide mediated by disulfide bond formation in the C-terminal cysteine-rich region (c-CRD), which contains 3 conserved cysteines and the nuclear export signal (NES). The H(2)O(2) or diamide-induced oxidation of the c-CRD in vivo correlates with induced Yap1p nuclear localization. Both were initiated within 1 min of application of oxidative stress, before the intracellular redox status of thioredoxin and glutathione was affected. The cysteine residues in the middle region of Yap1p (n-CRD) are required for prolonged nuclear localization of Yap1p in response to H(2)O(2) and are thus also required for maximum transcriptional activity. Using mass spectrometry analysis, the H(2)O(2)-induced oxidation of the c-CRD in vitro was detected as an intramolecular disulfide linkage between the first (Cys(598)) and second (Cys(620)) cysteine residues; this linkage could be reduced by thioredoxin. In contrast, diamide induced each pair of disulfide linkage in the c-CRD, but in this case the cysteine residues in the n-CRD appeared to be dispensable for the response. Our data provide evidence for molecular mechanisms of redox signal sensing through the thiol-disulfide redox cycle coupled with the thioredoxin system in the Yap1p NES.

Nuclear import of the yeast AP-1-like transcription factor Yap1p is mediated by transport receptor Pse1p, and this import step is not affected by oxidative stress

The yeast AP-1-like transcription factor, Yap1p, is essential for the oxidative stress response in budding yeast. Yap1p is located predominantly in the cytoplasm; however, upon imposition of oxidative stress, Yap1p concentrates in the nucleus and activates target genes. Yap1p is constitutively transported in and out of the nucleus. Oxidative stress inhibits the Crm1p/Xpo1p-dependent nuclear export step, resulting in nuclear accumulation of Yap1p. In this study, we examined the mechanism for Yap1p nuclear import, and determined whether the import step is affected by oxidative stress. The nuclear accumulation of Yap1p required the activity of the small GTPase, Ran/Gsp1p. Under conditions in pse1-1 cells carrying a temperature-sensitive mutation of the importin beta family member PSE1/KAP121, nuclear translocation of Yap1p was inhibited dramatically. In an in vitro assay, we showed that Yap1p could directly bind to Pse1p and that this interaction was dissociated by Ran-GTP. These results indicate that Pse1p is the nuclear import receptor for Yap1p. In addition to Pse1p, we suggest that Kap123p, which is homologous to Pse1p, has a minor effect on the nuclear import of Yap1p. Furthermore, we identified the nuclear localization signal of Yap1p and demonstrated that the nuclear import of Yap1p was not affected by oxidative stress.

Two nuclear proteins, Cin5 and Ydr259c, confer resistance to cisplatin in Saccharomyces cerevisiae

In an attempt to identify genes that can confer resistance to cisplatin, we introduced a yeast genomic library into Saccharomyces cerevisiae and selected for transformants that grew in the presence of a normally toxic concentration of cisplatin. Plasmids were rescued from the transformants and were analyzed for the presence of individual open reading frames that conferred resistance to cisplatin. We isolated two genes, CIN5 and YDR259c, that increased resistance to cisplatin when overexpressed in Saccharomyces cerevisiae. These genes encoded two proteins, Cin5 and Ydr259c, that were homologous to yAP-1, a basic leucine zipper transcriptional factor that is known to mediate cellular resistance to various toxic agents. The two proteins exhibited stronger homology to each other (33.2% identity, 49.2% similarity) than to all other gene products in S. cerevisiae. Overexpression of each of these proteins also conferred resistance to two DNA-alkylating agents, methylmethanesulfonate and mitomycin C. An experiment with fusion proteins with green fluorescent protein revealed that Cin5 and Ydr259c were localized constitutively in the nuclei of yeast cells. Our results suggest that Cin5 and Ydr259c might be involved in pleiotropic drug-resistance and might protect yeast against the toxicity of cisplatin and other alkylating agents via a single mechanism. These two nuclear proteins might act as transcriptional factors, regulating the expression of certain genes that confer resistance to DNA-alkylating agents.

GFAT as a target molecule of methylmercury toxicity in Saccharomyces cerevisiae

Using a genomic library constructed from Saccharomyces cerevisiae, we have identified a gene GFA1 that confers resistance to methylmercury toxicity. GFA1 encodes L-glutamine:D-fructose-6-phosphate amidotransferase (GFAT) and catalyzes synthesis of glucosamine-6-phosphate. Transformed yeast cells expressing GFA1 demonstrated resistance to methylmercury but no resistance to p-chloromercuribenzoate, a GFAT inhibitor. The cytotoxicity of methylmercury was inhibited by loading excess glucosamine 6-phosphate into yeast. Considering that GFAT is an essential cellular enzyme, our findings suggest that GFAT is the major target molecule of methylmercury in yeasts. This report is the first to identify the target molecule of methylmercury toxicity in eukaryotic cells.

Autografting with peripheral blood CD34-positive cells following high-dose chemotherapy against breast cancer

We report autologous CD34+ cell transplantation performed in 3 cases of recurrent breast cancer. The hematological recovery in these cases was assessed by comparing with that in the previous cases of autologous hematopoietic stem cell transplantation performed with the same high-dose chemotherapy regimen. Patient 1 was a 32-year-old woman with pulmonary and skeletal metastases; patient 2, a 55-year-old woman with pulmonary metastases; and patient 3, a 48-year-old woman with hepatic metastases. On day 1, cyclophosphamide 1000 mg/m2 and epirubicin 130 mg/m2 were administered concurrently with granulocyte colony-stimulating factor, and peripheral blood stem cells were harvested on days 14-16. These stem cells were processed using anti-CD34 monoclonal antibody and an immunomagnetic bead device, Isolex 300i. The high-dose chemotherapy regimen consisted of cyclophosphamide 2000 mg/m2/day, div, and thiotepa 200 mg/m2/day, div on day -5, -4, and -3. The harvested CD34+ cells numbered 3.9 +/- 2.8 x 10(6)/kg (range: 0.73-7.8/10(6)/kg), and the CFU-GM, 8.3 +/- 5.6 x 10(5)/kg (range: 1.2-15.1/10(5)/kg). After the separation, the percent of CD34+ cells was 81.9 +/- 11.6% (range: 65.8-96.4%), the CD34+ cell yield, 71.8 +/- 30.2% (range: 46.0-129.6%), and the CFU-GM yield, 48.9 +/- 9.1% (range: 35.3-62.0%). At the time of transplantation, the number of nucleated cells was 0.55 +/- 0.31 x 10(5)/kg, and that of CFU-GM, 31.2 +/- 17.8 x 10(5)/kg. Comparison of the hematological recovery in these three cases with that in patients receiving an identical high-dose chemotherapy regimen revealed recovery rates significantly faster than in patients having bone marrow transplants, and approximately identical with that in peripheral blood stem cell transplantation cases.

Overexpression of L-glutamine:D-fructose-6-phosphate amidotransferase provides resistance to methylmercury in Saccharomyces cerevisiae

To identify novel genes that confer resistance to methylmercury (MeHg), a yeast genomic DNA library was transfected into Saccharomyces cerevisiae. Two functional plasmids were isolated from transfected yeast clones D1 and H5 that exhibited resistance to MeHg. The yeast transfected with plasmid isolated from clone H5 was several-fold more resistant than yeast transfected with plasmid from clone D1. Functional characterization of the genomic DNA fragment obtained from clone H5 determined that the GFA1 gene conferred resistance to MeHg. GFA1 was reported to encode L-glutamine:D-fructose-6-phosphate amidotransferase (GFAT) which catalyzes the synthesis of glucosamine-6-phosphate from glutamine and fructose-6-phosphate. Accumulation of mercury in yeast clone W303B/pGFA1, which contains the transfected GFA1 gene, did not differ from that in control yeast clone W303B/pYES2. The W303B/pGFA1 strain did not show resistance to mercuric chloride, zinc chloride, cadmium chloride or copper chloride, suggesting that the resistance acquired by GFA1 gene transfection might be specific to MeHg. This is the first report of a gene involved in MeHg resistance in eukaryotic cells identified by screening a DNA library.

Intracellular redistribution of truncated La protein produced by poliovirus 3Cpro-mediated cleavage

The La autoantigen (also known as SS-B), a cellular RNA binding protein, may shuttle between the nucleus and cytoplasm, but it is mainly located in the nucleus. La protein is redistributed to the cytoplasm after poliovirus infection. An in vitro translation study demonstrated that La protein stimulated the internal initiation of poliovirus translation. In the present study, a part of the La protein was shown to be cleaved in poliovirus-infected HeLa cells, and this cleavage appeared to be mediated by poliovirus-specific protease 3C (3Cpro). Truncated La protein (dl-La) was produced in vitro from recombinant La protein by cleavage with purified 3Cpro at only one Gln358-Gly359 peptide bond in the 408-amino-acid (aa) sequence of La protein. The dl-La expressed in L cells was detected in the cytoplasm. However, green fluorescence protein linked to the C-terminal 50-aa sequence of La protein was localized in the nucleus, suggesting that this C-terminal region contributes to the steady-state nuclear localization of the intact La protein in uninfected cells. The dl-La retained the enhancing activity of translation initiation driven by poliovirus RNA in rabbit reticulocyte lysates. These results suggest that La protein is cleaved by 3Cpro in the course of poliovirus infection and that the dl-La is redistributed to the cytoplasm. dl-La, as well as La protein, may play a role in stimulating the internal initiation of poliovirus translation in the cytoplasm.

Crm1 (XpoI) dependent nuclear export of the budding yeast transcription factor yAP-1 is sensitive to oxidative stress

BACKGROUND

The yAP-1 transcription factor is crucial for the oxidative stress response of the budding yeast Saccharomyces cerevisiae; its activity is induced in response to oxidative stress, and as a consequence the expression of a number of target genes is enhanced. We have shown previously that yAP-1 is mainly found in the cytoplasm, but that upon the imposition of oxidative stress it localizes to the nucleus. In this study, we addressed the mechanism through which yAP-1 nuclear localization is regulated.

RESULTS

Here we show that yAP-1 localization is mediated by active export from the nucleus, resulting from the activity of Crm1 (XpoI), a conserved protein that functions as an export receptor which recognizes the nuclear export signal (NES). When Crm1 expression was repressed, yAP-1 was localized in the nucleus and induced the expression of a yAP-1 dependent target gene. Our results also suggest that the cysteine rich domain (CRD), at the C-terminus of yAP-1, functions as an export recognition sequence. yAP-1 and Crm1 interact in vivo and this interaction is reduced in response to oxidative stress.

CONCLUSIONS

These results suggest a novel regulatory mechanism of nucleocytoplasmic transport which is dependent upon a redox sensitive nuclear export pathway.

Reconstitution of immune systems in RAG2-/- mice by transfer with interleukin-12-induced splenic hematopoietic progenitor cells

The administration of a high dose of IL-12 into the mice resulted in the induction of splenomegaly. From the flow cytometry analysis of cellularity in an enlarged spleen, it was demonstrated that Thyl.2-CD45RB-c-Kit + Sca-1 + Lin- hematopoietic progenitor cells markedly increased in IL-12-administered mouse spleen compared with untreated mouse spleen. The IL-12-induced hematopoietic progenitor cells showed a greatly enhanced colony-forming activity in CFU-granulocyte/macrophage (CFU-GM), blast-forming units-erythroid (BFU-E) and CFU-spleen (CFU-S) assay. Moreover, it was initially demonstrated that the transfer of IL-12-induced splenic hematopoietic progenitor cells into immunodeficient RAG2-/- mice caused a complete reconstitution of their immune functions including T- and B-cell-mediated immunity. Thus, the evidence that IL-12 has a capability of inducing hematopoietic progenitor cells possessing stem cell-like activity in vivo, indicated another important immunomodulating activity of IL-12 in immunotherapy.

Regulation of the fission yeast transcription factor Pap1 by oxidative stress: requirement for the nuclear export factor Crm1 (Exportin) and the stress-activated MAP kinase Sty1/Spc1

The fission yeast Sty1 stress-activated MAP kinase is crucial for the cellular response to a variety of stress conditions. Accordingly, sty1- cells are defective in their response to nutrient limitation, lose viability in stationary phase, and are hypersensitive to osmotic stress, oxidative stress, and UV treatment. Some of these phenotypes are caused by Sty1-dependent regulation of the Atf1 transcription factor, which controls both meiosis-specific and osmotic stress-responsive genes. However, in this report we demonstrate that the cellular response to oxidative stress and to treatment with a variety of cytotoxic agents is the result of Sty1 regulation of the Pap1 transcription factor, a bZip protein with structural and DNA binding similarities to the mammalian c-Jun protein. We show that both Sty1 and Pap1 are required for the expression of a number of genes involved in the oxidative stress response and for the expression of two genes, hba2+/bfr1+ and pmd1+, which encode energy-dependent transport proteins involved in multidrug resistance. Furthermore, we demonstrate that Pap1 is regulated by stress-dependent changes in subcellular localization. On imposition of oxidative stress, the Pap1 protein relocalizes from the cytoplasm to the nucleus in a process that is dependent on the Sty1 kinase. This relocalization is the result of regulated protein export, rather than import, and involves the Crm1 (exportin) nuclear export factor and the dcd1+/pim1+ gene that encodes an Ran nucleotide exchange factor.

Specific interaction of polypyrimidine tract-binding protein with the extreme 3'-terminal structure of the hepatitis C virus genome, the 3'X

We previously identified a highly conserved 98-nucleotide (nt) sequence, the 3'X, as the extreme 3'-terminal structure of the hepatitis C virus (HCV) genome (T. Tanaka, N. Kato, M.-J. Cho, and K. Shimotohno, Biochem. Biophys. Res. Commun. 215:744-749, 1995). Since the 3' end of positive-strand viral RNA is the initiation site of RNA replication, the 3'X should contribute to HCV negative-strand RNA synthesis. Cellular factors may also be involved in this replication mechanism, since several cellular proteins have been shown to interact with the 3'-end regions of other viral genomes. In this study, we found that both 38- and 57-kDa proteins in the human hepatocyte line PH5CH bound specifically to the 3'-end structure of HCV positive-strand RNA by a UV-induced cross-linking assay. The 57-kDa protein (p57), which had higher affinities to RNA probes, recognized a 26-nt sequence including the 5'-terminal 19 nt of the 3'X and 7 flanking nt, designated the transitional region. This sequence contains pyrimidine-rich motifs and shows similarity to the consensus binding sequence of the polypyrimidine tract-binding protein (PTB), which has been implicated in alternative pre-mRNA splicing and cap-independent translation. We found that this 3'X-binding p57 is identical to PTB. The 3'X-binding p57 was immunoprecipitated by anti-PTB antibody, and recombinant PTB bound to the 3'X RNA. In addition, p57 bound solely to the 3'-end region of positive-strand RNA, not to this region of negative-strand RNA. We suggest that 3'X-PTB interaction is involved in the specific initiation of HCV genome replication.

A case of multiple endocrine neoplasia type 2B

A sporadic case of multiple endocrine neoplasia type 2B in a twenty-six year old man who manifested medullary thyroid carcinoma, multiple mucosal neuromas of the tongue and a marfanoid habitus is reported. At the time of diagnosis, he also had multiple liver and lung metastases. Genetic analysis of his lymphocytes revealed a point mutation in exon 16 of the RET proto-oncogene. Since multiple endocrine neoplasia type 2B has a relatively poor prognosis because of the occasional aggressive behavior of medullary thyroid carcinoma, the necessity of the genetic diagnosis of multiple endocrine neoplasia in the early stage is suggested.

A case of angiosarcoma of the breast

This is a case report of a 20-year-old woman who had primary angiosarcoma of the left breast, with metastases to the spleen and ovary. Eight months after detecting a mass in her breast, she underwent mastectomy with biopsy of the ipsilateral axillary lymph nodes, splenectomy and bilateral oophorectomy. Five months after the operation, the patient succumbed to lung metastases. Angiosarcoma of the breast is a rare condition with a poor prognosis, and there are no established chemotherapeutic regimens as yet. Immunohistochemical staining for endoglin, known to be expressed mainly on the surface of endothelial cells, was positive. This suggests the possibility of treating angiosarcoma with anti-endoglin monoclonal antibodies.

Regulation of yAP-1 nuclear localization in response to oxidative stress

The YAP1 gene of Saccharomyces cerevisiae encodes a bZIP-containing transcription factor that is essential for the normal response of cells to oxidative stress. Under stress conditions, the activity of yAP-1 is increased, leading to the induced expression of a number of target genes encoding protective enzymes or molecules. We have examined the mechanism of this activation. Upon imposition of oxidative stress, a small increase in the DNA-binding capacity of yAP-1 occurs. However, the major change is at the level of nuclear localization; upon induction the yAP-1 protein relocalizes from the cytoplasm to the nucleus. This regulated localization is mediated by a cysteine-rich domain (CRD) at the C-terminus, its removal resulting in constitutive nuclear localization and high level activity. Furthermore, the CRD of yAP-1 is sufficient to impose regulated nuclear localization of the GAL4 DNA-binding domain. Amino acid substitutions indicated that three conserved cysteine residues in the CRD are essential for the regulation. We suggest therefore, that these cysteine residues are important in sensing the redox state of the cell and hence regulating yAP-1 activity.

The Skn7 response regulator controls gene expression in the oxidative stress response of the budding yeast Saccharomyces cerevisiae

Deletion of the bacterial two-component response regulator homologue Skn7 results in sensitivity of yeast to oxidizing agents indicating that Skn7 is involved in the response to this type of stress. Here we demonstrate that following oxidative stress, Skn7 regulates the induction of two genes: TRX2, encoding thioredoxin, and a gene encoding thioredoxin reductase. TRX2 is already known to be induced by oxidative stress dependent on the Yap1 protein, an AP1-like transcription factor responsible for the induction of gene expression in response to various stresses. The thioredoxin reductase gene has not previously been shown to be activated by oxidative stress and, significantly, we find that it too is regulated by Yap1. The control of at least TRX2 by Skn7 is a direct mechanism as Skn7 binds to the TRX2 gene promoter in vitro. This shows Skn7 to be a transcription factor, at present the only such eukaryotic two-component signalling protein. Our data further suggest that Skn7 and Yap1 co-operate on the TRX2 promoter, to induce transcription in response to oxidative stress.

Immunological suppression after surgery in scoliosis patients

This is a prospective study to analyze the postoperative immunological changes in scoliosis surgery. Twenty-eight patients who underwent Harrington instrumentation were analyzed. Seven patients who underwent arthroscopic surgery were analyzed as a control group. The objective of this study is to determine whether surgery and surgical stress (minor versus major surgery) changed the immune capability of patients as indicated by the ratio of lymphocyte cell types and interferon induction. Pre- and postoperative blood from scoliosis and knee arthroscopy patients was analyzed at various times using antisera and two-color flow cytometry with monoclonal antibodies. Both scoliosis and knee arthroscopy patients had a postoperative decrease in the population of B-lymphocytes (Leu 12+) and a transient increase in the natural killer cells (Leu 4-/Leu 19+) and the cytotoxic T-lymphocytes (Leu 2a++/Leu 15-). These changes were significantly greater in the scoliosis patients, who also experienced a prolonged decrease in the inducer T-lymphocytes (Leu 8+/Leu 3a+) for 3 weeks following surgery. Production of interferon-alpha and interferon-gamma by lymphocytes was suppressed postoperatively and returned to preoperative levels within 3 weeks. Immunological depressive changes occurred postoperatively and lasted at least 1 week. These effects are more pronounced with longer surgeries, suggesting greater postoperative vigilance for infections in these cases.

High-dose chemotherapy with autologous hematopoietic stem-cell transplantation in breast cancer

Since 1981 we have conducted four studies of the treatment of metastatic and postoperative high-risk breast cancer with high-dose chemotherapy supported by autologous hematopoietic stem-cell transplantation (AHSCT). Study I, involving 56 metastatic cancer patients, proved that induction chemotherapy produces a lasting complete response (CR) in only a few cases despite the achievement of a CR rate higher than that expected from standard chemotherapy. Study II was designed to examine consolidation chemotherapy in metastatic cancer patients responding to induction chemotherapy. At a median follow-up of 26 months (range 2-66), consolidation therapy produced a 5-year progression-free survival rate of 27.1% in 30 patients showing a CR or a partial response to induction therapy and 58.6% in 13 patients showing a CR to consolidation therapy. No treatment-related death occurred during study II. The same regimen used in study I was employed for 58 postoperative high-risk patients in study III. The 10-year disease-free survival rate recorded for patients with > or = 10 positive axillary lymph nodes was significantly higher (P < 0.05) in the AHSCT-supported chemotherapy group than in the conventional chemotherapy group. A double high-dose regimen was adopted for 21 postoperative high-risk patients in study IV. The 3-year disease-free survival rate recorded for 9 patients with > or = 10 positive axillary lymph nodes was 71.4% at a median follow-up of 25 (range 8-45) months. No treatment-related death occurred during study IV. Peripheral blood stem-cell transplantation shortened the duration of bone marrow suppression more effectively than did bone marrow transplantation, thereby optimizing high-dose chemotherapy.

Use of metronidazole gel to control malodor in advanced and recurrent breast cancer

Intolerable malodor emanating from ulcerated tumors as a result of anaerobic infection is a serious problem in the management of advanced and recurrent breast cancer. Metronidazole can control this malodor, but its oral use may cause adverse reactions. We therefore formulated a metronidazole gel, since no equivalent preparation is commercially available in Japan, and used it in five female patients (four with advanced cancer and one with recurrent cancer) admitted to our hospital between March 1994 and July 1995. The patients were aged between 47 and 71 (median: 59) years, and the duration of morbidity in the four patients with advanced cancer ranged from 10 months to four years. In three patients, the tumors were larger than 10 cm x 10 cm. Metronidazole gel was applied to the surface of ulcerated tumors once or twice daily. Independent assessments by the patient, doctor and nurse were unanimous, and revealed that the malodor was alleviated in one patient after three days, and removed in four patients after two to five (median: four) days of metronidazole gel treatment. Culture of swabs showed a decrease or disappearance of anaerobic colonies. Adverse reactions characteristic of metronidazole did not occur. The topical use of metronidazole in a gel form will improve the quality of life for patients with malodorous ulcerated tumors and facilitate intensive treatment of the underlying disease.

Nucleotide and amino acid sequences for cytochrome caa3-type oxidase of Bacillus stearothermophilus K1041 and non-Michaelis-type kinetics with cytochrome c

A pseudo-sigmoidal cytochrome c-dependence curve of oxidase activity was observed with cytochrome oxidase from the Bacillus stearothermophilus strain K1041, while the other thermophilic Bacillus PS3 which has been extensively studied possessed normal Michaelis-Menten type kinetics. The genes coding for four subunits of cytochrome caa3-type oxidase and for heme O synthase were isolated from a genomic DNA library of K1041 by using a PS3 DNA fragment containing the highly-conserved region of the largest subunit as a probe, and sequenced. Most residues in subunits I (COI/caaB product), III (COIII/caaC product), and IV (COIV/caaD product) of K1041 were highly conserved when compared with those of PS3. However, the sequence of K1041 subunit II (COII/caaA product) was distinctly different from that of the PS3 subunit II. These Bacillus COIIs have an additional sequence for cytochrome c after the CuA binding protein portion with two transmembrane segments which is homologous to the mitochondrial counterpart, and represents the site of electron ingress. Several charged residues in the vicinity of cytochrome c moiety are replaced by oppositely charged residues. It is likely that these amino acid replacements in subunit II are the cause of the abnormal sigmoidal saturation curve for extrinsic cytochromes c of the K1041 enzyme.

Identification of peptide fragments chemically cross-linked in cytochrome c oxidase from thermophilic Bacillus PS3

In order to study steric arrangement of subunits in cytochrome c oxidase isolated from thermophilic Bacillus PS3, we developed a simple procedure including chemical cross-linking, two consecutive runs of electrophoresis, proteolytic digestion, and peptide sequencing for simultaneous identification of two cross-linked fragments. By this procedure, the cytochrome c domain of subunit 2 was found cross-linked to C-terminal region of subunit 1 including two hydrophobic transmembrane segments, suggesting that these two regions were located close each other. The present simple procedure might be applicable to proteins whose crystal structures are not revealed.

The expression of tyrosinase, tyrosinase-related proteins 1 and 2 (TRP1 and TRP2), the silver protein, and a melanogenic inhibitor in human melanoma cells of differing melanogenic activities

The expression of various melanogenic proteins, including tyrosinase, the tyrosinase-related proteins 1 (TRP1) and 2 (TRP2/DOPAchrome tautomerase), and the silver protein in human melanocytes was studied in six different human melanoma cell lines and compared to a mouse derived melanoma cell line. Analysis of the expression of tyrosinase, TRP1, TRP2, and the silver protein using flow cytometry revealed that in general there was a positive correlation between melanin formation and the expression of those melanogenic enzymes. Although several of the melanoma cell lines possessed significant activities of TRP2, the levels of DOPAchrome tautomerase in extracts of human cells were relatively low compared to those in murine melanocytes. Melanins derived from melanotic murine JB/MS cells, from melanotic human Ihara cells and HM-IY cells, from sepia melanin, and from C57BL/6 mouse hair were chemically analyzed. JB/MS cells, as well as Ihara cells and HM-TY cells, possessed significant amounts of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) derived melanins, this being dependent on the activity of TRP2. Kinetic HPLC assays showed that 5,6-dihydroxyindole (DHI) produced during melanogenesis was metabolized quickly to melanin in pigmented KHm-1/4 cells, whereas DHI was stable in amelanotic human SK-MEL-24 cells. A melanogenic inhibitor that has been purified from SK-MEL-24 cells that suppressed oxidation of DHI in the presence or absence of tyrosinase, but had no effect on DHICA oxidation. The sum of these results suggests that the expression of melanogenic enzymes as well as the activity of a melanogenic inhibitor are critical to the production of melanin synthesis in humans.

Superantigen-induced human CD4+ helper/killer T cell phenomenon. Selective induction of Th1 helper/killer T cells and application to tumor immunotherapy

Human CD4+ T cells activated with staphylococcal enterotoxin A (SEA) were fractionated by Percoll discontinuous density gradient centrifugation to enrich SEA-reactive CD4+ T cells. The SEA-reactive CD4+ T cells showed significant cytotoxicity, so-called superantigen-dependent cell-mediated cytotoxicity, against SEA-coated class II-positive tumor cells. During lysis of SEA-coated tumor cells, SEA-reactive CD4+ T cells produced high levels of IL-2 and IFN-gamma but not IL-4 in an Ag-specific manner. The skewing of human CD4+ T cells to Th1-type helper/killer T cells was also demonstrated when SEA-reactive CD4+V beta 5.3+ clonal T cells were cultured with SEA, but not with PHA or OKT3 mAb. Interestingly, the generation of SEA-reactive helper/killer T cells was negatively regulated by IL-4, but up-regulated by IL-12. The SEA-reactive CD4+ helper/killer T cells were able to generate from PBMC of tumor patients and could be expanded to 10(9) levels in a 7-day culture. The SEA-reactive CD4+ helper/killer T cells were specifically targeted to c-erbB-2 positive human colon cancer cells using SEA-conjugated-anti-c-erbB-2 mAb. These results initially demonstrated that SEA-activated human CD4+ T cells are a Th1 type of Th cell that has both helper and killer functions which may be useful for adoptive tumor immunotherapy in combination with SEA-conjugated antitumor mAb.

Superantigen-induced human CD4+ helper/killer T cell phenomenon. Selective induction of Th1 helper/killer T cells and application to tumor immunotherapy

Human CD4+ T cells activated with staphylococcal enterotoxin A (SEA) were fractionated by Percoll discontinuous density gradient centrifugation to enrich SEA-reactive CD4+ T cells. The SEA-reactive CD4+ T cells showed significant cytotoxicity, so-called superantigen-dependent cell-mediated cytotoxicity, against SEA-coated class II-positive tumor cells. During lysis of SEA-coated tumor cells, SEA-reactive CD4+ T cells produced high levels of IL-2 and IFN-gamma but not IL-4 in an Ag-specific manner. The skewing of human CD4+ T cells to Th1-type helper/killer T cells was also demonstrated when SEA-reactive CD4+V beta 5.3+ clonal T cells were cultured with SEA, but not with PHA or OKT3 mAb. Interestingly, the generation of SEA-reactive helper/killer T cells was negatively regulated by IL-4, but up-regulated by IL-12. The SEA-reactive CD4+ helper/killer T cells were able to generate from PBMC of tumor patients and could be expanded to 10(9) levels in a 7-day culture. The SEA-reactive CD4+ helper/killer T cells were specifically targeted to c-erbB-2 positive human colon cancer cells using SEA-conjugated-anti-c-erbB-2 mAb. These results initially demonstrated that SEA-activated human CD4+ T cells are a Th1 type of Th cell that has both helper and killer functions which may be useful for adoptive tumor immunotherapy in combination with SEA-conjugated antitumor mAb.

Interleukin-12 augments the generation of autologous tumor-reactive CD8+ cytotoxic T lymphocytes from tumor-infiltrating lymphocytes

Human tumor-infiltrating lymphocytes (TIL) were obtained from breast cancer, renal cancer or neuroblastoma to investigate the generation of autologous tumor-reactive CD8+ cytotoxic T lymphocytes (CTL). When TIL were cultured with interleukin (IL)-2 (100 U/ml), the growth of TIL peaked around 8-10 days after the initiation of culture. In contrast, the proliferation of TIL cultured with IL-2 plus IL-12 peaked around 4-5 days after culture and tumor cells rapidly disappeared from the culture. To determine the generation of autologous tumor-reactive CD8+ CTL, TIL-derived CD8+ T cells were separated by FACStar. Both IL-2-activated and IL-2 plus IL-12-activated TIL-CD8+ T cells showed the same level of lymphokine-activated killer activity against a variety of tumor cells. However, TIL-CD8+ T cells activated with IL-2 plus IL-12 revealed greatly augmented cytotoxicity against autologous tumor cells compared with that induced by IL-2 alone. The autologous tumor cell-killing activity of TIL-CD8+ CTL was significantly inhibited by the addition of F(ab)2 anti-CD3 monoclonal antibody, indicating that these CTL recognize autologous tumor antigen through T cell receptor. These results imply that IL-12 is a novel cytokine which facilitates the generation of autologous tumor-reactive CD8+ CTL from TIL.

Tumor-associated glycoantigen, sialyl Lewis(a) as a target for bispecific antibody-directed adoptive tumor immunotherapy

The KM231 mAb recognizing sialyl Lewis(a) (sLe(a)) epitope of glycoprotein or glycolipid expressed on various human cancers was used to prepare bispecific antibody (BSAb) containing anti-CD3 x anti-sLe(a) mAb. The effect of anti-CD3 x anti-sLe(a) BSAb on the induction of cytotoxicity by activated T cells was investigated. The activated CD3+ T cells expressing CD8 or CD4 were induced from human peripheral blood mononuclear cells by culture with recombinant IL-2 plus immobilized anti-CD3 mAb. The activated CD8+ and CD4+ T cells showed marginal cytotoxicity against tumor cells by themselves. However, addition of anti-CD3 x anti-sLe(a) BSAb resulted in a great augmentation of their cytotoxicity against gastrointestinal tumor cells. The BSAb also triggered IL-2 production of CD4+ helper/killer T cells during lysis of tumor cells. Moreover, the BSAb was demonstrated to have a potent in vivo antitumor activity against human colon cancer implanted in nude mice by combination with CD4+ helper/killer cells. These results demonstrated that sLe(a) antigen might be a good target molecule for BSAb-directed adoptive tumor immunotherapy.

[An efficient methods for the induction of human antitumor effector CD4+ and CD8+ T cells: their application to tumor immunotherapy]

It is an important issues to investigate an efficient methods to induce antitumor effector T cells from peripheral blood lymphocytes of tumor patients for the development of a novel tumor immunotherapy. We established a large scale culture system of human CD4+ helper/killer T cells which have both helper and killer functions. Targeting of CD4+ helper/killer T cells to tumor using anti-CD3 x anti-c-erbB-2 mAb caused the lysis of tumor and triggering of IL-2 production. It was also demonstrated that culture of human CD4+ T cells with staphylococcal enterotoxin A (SEA) or IL-12 caused a selective induction of Th1 type of CD4+ helper/killer T cells. IL-12 also revealed a novel effect on CD8+CTL functions. Culture of CD8+ T cells with IL-12 resulted in the augmentation of IFN-gamma production and cytotoxicity. Moreover, culture of tumor-infiltrating lymphocytes with IL-12 caused a marked enhancement of CD8+CTL against autologous tumor cells. These findings suggest that IL-12 will become a useful cytokine for the tumor immunotherapy. In this paper, we will discuss the key role of CD4+ T cells for the induction of antitumor immunity in tumor-bearing host.

Significance of VLA-4 and LFA-1 expressions in neoplastic follicle formation and its deterioration in B-cell non-Hodgkin's lymphomas

In an attempt to determine the roles of adhesion molecules in the formation and deterioration of neoplastic follicles, we used flow cytometry to investigate how strongly neoplastic B-cells express VLA-4 alpha and LFA-1 alpha on their surfaces. Neoplastic and normal B-cells were taken from 24 patients with B-cell non-Hodgkin's lymphomas (B-NHL) and 6 with B-cell chronic lymphocytic leukemia (B-CLL). The expression intensities of the adhesion molecules were graded as follows: (-), (+), (+2) and (+3). Normal B-cells expressed those molecules with an intensity of (+2). The data for VLA-4 alpha expression were as follows: follicular B-NHL [10/11; (+2) and 1/11; (+)], partially follicular [5/5; (+)], diffuse [8/8; (+)] and B-CLL [6/6; (-)]. Those for LFA-1 alpha were as follows: follicular B-NHL [7/11; (+2), 4/11; (+)], partially follicular [3/5; (+2), 2/5; (+)], diffuse [3/8; (+2), 5/8; (+)] and B-CLL [3/6; (+), 3/6; (-)]. These results suggest that VLA-4 molecules expressed on neoplastic B-cells may be involved closely in the formation and deterioration of neoplastic follicles, although the expression of LFA-1 molecules seems to play only a minor part in such events.

YAP1 dependent activation of TRX2 is essential for the response of Saccharomyces cerevisiae to oxidative stress by hydroperoxides

The role of the YAP1 transcription factor in the response of Saccharomyces cerevisiae cells to a variety of conditions that induce oxidative stress has been investigated. Cells deficient in YAP1 were found to be hypersensitive to hydroperoxides and thioloxidants, whereas overexpression of YAP1 conferred hyper-resistance to the same conditions. These treatments resulted in an increase in YAP1-specific binding to DNA together with an increase in YAP1 dependent transcription. Our results indicate that this increase is not due to an increase in synthesis of YAP1 protein, but rather results from modification of pre-existing protein. Using a specific genetic screen, the TRX2 gene, one of two genes of S. cerevisiae that encode thioredoxin protein, was identified as being essential for YAP1 dependent resistance to hydroperoxides. Furthermore, efficient expression of TRX2 was dependent on YAP1 and enhanced under conditions of oxidative stress.

[A two-dimensional analysis of B-lymphoma cells by flow cytometry--a comparative study with pathological classification]

In order to investigate the size variation of neoplastic cells from lymph nodes of 19 patients with B-cell non-Hodgkin's lymphomas (B-NHL), we have carried out the two-dimensional analysis by flow cytometry using the parameters of the forward light scatter (FLS) and the fluorescence intensity of surface immunoglobulin light chain (sIgL). Neoplastic B cells were identified as having the homogeneous characters of both FLS and sIgL (kappa or lambda) in comparison of normal B cells with the heterogeneity of counterpart sIgL (lambda or kappa). Then the size variation of neoplastic B cells was analyzed by regarding CD3+ T cells to a control scale. Consequently, the present procedures disclosed that B-NHL cases could be divided into five patterns from the view-point of the cell size and distribution. These results almost coincided with the cell types determined by the pathological diagnosis. Furthermore, it was also found that our data made it possible to classify small cleaved cell or large cell lymphomas into subtypes. The two-dimensional analysis by using the parameters of FLS and sIgL would be clinically useful for the rapid diagnosis of B-NHL and its malignant grade in addition to supporting pathological findings.

cDNAs and deduced amino acid sequences of subunits in the binding component of mouse bactericidal factor, Ra-reactive factor: similarity to mannose-binding proteins

The complement-dependent bactericidal factor, Ra-reactive factor, binds specifically to Ra polysaccharide, which is common to some strains of Gram-negative enterobacteria, and its is a complex of proteins composed of a polysaccharide-binding component and a component that is presumably responsible for the complement activation. The former component consists of two different 28-kDa polypeptides, P28a and P28b. We determined the partial amino acid sequences of P28a and P28b, and the results indicated that these polypeptides were similar to two species of mannose-binding protein, MBP-C and MBP-A (alternative names, liver and serum mannan-binding proteins, respectively), which have been isolated from rat liver and/or serum [Drickamer, K., Dordal, M. S., & Reynolds, L. (1986) J. Biol. Chem. 261, 6878-6887; Oka, S., Itoh, N., Kawasaki, T., & Yamashina, I. (1987) J. Biochem. 101, 135-144]. Thus, we cloned the respective cDNAs, using as probes synthetic oligonucleotides for which the sequences had been deduced from the amino acid sequences of P28a and P28b and of rat MBP cDNAs. The primary structures of P28a and P28b deduced from the cloned cDNAs are homologous to one another. They have three domains, a short NH2-terminal domain, a collagen-like domain, and a domain homologous to regions of some carbohydrate-binding proteins, as has been reported for rat MBPs. Southern and Northern blotting analyses using these cDNAs indicated that the P28a and P28b polypeptides are the products of two unique mouse genes which are expressed in hepatic cells.

Clinical and prognostic significance of monoclonal small cells in the peripheral blood and bone marrow of various B-cell lymphomas

Discordant lymphomas, in particular nodal large-cell lymphomas with marrow small-cell lymphoma, were discovered recently, and the prognosis of patients with such disease has been discussed. The small cells were reported to be small lymphocytic or small cleaved lymphoma cells. We have detected, by kappa-lambda imaging (KLI) with delta-curves, using a flow cytometer, small lymphoma cells in the peripheral blood (PB) and bone marrow (BM) of 41 untreated patients with various B-cell lymphomas expressing surface Ig (sIg+BCL), and evaluated their clinical and prognostic significance. Small cells were found in approximately 90% (37 of 41) of sIg+BCL patients when either PB or BM was analyzed and, overall, the presence of small cells correlated well with the disease activity. However, in some patients, a few cells remained in the PB (16%) or BM (27%) even when they were in remission, whereas in others, the cells were presented in the PB or BM several months before relapse. These results suggest that the detection of small cells in PB or BM by KLI may be helpful for screening and monitoring patients with sIg+BCL. When the patients were subdivided into three groups (normal, low, and high amplitude), according to the abnormal grade criteria of the delta-curves, which were based on the results of both PB-KLI and BM-KLI, the survival of the high-amplitude group tended to be shorter than that of the normal group (P = .068), which was particularly marked when the follow-up period exceeded 2 years. Moreover, as the group grading worsened (normal less than low less than high), the complete response rates deteriorated (100%, 71%, and 60%, respectively) and the respective relapse rates after complete remission increased (17%, 40%, and 67%). Thus, the determination of the proportion of small lymphoma cells in PB and BM by KLI may be useful for predicting the prognoses of patients with sIg+BCL.

Synthesis of a 3-ether analogue of lipid A

Lipid A 3-ether analogues were synthesized from allyl 2-deoxy-4,6-O-isopropylidene-2-trifluoroacetamido-alpha-D-glucopyr anoside and 3,4,6-tri-O-acetyl-2-trifluoroacetamido-alpha-D-glucopyranosyl bromide. The compound lost completely the endotoxic activity.

Identity of brain-associated small cell lung cancer antigen and the CD56 (NKH-1/Leu-19) leukocyte differentiation antigen and the neural cell adhesion molecule

Previous studies have demonstrated the monoclonal antibody, TFS-4, to recognize a cell surface antigen, 124,000 Daltons, of molecular weight expressed selectively on small cell lung cancer but not on non-small cell lung cancer, and to cross-react with the human brain, cardiac muscle and some smooth muscle cells. The cross-reactivity of TFS-4 with peripheral blood lymphocytes was examined by two color immunofluorescence analysis, using monoclonal antibodies to leukocyte differentiation antigens. Flow cytometric analysis revealed an identical subset of cells to express both BASCA and CD56(NKH-1 antigen). The immunofluorescence profiles for both TFS-4 and NKH-1 were, furthermore, identical to those of the background controls, identicating identical quantities of the antigens to be present on each cell within the population. Since CD56 has been show to be identical to the neural cell adhesion molecule (N-CAM), we determined the amino-terminal amino acid sequence of BASCA purified from the human brain. The amino-terminal amino acid sequence of BASCA was identical to that of N-CAM.

Strong inclination toward transition mutation in nucleotide substitutions by poliovirus replicase

A viable insertion mutant of the Sabin strain of type 1 poliovirus was constructed. The mutant carried an insertion sequence of 72 nucleotides at nucleotide position 702 in the 5' non-coding region (742 nucleotides long) of the genome of the Sabin strain. This mutant showed a small-plaque phenotype, as compared with the parental virus. Indeed, the final yield of the mutant in a single cycle of infection was tenfold fewer than that of the parental virus. Many large-plaque variants that are easily generated from the insertion mutant appeared to regain efficient viral replication and have single nucleotide changes. All nucleotide changes observed were limited to within three nucleotides of an AUG sequence in the insertion sequence. The result indicates strongly that the AUG sequence itself in this genome region functions in reducing the plaque size of the parental Sabin type 1 virus. The insertion mutant with a small-plaque phenotype may be the first in vitro mutant of poliovirus whose viability is lowered only by a primary sequence inserted into the 5' non-coding region of the genome. Base substitutions to alter the AUG sequence should largely be the result of errors of the virus-specific replicase, since variants with base substitutions must be subject to only minimum selection pressure. Accordingly, nucleotide sequence analysis of the genome region containing the AUG sequence was performed on a number of genomes of large-plaque variants to investigate types of nucleotide substitutions caused by characteristic errors in RNA replication. Only one transversion mutation was detected in the genomes of 44 independently isolated large-plaque variants with single base changes in the AUG sequence. This result suggests strongly that transition mutations occur predominantly as nucleotide substitutions caused by characteristic errors of poliovirus replicase.

Genetic variation occurring on the genome of an in vitro insertion mutant of poliovirus type 1

An insertion sequence of 72 nucleotides prepared from a polylinker sequence of plasmid pUC18 was introduced at nucleotide position 702 of the 5' noncoding sequence (742 nucleotides long) of the genome of the Sabin strain of poliovirus type 1 by using an infectious cDNA clone of the virus strain. The insertion mutant thus obtained showed a small-plaque phenotype compared with that of the parent virus. Apparent revertants (large-plaque variants) were easily generated from the insertion mutant. Nucleotide sequence analysis was performed on the revertant genomes to determine the mutation(s) by which the plaque size of the parent virus was regained. Some large-plaque variants lacked genomic sequences including all or a part of the insertion sequence. A computer-aided search for secondary structures with respect to the deletion sites detected possible supporting sequences which provided fairly stable secondary structures at the deletion sites. This result was consistent with our supporting sequence-loop model which had been proposed as a new copy-choice model for the generation of genetic rearrangements occurring on single-stranded RNA genomes (S. Kuge, I. Saito, and A. Nomoto, J. Mol. Biol. 192:473-487, 1986). The other large-plaque variants had point mutations at any one of three positions of an AUG existing in the insertion sequence. A small-plaque phenotype was observed when an AUG codon was inserted in frame or out of frame with regard to the initiation site of viral polyprotein synthesis. Our data strongly suggest that an AUG sequence in this genome region is deleterious for efficient poliovirus replication.

The basic study on kappa-lambda imaging by delta-curve for the detection of a monoclonal B-cell population in the peripheral blood

Recently, kappa-lambda analysis with the "D" value was developed by Ault to detect a minor population of malignant B cells in peripheral blood. This analysis is based on the Kolmogorov-Smirnov test, and the D value is calculated by a flowcytometer and a computer. We have recently devised a more sensitive parameter for the kappa-lambda analysis than the D value called the delta-curve (delta c); the delta c applies the same principle as that of the D value. Mixing experiments with kappa-type and lambda-type chronic lymphocytic leukemia cells revealed that the delta c could not only detect a minor population of malignant kappa-B cells, but also that of malignant lambda-B cells using more sensitivity than the D value. A total of 49 blood samples obtained from 27 patients with various B-cell malignancies were investigated. D values were abnormal in 37% of all samples, while abnormal patterns of the delta c were recognized in 71%. On the other hand, 59% of samples obtained from the patients with B-cell lymphoma in aleukemic phase showed abnormal delta c, whereas D values exceeded the upper limit of the normal value in only 15% of the samples. It was suggested that the delta c could detect 3% to 7% of malignant B cells that were mixed with a population of normal lymphocytes.

Construction of viable deletion and insertion mutants of the Sabin strain of type 1 poliovirus: function of the 5' noncoding sequence in viral replication

A number of deletion and insertion sequences were introduced into the 5' noncoding sequence (742 nucleotides long) of the genome of the Sabin strain of type 1 poliovirus by using an infectious cDNA clone of the virus strain. The genomes of all three poliovirus serotypes contained highly homologous sequences (nucleotide positions 509 to 639) as well as highly variable sequences (positions 640 to 742) in the 5' noncoding region. The viability of mutant viruses was tested by transfecting mutant cDNA clones into African green monkey kidney cells and then estimating the plaque sizes displayed on the cells. The results suggested that the highly variable sequence next to the VP4 coding region did not play an important role, at least in the in vitro culture system used, that the loci of highly conserved nucleotide sequences were not always expected to be the genome regions essential for viral replication, that the sequence between positions 564 and 599 carried genetic information to maintain the efficiency of certain steps in viral replication, and that the sequence between positions 551 to 563 might play an essential role in viral replication. Four-base deletion or insertion mutations were introduced into relatively variable sequences in the genome region upstream of position 509. The results suggest that variable sequences do not always indicate that the corresponding genome regions are less important. Apparent revertants (large-plaque variants) were easily generated from one of the viable mutants with the small-plaque phenotype. The determination of nucleotide sequences of the revertant genomes revealed the second mutation site. The results suggested that the different loci at around positions 200 and 500 might specifically interact with each other. This interaction may result in the formation of a functional structure that influences the efficiency of certain steps in the viral replication.

Complete nucleotide sequence of the genome of coxsackievirus B1

The complete nucleotide sequence of the genome of the coxsackievirus B1, a human enterovirus that belongs to the Picornaviridae, was determined by using molecular cloning and rapid sequence analysis techniques. Sequence analysis of the cloned cDNAs revealed that the virion RNA was 7389 nucleotides long and polyadenylylated at the 3' terminus. Similar to other picornavirus genomes, a single large open reading frame was identified. The translated sequence starts at nucleotide position 742 and ends at 7287 of the genome. Thus, the viral polyprotein should consist of 2182 amino acids. When the predicted amino acid sequence of the viral polyprotein was compared with those of other human enteroviruses such as polioviruses, a striking sequence homology was observed, especially in viral proteins 1B, 2C, and 3D. This allowed us to predict precise map locations of the viral structural and nonstructural proteins on the genome, although two proteolytic processing sites, between 1D and 2A and between 2B and 2C, were obscure. The result presented here implied important information with respect to the genetical variation of human enteroviruses.

Primary structure of poliovirus defective-interfering particle genomes and possible generation mechanisms of the particles

The genomes of defective-interfering (DI) particles derived from the Sabin strain of type 1 poliovirus (PV1(Sab] were characterized by nuclease S1 mapping using complementary DNA (cDNA) copies of PV1(Sab) genome as probes. The results demonstrated variety in the size and location of the deletions, which were compatible with our previous prediction. The results further indicated that the locations of the deletions were limited within the internal genome region encoding viral capsid proteins and that the deletion sites were clustered in certain areas on the genome. Sequence analysis of a number of cloned cDNAs to the DI genomes revealed that every DI genome retained the correct reading frame for viral protein synthesis. These results strongly suggested that one or all of the viral non-structural proteins might be cis-acting at least at a certain stage in viral replication. A computer search for secondary structures with regard to the deletion sites provided a possible common structure from which, supported by sequences existing on the plus or minus RNA strand of PV1(Sab), deletion regions looped out from the remaining sequences. Replicase might, therefore, skip these transiently formed loop structures with certain frequencies, resulting in the generation of DI genomes. This model could also be considered as a model for genetic recombination in these RNA genomes. Possible "supporting sequences" were also found for every rearranged site on the RNAs of influenza virus and sindbis virus. Thus, we propose a new copy-choice model, designated the "supporting sequence-loop model", for the generation of rearrangements occurring on single-stranded RNA genomes.

An infectious cDNA clone of the poliovirus Sabin strain could be used as a stable repository and inoculum for the oral polio live vaccine

Viruses were recovered from HeLa S3 cells and African green monkey kidney (AGMK) cells transfected with an infectious cDNA clone of poliovirus vaccine Sabin 1 strain. The viruses recovered from the different DNA-transfected cells were tested for the biological characteristics of temperature sensitivity (rct marker), plaque size, and bicarbonate concentration dependency (d marker). The results revealed that the above properties were similar to those obtained from tests on the Sabin 1 vaccine reference strain. The recovered viruses and the vaccine reference virus were passaged in AGMK cells at an elevated temperature of 37.5 degrees, and the passaged isolates were tested for the rct marker. The virus recovered from AGMK cells had the most stable rct phenotype while the virus from HeLa S3 cells had a similar stability to that of the reference virus, suggesting that the virus from AGMK cells would be more suitable as a vaccine strain than the other two viruses. Furthermore, an infectious cDNA clone of high specific infectivity, constructed by introducing SV40 large T antigen into the plasmid, was used for production of high titers of virus after transfection. The results of in vitro biological tests on the recovered virus suggested that virus produced in the transfected AGMK cells also had the high quality that is desirable in vaccine stocks. Monkey neurovirulence tests performed with these recovered viruses revealed that the recovered viruses were weakly neurovirulent, similar to the vaccine reference virus. The infectious cDNA clone of the poliovirus vaccine strain could therefore be used to generate a possible inoculum of the oral polio live vaccine. Our findings strongly suggest that an infectious cDNA clone of poliovirus RNA may be used to preserve the constancy and quality of the present seed viruses of the Sabin 1 vaccine strain.

Genetic analysis of the attenuation phenotype of poliovirus type 1

Seven different recombinant viruses from the virulent Mahoney and the attenuated Sabin parental strains of type 1 poliovirus were constructed in vitro by using infectious cDNA clones. Monkey neurovirulence tests (lesion score, spread value, and incidence of paralysis) using these recombinant viruses revealed that the loci influencing attenuation were spread over several areas of the viral genome, including the 5' noncoding region. In vitro phenotypic marker tests corresponding to temperature sensitivity of growth (rct marker), plaque size, and dependency of growth on bicarbonate concentration (d marker) were performed to identify the genomic loci of these determinants and to investigate their correlation with attenuation. Determinants of temperature sensitivity mapped to many areas of the viral genome and expressed strong but not perfect correlation with attenuation. Recombinant viruses with Sabin-derived capsid proteins showed a small-plaque phenotype, and their growth was strongly dependent on bicarbonate concentration, suggesting that these determinants map to the genomic region encoding the viral capsid proteins. Plaque size and the d marker, however, were found to be poor indicators of attenuation. Moreover, virion surface characteristics such as immunogenicity and antigenicity had little or no correlation with neurovirulence. Nevertheless, viruses carrying Sabin-derived capsid proteins had an apparent tendency to exhibit less neurovirulence in tests on monkeys compared with recombinants carrying Mahoney-derived capsid proteins. Our results suggest that the extent of viral multiplication in the central nervous system of the test animals might be one of the most important factors determining neurovirulence. Moreover, we conclude that the expression of the attenuated phenotype of the Sabin 1 strain of poliovirus is the result of several different biological characteristics. Finally, none of the in vitro phenotypic markers alone can serve as a good indicator of neurovirulence or attenuation.

Mapping and sequencing of RNAs without recourse to molecular cloning: application to RNAs of the Sabin 1 strain of poliovirus and its defective interfering particles

Complementary DNA to the genome of the Sabin 1 strain of poliovirus was prepared by reverse transcription with oligo(dT)10 as a primer and separated into six classes of DNA by their size. Each class of the DNA, after digestion with restriction endonuclease HaeIII, was analyzed by two-dimensional polyacrylamide gel electrophoresis. Comparison of the patterns of the restriction fragments led us to compose a possible arrangement of the restriction fragments on the viral genome. Sequence analysis of these fragments indicated that the arrangement was consistent with the known total nucleotide sequence of the genome. In the determined sequences, two bases were observed to differ from those of a cloned complementary DNA of the Sabin 1 genome. This suggested that the sequence of the cloned DNA reflected that of a mutated virus genome that was a minor component in the virus inoculation stock. The genomes of defective interfering particles generated from the Sabin 1 strain were also analyzed by this technique. The results suggested that the RNAs lacked an internal region of the Sabin 1 RNA encoding viral capsid proteins. The location of the deletion was further confirmed by determination of the nucleotide sequence of a cloned complementary DNA copy of the defective interfering particle RNA. Thus, the method described here is useful for mapping and sequencing of RNAs and for knowing whether cloned cDNAs represent the major population of RNA molecules or not.

Antigenic variation and resistance to neutralization in poliovirus type 1

Mutations have been identified in variants of poliovirus, type 1 (Mahoney) on the basis of their resistance to neutralization by individual monoclonal antibodies. The phenotypes of these variants were defined in terms of antibody binding; the pattern of epitopes expressed or able to be exploited for neutralization were complex. Single amino acid changes can have distant (in terms of linear sequence) and generalized effects on the antigenic structure of poliovirus and similarly constituted virions.