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Biomedical subjects

A R Davis

Publications and source records attributed to A R Davis.

At least 73 records · Page 4Linked to original sources
PubMed1994

Substrate specificity of the NS3 serine proteinase of hepatitis C virus as determined by mutagenesis at the NS3/NS4A junction.

Hepatitis C virus (HCV) encodes a polyprotein that is processed to produce the structural and nonstructural proteins of the virus. Nonstructural protein 3 (NS3) is a serine proteinase that cleaves the polyprotein to release the NS4A, NS4B, NS5A, and NS5B proteins. To characterize the substrate specificity of NS3, we synthesized by in vitro translation the polyprotein NS2*-NS3-NS4*P that includes 70% of the NS2 protein, the complete NS3 protein, and 25% of the NS4 protein region attached to substance P, an epitope tag. We demonstrated that NS3 cleaves at the NS3/NS4A junction to release the NS4*P protein. Subsequently, we used this reaction to evaluate the importance of conserved amino acids that flank the NS3/NS4A junction. We replaced amino acids in the P6, P1, and P1' positions of the scissile bond of this junction using site-directed mutagenesis. When the P6 aspartic acid was changed to asparagine, lysine, or serine, NS3-mediated cleavage occurred. When threonine in the P1 position was replaced with other polar amino acids or with amino acids having aliphatic side chains, cleavage occurred, although it was not detected when arginine or tyrosine was present. Replacement of serine in the P1' position with other polar amino acids, with amino acids having aliphatic side chains, or with arginine resulted in NS3-mediated cleavage. Thus, since fewer amino acids in the P1 position supported cleavage than in the P6 or P1' positions, the P1 position of the scissile bond may play a more important role in defining the substrate specificity of the HCV NS3 proteinase.

Amino Acid Sequence↗
PubMed1994

Satisfactorily attenuated and protective mutants derived from a partially attenuated cold-passaged respiratory syncytial virus mutant by introduction of additional attenuating mutations during chemical mutagenesis.

A cold-passaged RSV mutant, designated cp-RSV, which acquired host range mutations during 52 passages at low temperature in bovine tissue culture, was completely attenuated for seropositive adults and children but retained the capacity to cause upper respiratory disease in seronegative infants. We sought to introduce additional attenuating mutations, such as temperature-sensitive (ts) and small-plaque (sp) mutations, into the cp-RSV mutant, which is a ts+ virus, in order to generate a mutant which would be satisfactorily attenuated in seronegative infants and young children. Nine mutants of cp-RSV, which had acquired either the ts or small-plaque sp phenotype, were generated by chemical mutagenesis with 5-fluorouracil. The two ts mutants with the lowest in vitro shut-off temperature, namely the cpts-248 (38 degrees C) and cpts-530 (39 degrees C) mutants, were the most restricted of the nine cp-RSV mutant progeny tested for efficiency of replication in Balb/c mice. In seronegative chimpanzees, the cpts-248 mutant replicated fourfold less efficiently in the nasopharynx and caused significantly less rhinorrhoea than its cp-RSV parent. The cpts-248 mutant virus, like its cp-RSV parent, was 1000-fold restricted in replication in the trachea compared with wild-type RSV. Previously, another candidate RSV live attenuated vaccine strain, a mutant designated ts-1, exhibited some instability of its ts phenotype following replication in susceptible humans or chimpanzees. Hence, we sought cp-RSV ts progeny that exhibited a greater degree of stability of the ts phenotype than the prototype ts-1 mutant.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Immunogenicity of recombinant influenza virus haemagglutinin carrying peptides from the envelope protein of human immunodeficiency virus type 1.

Haemagglutinin (HA), the major surface glycoprotein of influenza virus, is a potent immunogen against which viral neutralizing antibodies are directed. Studies of the three-dimensional structure of HA have identified major antigenic sites on the molecule. We have exploited HA as a carrier for small antigenic regions (epitopes) of the HIV-1 envelope (env) glycoprotein. Using recombinant DNA techniques, the epitopes were inserted in-frame into a known antigenic site of HA to produce HA-epitope chimeras. Guinea-pigs and mice immunized with these chimeras in combination with adjuvant generated significant immune responses against the carrier HA and also produced epitope-specific antibodies that recognized the native whole HIV-1 env. One of the chimeras which contained a V3-loop sequence of HIV-1 env elicited neutralizing antibodies against the homologous strain of HIV-1. The antibodies against HA and the inserted epitopes remained at high levels for up to 72 weeks. Remarkably, these responses were generated with low doses of immunogens containing only nanogram quantities of the inserted epitopes. These results suggest the utility of HA as a carrier to allow selective antibody induction against foreign epitopes, and offer a new approach for vaccine development as well as for the production of monospecific antibodies useful in diagnostics and research.

AIDS Vaccines↗
PubMed1994

Efficacy of adenovirus-vectored respiratory syncytial virus vaccines in a new ferret model.

In the absence of an adequate small animal model for testing the efficacy of adenovirus-vectored respiratory syncytial virus (RSV) vaccines, a ferret model was established for this purpose. Recombinant adenovirus types 4, 5 and 7 expressing the RSV fusion glycoprotein (F), the attachment glycoprotein (G) or both F and G were constructed previously. These recombinants contain a deletion of a large portion of the E3 region of the respective adenovirus vector. In addition, an Ad7(E3+)F recombinant virus which contains an intact E3 region was constructed to assess whether E3 region functions might enhance vaccine immunogenicity. Evaluation of these viruses in the ferret model demonstrated that Ad4 and Ad5 recombinants, administered intranasally to ferrets, induce stronger seroresponses to RSV than do Ad7 recombinant viruses. Ad7(E3+)F did not show enhanced immunogenicity relative to E3-deleted recombinant viruses. However, measurement of RSV infectivity in nasal washes, following intranasal RSV challenge, showed that five different vaccination regimens, Ad7F/Ad4F, Ad7G/Ad4G, Ad7FG/Ad4FG, Ad4F/Ad7(E3+)F and Ad5F/Ad4F, protected ferrets from RSV infection in a dose-dependent manner.

Animals↗
PubMed1994

A further attenuated derivative of a cold-passaged temperature-sensitive mutant of human respiratory syncytial virus retains immunogenicity and protective efficacy against wild-type challenge in seronegative chimpanzees.

A cold-passage (cp), temperature-sensitive (ts) RSV mutant designated RSV cpts-248 (shut-off temperature 38 degrees C), which possesses host-range mutations acquired during 52 passages at low temperature in bovine tissue culture and a ts phenotype introduced by subsequent chemical mutagenesis, was found previously to be attenuated, immunogenic, and protective against wild-type challenge in seronegative chimpanzees. We sought to introduce additional attenuating mutations such as small-plaque (sp) and ts mutations into RSV cpts-248 by chemical mutagenesis with 5-fluorouracil with the intent of obtaining cpts-248 derivatives that are more attenuated in mice or chimpanzees and that are more genetically stable following replication in vivo. Ten mutants of RSV cpts-248 which had acquired a sp phenotype or a second ts mutation were generated by chemical mutagenesis. Five cpts-248 derivatives which had acquired mutations that specified a 36 degrees C shut-off temperature for plaque formation and one which had acquired only a sp phenotype were more restricted in replication in Balb/c mice than the cpts-248 parental strain. One mutant, designated RSV cpts-248/404 (shut-off temperature 36 degrees C), was 100 times more restricted in replication in the nasal turbinates of mice and 100 times more restricted in the nasopharynx of seronegative chimpanzees than its cpts-248 parent. The cpts-248/404 mutant was completely restricted in replication in the lower respiratory tract of chimpanzees even following direct intratracheal administration. The ts phenotype of the cpts-248/404 mutant was stable during replication in vivo in mice and chimpanzees.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Immunogenicity of high expression adenovirus-hepatitis B virus recombinant vaccines in dogs.

High yielding adenovirus (Ad)-hepatitis B recombinant (Ad-Hep B) viruses were prepared by insertion of the hepatitis B surface antigen (HBsAg) gene into the early region 3 (E3 region) of Ad4 or Ad7 vectors containing intact or largely deleted E3 regions. Both E3-deleted and non-deleted recombinants produced about six- to eight-fold higher amounts of HBsAg than previously reported recombinants. These recombinant viruses were evaluated for immunogenicity in dogs which sustain abortive lung infections by Ad4 and Ad7. Recombinants containing E3 deletions elicited 10- to 12-fold stronger anti-HBs primary responses than previously evaluated low yield recombinants. Further immunizations with heterotypic Ad-Hep B recombinants induced substantial anti-HBs booster responses as well as anti-'a' epitope responses. In contrast, recombinant viruses containing intact E3 regions induced only weak or negligible anti-HBs responses, although such viruses induced strong antibody responses to the Ad vectors. The immunogenicity of high-yielding Ad recombinants correlated with temporal expression of HBsAg and thus the dog represents a valuable model for evaluation of immune responses to heterologous proteins that are expressed early and that do not require efficient DNA replication. Recombinants expressing HBsAg late in the infectious cycle require further testing in the fully permissive chimpanzee model. This study establishes that the E3-deleted high yield Ad4 and Ad7 recombinants represent promising live oral hepatitis B vaccine candidates.

Adenovirus E3 Proteins↗
PubMed1994

Health care reform: federal and state initiatives.

Health care reform initiatives, addressing the three fundamental objectives of access, quality, and cost control, will serve to reorient health care from a facility-based to a coverage-based orientation. New Jersey physicians need to think about the changes in health care policy.

Cost Control↗
PubMed1994

Adenovirus vectored vaccines.

Human recombinant adenoviruses (Ad) have been employed to develop experimental vaccines against a number of infectious agents. Ad-vectored vaccines express recombinant proteins, including any post-translational modifications, into functioning replicas of the native proteins capable of eliciting neutralizing antibodies in both abortive and permissive animal models. Human Ad types 4, 5, and 7 were used to construct recombinant viruses that express the respiratory syncytial virus F or G glycoproteins, the hepatitis B surface antigen, and the HIV env or gag genes. The recombinant Ad-HIV viruses are of particular interest and have been examined for their immunogenicity in dogs and chimpanzees. Dogs were immunized intratracheally with Ad-env recombinants (10(9) pfu/dog). Excellent humoral anti-HIV responses, including neutralizing antibodies, were detected in the sera following booster immunization (12-18 weeks after primary immunization) with a second Ad-env recombinant made in a different Ad serotype (heterotypic booster). Chimpanzees were immunized in two ways, orally with lyophilized virus (10(9) to 10(10) pfu/virus) in enteric-coated capsules or intranasally (10(7) pfu/virus). Intranasal immunization was superior to oral immunization with respect to replication of recombinant viruses as well as induction of anti-Ad and anti-HIV antibodies. Administration by both routes resulted in stimulation of cellular immune responses, as measured by antigen proliferation assays. Anti-HIV antibodies were detected in chimpanzee secretions (salivary, nasal, rectal, vaginal) taken from animals following intranasal immunization with a heterotypic recombinant. Intranasal administration effectively primed chimpanzees to produce high-titred (320-640) serum neutralizing antibodies to HIV following boosting with a baculovirus-derived env (gp160) subunit vaccine.(ABSTRACT TRUNCATED AT 250 WORDS)

AIDS Vaccines↗
PubMed1993

Papillary serous carcinoma of the peritoneal surface: matched-case comparison with papillary serous ovarian carcinoma.

Between 1984 and 1991, 199 patients underwent laparotomy for epithelial "ovarian" malignancy. In 29 cases (15%) normal-sized ovaries (< 4 cm in diameter) with minimal invasion by papillary serous carcinoma were found. This entity in the setting of peritoneal carcinomatosis has been previously described and is reported here as papillary serous cancer of the peritoneal surface (PSPS). The clinical, surgical, and pathologic features of PSPS are compared with a group of age-, grade-, and stage-matched cases with papillary serous ovarian carcinomas (PSOC). PSPS was also characterized by ascites (mean = 3036 cc), malignant washings (91%), and omental involvement with bulky infiltration and/or multiple tumor nodules (96%). Mean cytoreduction in the PSPS group was 65.5% compared to 79% in the PSOC group (P = 0.049). Patients received combination chemotherapy with platinum-based regimens. In general, there was a poor response to treatment with a disease-free interval of 3.4 and median survival time of 19 months in PSPS compared to 11.7 and 31 months in the PSOC patients. Patients with PSPS have more limited cytoreduction, shorter disease-free interval, and shorter overall survival time. Such differences prompt re-evaluation of treatment modalities for PSPS and recognition that this is a condition distinct from PSOC.

Adult↗
PubMed1993

Identification of residues important for ligand binding to the human 5-hydroxytryptamine1A serotonin receptor.

The functional significance of the conserved amino acids within transmembrane regions II and VII of the human 5-hydroxytryptamine (5-HT)1A receptor was analyzed by oligonucleotide-directed mutagenesis followed by transient expression of the mutated receptor genes in COS-1 cells. The substitution of a conserved asparagine at position 396 (transmembrane region VII) with either alanine, phenylalanine, or valine resulted in a receptor that did not bind the 5-HT1A agonist 8-hydroxy-2-(di-n-[3H]propylamino)tetralin. In contrast, replacement of Asn396 with glutamine did not affect agonist binding. In addition, serine residues at positions 391 and 393 (transmembrane domain VII) were changed to alanine. Changing the less conserved Ser391 to alanine had no effect on ligand binding. However, replacement of the conserved Ser393 with alanine reduced ligand binding by 86%. Replacement of a conserved aspartate at position 82 (transmembrane region II) with alanine also produced a receptor without detectable agonist binding. Protein immunoblotting detected receptor protein of approximately 51 kDa in both wild-type and mutant receptor-expressing cells, indicating that these mutations probably did not affect expression or processing of the protein. Importantly, the sequence of the human 5-HT1A receptor described in this paper differs from the published sequence [Nature (Lond.) 329:75-79 (1987)] in transmembrane region IV. The present sequence encodes a protein of 422 amino acids, instead of the 421-amino acid protein that has been described previously [Nature (Lond.) 329:75-79 (1987)], and has a change in the sequence in transmembrane region IV from ... RPRAL ... to ... RRAAA ..., which corresponds to the published sequence [J. Biol. Chem. 265:5825-5832 (1990)] of the rat 5-HT1A receptor. Moreover, conversion of the transmembrane region IV sequence of the present clone to that of the published sequence by site-directed mutagenesis abolished ligand binding to the receptor.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1992

Adenovirus-human immunodeficiency virus (HIV) envelope recombinant vaccines elicit high-titered HIV-neutralizing antibodies in the dog model.

Recombinant human adenoviruses (Ads) (types 4, 5, and 7) expressing the HIV-1 envelope membrane glycoprotein (gp160) were tested for immunogenicity in the dog. Administration of recombinant Ad7-env by intratracheal inoculation resulted in a low serum antibody response to gp160, which developed over several weeks. A strong neutralizing antibody response to the Ad7 vector developed within 1 week of infection. A subsequent booster inoculation 12 weeks later with the heterotypic Ad4-env recombinant virus resulted in significantly enhanced humoral responses directed at the envelope antigen, as measured by both ELISA and Western blot analysis as well as high-titer type-specific neutralizing antibodies, with some animals achieving neutralization titers approaching 1000. Recombinant HIV envelope glycoprotein derived from Ad-HIV-infected cell cultures was used as a subunit booster injection for dogs that had previously received sequential immunizations with heterotypic recombinant Ads. Significant immune responses against the envelope developed as measured by ELISA, Western blot analysis, and neutralization assays. These data indicate that live recombinant Ad-HIV vaccines are capable of inducing high-titer type-specific neutralizing antibodies to gp160 in vivo. Recombinant HIV envelope glycoprotein subunit vaccines, prepared from Ad-env-infected cells, are capable of boosting these responses.

AIDS Vaccines↗
PubMed1992

Initial safety and immunogenicity studies of an oral recombinant adenohepatitis B vaccine.

Orally administered adenovirus may be a useful vaccine carrier of cloned antigens of other pathogens. A recombinant adenohepatitis vaccine Wy-Ad7HZ6-1, which expressed hepatitis B surface antigen and contained a large deletion in early region 3 (E3), was constructed and studied in humans. Volunteers received Wy-Ad7HZ6-1 (n = 3), adenovirus type 7 vaccine (n = 3) or placebo (n = 3). Recipients of Wy-Ad7HZ6-1 shed less vaccine virus in the stool for a shorter period and had a lower titre of anti-adenovirus type 7 antibodies than recipients of the adenovirus 7 vaccine. None of the three Wy-Ad7HZ6-1 vaccinees developed antibody to hepatitis B surface antigen after this one dose primary immunization regimen. The E3 region may be required for optimal enteric growth of adenovirus-vectored vaccines.

Adenoviruses, Human↗
PubMed1992

Cotton rats previously immunized with a chimeric RSV FG glycoprotein develop enhanced pulmonary pathology when infected with RSV, a phenomenon not encountered following immunization with vaccinia--RSV recombinants or RSV.

In studies conducted in the 1960s, children previously immunized with a formalin-inactivated respiratory syncytial virus (RSV) vaccine (FI-RSV) developed a greater incidence and severity of pulmonary disease during subsequent natural RSV infection than did controls. It was previously shown that cotton rats immunized with FI-RSV or immunoaffinity-purified fusion (F) glycoprotein developed enhanced pulmonary histopathology following intranasal challenge with RSV. In the present studies, various forms of immunization, including parenteral inoculation of an immunoaffinity-purified F glycoprotein or a chimeric FG glycoprotein produced in insect cells using a baculovirus vector (Bac-FG), intradermal infection with a vaccinia-F recombinant (Vac-F) or intranasal infection with an adenovirus-F recombinant (Ad-F) or RSV, were compared for immunogenicity, efficacy and ability to alter the host so that enhanced pulmonary histopathology developed during RSV infection 3 months after immunization. Immunization of cotton rats with F glycoprotein, Bac-FG, Vac-F, Ad-F or infection with RSV induced high levels of ELISA-F antibodies, but the antibodies induced by purified F glycoprotein of Bac-FG had low levels of neutralizing activity. Immunization with Vac-F or Ad-F, or infection with RSV induced a high level of resistance to pulmonary RSV replication, whereas animals immunized with Bac-FG or FI-RSV were only partially protected. Following RSV challenge, animals immunized with purified F glycoprotein or Bac-FG developed the highest levels of bronchiolar and alveolar histopathology, those immunized with FI-RSV had intermediate levels, and those immunized with Vac-F or RSV had histopathology scores at control levels. Ad-F immunized animals had elevated scores of bronchiolar but not alveolar histopathology; however, this finding was not reproducible. Passive transfer of pooled immune sera from animals infected with RSV or Vac-F and Vac-G was highly protective, whereas pooled sera from animals immunized with Bac-FG failed to protect the lungs against RSV challenge. Increased pulmonary histopathology was not observed in the passively immunized animals following RSV challenge, suggesting that the histopathology was mediated by RSV-specific T cells. These data indicate that subunit F glycoprotein or chimeric FG vaccines share with FI-RSV the properties of (i) induction of F antibodies with low neutralizing activity and (ii) enhancement of pulmonary histopathology during subsequent RSV infection. These observations confirm the need for caution in studies involving the administration of RSV subunit vaccines to seronegative humans.

Animals↗
PubMed1992

Immunogenicity of recombinant adenovirus-respiratory syncytial virus vaccines with adenovirus types 4, 5, and 7 vectors in dogs and a chimpanzee.

Recombinant adenovirus type 4, 5, and 7 expressing the fusion glycoprotein (F) gene, the attachment glycoprotein (G) gene, or both F and G genes of respiratory syncytial virus (RSV) was constructed. Intratracheal immunization of dogs with Ad7F induced moderate titers of RSV-neutralizing antibodies. After booster immunization with Ad4F, the dogs developed high titers of RSV-specific antibody. Subsequently, three two-dose vaccination regimens, Ad4F/Ad5F, Ad7G/Ad4G, and Ad7FG/Ad4FG, were compared with Ad7F/Ad4F for immunogenicity and protective efficacy. The results indicated that Ad4F/Ad5F was equal or greater in immunogenicity to Ad7F/Ad4F, but Ad7G/Ad4G and Ad7FG/Ad4FG were less effective than Ad7F/Ad4F in inducing RSV-neutralizing antibody. All vaccination regimens completely protected the lungs of dogs from RSV infection. A chimpanzee was sequentially immunized orally with Ad7F, Ad4F, and Ad5F. A low-level antibody response to RSV was induced after the primary immunization, but no significant increases were observed after booster immunizations.

Adenoviruses, Human↗