Preparation and activity of conjugate of monoclonal antibody HAb18 against hepatoma F(ab')(2) fragment and staphylococcal enterotoxin A

AIM

To prepare the conjugate of staphylococcal enterotoxin A (SEA) protein which is a bacterial SAg and the F(ab')(2) fragment of mAb HAb18 against human hepatocellular carcinoma (HCC), and identify its activity in order to use SAg in the targeting therapy of HCC.

METHODS

MAb HAb18 was extracted from the abdominal dropsy of Balb/c mice, and was purified through chromatography column SP 40HR with Fast protein liquid chromatography (FPLC) system. The F(ab')(2) fragment of mAb HAb18 was prepared by papainic digestion method. The conjugate of mAb HAb18 F(ab')(2) fragment and SEA was prepared with chemical conjugating reagent N succinimidyl 3 (2-pyridyldithio) propionate (SPDP) and purified through chromatography column Superose 12 with FPLC system. The molecular mass and purity of each collected peak were identified with SDS-PAGE assay. The protein content was assayed by Lowry's method. The antibody activity of HAb18 F(ab')(2) against HCC in the conjugate was identified by indirect immunocytochemical ABC method, and the activity of SEA in the conjugate to activate peripheral blood mononuclear cells (PBMC) was identified with MTT assay.

RESULTS

The IgG mAb HAb18 was extracted, and purified successfully. Immunocytochemical staining demonstrated that it reacted with most of HHCC cells of human HCC cell line. There were two peaks in the process of purification of the prepared HAb18 F(ab')(2) SEA conjugate. SDS-PAGE assay demonstrated that the molecular mass of the first peak was about 130 ku, and the second peak was the mixture of about 45 ku and a little 100 ku proteins. The immunocytochemical staining was similar in HAb18 F(ab') (2) SEA conjugate and HAb18 F(ab') (2), i.e.the cytoplasm and/or cell membranes of most HHCC cells were positively stained. The MTT assay showed that the optical absorbance (A) value at 490 nm of HAb18 F(ab') (2) SEA conjugate was 0.182 +/- 0.012, that of negative control was 0.033 +/- 0.009, and there was significant difference between them (P < 0.05).

CONCLUSION

SPDP is a good protein conjugating reagent and can be used in preparing protein conjugate. The conjugate of mAb HAb18 F(ab') (2) fragment and SEA protein was prepared successfully in present study and can be used in the experimental study of HCC targeting therapy with the conjugate of SAg and anti HCC mAbs or their fragments.

Immunohistochemical demonstration of CCAAT/enhancer binding protein (C/EBP) in human liver tissues of various origin

C/EBP is a sequence-specific DNA-binding protein. In order to identify its distribution and localization, immunohistochemical technique (ABC method) was done using anti-C/EBP polypeptide antibodies 1103#, 425# in liver specimens from 20 normal adults, 5 neonates, 6 patients with hepatitis, 25 with liver cirrhosis, 80 with hepatocellular carcinoma (40 cases were associated with surrounding nontumorous tissues) and 26 patients with cholangiocarcinoma (15 cases were associated with surrounding nontumorous tissues). The results showed that C/EBP was diffusely distributed in nuclei and cytoplasm of differentiated liver cells and very low or undetectable in liver cancer cells. The manifestation of C/EBP correlated with degree of differentiation of tumour cells, and was obviously weaker than that in surrounding nontumorous tissues. C/EBP positive staining has also been found in regenerating epithelial cells of bile ductules. The results suggested that C/EBP should play an important role in establishing and maintaining the differentiation of liver cells.

[Immunofluorescent localization of associated antigen of anti-human nasopharyngeal carcinoma cell monoclonal antibody]

The immunofluorescent localization of associated antigen of anti-human nasopharyngeal carcinoma (NPC) cell monoclonal antibody (McAb) was performed in different tissues (NPC, non-NPC tumor, chronic inflammation of nasopharyngeal mucosa, adult normal tissue and embryo tissue) with 5 control experiments. McAb (CN-1, Cs-C1) was produced by Department of Microbiology of our college and all the specimens were confirmed by pathology. The results revealed that Cs-C1 antigen was mainly found on the surface of NPC cells with a positive rate of 80.3%. Majority of the positive cells showed yellow-greenish linear fluorescence surrounding the cell membrane while some cells manifested granular fluorescence. In addition, Cs-C1 antigen was also found in a few embryo tissues, epithelial cells of the normal gastric mucosa and cells of the gastric cancer. It is suggested that Cs-C1 antigen be a kind of molecular structure, being gradually produced or increased in quantity during carcinogenesis, and belong to the tumor associated antigen. Cs-C1 antigen could be important in the study of carcinogenic mechanism of NPC cells and valuable to clinical immunodiagnosis.

[Primary malignant lymphoma of the central nervous system--a case report and review of literature]

One case of primary malignant lymphoma of the central nervous system is reported. The patient, a nine year old boy having headache, vomiting, seizures in the right limbs and unconsciousness, was admitted into our hospital and died the next day. A tumor at the base of the left frontal lobe was found on autopsy. There was no evidence of tumor elsewhere. A pathological diagnosis of T-cell malignant lymphoma was established. In this paper, the view that the T-cell lymphoma can arise from the central nervous system is proposed for the first time. Its clinical features, pathomorphology and histogenesis are discussed. Yet, how follicles are formed in the tumor tissue and its significance await further study.