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Biomedical subjects

W F Carman

Publications and source records attributed to W F Carman.

88 records · Page 5Linked to original sources
PubMed1991

Association of a precore genomic variant of hepatitis B virus with fulminant hepatitis.

A variant of hepatitis B virus has been described recently in HBsAg+ Mediterranean patients who lack HBeAg and who have an unusual and severe form of chronic hepatitis. This variant is unable to produce HBeAg because of the presence of a novel translational stop codon at the end of the precore region of the genome. By direct sequencing of DNA, generated by the polymerase chain reaction, we have evaluated the association between infection with this variant and the fulminant course of hepatitis B. Eighteen patients with fulminant hepatitis B were studied. Of the 15 cases from whose serum viral DNA could be sequenced, the variant was found in the admission sera of 8 of 9 HBeAg- patients but in none of 6 HBeAg+ patients who had fulminant hepatitis B. Patients harboring the variant progressed more rapidly into hepatic encephalopathy, but those infected with the variant strain alone had a greater likelihood of survival than those infected with the normal strain or a mixture. The mutant strain may emerge spontaneously during fulminant hepatitis as occurs in chronic hepatitis B infection during seroconversion from HBeAg to antibody. Alternately, and perhaps less commonly, patients may be infected with the variant ab initio.

Base Sequence↗
PubMed1991

Detection of hepatitis B virus DNA sequences in liver in HBsAg seronegative patients with liver disease with and without anti-HBc antibodies.

Excluding studies from Brechot and co-workers, little support has been found for a role of the hepatitis B virus in the pathogenesis of HBsAg seronegative patients with predominantly chronic liver diseases, including primary liver cancer. In this study liver DNA from 59 predominantly British patients (four cases with paired biopsies, 6-12 months apart) with different, mostly chronic, liver diseases was analysed by molecular hybridization. All were seronegative for HBsAg and serum hepatitis B virus DNA (dot blot hybridization) and their liver diseases were believed to be unrelated to hepatitis B virus infection. Hepatitis B virus DNA was detected in liver of 11 (18.6 per cent) patients; nine had episomal (3.2 Kb) DNA and eight had higher molecular weight bands suggesting integrated forms. Six patients were also seronegative for anti-HBc. Patients of UK and non-UK origin were equally represented. Hepatitis B virus DNA was detected in serum of six of nine patients tested using the polymerase chain reaction. The detection of hepatitis B virus DNA in liver and in serum by this assay in a significant proportion of patients with chronic liver disease, hitherto unsuspected of being hepatitis B virus-related, suggests a possible role for this virus in low- as well as high-prevalence countries.

Adult↗
PubMed1990

Vaccine-induced escape mutant of hepatitis B virus.

In southern Italy, 44 contacts of hepatitis B virus carriers, including infants of carrier mothers, became HBsAg positive despite passive and active immunisation according to standard protocols. In 32 of these vaccinees infection was confirmed by the presence of additional markers of viral replication. In 1 infant, serious disease occurred. The virus from this patient is an escape mutant with a different sequence from that of the isolate from the mother. A point mutation from guanosine to adenosine at nucleotide position 587 resulted in an aminoacid substitution from glycine to arginine in the highly antigenic a determinant of HBsAg. This mutation is stable: it is present in an isolate from the child 5 years later. In some of these patients, including this child, the a determinant, to which a large part of the vaccine-induced immunity is directed, has been partly lost. Binding to HBsAg of a monoclonal antibody, previously mapped to the region of the mutation, was reduced in the child relative to that of the mother.

Biomarkers↗
PubMed1990

The hepatitis B virus.

Of all the hepatotropic viruses, HBV is associated with the greatest worldwide morbidity and mortality. This is because of the ease of transmission and the potential for progression to a chronic infective carrier state, with the complications of cirrhosis and hepatocellular carcinoma. The use of PCR has shown that some of the earlier concepts concerning the interpretation of serological data were inaccurate. Many patients with anti-HBe and anti-HBs have viral DNA detectable by PCR, and some hepatocellular carcinoma patients have detectable HBV DNA in their livers in the absence of all serological markers of HBV disease. The clearance of HBV infected cells from the liver is dependent on the interplay between the interferon system and the cellular limb of the host immune response. The importance of the nucleocapsid proteins as targets for sensitized cytotoxic T cells has been established for chronic HBV infection. The importance of pre-S sequences as inducers and targets of the virus-neutralizing humoral immune response is becoming established, but their precise role must await the development of in vitro models of hepadnavirus infection and a greater understanding of the mechanisms of viral uptake. The epidemiology and clinical course of the disease can be modified by immunization, immune stimulation and antiviral chemotherapy. For the developing world, a programme of immunization at birth would be the most effective way of eliminating this disease, but at present the cost is prohibitive. For the developed world, immunization is realistic for the at-risk population, and anti-viral and immunostimulatory therapy available for those already infected. In adult acquired chronic HBV infection alpha-interferon produces HBe antigen clearance in 40-60% of cases and is followed by resolution of the hepatic inflammation. Results in neonatally acquired infection are less impressive and prednisolone priming followed by interferon may be needed. The presence of a mutation in the pre-core region of some virus isolates has recently been described. Hepatocytes infected with this virus cannot produce HBe antigen and the course of the liver disease is fairly rapid. Whether this mutant causes liver damage in the same way as the wild virus or is directly cytopathic remains unclear, and its relationship to fulminant hepatitis is under investigation.

Adolescent↗
PubMed1989

Mutation preventing formation of hepatitis B e antigen in patients with chronic hepatitis B infection.

Some patients with chronic hepatitis B virus (HBV) infection are HB e antigen (HBeAg) negative, have circulating HBV particles, and often have especially severe chronic hepatitis. To test the hypothesis that the absence of HBeAg production may be due to a change in the nucleotide sequence of the pre-core region of the genome, 18 Greek and 3 non-Greek patients positive for HB surface antigen underwent direct sequencing of HBV-DNA amplified from sera. In 7 out of 8 HBeAg negative patients, two mutations (guanosine to adenosine) were found in the terminal two codons of the pre-core region, giving the sequence TAGGACATG. The remaining patient had the first mutation only. The sequence TGGGGCATG was found in 4 of 5 of the HBeAg positive patients. The first mutation results in a translational stop codon that is predicted to result in failure to produce HBeAg. The rest of the pre-core region in the HBeAg negative patients was otherwise homologous to that of the HBeAg positive patients and to known sequences.

Amino Acid Sequence↗
PubMed1989

Blastomyces dermatitidis infections in the RSA.

Twenty cases of blastomycosis have been confirmed in the RSA, 9 of which are presented for the first time. Patients came from all four provinces and the mean age was 40 years. Six cases were diagnosed between 1985 and 1987. Differences between strains of Blastomyces dermatitidis isolated in the RSA and in North America include morphological and cultural characteristics, mycelial-yeast conversion, antigenic structure, and compatibility in cross-mating experiments. The diagnosis of this disease can be made by direct examination of unstained specimens, by histological examination or by culture of the organism. Culture should be attempted in all cases for confirmation of microscopic findings.

Adult↗
PubMed1989

Blastomycosis in Africa. A review of known cases diagnosed between 1951 and 1987.

The known African cases of blastomycosis to 1987 are presented, including thirteen previously undescribed cases. This brings to 81 the total number of cases known to have occurred in Africa. The question of whether the disease in Africa is the same in all respects as that in North America is addressed; the age and sex distributions of patients are similar. Minor differences in the clinical features relate particularly to the type of skin lesion, the more frequent bone involvement and the less frequent central nervous system involvement in the African patient. Little is known about the epidemiology of blastomycosis in Africa; one noteworthy feature is the apparent absence of the disease in dogs. Isolates of Blastomyces dermatitidis from the two continents, although closely related, differ in some respects.

Africa↗
PubMed1989

Reverse transcription and subsequent DNA amplification of rubella virus RNA.

A method is described whereby rubella virus RNA was reverse transcribed and the resulting cDNA enzymatically amplified using Taq polymerase. The reactions were carried out in a single reaction vessel, with only minor modifications to the buffer conditions between the reverse transcription and the subsequent amplification step. Using an oligonucleotide probe to the E1 glycoprotein region and limited restriction endonuclease mapping, the resulting amplified products were shown to be specific for rubella virus. This method was also successfully applied to crude cell lysates, without the need for RNA purification. The possible applications of the polymerase chain reaction as applied to RNA sequences are discussed.

Animals↗
PubMed1989

An assessment of optimal conditions for amplification of HIV cDNA using Thermus aquaticus polymerase.

Optimal conditions for in-vitro enzymatic DNA amplification using Thermus aquaticus polymerase were defined using env and gag sequences of human immunodeficiency virus type I as templates. It was found that specific amplification of the target sequence occurred when the primer annealing temperature was above 55 degrees C. Polymerase added once at the beginning of the procedure was sufficient for good results. Deoxynucleotide and primer concentrations and chain elongation time were not found to be important as long as they were kept above a critical level. Differences were noted between the efficiency of specific amplification from purified plasmid and genomic DNA. A rapid and simple method without the use of radioactive reagents for confirmation of a suggestive positive result on gel electrophoresis using restriction enzyme digestion of the amplified products is described. Some possible drawbacks of the technique particularly if used as a diagnostic tool are discussed.

Base Sequence↗
PubMed1989

Detection of enzymatically amplified human immunodeficiency virus DNA by oligonucleotide solution hybridization and by incorporation of radiolabeled deoxynucleotides.

Two methods are described for the detection of in vitro enzymatically amplified DNA. The first method involves solution hybridization of labeled oligonucleotides to amplified products. Hybridization of primers to a dilution series of known concentration of amplified DNA showed that approximately 5 pg of DNA could be detected by this method. In the second method, radiolabeled deoxynucleotides were incorporated into the elongating DNA chain. Both methods were able to detect amplified products 10 cycles before detection by ethidium bromide staining. Some variations of these techniques are discussed.

Autoradiography↗
PubMedDate not supplied

S gene variation of HBV.

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Gene Expression Regulation, Viral↗