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S M Lemon

Publications and source records attributed to S M Lemon.

At least 109 records · Page 6Linked to original sources
PubMed1990

Molecular epidemiology of human hepatitis A virus defined by an antigen-capture polymerase chain reaction method.

We describe an immunoaffinity-linked nucleic acid amplification system (antigen-capture/polymerase chain reaction, or AC/PCR) for detection of viruses in clinical specimens and its application to the study of the molecular epidemiology of a picornavirus, hepatitis A virus (HAV). Immunoaffinity capture of virus, synthesis of viral cDNA, and amplification of cDNA by a polymerase chain reaction (PCR) were carried out sequentially in a single reaction vessel. This approach simplified sample preparation and enhanced the specificity of conventional PCR. AC/PCR detected less than one cell culture infectious unit of virus in 80 microliters of sample. Sequencing of AC/PCR reaction products from 34 virus strains demonstrated remarkable conservation at the nucleotide level among most strains but revealed hitherto unsuspected genetic diversity among human isolates. Epidemiologically related strains were identical or closely related in sequence. Virus strains recovered from epidemics of hepatitis A in the United States and Germany were identical in sequence, providing evidence for a previously unrecognized epidemiologic link between these outbreaks.

Animals↗
PubMed1990

In vivo replication and reversion to wild type of a neutralization-resistant antigenic variant of hepatitis A virus.

Six seronegative owl monkeys were intravenously inoculated with an antigenic variant (S18) of hepatitis A virus that is highly adapted to growth in cell culture and resists neutralization by monoclonal antibodies due to replacement of aspartic acid 70 of capsid protein VP3 with histidine. Each developed hepatitis 22-33 days after inoculation. Virus in feces, serum, and liver was quantified by radioimmunofocus assay. Viremia developed 7-11 days after inoculation, in parallel with fecal shedding of virus, and persisted for a mean of 20.5 days. Although the antigenic variant was recovered from feces or liver of three animals, virus in liver at the time of enzyme elevations was predominantly wild-type antigenic phenotype. Virus was not recovered from liver 96 days after challenge. These studies further define virologic events in hepatitis A and show that in vivo replication of an antigenic variant was restricted compared with that of wild-type virus.

Animals↗
PubMed1990

Immunogenic domains of hepatitis delta virus antigen: peptide mapping of epitopes recognized by human and woodchuck antibodies.

Hepatitis delta virus (HDV) is a defective RNA virus which is dependent on hepatitis B virus for essential helper functions. Only a single highly basic phosphoprotein, HDV antigen (HDAg), is expressed by the HDV genome during infection in humans. Antibody directed to HDAg is important in the diagnosis of HDV infection, and it is likely but not yet proven that the immune response to HDAg provides significant protection against subsequent exposures to HDV. In an effort to map the antigenic domains of HDAg, 209 overlapping hexapeptides, spanning the entire 214 amino acid residues of the protein, were synthesized on polyethylene pins and probed by enzyme-linked immunosorbent assay with sera containing high titers of anti-HD antibodies. Domains recognized by antibodies present in serum from human chronic carriers of this virus included residues 2 to 7, 63 to 74, 86 to 91, 94 to 100, 159 to 172, 174 to 195, and 197 to 207. Antibody from an acutely superinfected woodchuck recognized similar epitopes, as well as a domain spanning residues 121 to 128. Together, residues in these antigenic domains constitute 41% of the HDAg molecule. Oligopeptides 15 to 29 residues in length and representing epitopes of HDAg found to be dominant in humans (residues 2 to 17, 156 to 184, and 197 to 211) were synthesized in bulk and found to possess significant antigenic activity by microdilution enzyme-linked immunosorbent assay. The reactivity of peptide 197-211 with human sera confirms that the entire 214 amino acids of HDAg are expressed during infection in vivo. In addition, these results suggest that synthetic peptides may be useful reagents for development of new and improved diagnostic tests for HDV infection.

Amino Acid Sequence↗
PubMed1989

Horizontal transmission of hepatitis B virus.

Meta-analysis of seroprevalence surveys shows that horizontal transmission of hepatitis B virus (ie, that occurring without apparent parenteral, sexual, or perinatal exposure) is common in areas endemic for the virus. It occurs especially in pre-adolescent children. In developed countries, where endemicity of hepatitis B virus is low, horizontal transmission (probably via saliva or open wounds) may occur in households with a persistent carrier, but it is less efficient a means of infection than is sexual or perinatal transmission. Horizontal transmission also seems possible in pre-school day-care centres in developed countries, despite the small numbers of carriers in such places.

Adolescent↗
PubMed1989

Characterization of a simian hepatitis A virus (HAV): antigenic and genetic comparison with human HAV.

PA21, a strain of hepatitis A virus (HAV) recovered from a naturally infected captive owl monkey, is indistinguishable from human HAV in polyclonal radioimmunoassays and cross-neutralization studies. However, cDNA-RNA hybridization has suggested a significant difference at the genomic level between PA21 and a reference human virus, HM175. Further characterization of this unique HAV was undertaken in an effort to determine the extent of genetic divergence from human HAV and its relation to the conserved antigenic structure of the virus. The close similarity between PA21 and HM175 antigens was confirmed with an extended panel of 18 neutralizing murine monoclonal antibodies: a reproducible difference in binding to the two viruses was detected with only one antibody (B5-B3). The nucleotide sequence of the P1 region of the PA21 genome had only 83.2% identity with HM175 virus, a difference approximately twice as great as that found between any two human strains. Most nucleotide changes were in third base positions, and the amino acid sequences of the capsid proteins were largely conserved. Amino acid replacements were clustered in the carboxy terminus of VP1 and the amino-terminal regions of VP2 and VP1. These data indicate that PA21 virus represents a unique genotype of HAV and suggest the existence of an ecologically isolated niche for HAV among feral owl monkeys.

Amino Acid Sequence↗
PubMed1988

Long-term acyclovir suppression of frequently recurring genital herpes simplex virus infection. A multicenter double-blind trial.

Normal adults with six or more episodes of genital herpes in the previous year were enrolled in a one-year, multicenter, double-blind trial comparing placebo with 400 mg of acyclovir administered orally twice daily. Patients with episodes during the study were offered 200 mg of acyclovir administered orally five times daily for five days; this allowed comparison of suppressive and episodic treatment. After one year, 227 (44%) of 519 patients receiving suppressive treatment and seven (2%) of 431 receiving placebo (episodic) treatment remained free of recurrences, and the mean numbers of recurrences per year were 1.8 and 11.4, respectively. Among 67 patients who had received suppressive therapy for one year, the mean duration of lesions in the first episode following the discontinuation of treatment was 9.3 days compared with 7.3 days among 45 patients who had received episodic therapy for one year. Treatment was well tolerated, and no changes were noted in the in vitro susceptibility to acyclovir of herpes simplex virus cultured during or after the one-year trial. Continuous or episodic oral acyclovir therapy for one year remained safe and effective.

Acyclovir↗
PubMed1988

Complete nucleotide sequence of a cell culture-adapted variant of hepatitis A virus: comparison with wild-type virus with restricted capacity for in vitro replication.

To determine the molecular changes associated with adaptation of hepatitis A virus (HAV) to growth in cell culture, the genome of a cell culture-adapted variant of HM175 strain HAV (p16 HM175, 16th in vitro passage level) was molecularly cloned and the complete nucleotide sequence of the virus was determined. Compared with wild-type virus, p16 HM175 replicates efficiently in monkey kidney (BS-C-1) cells (approximately 58 RNA-containing particles per one infectious unit, compared with 2.4 x 10(5) for wild-type HM175). The nucleotide sequence of p16 HM175 revealed a total of 19 mutations from the wild-type genome, including 5 mutations in the 5' nontranslated region, 1 mutation in the 3' nontranslated region, and 13 mutations predicting 8 changes in the amino acid sequences of HAV proteins. Only one amino acid substitution occurred among the capsid proteins (VP2), while others involved proteins 2A, 2B, 2C, VPg, and 3Dpol. When the sequence of p16 virus was compared with that reported previously for an independently isolated, cell culture-adapted variant of HM175 virus (J.I. Cohen et al., (1987). Proc. Natl. Acad. Sci. USA 84, 2497-2501), there were three identical mutations in nontranslated regions of the RNA, and four mutations involving identical amino acids in proteins VP2, 2B, and 3Dpol. The distribution of these mutations within the genome suggests that changes in RNA replication may be of primary importance in adaptation of the virus to growth in vitro. These data are thus helpful in understanding the molecular basis of adaptation of HAV to cell culture and, since attenuation frequently accompanies adaptation of virus to growth in cell culture, may be of benefit in planning for attenuated vaccine development.

Amino Acid Sequence↗
PubMed1988

Identification of an immunodominant antigenic site involving the capsid protein VP3 of hepatitis A virus.

Hepatitis A virus, an hepatotropic picornavirus, is a common cause of acute hepatitis in man for which there is no available vaccine. Competitive binding studies carried out in solid phase suggest that neutralizing monoclonal antibodies to hepatitis A virus recognize a limited number of epitopes on the capsid surface, although the polypeptide locations of these epitopes are not well defined. Neutralization-escape mutants, selected for resistance to monoclonal antibodies, demonstrate broad cross-resistance to other monoclonal antibodies. Sequencing of virion RNA from several of these mutants demonstrated that replacement of aspartic acid residue 70 of capsid protein VP3 (residue 3070) with histidine or alanine confers resistance to neutralization by monoclonal antibody K2-4F2 and prevents binding of this antibody and other antibodies with similar solid-phase competition profiles. These results indicate that residue 3070 contributes to an immunodominant antigenic site. Mutation at residue 102 of VP1 (residue 1102) confers partial resistance against antibody B5-B3 and several other antibodies but does not prevent antibody attachment. Both VP3 and VP1 sites align closely in the linear peptide sequences with sites of neutralization-escape mutations in poliovirus and human rhinovirus, suggesting conservation of structure among these diverse picornaviruses. However, because partial neutralization resistance to several monoclonal antibodies (2D2, 3E1, and B5-B3) was associated with mutation at either residue 3070 or residue 1102, these sites appear more closely related functionally in hepatitis A virus than in these other picornaviruses.

Alanine↗
PubMed1987

Prevention of endemic icteric viral hepatitis by administration of immune serum gamma globulin.

In a further analysis of a randomized, double-blind study of 107,803 U.S. soldiers receiving either immune serum gamma globulin (ISG) or placebo, serum specimens from the first week of clinical illness from 210 soldiers consecutively hospitalized with icteric hepatitis were reexamined by using modern immunologic methods to test for evidence of hepatitis A and B. Prophylactic intramuscular injection of 5 or 10 ml of ISG containing antibody to hepatitis A virus and antibody to hepatitis B surface antigen provided significant protection against development of endemic type A, type B, and non-A, non-B icteric hepatitis for six months if it was administered before exposure. Failure to receive a second injection of either 5 or 10 ml of ISG permitted an occurrence of hepatitis that was not significantly different from that among subjects who failed to receive a second placebo injection. ISG at 2 ml appeared equally effective in preventing hepatitis A but may be less effective in preventing hepatitis B and non-A, non-B hepatitis.

Hepatitis A↗
PubMed1987

Quantitative analysis of hepatitis B virus DNA in saliva and semen of chronically infected homosexual men.

Serum, saliva, and semen from fifteen homosexual men who were chronic surface antigen (HBsAg) carriers were quantitatively assayed for hepatitis B virus (HBV) DNA by Southern analysis. HBV DNA (2 pg/ml-42,000 pg/ml) was detected in 11 carriers and correlated with endogenous DNA polymerase activity and e antigen (HBeAg) titer greater than or equal to 1:640. Viral DNA was detected in the saliva, at concentrations indicating a virus titer of 10(5)-10(7)/ml, of eight carriers and in semen from three patients (10(6)-10(7) virions/ml). HBV DNA in saliva and semen had electrophoretic mobilities similar to those in serum HBV DNA, but HBV DNA was present at much lower concentrations (10(-2)-10(-4) that of serum DNA). Results of isopycnic centrifugation suggested that DNA in saliva and semen was virion associated. These data provide an indication of the quantity of virus present in the semen and saliva of HBV carriers and the relative frequency with which shedding of high titers of virus (greater than 10(5) virions/ml) occurs in these secretions.

Adult↗
PubMed1987

Neutralization escape mutants define a dominant immunogenic neutralization site on hepatitis A virus.

Hepatitis A virus is an hepatotrophic human picornavirus which demonstrates little antigenic variability. To topologically map immunogenic sites on hepatitis A virus which elicit neutralizing antibodies, eight neutralizing monoclonal antibodies were evaluated in competition immunoassays employing radiolabeled monoclonal antibodies and HM-175 virus. Whereas two antibodies (K3-4C8 and K3-2F2) bound to intimately overlapping epitopes, the epitope bound by a third antibody (B5-B3) was distinctly different as evidenced by a lack of competition between antibodies for binding to the virus. The other five antibodies variably blocked the binding of both K3-4C8-K3-2F2 and B5-B3, suggesting that these epitopes are closely spaced and perhaps part of a single neutralization immunogenic site. Several combinations of monoclonal antibodies blocked the binding of polyclonal human convalescent antibody by greater than 96%, indicating that the neutralization epitopes bound by these antibodies are immunodominant in humans. Spontaneously arising HM-175 mutants were selected for resistance to monoclonal antibody-mediated neutralization. Fourteen clonally isolated mutants demonstrated substantial resistance to multiple monoclonal antibodies, including K3-4C8-K3-2F2 and B5-B3. In addition, 13 mutants demonstrated a 10-fold or greater reduction in neutraliztion mediated by polyclonal human antibody. Neutralization resistance was associated with reduced antibody binding. These results suggest that hepatitis A virus may differ from poliovirus in possessing a single, dominant neutralization immunogenic site and therefore may be a better candidate for synthetic peptide or antiidiotype vaccine development.

Animals↗
PubMed1987

Genomic heterogeneity among human and nonhuman strains of hepatitis A virus.

Cloned cDNA probes derived from the P1 and P2 regions of the genome of HM175 virus, a reference strain of human hepatitis A virus (HAV), failed to hybridize under standard stringency criteria with RNA from PA21 and PA33 viruses, two epizootiologically related HAV strains recovered from naturally infected New World owl monkeys. Hybridization of these probes to PA21 RNA was only evident under reduced stringency conditions. However, cDNA representing the 5' nontranslated region of the HM175 genome hybridized equally to HM175 and PA21 RNA under standard stringency conditions, while a probe derived from the 3' 1,400 bases of the genome yielded a reduced hybridization signal with PA21 RNA. In contrast, no differences could be discerned between HM175 virus and three other HAV strains of human origin (GR8, LV374, and MS1) in any region of the genome, unless increased stringency conditions were used. These results suggest that PA21 and PA33 are unique among HAV isolates and may represent a virus native to the owl monkey. Despite extremely poor homology within the P1 region, which encodes capsid polypeptides, monoclonal antibody analysis confirmed that the immunodominant neutralization epitopes of HAV were highly conserved between HM175 and PA21 viruses. Furthermore, experimental challenge of the owl monkey with successive PA33 and HM175 inocula confirmed a high but incomplete degree of cross-protection. Only one of six monkeys previously infected with PA33 developed recurrent hepatitis 28 days after intravenous HM175 challenge, while none of six monkeys previously infected with HM175 had demonstrable hepatitis following PA33 challenge. These data provide molecular evidence for the existence of HAV strains unique to nonhuman primate species and indicate that strict conservation of antigenic function may accompany substantial genetic divergence in HAV.

Animals↗
PubMed1987

Induced oral infection of the owl monkey (Aotus trivirgatus) with hepatitis A virus.

Several species of nonhuman primates have served as animal models for hepatitis A virus (HAV) infection and disease. This study was to determine the suitability of Aotus trivirgatus as an orally induced model for HAV infection and to reconfirm the owl monkey's susceptibility to the intravenous route of inoculation. Animals were inoculated, either orally or intravenously, with varying concentrations of PA-33 strain of HAV. Serum enzymes ALT, AST and GGTP levels were monitored and liver biopsies performed when values exceeded three standard deviations above individualized mean baseline values. All animals had postinoculation elevations of serum ALT and AST values, shed virus in their feces, and were seropositive to HAV by 60 days after inoculation. Eight of the ten postinoculation biopsy specimens had histologic lesions compatible with acute viral hepatitis. We conclude that the owl monkey is a useful and valuable model for the study of HAV disease.

Administration, Oral↗
PubMed1986

A second site for Epstein-Barr virus shedding: the uterine cervix.

Epstein-Barr virus (EBV) infection of the human uterine cervix was detected in 5 out of 28 women by means of culture and cytohybridization analysis of cervical secretions. Cervical samples from 2 of 14 women contained epithelial cells with EBV DNA, and filtered cervical washings from 4 women contained infectious EBV. The discovery of EBV shedding in its cell-free infectious form from the uterine cervix raises the possibility of venereal transmission, neonatal infection, and EBV involvement in cervical pathology.

Adolescent↗