Kazuo Yamakami

Nephritis-Associated Plasmin Receptor and Acute Poststreptococcal Glomerulonephritis: Characterization of the Antigen and Associated Immune Response

The role of nephritis-associated antigen as a virulence factor for acute poststreptococcal glomerulonephritis (APSGN) remains to be fully clarified. Nephritis-associated plasmin receptor (NAPlr) was previously isolated from group A streptococcus (GAS) and shown to bind plasmin(ogen). The nucleotide sequence of the naplr gene from GAS isolates obtained from patients with APSGN was determined. The sequence of the putative open reading frame (1011 bp) showed 99.8% identity among isolated strains. Homology screen revealed an exact match with streptococcal glyceraldehyde-3-phosphate dehydrogenase (GAPDH). NAPlr exhibited GAPDH activity in zymography, and it activated the complement pathway in vitro. In APSGN kidney biopsy specimens, NAPlr was observed mainly in the early stage of the disease (1 to 14 d after onset) but was not colocalized with either C3 or IgG as assessed by double immunofluorescence staining. Sera of patients with APSGN, patients with GAS infection without renal involvement, nonrenal pediatric patients, and healthy adults as controls were assayed for anti-NAPlr antibody titers. Anti-NAPlr antibodies were present most frequently in APSGN sera, and antibody titers were also significantly higher than in patients with GAS infection alone or in other control patients. Moreover, antibody titers remained elevated during the entire 10-yr follow-up period.

Intraperitoneal immunization with oligomannose-coated liposome-entrapped soluble leishmanial antigen induces antigen-specific T-helper type immune response in BALB/c mice through uptake by peritoneal macrophages

The present study demonstrates that the intraperitoneal administration of soluble leishmanial antigen (SLA) entrapped in liposomes coated with neoglycolipids containing oligomannose residues (mannopentaose or mannotriose) strongly induces an antigen‐specific T‐helper type 1 (Th1) immune response in BALB/c mice. In response to in vitro stimulation with SLA, spleen cells from mice that had received oligomannose‐coated liposomes encasing SLA (SLA‐OML) displayed greater interferon (IFN)‐γ and interleukin (IL)‐2 production and lower IL‐4 and IL‐5 production than spleen cells from mice that had received SLA alone, indicating that the SLA‐specific Th1 immune response had predominantly been induced in the mice that had received SLA‐OML. After subsequent infection with Leishmania major, mice that had received SLA‐OML were effectively protected against the disease, with a predominant production of IFN‐γ. OML were preferentially and rapidly incorporated into peritoneal macrophages, and the transplantation of macrophages containing SLA‐OML into the peritoneal cavity also induced protection against L. major infection. Thus, SLA‐OML were shown to successfully induce a specific Th1 immune response capable of controlling L. major infection in BALB/c mice through the effective uptake of OML by peritoneal macrophages.

Glomerular plasmin-like activity in relation to nephritis-associated plasmin receptor in acute poststreptococcal glomerulonephritis.

A nephritogenic antigen for acute poststreptococcal glomerulonephritis (APSGN) was isolated recently from group A streptococcus and termed nephritis-associated plasmin receptor (NAPlr). In vitro experimental data indicate that the pathogenic role of NAPlr occurs through its ability to bind to plasmin and maintain its proteolytic activity. However, the mechanism whereby this antigen induces glomerular damage in vivo has not been fully elucidated. Renal biopsy tissues from 17 patients with APSGN, 8 patients with rapidly progressive glomerulonephritis, and 10 normal kidneys were analyzed in this study. Plasmin-like activity was assessed on cryostat sections by in situ zymography with a plasmin-sensitive synthetic substrate. Serial sections were simultaneously assessed for NAPlr deposition by immunofluorescence staining. Glomerular plasmin-like activity was absent or weak in normal controls and in patients with rapidly progressive glomerulonephritis, although tubulointerstitial activity was occasionally detected. Prominent glomerular plasmin-like activity was found in patients who had APSGN and in whom glomerular NAPlr was positive, whereas it was absent or weak in patients who had APSGN and in whom glomerular NAPlr was negative. The distribution of glomerular plasmin-like activity was identical to that of NAPlr deposition but was generally different from that of fibrin(ogen) deposition as assessed by double staining. The activity was abolished by the addition of aprotinin to the reaction mixture but was not altered by the addition of a matrix metalloprotease inhibitor, a cysteine protease inhibitor, or inhibitors of plasminogen activators. Thus, upregulated glomerular plasmin-like activity in relation to NAPlr deposition in APSGN was identified. This result supports the nephritogenic character of NAPlr and offers insight into the mechanism whereby this antigen induces nephritis.

Protection against Leishmania major infection by oligomannose-coated liposomes

Liposomes coated with neoglycolipids constructed with mannopentaose and dipalmitoylphosphatidylethanolamine (Man5-DPPE) have been shown to induce cellular immunity against antigens encapsulated in the liposomes. To assess whether these neoglycolipid-coated liposomes can elicit protective immune response against challenge infection, effects of immunization with soluble leishmanial antigens encapsulated in the liposomes were evaluated using Leishmania major infection in susceptible BALB/c mice. Intraperitoneal immunization of mice with leishmanial antigens in the Man5-DPPE-coated liposomes significantly suppressed footpad swelling in comparison to the control, non-immunized mice, while progression of the disease was observed in mice administered antigens in uncoated liposomes and those administered soluble antigens alone, as seen with control mice. Similarly, the number of parasites decreased substantially in local lymph nodes of mice immunized with the antigen in the Man5-DPPE-coated liposomes. Protection against L. major infection in the immunized mice also coincided with an elevated ratio of antigen-specific IgG2a/IgG1 antibodies, which is a profile of T helper-type 1-like immune response. Taken together, these results indicate the possibility that Man5-DPPE-coated liposome-encapsulated antigens could serve as a vaccine that triggers protection against infectious disease.

Administration of plasmids expressing interleukin‐4 and interleukin‐10 causes BALB/c mice to induce a T helper 2‐type response despite the expected T helper 1‐type response with a low‐dose infection ofLeishmania major

BALB/c mice are susceptible to developing an infection with Leishmania major as a result of a fatal T helper 2 (Th2)‐type response. However, mice infected with a low dose of parasites are reported to be able to overcome the lesions associated with a T helper 1 (Th1)‐type response. To clarify why a difference in the dose of parasites induces a difference in the polarization of the Th phenotype, we first attempted to measure cytokine production. Soon after infection, the mice given high doses of parasites produced elevated levels of both Th1 [interferon‐γ (IFN‐γ)] and Th2 [interleukin (IL)‐4 and IL‐10] cytokines. However, when assessed at 1 and 2 weeks after infection, no significant difference in the balance of Th1 and Th2 cytokines could be detected between mice infected with low or high doses of L. major. These results support the notion that the Th2 cytokine levels at an early phase of infection could be a key factor for the induction of a Th2 response. In order to assess the efficacy of Th2 cytokines, the mice infected with low doses of L. major were co‐administered IL‐4 plasmid and IL‐10 plasmid. Consequently, the mice (which originally exhibited a Th1 response) showed progressive disease and developed a Th2 response. However, administration of these plasmids at 7 days postinfection could not alter the Th polarization. Furthermore, production of IL‐12 from the spleen cells stimulated by L. major was suppressed in the presence of IL‐4 and IL‐10. These results strongly suggest that the susceptibility to L. major in BALB/c mice depends on the persistence of Th2 cytokine levels at an early phase of infection.

Immunosuppression by a neutral thiol protease from parasitic helminth larvae in mice

The composition and immunological suppression of a novel proteinaceous material, a neutral thiol protease (NTP), isolated from the metacercaria of the helminth Paragonimus westermani are reported. From cDNA cloning and sequencing, the protease was found to be composed of 215 amino acid residues and closely resembled the known cysteine proteases. Treatment of adult mice with the enzyme suppressed the delayed footpad reaction and haemagglutinin antibody production, and reduced expression of the major histocompatibility complex and interleukin 2 receptor on lymphocytes, and induced suppressor cells in the spleen. In addition, stable and long‐term skin graft survival was achieved by concomitant administration of the enzyme at a low dose.

Sustainable inhibition efficacy of liposome-encapsulated nisin on insoluble glucan-biofilm synthesis by Streptococcus mutans

Context: Dental caries are an infectious oral bacterial disease caused by cariogenic streptococci. These streptococci inhabit dental biofilms which comprise insoluble glucans. Objective: To prevent dental caries, nisin, a suitable agent active against Gram-positive bacteria, was examined in vitro for its ability to suppress insoluble glucan-biofilm synthesis by cariogenic streptococci. Materials and methods: To investigate glucan-biofilm synthesis by a typical cariogenic streptococcus, Streptococcus mutans 10449, the naked form of nisin was loaded onto a 96-well microplate in vitro model. To prolong the efficacy of nisin as a preventive agent, liposome-encapsulated nisin (nisin-liposome) was examined for its ability to inhibit the synthesis of glucan-biofilms on microplates. Results: Naked nisin (100 pmol) completely suppressed insoluble glucan-biofilm synthesis by S. mutans 10449 following 1 h cultivation in 96-well microplates. The concentration of nisin-liposome required for the efficacious inhibition of glucan-biofilm synthesis was four times lower than that of naked nisin following 2 h cultivation. In particular, nisin-liposome (30 pmol nisin equivalent) prolonged the inhibitory activity of nisin against glucan-biofilm synthesis by S. mutans 10449 for up to 6 h, while naked nisin (30 pmol) gradually lost this inhibitory activity over the same period. In vitro release assay of nisin from the liposome showed that 76% nisin was released within 6 h. Discussion and conclusion: The findings indicate the usefulness of nisin-liposome for the sustained release of nisin. Thus, nisin-liposome could play a potential role in preventive medicine as an inhibitor of the glucan-biofilm synthesis.

A single intradermal administration of soluble leishmanial antigen and plasmid expressing interleukin-12 protects BALB/c mice from Leishmania major infection

In murine leishmaniasis, the induction of the T-helper type 1 (Th1) response contributes to infection resistance, whereas the establishment of the Th2 response makes the mice susceptible to infection. Interleukin-12 (IL-12) plays a pivotal role in the diversification of immune responses to the Th1 type. In this study, we tested whether the co-administration of IL-12 expression plasmid which compose p35 and p40 subunits and soluble leishmanial antigen (SLA) will skew the susceptible BALB/c mice to Th1 response and protect from leishmaniasis. When the mice were intradermally injected with the combination of IL-12 plasmid and SLA 7 days prior to the challenge with 1x10(6) promastigotes of Leishmania major, the local lesions completely healed and the parasite burden in the local lymph nodes significantly decreased. The cured mice attained long-term immunity, and were resistant to any subsequent rechallenge of the lethal dose of the parasite. The protective effect was associated with the development of a Th1 response, as demonstrated by the enhanced level of antigen-specific interferon-gamma (IFN-gamma) and dominant production of IgG2a in the serum. In contrast, the administration of empty plasmid plus SLA or IL-12 plasmid alone failed to protect the disease and shape the Th1 response. Furthermore, the protective efficiency induced by the vaccination was clearly prevented by the injection of either neutralizing anti-IL-12 mAb or anti-IFN-gamma mAb. The IL-12 expression plasmid is thus an effective adjuvant for the elicitation of a protective Th1 response against leishmaniasis and is therefore, considered to be appropriate for vaccinations that require the induction of Th1 type immunity.

Purification and properties of a neutral thiol protease from larval trematode parasite Paragonimus westermani metacercariae

1. A neutral thiol protease was isolated from the extract of larvae of the mammalian trematode parasite, Paragonimus westermani metacercariae, by arginine-Sepharose, Ultrogel AcA-54 and DEAE-toyopearl column chromatography, measuring its activity by the hydrolysis of Boc-Val-Leu-Lys-MCA as a substrate. 2. The molecular weight of the purified enzyme was estimated to be 22,000 as a single polypeptide by SDS-polyacrylamide gel electrophoresis and was estimated to be 20,000 by size exclusion high-performance liquid chromatography. 3. The activity was suppressed by antipain, E-64, leupeptin, chymostatin, N-tosyl-L-lysine chloromethyl ketone, but was not affected by metallo protease inhibitors or serine protease inhibitors. 4. Studies on the substrate specificity showed that the enzyme hydrolyzed Boc-Val-Leu-Lys-MCA, Z-Phe-Arg-MCA, fluorescein isothiocyanate-labeled collagen, azocoll and casein. 5. The enzyme was found to hydrolyze peptide bonds of oxidized insulin B chain preferentially at the carboxy side of hydrophobic and basic amino acids.

Purification and properties of a thiol protease from lung fluke adult Paragonimus ohirai

The thiol protease was purified from adult Paragonimus ohirai by alpha 1-antitrypsin-Sepharose, Sephadex G-75 and CM-cellulose, measuring its activities to hydrolyze hemoglobin and tosyl-L-lysine alpha-naphthyl-ester. The purified protease showed a single band on polyacrylamide disc gel isoelectrophoresis as zymogram with Tos-Lys-NE and also by protein staining, and its pI was found to be 6.4. The molecular weight was calculated to be 29,000 by gel filtration and 27,000 by SDS-polyacrylamide gel electrophoresis as a single polypeptide. The protease hydrolyzed hemoglobin and Tos-Lys-NE optimally at pH 4.0 and 5.0, respectively. The both hydrolyzing activities were inhibited by alpha 1-AT and soybean trypsin inhibitor as well as thiol protease inhibitors such as antipain, E-64 and p-hydroxymercuriphenylsulfonate. These results indicate that this enzyme is a new type thiol protease.