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Biomedical subjects

M S Ho

Publications and source records attributed to M S Ho.

At least 37 records · Page 2Linked to original sources
PubMed1997

Altered antigenicity of 'a' determinant variants of hepatitis B virus.

The 'a' determinant of hepatitis B virus (HBV) surface antigen (HBsAg) is the most important target for diagnosis and immunoprophylaxis. Several HBV variants with point mutations within the 'a' determinant have been identified among fully vaccinated children in Taiwan. We investigated the effect of each of these mutations on the antigenic nature of the S protein by cloning and expression of the mutant S antigens in Pichia pastoris. Four variants, Ser-126, His-129, Arg-129 and Arg-145, all exhibited various degrees of altered binding of HBsAg to several monoclonal antibodies. Arg-145, a well-characterized immune escape mutant, and Arg-129 had the lowest binding capacities to all monoclonal antibodies as compared with other variants. Similar to Arg-145, the Arg-129 variant could be isolated from both vaccinated children and unvaccinated adults, thus representing a naturally occurring mutant with an altered 'a' determinant. Whether these 'a' determinant variants with altered antigenicity might gradually become major circulating strains, as a consequence of the immune pressure against the wild-type HBV created by vaccination, remains to be monitored.

Adult↗
PubMed1997

Serum alanine aminotransferase level in relation to hepatitis B and C virus infections among blood donors.

To assess the serum alanine aminotransferase (ALT) activity in relation to hepatitis B virus (HBV) and hepatitis C virus (HCV) infections among blood donors, antibodies to HCV (anti-HCV) and hepatitis B surface antigen (HBsAg) were detected in 400 blood donors with normal ALT level (< or = 750 mumol/s per liter), and 76 blood donors with raised ALT level. The prevalence of anti-HCV (10.5%) and HBsAg (28.9%) in the latter was higher than that (2.0% and 17.5%, respectively) in the former (p < 0.001 and p < 0.03, respectively). There was a trend that indicated that the risk of anti-HCV positivity increased with increasing age (p < 0.001). Thirty of 76 (39.5%) donors with raised ALT level were positive for anti-HCV or HBsAg. Compared with HBsAg-positive donors, donors with anti-HCV had higher serum ALT levels (p < 0.01) and greater mean age (p < 0.01). Multivariate analysis indicated that both anti-HCV (odds ratio: 6.2; 95% confidence interval: 2.2-17.8) and HBsAg (odds ratio: 2.2; 95% confidence interval: 1.3-3.9) were significantly associated with raised serum ALT activity. The estimated population-attributable risk was 8.6% for anti-HCV, and 13.8% for HBsAg. In conclusion, although HBV and HCV infections are independent risk factors of raised ALT activity among blood donors, they play a minor role in the etiology of raised ALT activity.

Adult↗
PubMed1997

Detection of Neospora from tissues of experimentally infected rhesus macaques by PCR and specific DNA probe hybridization.

Neospora is a newly recognized Toxoplasma-like cyst-forming coccidian parasite that causes abortion or congenital infections in naturally or experimentally infected animals. In this study, pregnant rhesus macaques were inoculated with culture-derived tachyzoites of a bovine Neospora isolate, and tissue samples from various major organs were collected from dams and fetuses for the detection of parasite DNA by using oligonucleotide primers COC-1 and COC-2 for PCR amplification of a conserved coccidial nuclear small-subunit rRNA gene sequence, and amplification products were confirmed by hybridization with a Neospora-specific DNA probe. PCR products were amplified from DNAs of different fetal monkey tissues, including brain, heart, lung, liver, spleen, skeletal muscle, skin, and placenta. In addition, Neospora DNA was amplified from the brain, heart, and lung tissues of infected rhesus macaque dams. The PCR and probe hybridization system may provide an effective method for the detection of Neospora infection in fetuses and dams from nonhuman primates and may be useful in determining the zoonotic potential of Neospora.

Animals↗
PubMed1997

[Seroepidemiology of Japanese encephalitis viral infection among 3-6 years old children from mountainous and plains townships located in the northern, central, southern and eastern Taiwan].

In order to evaluate the Japanese encephalitis virus (JEV) vaccination program in rural Taiwan, we conducted a seroepidemiological survey of JEV among rural children 3 to 6 years of age in Taiwan. The children were selected through a systemic sampling following stratification by age of children in 4 selected aboriginal villages and 4 adjacent nonaboriginal villages. The overall vaccine coverage rate for the primary (2 doses) dose was 81.2% (1853/2281) with higher rates (87.7%-87.9%) found among the more recent birth cohort of 3 to 4 years of age. The neutralizing antibody (NT) against JEV was measured with plaque reduction neutralization test (PRNT) using Nakayama strain as the virus. With a positive NT antibody defined as > or = 1:10 dilution of serum yielding more than 50% plaque reduction, the overall JEV NT antibody positive rate among children receiving 3 doses of vaccine was 67%. However, the age-specific positive rates varied significantly with varying ages; the lowest of 47% being among children 4 years of age which was lower than the rates of 68%, 76% and 87% among children of 3, 5 and 6 years of age, respectively. This trend of rising seropositive rates of JEV antibody with increasing age among 4 and 6 years of age was also noted among children who had received no vaccine, suggesting the importance of natural infection among rural Taiwanese children. Despite the high frequency of natural infection, the seropositive rates of JEV antibody still correlated well with the dose of vaccine received, i.e., 67% (1122/1664), 66% (65/97), 33% (4/12) and 40% (19/47) for children receiving 3, 2, 1, and 0 dose of JE vaccines, respectively (P < 0.0001 Chi-square for trend test). When stratified analysis by dose and by type of vaccines was conducted, a significantly higher seropositive rate of JEV NT antibody was noted among children receiving JE vaccine of Beijing type (87%) than children receiving Nakayama type (39%) (p < 0.0001, Chi-square test). Our data indicated that the JEV vaccination, in conjunction with JEV natural infection, has maintained high JEV NT antibody level among rural children of Taiwan.

Age Factors↗
PubMed1997

Detection of Neospora sp. from infected bovine tissues by PCR and probe hybridization.

Neospora sp. can cause fetal abortion or neurological disease in congenitally infected calves. Latent tissue stages in infected cows may contribute to vertical transmission of Neospora sp. from dam to offspring in multiple pregnancies. In this investigation, the polymerase chain reaction (PCR) and Neospora-specific assay were employed to detect Neospora sp. by amplification of nuclear small-subunit rRNA gene sequences in infected cattle tissues. Tissues from 11 cattle, including 6 experimentally and 2 naturally infected cows, 1 naturally infected newborn calf, and 2 uninfected control cows, were evaluated in this study. Neospora-specific PCR products were amplified from DNAs of different bovine tissues, including brain, spinal cord, heart, lung, kidney, diaphragm, skeletal muscle, and placenta, as well as amniotic fluid samples of infected cattle. The PCR-based amplification and probe hybridization system proved useful in assessing the location of tissue-stage parasites in naturally and experimentally infected cattle, even when Neospora sp. antibody titers fall below normal cut-off values by an indirect immunofluorescent antibody test.

Abortion, Veterinary↗
PubMed1996

Ethnic differences in immune responses to hepatitis B vaccine.

A national vaccination program against hepatitis B virus (HBV) to immunize every newborn was initiated in Taiwan in 1986. A serologic survey of 1,812 fully vaccinated children residing in four aboriginal villages and four adjacent nonaboriginal Han Chinese rural villages was conducted in 1993. Children in three of the four aboriginal villages had significantly lower titers of antibody against hepatitis B surface antigen (anti-HBs) than did children in the nonaboriginal villages. Evaluation of cold chain operation for vaccine storage and transport suggested that cold chain failure was not responsible for the fact that children residing in the more remote aboriginal villages had lower mean titers of anti-HBs. However, children whose parents were both aborigines had lower anti-HBs mean titer than did children whose parents were both ethnic Han Chinese. Children of mixed parental origins had intermediate mean titer of anti-HBs. Serologic responses to Japanese encephalitis virus and diphtheria vaccines did not show such correlation with ethnic groups, indicating that the determinant for HBV hyporesponsiveness among the aboriginal children is distinct from that of other childhood vaccines. It was therefore concluded that host factors pertaining to ethnic origin might be responsible for the hyporesponsiveness to HBV vaccine in the aboriginal populations. This finding, if substantiated with further prospective studies, might provide possible means for more targeted trials to improve vaccine response and to reduce vaccine failure among these well-defined ethnic groups.

Child↗
PubMed1996

Increased IgM class circulating immune complexes in acute hepatitis A virus infection.

For assessing the role of circulating immune complexes (CIC) in acute hepatitis A, IgM- and IgG-specific CIC were determined, by C1q and conglutinin (K) assays, in 205 patients with acute hepatitis A and 60 healthy controls. The concentration of each type of CIC in patients was higher than healthy controls (P=0.0001). CIC was a common feature of acute hepatitis A with 95.6% of cases having at least one abnormal test result. The prevalence of abnormal IgM class CIC was significantly higher than IgG class CIC. There were significantly inverse correlations between levels of IgM class CIC and interval between onset of symptoms and patient presentation. The prevalence of abnormal IgM CIC was higher in patients with higher alanine aminotransferase (P=0.001) and patients with jaundice (P=0.0002). In conclusion, IgM class CIC is the predominant CIC in acute hepatitis A and correlated with disease activity. CIC may play a role in the pathogenesis of acute hepatitis A.

Acute Disease↗
PubMed1996

Hepatitis B surface antigen- and immunoglobulin-specific circulating immune complexes in acute hepatitis B virus infection.

For assessing the role of circulating immune complexes (CICs) in acute hepatitis B, CICs containing HBsAg, IgM, and IgG were determined, by C1q and conglutinin (K) assays, in 242 patients with acute hepatitis B and 60 healthy controls. CIC is a common feature of acute hepatitis B with 90.9% of cases having at least one abnormal test result. Patients with shorter interval (< 1 week) between onset of symptoms and patient presentation have significantly higher frequency of abnormal IgM class CIC, HBsAg-specific CIC, and higher frequency of raised alanine aminotransferase activity (> 30-fold upper limit of normal). The prevalence of raised alanine aminotransferase in patients with CIC containing HBsAg and IgM is higher than those without (P = 0.001). There is significant association between HBsAg-CIC and C1q-CIC. In conclusion, HBsAg-CIC and IgM class CIC correlate with disease activity. C1q-binding CIC is the predominant CIC that may play a role in the pathogenesis of acute hepatitis B.

Acute Disease↗
PubMed1996

Independent and additive effect modification of hepatitis C and B viruses infection on the development of chronic hepatitis.

BACKGROUND/AIMS: This study aimed to assess the effects and interaction between hepatitis B virus and hepatitis C virus infection on the development of chronic hepatitis. METHODS: Anti-HCV and HBsAg were detected in 125 histology-proven chronic hepatitis and 250 sex-matched and age-matched healthy controls. RESULTS: The prevalences of anti-HCV (24.8%) and HBsAg (68.0%) in patients were higher than in controls (2.4% and 18.0%, respectively; each p < 0.0001). Univariate analysis showed that anti-HCV and HBsAg were strongly associated with the development of chronic hepatitis. Calculation of synergy index and Mantel extension test for trend indicated that there was additive effect modification between HCV and HBV. Multivariate analysis indicated that anti-HCV (odds ratio, 46.1; 95% confidence interval, 9.1-233.2) and HBsAg (odds ratio, 25.8; 95% confidence interval (9.3-67.2) were independent risk factors of chronic hepatitis. The population-attributable risk was estimated as 15.6% for anti-HCV alone, 52.4% for HBsAg alone and 6.8% for both anti-HCV and HBsAg. The frequency of chronic active hepatitis in patients with anti-HCV alone (100%) was higher than in patients with HBsAg alone (75%, p < 0.001). CONCLUSIONS: HCV and HBV infections are risk factors of chronic hepatitis. They act independently and probably with additive effect modification.

Adolescent↗
PubMed1996

Additive effect modification of hepatitis B surface antigen and e antigen on the development of hepatocellular carcinoma.

To assess the role of hepatitis B e antigen (HBeAg) and its interaction with hepatitis B surface antigen (HBsAg) on the development of hepatocellular carcinoma (HCC), this case-control study included 361 age- and sex-matched pairs of patients with histologically proven HCC and healthy control subjects. HBsAg, HBeAg and antibody to HBeAg (anti-HBe) were detected by radioimmunoassay. Antibodies to hepatitis C virus (anti-HCV) were detected by second-generation enzyme immunoassay. The prevalences of HBeAg (20.2%), HBsAg (80.3%) and anti-HCV (29.5%) in cases were higher than in controls (1.9%, 20.7%, and 2.7% respectively; each P < 0.0001). Using patients negative for HBsAg, HBeAg and anti-HBe as a referent group, univariate analysis indicated that HBsAg alone or HBsAg and HBeAg were risk factors for HCC (P for trend < 0.0001). Calculation of incremental odds ratio indicated that there was additive interaction between HBsAg and HBeAg. Multivariate analysis indicated that HCC development was strongly associated with the presence of HBeAg (odds ratio, 8.1; 95% confidence interval, 2.4-27.1), HBsAg (odds ratio, 68.4; 95% confidence interval, 20.5-227.8) and anti-HCV (odds ratio, 59.3; 95% confidence interval, 13.6-258.4). In conclusion, HBsAg, HBeAg and anti-HCV are independent risk factors for HCC. There is additive and independent effect modification between HBsAg and HBeAg on the development of HCC.

Adult↗
PubMed1996

The epidemiology of rotavirus diarrhea in the United States: surveillance and estimates of disease burden.

The decision to develop rotavirus vaccines was predicated on the extensive burden of rotavirus disease among children worldwide. US reports on nationwide hospitalizations (1979-1992) and deaths (1968-1991) due to diarrhea and weekly reports of rotavirus infection by 74 laboratories were reviewed to estimate the burden of rotavirus disease, identify epidemiologic trends, and consider methods for evaluating an immunization program when a vaccine becomes available. From 1968 to 1985, diarrhea-related deaths among US children <5 years old declined from 1100 to 300/year. This decline was associated with the disappearance of winter peaks for diarrhea-related deaths previously associated with rotavirus infection among children 4-23 months old. From 1979 to 1992, however, hospitalizations for diarrhea averaged 186,000/year and retained their winter peaks, which have been linked to rotavirus infections. Each year an estimated 54,000-55,000 US children are hospitalized for diarrhea, but <40 die with rotavirus. A rotavirus vaccine program will require improved surveillance, including the timely collection of data from sentinel hospitals, in which a diagnosis of rotavirus can be established or ruled out for all children hospitalized for diarrhea.

Child↗
PubMed1996

Identification of bovine Neospora parasites by PCR amplification and specific small-subunit rRNA sequence probe hybridization.

Neospora is a newly recognized genus of pathogenic coccidia, closely related to Toxoplasma gondii, that can cause abortion or congenital disease in a variety of domestic animal hosts. On the basis of the small-subunit rRNA gene sequences of Neospora spp. and other apicomplexa coccidia, oligonucleotide primers COC-1 and COC-2 were used for PCR amplification of conserved sequences of approximately 300 bp in size. A Neospora-specific chemiluminescent probe hybridized to Southern blots of amplification products from Neospora DNA but not to Southern blots with amplified DNA from the other coccidian parasites tested. A Toxoplasma-specific probe whose sequence differed from that of the probe for Neospora spp. by a single base pair was used to distinguish these parasites by specific Southern blot hybridization. The PCR system detected as few as one Neospora tachyzoite in the culture medium or five tachyzoites in samples of whole blood or amniotic fluid spiked with Neospora parasites. In addition, Neospora PCR products were successfully amplified from whole blood and amniotic fluid samples of experimentally infected bovine and rhesus macaque fetuses. These results indicate that this PCR and probe hybridization system could be a valuable adjunct to serology and immunohistochemistry for the diagnosis of Neospora infections in bovine or primate fetuses.

Abortion, Veterinary↗
PubMed1996

Surgery for inflammatory bowel disease in Singapore.

Inflammatory bowel disease is uncommon in Asians and reports of surgery in these populations are rare. Eighty-two patients with inflammatory bowel disease were seen in the Department of Colorectal Surgery over a five-year period (1989-1994). Twenty-three patients underwent surgery for their disease. There were 12 males and 11 females with 16 Chinese, 4 Indians and 3 Malays. Twelve had Crohn's disease and 11, ulcerative colitis. The majority of patients with Crohn's disease had emergency surgery for bleeding, perforation, abdominal masses and intestinal fistulae. Fifty percent of these had the diagnosis made intraoperatively or post-operatively. Surgery for ulcerative colitis was indicated because of multiple relapses, non-response to medical treatment, side effects of therapy or malignant change. The median age at surgery of patients with Crohn's disease and ulcerative colitis was 39 years (range 24-84) and 40 (range 18-60) respectively. The median follow-up was 22.4 months (range 9-50). The results of surgical therapy in these patients show that surgery when indicated can be done with minimum morbidity and mortality.

Adult↗
PubMed1995

Circulating immune complexes in chronic hepatitis C.

For assessing the role of circulating immune complexes (CIC) in chronic hepatitis C, the relative frequency of CIC was determined in 54 patients with chronic hepatitis C, 15 asymptomatic hepatitis C virus (HCV) carriers, and 54 healthy controls. IgM and IgG containing CIC were studied using both C1q and conglutinin (K) in an immunoglobulin-specific solid-phase enzyme immunoassay. CIC were a common feature of chronic hepatitis C with 96.3% of patients with at least one abnormal test result. The prevalence of elevated IgG-K, IgM-K, IgG-C1q, and IgM-C1q CIC was 70.3%, 50.0%, 64.8%, and 35.1%, respectively. The prevalence of IgG class CIC was higher than IgM class CIC (P = 0.038 for K-CIC and P = 0.01 for C1q-CIC, respectively). There is correlation between IgG-K CIC and IgG-C1q CIC (r = 0.445, P = 0.002), IgG-K CIC and IgM-C1q CIC (r = 0.348, P = 0.020), IgM-K CIC and aspartic aminotransferase (r = 0.321, P = 0.015), IgM-K CIC and alanine aminotransferase (r = 0.301, P = 0.027). Compared to patients with chronic persistent hepatitis and chronic lobular hepatitis, patients with chronic active hepatitis have a higher prevalence of elevated IgG-K CIC (77.2% vs. 40.0%, P = 0.029) and IgM-K CIC (56.8% vs. 20.0%, P = 0.038). The concentration of IgG-K, IgM-K, and IgM-C1q CIC in the former was significantly higher than that in the latter, respectively. In conclusion, IgG class CIC is the major type of CIC in chronic hepatitis C.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Circulating immune complexes in chronic hepatitis related to hepatitis C and B viruses infection.

Circulating immune complexes (CIC) may be involved in tissue damage and/or viral clearance in viral hepatitis. To assess the frequency of raised CIC in chronic hepatitis related to hepatitis B and C, IgM, IgG, and hepatitis B surface antigen (HBsAg) containing CIC were determined, by conglutinin (K) and C1q assays, in 101 patients with chronic hepatitis B alone, 24 patients with chronic hepatitis B and C, 48 patients with chronic hepatitis C alone, and 54 healthy controls. Compared to patients with hepatitis B alone, patients with dual infection had higher frequency of raised IgM-C1q CIC (P < 0.001) and IgM-K CIC (P < 0.01). There is no difference in the prevalence of HBsAg-CIC between patients with hepatitis B alone and those with dual infection. Among patients with chronic hepatitis C alone, conglutinin-binding CIC is the predominant type of raised CIC and correlated with more severe liver damage. In conclusion, CIC may play a role in the pathogenesis of chronic hepatitis C virus infection.

Adult↗
PubMed1995

Epidemiology of measles in Taiwan: dynamics of transmission and timeliness of reporting during an epidemic in 1988-9.

We analysed nation-wide reported measles cases during the 1988-9 epidemic and found that longer duration and wider spread were two major characteristics of the outbreak. All the 22 county/city index cases were reported with a delay of > 4 days and 64% were aged 5-14 years. This epidemic occurred mainly among 5-14-year-old school-children (59%), infants under 1 year (19%), and pre-school children (18%). The overall attack rate was 0.63 cases per 10,000 population, with the highest attack rate (7.4 cases per 10,000 population) occurring in infants. Among 280 confirmed cases < 15 months of age, 9-month-old infants (42 cases) had a higher risk of measles and peaked at 10 months (49 cases). This epidemic started in March 1988 among 5-9-year-old children in the northern suburban area, then spread to Taipei City and neighbouring counties or cities. It continued to spread from the northern to southern and western areas during the summer vacation and New Year holidays. Multiple logistic regression analysis showed that the delay of measles reporting was strongly associated with the cases infected early in the epidemic (OR = 6.9, P < 0.001) and reported from teaching hospitals (OR = 2.6, P < 0.001). The reappearance of high attack rates among 5-9-year-old children in the 1985 and 1988-9 measles epidemics in Taiwan indicated the persistence of pockets of susceptible individuals even after mass immunization.

Adolescent↗
PubMed1995

Clinical evaluation of serum alpha-fetoprotein and circulating immune complexes as tumour markers of hepatocellular carcinoma.

To evaluate the diagnostic application of serum alpha-fetoprotein (AFP) and circulating immune complexes (CICs), AFP, 3% polyethylene glycol (PEG)-CICs, 4% PEG-CICs, and C1q-CICs were determined in 101 patients with cirrhosis alone, 101 sex-matched and age-matched cirrhotic patients with hepatocellular carcinoma (HCC) and 54 healthy controls. Multivariate analysis indicated that AFP (odds ratio 1.014; 95% confidence interval 1.004-1.024) and 3% PEG-CICs (odds ratio 1.011; 95% confidence interval 1.005-1.017) are associated, in a dose-related fashion, with an increased risk for HCC. A receiver operative characteristic (ROC) curve was used to determine the optimal cut-off values of AFP (120 ng ml-1) and 3% PEG-CICs (310 micrograms aggregated IgG equivalent ml-1). The area under ROC curve was 0.875 for AFP and 0.812 for 3% PEG-CIC. Both AFP and 3% PEG-CICs show a high specificity (100%) and positive likelihood ratio. The sensitivity was 65.3% for 3% PEG-CICs and 67.3% for AFP. Determination of both markers in parallel significantly increase the diagnostic accuracy (92.1%) and sensitivity (84%), with a high specificity (100%) and positive likelihood ratio (> 84). In conclusion, both 3% PEG-CICs and AFP are independent risk factors of HCC, and may be used as complementary tumour markers to discriminate HCC from cirrhosis. Determination of 3% PEG-CICs should be performed in cirrhotics negative for AFP to improve detection of HCC.

Adult↗