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Biomedical subjects

S L Hu

Publications and source records attributed to S L Hu.

At least 73 records · Page 4Linked to original sources
PubMed1991

Safety of and immunological response to a recombinant vaccinia virus vaccine expressing HIV envelope glycoprotein.

In a randomised phase I trial of a recombinant vaccina virus vaccine expressing the gp160 envelope gene of the human immunodeficiency virus (HIVAC-1e) 35 healthy, HIV-seronegative males, 31 of whom had a history of smallpox immunisation and 4 of whom were vaccinia naive, were vaccinated and then boosted 8 weeks later with HIVAC-1e or standard NY strain vaccinia virus. The frequency, duration, and titre of virus isolation from the vaccination site and occurrence of local side-effects were similar between the two groups of vaccinees. Vaccinia-naive (vac-n) subjects shed virus from the vaccination site for longer and at a higher titre than did vaccinia-primed (vac-p) individuals (19 vs 7 days and 10(7) vs 10(5) pfu/ml, respectively). In-vitro T-cell proliferative responses to one or more HIV antigen preparations developed in 13 of 16 vaccinia-primed subjects inoculated with HIVAC-1e. T-cell responses were, however, transient and in no subject did antibodies to HIV become detectable. The 2 vaccinia-naive subjects vaccinated with HIVAC-1e showed strong T-cell responses to homologous and heterologous strains of whole virus and to recombinant gp160 protein that remained detectable for over a year; antibodies to HIV envelope also developed in both. Recombinant vaccinia virus vaccines induce T-cell priming to the foreign gene products in most individuals. If used as the sole immunising agent they will be most efficacious in vaccinia-naive individuals.

Adult↗
PubMed1991

Dual action of endothelin-1 on the Ca2(+)-activated K+ channel in smooth muscle cells of porcine coronary artery.

The effects of endothelin-1 (ET-1) on the activity of the large Ca2(+)-activated K+ channel (BK channel) in enzymatically dissociated smooth muscle cells of porcine coronary artery were studied with the cell-attached patch-clamp technique. ET-1 at concentrations between 0.1 and 10 nM potentiated the BK channel activity. This effect was maximal at 1 nM ET-1, resulting in an average of 4.2-fold increase in channel open-state probability as compared with control. ET-1 at concentrations higher than 10 nM produced an irreversible inhibition of the BK channel activity, primarily due to a marked decrease in the channel mean open-time. The activation by lower doses of ET-1, but not the inhibition by higher doses of ET-1, of the BK channel was blocked by 0.1 microM PN 200-110, a Ca2+ channel blocker. The modulation of the BK channel activity in smooth muscle cell membrane may be a possible mechanism for ET-induced vasodilator and vasoconstrictor actions.

Animals↗
PubMed1991

Human papillomavirus type 16 nucleoprotein E7 is a tumor rejection antigen.

It has been speculated that immunological mechanisms play an important role in the control of carcinomas associated with human papillomavirus (HPV), such as cervical cancers. We have now demonstrated that immunization of C3H/HeN mice by syngeneic nontumorigenic fibroblast-like cells that contain the transfected HPV-16 E7 gene conferred protection against transplanted cells from a HPV-16 E7-positive syngeneic tumor. This protection was HPV-16 E7-specific and was mediated by CD8+ lymphocytes, which presumably were cytotoxic T lymphocytes. These results indicate that tumor cells containing HPV-16 E7, either as a result of transfection, as in our studies, or naturally, as occurs in many human carcinomas, can induce a tumor-specific rejection response and serve as targets for such a response. The system described here provides an animal model to further study immune responses to HPV-associated malignancies and to test the efficacy of anti-HPV vaccines toward the therapy and prevention of such tumors.

Animals↗
PubMed1991

HIV-specific humoral and cellular immunity in rabbits vaccinated with recombinant human immunodeficiency virus-like gag-env particles.

Recombinant human immunodeficiency virus type-1 (HIV-1)-like gag-env particles produced in mammalian cells were inoculated into two New Zealand white rabbits. In parallel, two control rabbits were inoculated with the homologous HIV-1 virions inactivated by ultra violet light (uv) and psoralen treatments. The humoral and cellular immune responses to HIV-1 were evaluated for both groups of animals. Recombinant particles elicited humoral immunity that was specific for all the viral structural proteins. The antibodies recognized both denatured and nondenatured proteins. Moreover, the sera neutralized the in vitro infectivity of the homologous virus in CEM cells. Importantly, the recombinant particles also generated a T helper response by priming with the HIV proteins. Similar results were observed with inactivated virus immunization. Therefore, our results suggest that the recombinant HIV-like particles elicit functional humoral immunity as well as cellular immunity and represent a novel vaccine candidate for AIDS.

Animals↗
PubMed1991

Interactions of neosaxitoxin with the sodium channel of the frog skeletal muscle fiber.

Neosaxitoxin (neoSTX) differs structurally from saxitoxin (STX) in that the hydrogen on N-1 is replaced by a hydroxyl group. On single frog skeletal muscle fibers in the vaseline-gap voltage clamp, the concentrations for reducing the maximum sodium current by 50% (ED50) at pH's 6.50, 7.25, and 8.25 are, respectively, 4.9, 5.1, and 8.9 nM for STX and 1.6, 2.7, and 17.2 nM for neoSTX. The relative potencies of STX at the different pH's closely parallel the relative abundance of the protonated form of the 7,8,9 guanidinium function, but the relative potencies of neoSTX at the same pH's vary with the relative abundance of the deprotonated N-1 group. In constant-ratio mixtures of the two toxins, the observed ED50's are consistent with the notion that the two toxins compete for the same site. At pH's 6.50 and 7.25, the best agreement between observed and computed values is obtained when the efficacy term (epsilon) for either toxin is 1. At pH 8.25 the best agreement is obtained if the efficacy is 1 for STX but 0.75 for neo-STX. The marked pH dependence of the actions of neoSTX probably reflects the presence of a site in the receptor that interacts with the N-1 -OH, in addition to those interacting with the 7,8,9 guanidinium and the C-12 hydroxyl groups. Considering the three-dimensional structure of the STX and neoSTX molecules, the various site points are probably located in a fold or a crevice of the channel protein, where the extracellular orifice of the sodium channel is located.

Animals↗
PubMed1991

Neutralizing antibodies against HIV-1 BRU and SF2 isolates generated in mice immunized with recombinant vaccinia virus expressing HIV-1 (BRU) envelope glycoproteins and boosted with homologous gp160.

Anti-human immunodeficiency virus type 1 (Anti-HIV-1) antibody response was compared in four groups of mice following inoculation with HIV-1 gp160, with live recombinant vaccinia virus expressing HIV-1 envelope glycoproteins, or with both immunogens in alternate orders for primary or secondary immunizations. Both subunit and recombinant virus immunogens induced similar levels of antibody response following primary immunization. However, after secondary immunization, mice primed with live recombinant virus and then boosted with subunit gp160 immunogen showed significantly higher antibody response than those in the other three groups. Neutralizing antibodies were generated only in this group of mice and were shown to neutralize both the homologous virus (BRU) and a divergent isolate (SF2) of HIV-1. On the other hand, their reactivities to peptide sequences from the principal neutralizing determinant (PND) of gp120 were limited to the BRU isolate, not SF2 or MN, indicating that the cross-neutralizing activities were directed against determinants other than the linear epitope(s) within the PND. These results also indicate that combined immunization by priming with liver recombinant virus and boosting with subunit immunogen may be more effective than immunization by either immunogen alone.

AIDS Vaccines↗
PubMed1991

An epidemic of hepatitis A attributable to the ingestion of raw clams in Shanghai, China.

An epidemic of hepatitis A in 1988 in Shanghai had an overall attack rate of 4083/100,000 population (292,301 cases). The epidemic curve showed three peaks in January and February. A case-control study of 1208 matched pairs supported that clams were the vehicle for the virus (summary odds ratio, 9.47; P less than .001). Analysis of subsets who had eaten clams indicated that only 3.5% with hepatitis A had cooked their clams compared with 18.1% without hepatitis A, and those with the disease consumed more clams. A historical cohort study indicated that approximately 31.7% of the population had eaten clams one or more times between 9 December 1987 and 3 January 1988. The estimated attack rates in those who had and had not eaten clams were 11.93% and 0.52%, respectively (relative risk, 22.94; attributable risk, 11.41%). The three peaks in the consumption curve correlated with those in the epidemic curve. Hepatitis A virus was demonstrated in clams taken from the Shanghai markets and from the catching area.

Acute Disease↗
PubMed1991

Effects of mutations in glycosylation sites and disulphide bonds on processing, CD4-binding and fusion activity of human immunodeficiency virus envelope glycoproteins.

Site-directed mutagenesis was used to study the biological significance of a disulphide bridge and two N-linked oligosaccharides in the CD4-binding region of the envelope glycoproteins of human immunodeficiency virus type 1. Mutagenesis was performed in a phage M13 system at sites corresponding to the cysteine residue (amino acid 402) and the asparagine residues (390 and 447) of the env gene. The mutated env gene was inserted into a recombinant vaccinia virus under the control of the vaccinia virus 7.5K promoter and the expression of mutated env proteins was analysed by SDS-PAGE, a conventional indirect immunofluorescence assay and by a fluorescence-activated cell sorter. Cysteine 402 was found to be essential for the specific cleavage of gp160 into gp120 and gp41, and for intracellular transport of the protein to the cell surface. CD4-binding and syncytium formation assays demonstrated that the disulphide bridge of cysteine 402 stabilized a conformation essential for receptor binding as well as syncytium formation by CD4+ cells. No altered biological activity compared to that of the wild-type proteins could be detected for the mutant proteins lacking the N-glycosylation sites. These data show that the two conserved glycans attached to asparagine residues 390 and 447 do not play any active role in the formation of the disulphide bridge involving cysteine 402 or in the maintenance of an active conformation of the protein, despite their location within the functionally important CD4-binding region.

Amino Acid Sequence↗
PubMed1990

Tumorigenic poxviruses: characterization of the expression of an epidermal growth factor related gene in Shope fibroma virus.

The transcription and translation of an epidermal growth factor (EGF) related gene in the Leporipoxvirus Shope fibroma virus (SFV), termed the Shope fibroma growth factor (SFGF), have been characterized. Three early RNA transcripts complimentary to an anti-SFGF oligonucleotide were detected by Northern blot analysis, while no late transcripts were expressed. The activity of the SFGF early promoter was measured using a transient gene expression assay in SFV-infected cells using the bacterial choloramphenicol acetyltransferase as a reporter gene. Deletion analysis showed that the functional SFGF promoter domain is an AT-rich sequence contained within 30 bp of the major transcriptional initiation site as is typical of early poxvirus promoters. An intracellular form of the SFGF gene product was immunoprecipitated from infected lysates using rabbit antisera raised against a synthetic SFGF (amino acids 26-80). A 16-kDa product was detected, while in cells infected in the presence of tunicamycin, the immunoprecipitated product had a mobility on SDS-polyacrylamide gels of approximately 6 kDa, indicating that the SFGF gene product is extensively post-transcriptionally modified. The intracellular 16-kDa form can be pulse-chased to a 14-kDa form but the secreted form of SFGF could not be detected in the medium using this anti-peptide antiserum.

Base Sequence↗
PubMed1990

Processing, assembly, and immunogenicity of human immunodeficiency virus core antigens expressed by recombinant vaccinia virus.

Recombinant vaccinia viruses that contained regions of the gag-pol open reading frames of human immunodeficiency virus type 1 (HIV-1) were constructed. Cells infected with recombinants containing both gag and protease genes expressed and processed HIV gag antigens efficiently. Processing was much reduced in cells infected with recombinants containing only gag, but not the protease gene. However, significant amounts of p41 were produced by protease-defective recombinants. This protein was immunoreactive with p24-specific monoclonal antibodies and was produced in a truncated form by a recombinant containing a 3' deletion in the p15 coding region of gag ORF. These results indicate that p41 could represent an alternative gag precursor with N-terminal sequences derived from p24 and C-terminal from p15. Ultrastructural analysis of recombinant-infected cells revealed that the gag antigens expressed were assembled into retrovirus-like particles and were secreted into culture medium. This assembly process was not dependent on HIV protease function, because immature core particles were produced by recombinants lacking HIV-1 protease functions. Immunization of mice and chimpanzees with vaccinia-HIVgag recombinant viruses generated both antibody and cell-mediated immune responses to HIV gag antigens. These recombinants are therefore useful not only for studying HIV virion processing and assembly, but also for designing immunogens for the prophylaxis and immunotherapy against AIDS.

Animals↗
PubMed1990

Risk factor analysis of an epidemic of hepatitis A in a factory in Shanghai.

Investigation of an epidemic of hepatitis A which occurred in Shanghai in early 1988 was conducted at the Shanghai No. 2 Yarn Dyeing and Weaving Mill. In this factory the attack rate between January and April 1988 was 9%. The rate was highest among staff who ate raw clams (18%) and higher among those who ate cooked clams (7%) than among those who did not eat clams (2%). In addition, independent risk factors for infection were: age below 30 years (relative risk (RR) = 3.0, 95% Cl: 2.0, 4.5) shift work (RR = 3.3, 95% Cl: 1.9, 5.8) and eating out (RR = 4.7, 95% Cl: 2.3, 9.7). Consumption of clams contaminated with hepatitis A was the main risk factor in this episode. The study indicates that strengthening surveillance of shellfish hygiene is important in preventing future epidemics of hepatitis A.

Adult↗
PubMed1990

Human immunodeficiency virus-like, nonreplicating, gag-env particles assemble in a recombinant vaccinia virus expression system.

We report the assembly of human immunodeficiency virus (HIV)-like particles in African green monkey kidney cells coinfected with two recombinant vaccinia viruses, one carrying the HIV-1 gag and protease genes and the other the env gene. Biochemical analysis of particles sedimented from culture supernatants of doubly infected cells revealed that they were composed of gag proteins, primarily p24, as well as the env proteins gp120 and gp41. Thin-section immunoelectron microscopy showed that these particles were 100 to 120 nm in diameter, were characterized by the presence of cylindrical core structures, and displayed the mature gp120-gp41 complexes on their surfaces. Furthermore, thin-section immunoelectron microscopy analysis of infected cells showed that particle assembly and budding occurred at the plasma membrane. Nucleic acid hybridization suggested that the particles packaged only the gag mRNA but not the env mRNA. Therefore, the system we present is well suited for studies of HIV virion maturation. In addition, the HIV-like particles provide a novel and attractive approach for vaccine development.

Animals↗
PubMed1990

Alterations by glyburide of effects of BRL 34915 and P 1060 on contraction, 86Rb efflux and the maxi-K+ channel in rat portal vein.

Effects of the K+ channel blocking agent, glyburide, on the actions of two K+ channel openers, BRL 34915 (cromakalim) and P 1060 (Leo), a potent pinacidil derivative (N-(t-butyl)-N"-cyano-N'-3-pyridyl-guanidine), were ascertained. Tension responses and 86Rb fluxes in rat portal vein strips and single channel electrophysiological recordings in enzymatically dissociated rat portal vein cells were obtained. Glyburide (0.3 microM) increased spontaneous contractile activity and caused concentration-dependent shifts in the relaxation responses to BRL 34915 and P 1060. Increases in 86Rb efflux were obtained only at much higher concentrations of BRL 34915 or P 1060, and these increases were blocked only at higher concentrations of glyburide (5.0 microM). BRL 34915 and P 1060 specifically increase the open-state probability of the Ca+(+)-activated K+ (maxi-K+) channel, and these actions are blocked by glyburide and also by charybdotoxin. Changes in single channel activity and contractile responsiveness occur at similar concentrations of agonists and antagonists. Thus, the membrane channel in rat portal vein affected by glyburide, BRL 34915 and P 1060 appears to be the Ca+(+)-activated maxi-K+ channel (that does not show ATP dependence under the conditions of these experiments). Concentrations of agonists and antagonists effective on maxi-K+ channel activity correspond to those affecting contractile responsiveness and are lower than those eliciting changes in 86Rb flux.

Animals↗
PubMed1990

Inoculation of Macaca fascicularis with simian immunodeficiency virus, SIVmne immunologic, serologic, and pathologic changes.

Previous studies had tested the susceptibility of two macaque species, Macaca nemestrina and M. mulatta, to infection with the primate lymphotropic lentivirus SIVmne. In this report we describe the results obtained after infecting eleven M. fascicularis with SIVmne. Six of the animals had previously been immunized with a recombinant vaccinia virus expressing the envelope gene of HIV-1. All eleven animals became seropositive. To date ten animals have died 43 to 155 weeks post infection of an AIDS-like disease.

Animals↗
PubMed1989

Diamphidia toxin, the bushmen's arrow poison: possible mechanism of prey-killing.

The effects of a 60,000 mol. wt protein from the pupae of the beetle, Diamphidia nigro-ornata have been studied. In concentrations as high as 50 micrograms/ml, the toxin has little effect on the propagated compound action potential of isolated nerve trunks, or on the voltage-gated sodium and potassium channels of voltage-clamped single skeletal muscle fibers. In the anesthetized cat, the toxin has no specific effect on the neuro-muscular or the cardiovascular systems. It has a markedly hemolytic effect, and could reduce hemoglobin levels by as much as 75%. Plasma hemoglobin is increased, with resultant extensive hemoglobinuria and associated histopathological changes in the kidneys. Blood pressure, heart rate, PO2, PCO2, and oxygen-saturation remain essentially normal until the terminal stages of intoxication. Contrary to previous conclusions, we find no support for any particular neurotoxicity of the poison. The complex systemic effects, and possibly the prey-killing, can probably be attributed to the extensive hemolysis, reduced oxygen-carrying capacity, and generalized tissue hypoxia.

Action Potentials↗