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S Songsivilai

Publications and source records attributed to S Songsivilai.

30 records · Page 2Linked to original sources
PubMed1996

The newly discovered non A-E hepatitis viruses.

Two biotechnology companies have recently announced the discovery of 4 new hepatitis viruses, provisionally named HGV and GBV agents (GBV-A, GBV-B, and GBV-C). Using a molecular biological approach, the genomes of these viruses were identified from non-A-E hepatients patients who had no markers to any previously known hepatitis viruses. The new viruses are members of family Flaviviridae, and are closely related to hepatitis C virus (HCV). Preliminary studies show that the prevalence of GBV agents and HGV are alarmingly high in blood donors in the United States, Europe, Africa and Japan. The viruses are transmitted parenterally, similar to HCV and hepatitis B virus (HBV), Chronic infection is common and can lead to cirrhosis. Some chronic hepatitis cases caused by these viruses respond to interferon treatment. The viruses can coinfect with HCV and/or HBV. A number of questions about these new viruses remain to be answered, including the magnitude of the problems, clinical significance, mode of transmission and populations at risk, as well as the appropriate treatment.

Blood Donors↗
PubMed1996

Improved amplification system for detection of hepatitis C virus genome that simultaneously differentiates viral genotypes.

An improved system for amplification of hepatitis C virus genome (HCV) was developed based on a multiplex nested polymerase chain reaction format. Two sets of oligonucleotide primers were used simultaneously. One was derived from the conserved sequences in the 5' non-coding region of the viral genome which can bind to the viral genome of all genotypes. The other set of primers was designed from a sequence in the nonstructural-5 region of HCV. HCV genotypes 1 and 3 can be differentiated by the banding patterns of amplified DNA products. All of 39 samples containing the HCV genotype 1 could be amplified with primers in the 5' non-coding region only, whereas 92% of those with genotype 3 could be amplified by both primer sets. In addition, HCV RNA can be detected in 81% of 84 anti-HCV-positive blood donors and in 0% of 34 anti-HCV-negative cases. Of the HCV RNA-positive specimens, 69% showed genotype 1-like patterns while 31% showed genotype 3-like patterns. The detection rate of HCV RNA in this study was much higher than that in our previous report due to the improvement of new primers which can detect all genotypes of the virus. In conclusion, this improved amplification system is a sensitive method for rapid identification of HCV RNA in clinical specimens that can simultaneously differentiate the two most common genotypes of HCV found in Thailand.

Blood Donors↗
PubMed1995

Hepatitis B- and hepatitis C-associated hepatocellular carcinoma: evaluation of alpha-fetoprotein as a diagnostic marker.

Hepatocellular carcinoma (HCC) is one of the most common cancers, especially in Asia and Africa. The prognosis of HCC is very poor because of the high malignancy and the failure of early diagnosis which is mainly dependent on the late onset of clinical symptoms. Chronic infection with hepatitis B virus (HBV) and/or hepatitis C virus (HCV) is the most commonly known risk factor for developing HCC. Mass screening and monitoring of general population or of high-risk population, by measurement of serum alpha-fetoprotein (AFP), have been implemented in several countries. However, the use of AFP as a diagnostic marker for HCC is questionable due to its limited sensitivity and specificity. This article analyzed the serum level of AFP in 72 histopathologically confirmed hepatocellular carcinoma cases in Thailand. Elevation of serum AFP was detected in 75.6%, 88.9%, 79.2% and 80.0% of patients with HBsAg, anti-HCV antibody, HBV DNA, and HCV RNA, respectively. However, only 58.8% of HCC patients without any of the four markers had elevation of serum AFP. AFP is thus not a sensitive screening marker for HCC in general population, especially in those not associated with HBV or HCV. However, since elevated serum AFP was found in most patients with evidence of HBV or HCV infection, the monitoring of serum AFP level in those high-risk patients can be valuable for screening and monitoring of hepatocellular carcinoma.

Adolescent↗
PubMed1994

Fusion protein of Salmonella typhi flagellin as antigen for diagnosis of typhoid fever.

We previously established the specific 52 kDa antigen of Salmonella typhi, detected by our monoclonal antibodies, which was a flagellin protein. Comparison of the nucleotide sequences of phase-1 flagellin of Salmonella species available through GenBank database showed high homology at both ends of the genes with lower degree of homology in the middle portion which contained the antigenically variable regions. Thus, proteins from the central regions of flagellin genes should be species specific and could be used as specific antigens for the immunodiagnostic tests. In this report, recombinant protein derived from the central region of S. typhi flagellin was produced as a fusion protein with glutathione-S-transferase. This fusion protein was used as specific S. typhi antigen for the immunodiagnostic test to detect IgM antibodies in sera using enzyme-linked immunosorbent assay. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of this test were 53.5, 98.0, 91.5, 82.1 and 92.4%, respectively.

Antibodies, Bacterial↗
PubMed1993

Molecular cloning and expression of Salmonella typhi flagellin: characterization of 52 kDa specific antigen of S. typhi.

We previously reported monoclonal antibodies (MAbs) specific to S. typhi 52 kDa antigen which do not cross react with related protein antigens from 11 bacteria causing enteric fever and enteric fever-like illness. Using the combination of these specific MAbs and recombinant DNA technology, expression plasmids containing the antigen gene producing substantial amount of the S. typhi protein antigen have been established. Plasmid pSKM-T7 containing the specific 52 kDa antigen gene was cloned and the antigen expressed was detectable by immunoblotting using specific mAbs. The complete nucleotide sequence of this gene was compared with other bacterial sequences and found to be highly homologous with the flagellin gene H1-d of S. muenchen except in the hypervariable region in the central portion. The specific 52 kDa antigen of S. typhi detected by our MAbs is thus a flagellin.

Antibodies, Monoclonal↗
PubMed1992

Germline variable region gene segment derivation of human monoclonal anti-Rh(D) antibodies. Evidence for affinity maturation by somatic hypermutation and repertoire shift.

To date, there has been no systematic study of the process of affinity maturation of human antibodies. We therefore sequenced the variable region genes (V genes) of 14 human monoclonal antibodies specific for the erythrocyte Rh(D) alloantigen and determined the germline gene segments of origin and extent of somatic hypermutation. These data were correlated with determinations of antibody affinity. The four IgM antibodies (low affinity) appear to be derived from two germline heavy chain variable region gene segments and one or two germline light chain variable region gene segments and were not extensively mutated. The 10 IgG antibodies (higher affinity) appear to be derived from somatic hypermutation of these V gene segments and by use of new V gene segments or V gene segment combinations (repertoire shift). Affinity generally increased with increasing somatic hypermutation; on average, there were 8.9 point mutations in the V gene segments of the four IgM antibodies (Ka = 1-4 x 10(7)/M-1) compared with 19 point mutations in the V gene segments of the 10 IgG antibodies. The four highest affinity antibodies (Ka = 0.9-3 x 10(9)/M-1) averaged 25.5 point mutations. The use of repertoire shift and somatic hypermutation in affinity maturation of human alloantibodies is similar to data obtained in inbred mice immunized with haptens.

Antibodies, Monoclonal↗
PubMed1990

An improved method for the detection of cell surface antigens in samples of low viability using flow cytometry.

A high non-specific background fluorescence signal was observed when cell surface antigen analysis was carried out using flow cytometry on a cell sample which contained a high proportion of dead and dying cells. To overcome this problem it was necessary to analyse the cells in three stages. First the intact cells were identified by their forward (FWD) and 90 degree scatter profile. These cells were gated-on, then analysed on the basis of their FWD scatter and propidium iodide (PI) signal, allowing the dead PI positive cells to be gated out. The PI negative cells were then displayed using their 90 degree scatter and fluorescence signals following staining with the irrelevant antibody control. This revealed a population of dead cells, which despite being PI negative, were non-specifically binding antibody molecules. Such multiparameter analysis permitted the successful analysis of cell surface antigens in preparations of low viability by gating out the high background fluorescence associated with dead PI positive and negative cells.

Animals↗
PubMed1990

Cloning and sequencing of human lambda immunoglobulin genes by the polymerase chain reaction.

Universal oligonucleotide primers, designed for amplifying and sequencing genes encoding the rearranged human lambda immunoglobulin variable region, were validated by amplification of the lambda light chain genes from four human heterohybridoma cell lines and in the generation of a cDNA library of human V lambda sequences from Epstein-Barr virus-transformed human peripheral blood lymphocytes. This technique allows rapid cloning and sequencing of human immunoglobulin genes, and has potential applications in the rescue of unstable human antibody-producing cell lines and in the production of human monoclonal antibodies.

Amino Acid Sequence↗
PubMed1990

Bispecific antibody: a tool for diagnosis and treatment of disease.

Antibodies with two distinct binding specificities have great potential for a wide range of clinical applications as targeting agents for in vitro and in vivo immunodiagnosis and therapy, and for improving immunoassays. They have shown great promise for targeting cytotoxic effector cells, delivering radionuclides, toxins or cytotoxic drugs to specific targets, particularly tumour cells. We discuss potential applications of bispecific antibodies, the theoretical basis and problems associated with their production and purification, cell fusion and chemical conjugation techniques, and propose a new manufacturing strategy by genetic engineering. This approach has enormous potential applications for producing tailor-made bispecific antibodies, and will enable widespread clinical uses of these antibodies both for diagnostic purposes and therapy.

Animals↗
PubMed1989

A novel strategy for producing chimeric bispecific antibodies by gene transfection.

We have used genetic manipulation to produce chimeric bispecific antibodies. Plasmids containing variable regions of immunoglobulin from a murine hybridoma secreting anti-hepatitis B surface antigen were joined to human constant regions. These chimeric plasmids were introduced into transfectomas, secreting chimeric antibodies to iodo-hydroxy-nitrophenyl, by electroporation. Transfectomas secreting bispecific antibodies were identified. This approach has advantages over the fusion of hybridomas or chemical linking of two antibody molecules and will enable the use of bispecific antibodies in vivo.

Animals↗
PubMedDate not supplied

Hepatitis C virus genotypes in patients with hepatocellular carcinoma and cholangiocarcinoma in Thailand.

The prevalences of infections with hepatitis C virus (HCV) and hepatitis B virus (HBV) were determined in 110 Thai patients with liver cancer, of whom 80 and 30 had histological diagnoses of hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), respectively. Hepatitis B surface antigen was detected in 63.8% of HCC patients and 16.7% of those with CCA. Antibodies to HCV, detected by a third-generation enzyme immunoassay, were found in 11.3% of HCC patients and in no CCA patient. HCV ribonucleic acid (RNA) was detected by polymerase chain reaction in 6 anti-HCV positive patients, and also in 2 patients who had no detectable anti-HCV antibody. A total of 11 patients had evidence of HCV infection, 8 of whom were infected with HCV alone. HCV genotypes were determined in all 8 patients who had HCV RNA; genotype 3a was the most common (62.5%). These results demonstrate that, in Thailand where both HBV and HCV are endemic, HBV infection is still the most important risk factor for HCC, but HCV also has an important role in those without HBV infection. In addition, the genotypic distribution of HCV in HCC in Thailand is similar to that in the general population. No specific association between genotype 1b and HCC was observed.

Adult↗