Preparation and preliminary application of monoclonal antibodies against Trichokirin-S1, a small ribosome-inactivating peptide from the seeds of Trichosanthes kirilowii.

Trichokirin-S1, a small ribosome-inactivating peptide recently purified from the seeds of Trichosanthes kirilowii, has potential clinical applications because of its small molecular mass. Two stable strains of hybridomas (1F11 and 2A5) that can secrete highly specific monoclonal antibodies (mAbs) against Trichokirin-S1 have been developed using the hybridoma technique. The isotypes of these two mAbs, 1F11 and 2A5, were determined to be IgG2a and IgG1, respectively. The affinity constants, which were measured by non-competitive ELISA, were found to be 2.3 x10(8) M(-1) and 2.8 x 10(8) M(-1), respectively. An immunoaffinity method using 2A5-coupled Sepharose 4B was successfully developed to purify Trichokirin-S1. These two antibodies have also been used to detect Trichokirin-S1 in Western blot.

Identification of the immunogenic domains in HBsAg preS1 region using overlapping preS1 fragment fusion proteins.

AIM: The incorporation of hepatitis B virus (HBV) preS1 region into epitope-based vaccines against HBV has been accepted widely, but the incorporate site and size of preS1 sequence is controversial. Therefore our purpose was to further investigate its immunogenic domains for the epitope-based hepatitis B vaccine design. METHODS: Eight GST fusion proteins containing overlapping preS1 fragments in preS1 (21-119) region were expressed in E.coli. Using these purified fusion proteins, the immunogenic domains in preS1 region were identified in detail in mice and humans by Western blot analysis and ELISA. RESULTS: The results in mice showed that the immu-nogenic domains mainly existed in preS1 (21-59) and preS1 (95-109). Similarly, these fragments had strong immunogenicity in humans; whereas the other parts except for preS1 (60-70) also had some immunogenicity. More importantly, a major immunogenic domain, preS1 (34-59), which has much stronger immunogenicity, was identified. Additionally, the antibodies against some preS1 fragments, especially preS1 (34-59), were speculated to be virus-neutralizing. CONCLUSION: Eight GST fusion proteins containing overlapping preS1 fragments were prepared successfully. They were used for the study on the immunogenic dom-ains in preS1 (21-119) region. The preS1 (34-59) fragments were the major immunogenic domains in the preS1 region, and the antibodies against these fragments were speculated to be virus-neutralizing. Therefore, the incorporation of preS1 (34-59) fragments into epitope-based HBV vaccines may be efficient for enhancement of immune response. Additionally, the results also imply that there are more complex immune responses to preS1 region and more abundant immunogenic domains in humans.

Expression of overlapping PreS1 fragment recombinant proteins for the determination of immunogenic domains in HBsAg PreS1 region.

In this study, eight preS1 fragments overlapped in preS1 (21-119) region of HBV adr subtype, i.e. preS1 (21-47), preS1 (34-59), preS1 (48-70), preS1 (60-85), preS1 (71-94), preS1 (86-109), preS1 (95-119) and preS1 (21-119), were cloned by PCR, and expressed as GST fusion proteins. These GSTpreS1 fusion proteins were highly expressed in soluble form in E. coli, and about 50 to 90 mg soluble fusion proteins were purified from 1 L culture. Using these fusion proteins, the immunogenic domains in preS1 (21-119) region were identified by Western blot analysis and competitive ELISA. The results showed that the immunogenic domains mainly existed in preS1 (21-59) in N-terminus and preS1 (95-109) in C-terminus, and more importantly, a major immunogenic domain preS1 (34-59), which has much stronger immunogenicity, was identified. It was also supported by the predictions of secondary structure and immunological property in the preS1 (21-119) region. The results here would be helpful for the design of new vaccines against HBV.

Preparation and primary application of monoclonal antibodies against a novel ribosome-inactivating protein Moschatin from pumpkin seeds.

Plant ribosome-inactivating proteins (RIPs) have multiple biological functions, and have been widely used in the studies on biomedical and agronomic applications. Moschatin is a novel single-chain RIP recently purified from pumpkin seeds, and it has been successfully applied to construct the immunotoxin that can selectively kill the cultured human melanoma cells. Six stable strains of hybridomas (2H8, 4A8, 5B6, 6F8, 4H10 and 6C2) that can secrete high specific monoclonal antibodies against Moschatin have been successfully prepared using hybridoma technique. The isotypes of these monoclonal antibodies are IgG1, IgG1, IgG1, IgG1, IgG2a and IgGM. Their affinity constants were determined to be 1.42x10(8), 2.71x10(8), 8.72x10(7), 2.06x10(8), 1.36x10(8) and 1.51x10(8) M(-1) in a sequent order, measured by non-competitive ELISA. The monoclonal antibody 4A8 has been used to detect Moschatin in Western blot. An immunoaffinity gel, which consisted of a monoclonal antibody 4H10 and Sepharose 4B, was prepared and used to purify Moschatin from pumpkin seeds crude extract.

Purification and characterization of Moschatin, a novel type I ribosome-inactivating protein from the mature seeds of pumpkin (Cucurbita moschata), and preparation of its immunotoxin against human melanoma cells.

A novel ribosome-inactivating protein designated Moschatin from the mature seeds of pumpkin (Cucurbita moschata) has been successively purified to homogeneity, using ammonium sulfate precipitation, CM-cellulose 52 column chromatography, Blue Sepharose CL-6B Affinity column chromatography and FPLC size-exclusion column chromatography. Moschatin is a type 1 RIP with a pI of 9.4 and molecular weight of approximately 29 kD. It is a rRNA N-glycosidase and potently blocked the protein synthesis in the rabbit reticulocyte lysate with a IC50 of 0.26 nM. Using the anti-human melanoma McAb Ng76, a novel immunotoxin Moschatin-Ng76 was prepared successfully and it efficiently inhibited the growth of targeted melanoma cells M21 with a IC50 of 0.04 nM, 1500 times lower than that of free Moschatin. The results implied that Moschatin could be used as a new potential anticancer agent.