Three forms of the major surface antigen (SAG1)of Toxoplasma gondii, that is the membrane form, the secrete form and the intracellular form, were constructed and used to immunize BALB/c mice. The humoral response in the mice immunized with the membrane form and the secrete form of SAG1 appeared earlier and stronger than those mice immunized with the intracellular form. Result from the challenging infection demonstrated that the protection in the mice immunized with the membrane and the secrete forms was also stronger than in the mice immunized with the intracellular form. We suggest that the immune efficiency of the three forms of SAG1 in the mouse model is different.

Objectve To detect whether the CTP(phosphocholine cytidylyltransferase) gene was expressed in the asexual erythrocytic stages of Plasmodium falciparum (FCC 1/HN )by using the RT - PCR and to construct eukaryotic expression vector of CTP. Method The erythrocytic stage parasites of Plasmodium falciparum were cultured as described by Trager and Jensen. RNA from erythrocytic stage parasite was extracted by using Trizol reagent. The complete genes coding for CTP gene isolates FCCI/HN were amplified by reverse transcriptase -polymerase chain reaction(RT- PCR). CTP gene was cloned into eukaryotic expression vector pcDNA3. Results CTP encoding gene was amplified from the erythrocytic stages of Plasmodiumfalciparum (FCC 1/HN) and eukaryotic expression vector of CTP was constructed. Conclusion CTP gene was expressed in the erythrocytic stages of Plasmodium falciparum (FCC 1/HN) and eukaryotic expression vector of CTP was successfully constructed.

The major challenge in vaccine development a gainst various disease-causing organisms is to use defined antigen to stimulate appropriate immune responses that lead to resistance. The use of peptide-based vaccine is gaining greater attention asits flexibility in the incorporation of multiple defined and different epitopes into a single construct for eliciting d esirable arms of the immune system. It is generally safer than the use of live a ttenuated vaccine while it is relative ease of manufacture than subunit vaccine. However, development of peptide-based vaccine faces significant challenges. This approach has limited ability to elicit immune responses in a genetically dive rse outbred population due to the Major Histocompatibility Complexes (MHC) polym orphism. For the same reason, peptide immunizations often elicit inadequate cyto toxic T lymphocyte (CTL) and antibody (Ab) responses due to the lack of appropri ate helper Tlymphocyte (HTL) activity. Another possible disadvantage of using linear peptide construct is that, for eliciting appropriate antibody responses, s urface immunoglobulin (Ig) receptor clustering is needed in order to activate th e resting B cells. Problems caused by MHC polymorphism may be circumvented by the use of promiscuous T-cell epitopes. Promiscuous T-cell epitopes from the mea sles virus F protein (amino acid [aa] 288 to 302) and a murine defined T-helper cell epitope (V1E8, aa 191-209) that bind to multiple MHC molecules have bee n identified and have been used in highly immunogenic constructs to overcome hap lotype-restricted immune responses. Synthetic non-natural Pan DR Epitope (PADR E) which have degenerate binding capacity to several common HLA-DR can enhance immunogenicity of short-peptide immunogen, both in terms of absolute titers and quality of antibody responses. Besides, a number of so called "promiscuous" T -cell epitopes from Influenza virus hemagglutinin (HA), Plasmodium falciparum pre-erythrocytic stage antigens and mycobacterial proteins have been reporte d to be universally immunogenic. For promiscuous binding to several isotypic and allotypic forms of MHC class Ⅱ molecules, these peptides should display overla pping MHC-binding motifs or should use anchors that are conserved among ligands and should lack allele-specific anchor residues that would prevent binding wit h the other class Ⅱ molecules. Understanding the biophysical basis for both the promiscuity and the specificity of peptide recognition by MHC Ⅱ molecules will provide a molecular rationale for strategies to overcome genetic restriction in the context of vaccine design.

Objective To screen cell growth and senescence-related genes of the parasitic pmtist Trichomonas vaginalis,we launched an EST program and isolated two cDNA clones from a T.vaginalis cDNA library,which showed high homology in deduced amino acid sequences to yeast Sir2 and designated as TvSir2 and TvSir2-like.Method The cDNA sequence of TvSIR2 had a length of 1034 base pairs (bp) with an open reading frame of 915 bp,and TvSIR2-like,1214 bp with an open reading frame of 1116 bp.Result The two deduced amino acid sequences shared all the three conserved cole domains with yeast Sir2 and its homologues,suggesting that the two clones were Sir2 homologues. A cDNA fragment from each cDNA clone was subvloned into the expression vector pET-41a.The expression of the fusion proteins in E.coli BL21 stains was induced by isopropylthio-β-D-galactoside (IPTG).Two anti-sera were prepared by immunizing two guinea pigs with the purified fusion proteins, Western-blot analysis demonstrated that each anti-serum reacted with the corresponding recombinant protein and detected a clear band (TvSir2,34 000 Mr;TvSir2-like,42 000 Mr)in protein extracts of the protist.Immunofluolescence techniques showed that TvSir2 and TvSir2-like proteins were both localized in the legions of perinuelear (ER) and Golgi complex.Conclusion Our data suggest that TvSir2 and TvSir2-like were two members of Sir2 family.Their biological functions in the protist would be further studied.

Objective To investigate the polymorphism of human cytomegalovius UL143 gene of low passage clinical isolates in Guangzhou,China.Method PCR was performed to amplify the entire HCMV ULl43 gene region of 3 clinical isolates,which had been proven by multiplex PCR.The amplification products were cloned into pMD18-T-Vector and subjected to sequencing.The result of DNA sequences were analyzed together with the one of published homologous sequences in GenBank from 14 clinical isolates.Result There were several stop codons in UL143 gene due to a base deletion in open reading frame (ORF) of D3 isolate,which could lead to produce non-functional protein.UL143 ORF of Toledo isolate consisted of 279 nueleotides,encoding a protein with 92 amino acids.UL143 ORFs of other isolates consisted of 252 nueleotides,encoding a protein with 83 amino acids.The DNA sequences were quite conserved and all the variations were base substitution.The amino acid sequences of different isolates were highly conserved.with variation of 1.2%-2.4%.There were no additional or deleted sites of post translational modification of UL143 protein in all clinical isolates except Toledo isolate.There were some differences in the secondary structure among different isolates.The isoelectric point of UL143 protein of all clinical isolates except Toledo isolate was 8.75.Conclusion All DNA and deduced amino acid sequences of UL143 gene shared great similarity among HCMV clinical strains regardless of their polymorphism.

Objective To construct the eukaryotic expression plasmid for the expression of human Connexin26 in COS-7 cells.Methods Total RNA was isolated from human peripheral blood lymphocytes and used as template for the PCR cloning of the human Connexin26 gene.The human Cx26 cDNA containing the 678 bp whole coding region of the human Connexin26 gene was amplified by PCR using specific primers and cloned into the pCI-neo vector to construct the recombinant eukaryotic expression plasmid,pCI-Cx26.The recombinant plasmid was identified by restriction endonuclease digestion,and transfected into COS-7 cells by liposome.The expression of Cx26 mRNA and the protein were analyzed by RT-PCR and SDS-PAGE,respectively.Results Restriction endonuclease digestion analysis verified successful construction of the recombinant plasmid,pCI-Cx26.The expression of Cx26 mRNA and protein in the transfected COS-7 cells were detected by RT-PCR and SDS-PAGE,respectively.Conclusion The eukaryotic expression plasmid for human Cx26 has been constructed successfully with the capability of expression in COS-7 cells.

Objective To determine the taxonomic position of medically important gamasid mites and to compare numerical taxonomy with the traditional systematics in the classification of gamasid mites. Methods Based on hierarchical cluster analysis, numerical taxonomy was applied to study fifty-seven species of medically important gamasid mites. Results The results of cluster analysis based on squared euclidean distance showed that Hirstionyssus Fonseca and Echinonyssus Hirst should be separated from Laelapidae Berlese and formed an independent family. The taxonomic position of the remaining species remains the same as those in the traditional systematics. Conclusion Numerical taxonomy can objectively reflect the taxonomic position of the medically important gamasid mites. The result of classification by numerical taxonomy is consistent with traditional systematics for gamasid mites.

Objective To evaluate the measurement of kappa and lambda immunoglobulin free light chains(FLC) in patient samples using a new enzyme-linked immunosorbent assay for early diagnosis of multiple myeloma.Methods An ELISA method for quantifying kappa and lambda free light chains were used to study serum and urine samples from patients with multiple myeloma, and the results were compared with those obtained using immunofixation electrophoresis and nephelometric immunoassay methods. Results The FLC-ELISA method had great successful rate in identifying the multiple myeloma in all 40 myeloma patients. In contrast,immunofixation electrophoresis and nephelometric immunoassay could only identify 57.5% and 85.5% of the multiple myeloma in all the myeloma patients,respectively. Furthermore, retrospective diagnosis of specimens obtained from patient indicated that the ELISA method could help early diagnosis of the disease by over two years. Conclusion The ELISA method for measuring free light chains is sensitive, accurate and reproducible. Therefore it is a useful tool for early diagnosis of multiple myeloma,monitoring the disease progression and evaluating treatment responses.

Objective To detect circulating antigen (Cag) for diagnosing neurocysticercosis. Method ELISA was performed with monoclonal antibody 4B6 against the cyst fluid antigen of Cyticercus cellulosae for detecting Cag in serum and/or cerebrospinal fluid (CSF) of patients with neurocysticercosis or with other diseases. Results In the group of 82 cases of neurocysticercosis, the positive rate of serum Cag was 79.2% (65/82) and the positive rate of CSF Cag was 100% (26/26). After chemotherapy for 20 cases with positive serum Cag, the titer of serum Cag in 17 cases dropped to zero(85% ). Cag could not be detected in specimens from patients with other diseases. Conclusion These results indicate that the determination of Cag, especially of the CSF Cag, is useful for the diagnosis of neurocysticercosis and the drop in serum Cag is a good parameter for the evaluation of the effectiveness of chemotherapy.

The article clarified, according to the recent research results which have been done in Poyang Lake region of Jiangxi province, bovines are the most important animal hosts of Schistosoma japonicum and infected bovines are main infectious sources of Schistosomiasis in Poyang Lake region. Spring (March to June) is the " cross transmission stage" between definitive host and intermediate host, that is, spring is not only the susceptible season of infection for livestock and human, but also is the susceptible season of infection for snails. In flood season (July to August), the transmission of Schistosomiasis between livestock and snails belong to " low level phase" . Autumn (September to Octber) is the second seasonal peak of cercariae and is the susceptible season of infection for livestock and human. Winter(November to Feburary in next year) is the non- susceptible season of infection. Most of the susceptible zones of infection for livestock, human and snails are the marshlands near the endemic villages.