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T T Wu

Publications and source records attributed to T T Wu.

At least 19 recordsLinked to original sources
PubMed1992

Subgroups of Tcr alpha chains and correlation with T-cell function.

T-cell receptor (Tcr) alpha chains are classified into four subgroups (I, II, III, and miscellaneous) based on the amino acid residues at positions 61 and 62. Subgroup I has Gly Phe at these positions, subgroup II has Arg Phe, subgroup III has Arg Leu, and subgroup miscellaneous has several other combinations. Variability plots for subgroups I, II, and III sequences show higher values around positions 93-103, 105, 108, 111, 113, and 115, suggesting that these positions may interact with the processed antigen molecules. Smaller peaks are present at various other regions which may bind the major histocompatibility complex class I or II molecules. The patterns of variability within one subgroup are similar for all species, for human alone, and for mouse alone. These subgroup patterns appear much less complicated than patterns for sequences in all subgroups taken together, implying that subgroups may be related to Tcr functions. Among 83 mouse chains, 15 are from cytotoxic cells and 40 from helper cells. Of the 15 from cytotoxic cells, 11, 2, 0, and 2 are in subgroups I, II, III, and miscellaneous; and of the 40 from helper cells, 9, 16, 12, and 3 are in subgroups I, II, III, and miscellaneous, respectively. Thus, a correlation between sequence and function of Tcr alpha chains seems possible.

Amino Acid Sequence↗
PubMed1992

Replication of DHBV genomes with mutations at the sites of initiation of minus- and plus-strand DNA synthesis.

We have examined the consequences on duck hepatitis B virus DNA synthesis of deleting the 5' and 3' copies of the 12 base sequence, DR1, from the viral pregenome. With the wild-type virus, reverse transcription initiates at nt 2537 within the 3' copy of DR1. When this sequence was deleted, initiation of reverse transcription was found at two other sites located closer to the 3' end of the pregenome (nt 2576 and nt 2644). The 3-base motif UUA was the only sequence common to these sites as well as the wild-type initiation site in DR1. Deletion of the 5' copy of DR1 did not alter minus strand synthesis, but led to aberrant priming of plus strand synthesis to generate predominantly linear rather than relaxed circular, double-stranded viral DNA, in agreement with the recent report by Loeb et al. (EMBO J. 10, 3533-3540, 1991). A mutant lacking only the 3' copy of DR1 rapidly converted to wild type in transfected cells. This apparently occurred as a consequence of conversion of newly synthesized relaxed circular to covalently closed circular (CCC) DNA, which might then serve as a template for the synthesis of wild-type viral RNAs. A mutant lacking only the 5' copy of DR1 did not exhibit this behavior. These results support the conclusion that amplified CCC DNA serves as transcriptional template.

Animals↗
PubMed1992

Possible use of similar framework region amino acid sequences between human and mouse immunoglobulins for humanizing mouse antibodies.

We have previously noted that a specific amino acid sequence could form the second framework region of human, mouse and rabbit immunoglobulin light chains, suggesting that this sequence has been preserved for 80 million years. Through divergent evolution, each species has acquired a different set of framework region sequences; however, these sets still share a few similar or identical amino acid sequences. In the present study, we have identified such sequences for all four framework regions between human and mouse immunoglobulin light and heavy chains. They may be useful in humanizing or reshaping mouse or rat antibodies for therapeutic applications in human patients.

Amino Acid Sequence↗
PubMed1992

Rapid resolution of duck hepatitis B virus infections occurs after massive hepatocellular involvement.

A study was carried out to determine some of the factors that might distinguish transient from chronic hepadnavirus infection. First, to better characterize chronic infection, Pekin ducks, congenitally infected with the duck hepatitis B virus (DHBV), were used to assess age-dependent variations in viremia, percentage of DHBV-infected hepatocytes, and average levels of DNA replication intermediates in the cytoplasm and of covalently closed circular DNA in the nuclei of infected hepatocytes. Levels of viremia and viral DNA were found to peak at about the time of hatching but persisted at relatively constant levels in chronically infected birds up to 2 years of age. The percentage of infected hepatocytes was also constant, with DHBV replication in virtually 100% of hepatocytes in all birds. Next, we found that adolescent ducks inoculated intravenously with a large dose of DHBV also developed massive infection of hepatocytes with an early but low-level viremia, followed by rapid development of a neutralizing antibody response. No obvious quantitative or qualitative differences between transiently and chronically infected liver tissue were detected in the intracellular markers of viral replication examined. However, in the adolescent duck experiment, DHBV infection was rapidly cleared from the liver even when up to 80% of hepatocytes were initially infected. In all of these ducks, clearance of infection was accompanied by only a mild hepatitis, with no evidence that massive cell death contributed to the clearance. This finding suggested that mechanisms in addition to immune-mediated destruction of hepatocytes might make major contributions to clearance of infections, including physiological turnover of hepatocytes in the presence of a neutralizing antibody response and/or spontaneous loss of the capacity of hepatocytes to support virus replication.

Age Factors↗
PubMed1991

Identical V region amino acid sequences and segments of sequences in antibodies of different specificities. Relative contributions of VH and VL genes, minigenes, and complementarity-determining regions to binding of antibody-combining sites.

By examining a large database of amino acid sequences of antibodies of various specificities, we have found that many antibodies of distinctly different specificities assemble identical VL domains with different VH domains. In contrast, rarely is the same VH domain found in sets of antibodies of different specificities. We identified additional sets of antibodies of different specificities and identical sequences covering amino acid residues VH 1 to 94 and VL 1 to 95. In addition, there were segments of additional antibodies for which complete sequences were not available, but identities were seen in VL CDR1, VL CDR2, and VL CDR3 up to the VL-JL junction. The finding that there are many identical VL 1 to 95 segments with different VH 1 to 94 sequences, and vice versa, raises important questions as to the role of VH in influencing the conformation of VL and, conversely, the role of VL in influencing the conformation of VH. Evidence is also cited indicating that a single amino acid change may seriously disrupt site structure and in some instances abolish binding. Our findings suggest that it will be important in the future to investigate further conformational effects on antibody structure by using X-ray crystallography, nuclear magnetic resonance spectroscopy, or other methods, to obtain a better understanding of the functions and topography of antibody-combining sites.

Amino Acid Sequence↗
PubMed1991

Evidence that less-than-full-length pol gene products are functional in hepadnavirus DNA synthesis.

Duck hepatitis B virus mutants containing frameshift or stop codon mutations in a portion of the viral pol gene separating the terminal protein and reverse transcriptase domains had a leaky phenotype and, depending on the location and type of mutation, synthesized up to 10% as much viral DNA as did the wild type. This region of the pol gene had previously been reported to be refractory to missense mutations; in fact, the leakiness of most of our mutants appeared attributable to translational suppression, which would also be expected to introduce amino acid changes. However, at least one mutant (pH1093 + 2), which was ca. 10% as active as the wild type, appeared to use a novel pathway to express the viral pol gene. Our analyses indicated that pH1093 + 2 synthesized the viral reverse transcriptase as a fusion protein with the amino-terminal portion of the pre-S envelope protein. Thus, in this case, the products of the terminal-protein and reverse transcriptase domains of the pol gene would function as separate protein species, though perhaps noncovalently joined in a dimeric structure during assembly of DNA replication complexes. Evidence was also obtained that was consistent with the idea that the wild-type pol gene may, at least in certain instances, be expressed as functional, subgenic polypeptides.

Base Sequence↗
PubMed1991

Autosomal dominant polycystic kidney disease: an unusual presentation as unilateral renal mass in the infant.

The onset of autosomal dominant polycystic kidney disease in infants and children is unusual, and renal involvement is typically bilateral. The presentation of a unilateral renal mass in such a disorder is extremely rare. We report a 2-month-old infant with autosomal dominant polycystic kidney disease presenting with unilateral renal involvement; the literature concerning this entity is reviewed.

Female↗
PubMed1990

Antigenic and functional analysis of a neutralization site of HSV-1 glycoprotein D.

Herpes simplex virus glycoprotein D is a component of the virion envelope and appears to be involved in attachment, penetration, and cell fusion. Monoclonal antibodies (MAbs) against this protein can be arranged in groups, on the basis of a number of biological and biochemical properties. Group I antibodies are type-common, have high complement-independent neutralization titers, recognize discontinuous (conformational) epitopes, and block each other in a binding assay. The sum of their epitopes constitutes antigenic site I of gD. Using a panel of neutralization-resistant mutants, we previously found that group I MAbs can be divided into two subgroups, Ia and Ib, such that mutations selected with Ia antibodies have little or no effect on binding and neutralization by Ib antibodies, and vice versa. Antigenic site I therefore consists of two parts, Ia and Ib. We have now identified the point mutations which prevent neutralization. Two Ib MAbs (DL11 and 4S) selected a Ser to Asn change at residue 140; this alteration creates a new N-linked glycosylation site, which is used. A third Ib MAb (D2) selected a Gln to Leu change at 132. The mutation selected by the Ia MAb HD1 (Ser to Asn at residue 216) is identical to that selected by MAb LP2, another Ia antibody. By using oligonucleotide-directed mutagenesis, we have produced gD genes with combinations of the above mutations. Attempts to recombine these genes into the virus genome were unsuccessful, suggesting that the combinations are lethal. This was confirmed by a complementation assay which measures the ability of gD transiently expressed in transfected Vero cells to rescue the production of infectious virus by the gD-minus mutant F-gD beta.

Base Sequence↗
PubMed1990

In hepatocytes infected with duck hepatitis B virus, the template for viral RNA synthesis is amplified by an intracellular pathway.

During the productive phase of chronic hepadnaviral infections, virion DNA synthesis occurs in the cytoplasm of the infected hepatocyte, but viral RNA is synthesized in the nucleus, apparently from a covalently closed, circular (CCC) viral DNA. J. Tuttleman, C. Pourcel, and J. Summers (1986a, Cell 47, 451-460) have shown that the intracellular levels of CCC DNA can increase during initiation of infection of duck hepatocytes in vitro with duck hepatitis B virus and during long term culture of infected duck hepatocytes in vitro. This amplification of CCC DNA occurs through the reverse transcription pathway. To distinguish between an entirely intracellular process of amplification and amplification due to multiple infections by extracellular virus in the virus producing cultures, suramin was added to the infected cultures to block superinfection. We found that CCC DNA amplification occurred at least as efficiently in the presence of suramin as in its absence. First, there was a net increase in the total amount of CCC DNA in the cultures both in the presence and in the absence of suramin. Second, synthesis of CCC DNA in the presence and absence of suramin was observed by density labeling of this viral DNA by growth of the cultures in medium containing BUdR. Amplification was also demonstrable in the presence of neutralizing duck antibodies. These results support the hypothesis of Tuttleman et al. (1986a) that CCC DNA amplification in chronically infected cultures and, by inference, the mechanism of persistent infection involves primarily intracellular regulatory mechanisms.

Animals↗
PubMed1990

Efficient duck hepatitis B virus production by an avian liver tumor cell line.

Duck hepatitis B virus (DHBV) is produced in small amounts following transfection of human hepatoma or hepatoblastoma cell lines with cloned viral DNA. In a search for better hosts for DHBV replication, two avian liver cell lines were investigated. One of these cell lines, LMH, produced 5 to 10 times more DNA replicative intermediates and 10 to 20 times more infectious DHBV than did either of the two human cell lines, HuH-7 and Hep G2. Utilization of cell lines in genetic analyses of virus replication is often dependent upon obtaining efficient complementation between cotransfected viral genomes. We assayed transcomplementation of a viral polymerase (pol) gene mutant, which is rather inefficient in transfected human cells, and found that viral DNA synthesis was at least 20 times more efficient following cotransfection of LMH cells than in similarly transfected HuH-7 cells. Recombination, a potential interpretation problem in complementation assays, occurred at low levels in the cotransfected cultures but was substantially reduced or eliminated by creation of an LMH subline stably expressing the viral polymerase. This cell line, pol-7, supported the replication of DHBV pol mutants at ca. 10 to 15% of the level of virus replication obtained following transfection with wild-type viral DNA. By transcomplementation of a pol gene mutant in LMH cells, we were able to produce sufficient virus with the mutant genome to investigate the role of polymerase in covalently closed circular DNA amplification. Our results substantiate the hypothesis that covalently closed circular DNA is synthesized by the viral reverse transcriptase.

Animals↗
PubMed1989

Biologic significance of the detection of HBsAg and HBcAg in liver and tumor from 204 HBsAg-positive patients with primary hepatocellular carcinoma.

Hepatitis B virus surface and core antigens (HBsAg, HBcAg) were examined in the resected primary hepatocellular carcinoma from 204 patients who had HBsAg in serum. Ninety patients had small (less than 5 cm) and 114 had large hepatocellular carcinoma (greater than 5 cm). HBsAg was detected in hepatocellular carcinoma in 65 cases (32%) and HBcAg in 30 cases (14.7%); hepatitis B virus antigens were more frequently detected in small (HBsAg in 42.2% and HBcAg in 20%) than in large hepatocellular carcinoma (HBsAg 23.7% and HBcAg 10.5%). These results suggest that replicative forms of hepatitis B virus DNA may exist in hepatocellular carcinoma more frequently than previously believed and that the malignant hepatocytes can support hepatitis B virus replication. A lymphocytic infiltration in hepatocellular carcinoma was more often observed in hepatocellular carcinoma expressing HBsAg (71%) or HBcAg (63%) than in hepatocellular carcinoma with no detectable HBsAg (26%) or HBcAg (37%), p less than 0.01. The reaction was mild in the majority (85%) of the cases. These findings suggest that hepatitis B virus antigen expression in hepatocellular carcinoma can provoke a local immune response. The most striking finding was that patients with hepatitis B virus antigens in small hepatocellular carcinoma had a 5-year survival rate (13%) lower than that (50%) of the antigen-negative patients (p less than 0.05). In contrast, patients with a marked local immune response in hepatocellular carcinoma, regardless of the viral antigen status, had significantly better 5-year survival rates (43%) than those with no or a mild lymphocytic reaction (18%). These findings indicate that a marked immune response in hepatocellular carcinoma is a favorable prognostic sign.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinoma, Hepatocellular↗
PubMed1989

In vitro infection of woodchuck hepatocytes with woodchuck hepatitis virus and ground squirrel hepatitis virus.

Primary cultures of woodchuck hepatocytes were demonstrated to be susceptible to in vitro infection by both woodchuck hepatitis virus and ground squirrel hepatitis virus, as evidenced by the appearance of DNA species characteristic of hepadnavirus replication. Initiation of infection by woodchuck hepatitis virus was blocked by the presence of suramin, polybrene, or dideoxycytidine. Viral CCC DNA, the putative template for viral RNA transcription, was detected at 2 days postinfection. Accumulation of intracellular intermediates in virion DNA synthesis was negligible until 7-10 days postinfection, but these DNA intermediates then increased dramatically in amount over the next few weeks. Results were obtained which suggested that the prolonged accumulation of intermediates in virion DNA synthesis was an intrinsic property of the infection of individual cells, and not the result of a slow spread of virus through the cultures.

Animals↗
PubMed1989

Adult Hirschsprung's disease.

This report presents a series of 17 patients with adult Hirschsprung's disease treated at the National Taiwan University Hospital and its affiliated hospitals from 1965 to 1988. Adults with Hirschsprung's disease may present with symptoms and operative findings different from those of children with Hirschsprung's disease. The symptoms, signs, criteria for diagnosis, operative findings, and operative procedures are presented.

Adolescent↗
PubMed1988

Evolution of expression of hepatitis B surface and core antigens (HBsAg, HBcAg) in resected primary and recurrent hepatocellular carcinoma in HBsAg carriers in Taiwan. Correlation with local host immune response.

Studies were conducted on the evolution of hepatitis B virus (HBV) surface and core antigens (HBsAg and HBcAg) in the tumors of both primary and recurrent hepatocellular carcinoma (HCC) in 27 HBsAg carriers; these were followed for up to 8 years after the resection of the primary tumor. Twenty-seven primary and 34 recurrent tumors were included. HBV antigens were detected in the tumor of the primary HCC in ten cases (37%): six (22.2%) had both antigens (Group I) and four (14.8%) had HBsAg alone (Group II). The remaining 17 cases were negative for both antigens (Group III). Intrahepatic tumor recurrence occurred in 17 cases; both HBcAg and HBsAg were found in the recurrent HCC in four of five HBcAg-positive cases (Group I). In contrast, HBcAg was detected in none of the other 12 cases (Group II, 0 of one; Group III, 0 of 11), and HBsAg in only one (Group II, 0 of one; Group III, one of 11), P less than 0.03 and P less than 0.02, respectively. Groups I, II, and III had extrahepatic recurrence in two, four, and seven cases, respectively. HBcAg was detected in none, while HBsAg was found in only one case (7.7%). The frequent detection of both antigens in the primary HCC and even in the intrahepatic recurrences suggests that HBV replication in HCC may occur more commonly than previously perceived, especially in the small HCC. Failure to detect HBV antigens in the extrahepatic recurrences suggests that the switch-off of the viral gene expression, particularly the core gene, may be an event related to the extrahepatic growth of HCC. HBV antigen expression in HCC is associated with more evident lymphocyte infiltration; this local host immune response may in turn result in a negative selection and expansion of the antigen-negative HCC cell clones. This suggestion is in accord with the fact that HBV antigens, particularly HBcAg, are rarely detected in advanced HCC.

Carcinoma, Hepatocellular↗
PubMed1988

Tumor invasiveness and prognosis in resected hepatocellular carcinoma. Clinical and pathogenetic implications.

In order to elucidate the biologic behavior of hepatocellular carcinoma (HCC), the long-term prognostic impact of the pathologic features of 143 surgically resected HCC were studied. Seventy-four were smaller than 5 cm in diameter (small HCC), and 69 were larger (large HCC). This study confirmed that tumor size was an important but not the only determining prognostic factor in HCC. Although cirrhosis could cause hepatic failure, patient mortality was mainly attributable to tumor recurrence, which, in turn, was strongly correlated with the invasive nature of HCC. Tumor invasion to the liver and the intraportal spread were very frequent and particularly extensive in large HCC. In both small and large HCC the noninvasive groups not only had high 4-year actuarial survival (84.6% and 90%, respectively), but there was also no patient mortality from intrahepatic tumor recurrence. Therefore, it was concluded that invasiveness of an HCC is the most crucial factor in determining the long-term outcome for the patient, and that the clinical course of resected HCC is predictable in a great majority of the cases. In our small HCC series only 2.4% of HCC were regarded as having true multicentric origin. These findings suggest that the majority of HCC occur unicentrically, and that multiplicity and tumor recurrence result mostly from intrahepatic dissemination. In both small and large HCCs invasive tumors were accompanied by high patient mortality from tumor recurrence even when the tumor was small, indicating that intrahepatic spread may start very early during the growth of HCC.

Carcinoma, Hepatocellular↗
PubMed1988

Matching nucleotide sequences of human antibodies with other known sequences.

From an evolutionary point of view, the complementarity-determining regions of antibodies are distinct from other proteins including the framework regions of antibodies. A search for identical nucleotide sequences of eighty-four 15 consecutive bp in the complementary-determining regions of human antibody heavy chains with other known sequences yielded four matches: two sequential 15-bp matches, or one 16-bp match, with the coding region of a sea-urchin testis histone H2b-2, one 15-bp match with the promotor region of a cauliflower mosaic virus inclusion body protein, and a 15-bp match with an intron between exons 1 and 2 of human factor IX. As a control, an identical search of eighty-four 15 consecutive bp in the framework regions of human antibody heavy chains yielded no matches with other sequences except those from other antibody framework regions. Since the currently available nucleotide sequence database used in the search consisted of about 1 x 10(7) bp, finding such matches in the complementarity-determining regions might not be random.

Antibodies↗