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Biomedical subjects

R J Ho

Publications and source records attributed to R J Ho.

At least 37 records · Page 2Linked to original sources
PubMed1996

Development of a chronically catheterized maternal-fetal macaque model to study in utero mother-to-fetus HIV transmission: a preliminary report.

The lack of a representative animal model that permits frequent in utero fetal blood sampling is a major limiting factor for the study of maternal-fetal HIV transmission. Therefore, we have developed a maternal-fetal virus infection model using chronically catheterized macaques to simultaneously study the time-course of viral infection in the mother and the response of the fetus to maternal HIV infection. Pregnant macaques were infected with 10(3) infectious units of HIV-2(287); every 3 days blood samples from both the mother and the fetus as well as amniotic fluid samples were collected. We found a varying degree of peak and time-to-peak virus load, virus-infected PBMCs, and free virus (determined by QC-RNA-PCR method) in maternal blood. Two of the three mothers with more than 10(8) copies of viral RNA/ml of plasma at peak viremia transmitted the virus to their fetuses at about 14 days post-infection. As observed with HIV-2(287) infected mothers, virus-infected fetuses also produced a rapid rate of CD4+ cell decline in utero.

Animals↗
PubMed1995

Interaction of manganese-mesoporphyrin with oleic acid vesicles.

We investigated the interaction between manganese(III)mesoporphyrin (MnMeso), a metalloporphyrin, and liposome membranes containing oleic acid (OA; cis-9-octadecenoic acid). MnMeso associates preferentially with OA but minimally with egg phosphatidylcholine (EPC). Using small unilamellar vesicles, we characterized the MnMeso-OA binding at neutral pH. Our data suggest that MnMeso binds to the OA bilayer with Kd = 6.8 x 10(-4) M; the binding stoichiometry of MnMeso-OA was 1:3.4. This OA-MnMeso interaction was analyzed further for changes in the T1 relaxation property of MnMeso. OA increased the T1 of MnMeso significantly more than did EPC, suggesting that the OA-MnMeso interaction was stronger than that of PC-MnMeso. The side-chain specificity of the OA interaction with this porphyrin derivative was further supported in an experiment with manganese mesotetra(4-sulfonatophenyl)porphine, which lacks hydrophobic side chains for OA interaction. The association of MnMeso with the OA membrane was proposed according to the structure of MnMeso and OA and further verified using electron microscopy. A strong association of MnMeso with OA, an absorption enhancer of the gastrointestinal tract, may be useful for delivery of MnMeso as an oral contrast agent for magnetic resonance imaging.

Animals↗
PubMed1995

Magnetic resonance imaging of the hepatobiliary system: intestinal absorption studies of manganese mesoporphyrin.

RATIONALE AND OBJECTIVES: We studied the intestinal absorption of manganese mesoporphyrin (Mn-mesoporphyrin), a potential oral hepatobiliary contrast agent. METHODS: Mn-mesoporphyrin was complexed with monoolein and taurocholate (mixed micelles). Portal venous delivery and biliary excretion were measured after intestinal administration in rats and rabbits, and the mechanism of intestinal transport was studied in a combined lymph-bile fistula model in rats. T1-weighted magnetic resonance (MR) images of the liver were obtained in rats and domestic pigs before and after gastric administration of Mn-mesoporphyrin in mixed micelles. RESULTS: A 2.2-fold increase of portal venous Mn concentration was found 90 min after intestinal administration of the complex. None was found in the lymph collected from the thoracic duct, indicating a transcellular transport mechanism through the intestinal mucosa with portal venous delivery. Mn-mesoporphyrin levels in bile peaked between 240 and 270 min after administration (200-fold increase). The greatest liver enhancement (20-90%) was measured 360 min after administration. CONCLUSION: The feasibility of intestinal delivery of Mn-mesoporphyrin, a lipophilic hepatobiliary contrast agent was demonstrated.

Animals↗
PubMed1995

Simian immunodeficiency virus infection of macaque primary placental cells.

We have characterized the ability of a simian immunodeficiency virus, SIVmne strain E11S, to infect macaque placental trophoblast and Hofbauer cells. These primary placental cells were permissive to SIVmne infection, regardless of gestational age. Virus production by the infected cells was determined as time-dependent viral core antigen p27 production, followed by verification of the proviral gag/LTR DNA sequences in the infected cells using a polymerase chain reaction assay. Of more than six placentas tested, SIVmne infection of placental cells at an early gestational age (i.e., days 55 or 78) produced more than 10-fold the amount of virus core antigen p27 than did placental cells infected at a late gestational age (i.e., days 135 or 165). In addition, SIVmne infection of trophoblast cells was inhibited by SIVmac neutralizing macaque serum but not by normal serum, indicating the specificity of virus infection. Furthermore, the amount of SIV core antigen p27 produced by the virus-infected trophoblast and Hofbauer cells was shown to be dependent on the multiplicity of virus infection. Collectively, our results indicate that macaque trophoblast and Hofbauer cells can be infected by SIV and that both gestational age and viral dose may play a role in the extent of viral infection.

Animals↗
PubMed1995

Antinociception and side effects of L- and D-dipalmitoylphosphatidyl choline liposome-encapsulated alfentanil after spinal delivery in rats.

We have observed that spinal liposome administration in the rat resulted in in an allodynia evoked by light touch. We later determined that liposomes composed of D-isomer phospholipids were essentially non-toxic. This study examines the effects of alfentanil encapsulated in liposomes made from the natural L-isomer and synthetic D-isomer of dipalmitoyl phosphatidyl choline on antinoceiception, side effects, and algogenic behaviour. Both unilamellar and multilamellar liposomes were studied. Rats prepared with chronic intrathecal catheters received intrathecal injections of alfentanil (5 or 50 micrograms) in saline or encapsulated in liposomes composed of either L- or D-isomers of dipalmitoyl phosphatidyl choline (DPPC) in unilamellar or multilamellar liposome formulations. Antinociception was measured using the hot plate test (52.5 degrees). Side effects were measured by catalepsy, corneal responses, pinna response, righting reflex, and paw step. Allodynia was measured by lightly stroking the animal's back. Intrathecal alfentanil in saline or in the liposomes produced a dose-dependent increased latency in the hot plate response. Encapsulation of alfentanil in the liposomes produced a significant decrease in the loss of corneal, paw step and righting reflex and a slight decrease in catalepsy and loss of the pinna response. There was no significant difference between liposome preparations in preventing side effects. L-multilamellar-DPPC produced allodynia in 100% of the animals whereas significantly less allodynia was observed with the other preparations. This study indicates that liposomal preparations can significantly enhance the therapeutic ratio of a lipid soluble opioid after spinal delivery. However, the choice of lipids for the formulation of liposomes intended for spinal drug delivery must be considered since the L-isomer and larger lipid load of multilamellar liposomes have a direct spinal effect leading to alledynia. Previous studies have in fact shown that spinal lysolecithin can yield focal demyelination.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Regression of LNCaP human prostate tumor xenografts in athymic nude mice by 13-cis-retinoic acid and androgen ablation.

The present study was designed to investigate the effects of 13-cis-retinoic acid (13-cis-RA) (100 micrograms/mouse/day) and androgen ablation (castration) alone and in combination on growth of a human prostatic carcinoma line (LNCaP) transplanted to athymic nude mice as an experimental model. The results of these studies suggest that; (1) androgen ablation (castration) significantly decreased the size of LNCaP xenograft as compared to untreated animals; (2) when 13-cis-RA was administered to nude mice carrying established tumors (0.51 +/- 0.04 cm3), the tumor size was significantly reduced as compared to untreated controls (0.65 +/- 0.06 cm3 versus 1.63 +/- 0.12 cm3). About 50% of the animals in this group showed xenografts necrosis followed by complete regression of tumors by five months; (3) the combination of androgen ablation and 13-cis-RA treatment to nude mice carrying tumors showed synergistic effect in decreasing the tumor size. These results indicate that combination therapies based on androgen ablation and retinoid administration may be a useful approach for the treatment of prostate cancer.

Animals↗
PubMed1994

Metabolism of 3'-azido-3'-deoxythymidine (AZT) in human placental trophoblasts and Hofbauer cells.

3'-Azido-3'-deoxythymidine (AZT) is currently under clinical investigation to assess its potential to inhibit maternal-fetal HIV transmission. To determine the activation of AZT to its phosphorylated metabolites by placental cells, we characterized the intracellular phosphorylation of AZT in two major cell types of the placenta, namely trophoblasts and Hofbauer cells. Although phosphorylation of AZT in trophoblast and Hofbauer cells is 50- to 100-fold lower than that in human lymphocytic cell lines or activated lymphocytes, both cell types are capable of activating AZT to AZT triphosphate (AZTTP) at a level comparable to that of resting lymphocytes. We found that AZT monophosphate (AZTMP) was the major phosphorylated AZT metabolite, while AZT diphosphate (AZTDP) and AZTTP constituted less than 4% of the intracellular phosphorylated AZT pool. This result was independent of AZT concentration and exposure time in both types of placental cells. The rate-limiting step in the conversion of AZT to AZTTP was determined to be thymidylate kinase-catalyzed conversion of AZTMP to AZTDP. Trophoblasts and Hofbauer cells exhibited different time-course and concentration-dependent profiles of intracellular AZT phosphorylation, suggesting that these two placental cells may have anabolic or catabolic enzymes of different composition or efficiency. AZTTP decayed in both trophoblasts and Hofbauer cells with a half-life of 4-6 hr. These results should be useful in rationally designing AZT dosage regimens to treat HIV-infected women for prevention of maternal-fetal HIV transmission.

Cell Line↗
PubMed1994

Disposition of antigen-presenting liposomes in vivo: effect on presentation of herpes simplex virus antigen rgD.

Antigen-presenting liposomes (APLs) containing a lipophilic derivative of muramyl tripeptide (MTP-PE) have previously been shown to enhance the immunotherapeutic effects mediated by HSV recombinant protein gD (rgD) after HSV type 2 infection is established. In this study, both the in vivo disposition of rgD and the immunological activity of in vivo-delivered rgD were determined. Following intravenous administration, most of the liposome-encapsulated rgD accumulated rapidly, mainly in the spleen, while most of the soluble rgD was quickly eliminated through the kidney. We have compared the T-cell stimulatory effects of macrophages, B cells and dendritic cells from the spleens of animals treated with rgD in vivo. Of these antigen-presenting cells, only adherent macrophages, isolated from the spleens of animals treated with rgD encapsulated in APLs for 90 minutes, were capable of stimulating HSV-sensitized autologous T and B cells. Additional in vitro exposure of macrophages to rgD was not required. In contrast, spleen macrophages from HSV-sensitized animals exposed to either empty liposomes or free rgD did not exhibit such immune responses, indicating that the immunobiological effect of the rgD delivered in APLs is antigen- and carrier-specific. The enhanced delivery of antigen to spleen cells, coupled with MTP-PE immunostimulatory activity, may be the key factors for the enhanced therapeutic effects observed in treating HSV-2 disease in guinea pigs. This approach will be useful to enhance the induction of secondary immune responses in postinfection vaccination schemes.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1994

Biological response of recombinant interleukin-7 on herpes simplex virus infection in guinea-pigs.

We investigated the biological activity of human recombinant interleukin-7 (rhIL-7) on guinea-pig cells in vitro and in vivo. RhIL-7 can stimulate plastic non-adherent cells of guinea-pigs to proliferate in vitro at a degree comparable to that of human cells. Administration of rhIL-7 to guinea-pigs significantly increased their white blood cell concentration, specifically the lymphocyte population. The effect of rhIL-7 on circulating blood cells was dose dependent, in that 14 doses of twice daily subcutaneous injections at 8 x 10(5) U kg-1 and 2.4 x 10(6) U kg-1 rhIL-7 increased peripheral blood lymphocyte concentrations by 38% (p = 0.047) and 139% (p = 0.0005), respectively, compared with the placebo group. Two weekly doses of rhIL-7 liposome (5.6 x 10(6) U kg-1 dose, equivalent to 11.2 x 10(6) U kg-1 total dose) elicited a similar effect on the lymphocyte population, comparable to that of the twice daily administrations of 8 x 10(5) U kg-1 soluble rhIL-7 for 7 days (7 days x two doses/day x 8 x 10(5) U kg-1 = 11.2 x 10(6) U kg-1 total dose). However, the increased lymphocyte count induced by rhIL-7 administration did not protect guinea-pigs from the primary herpes simplex virus (HSV)-2 infection. Only when rhIL-7 was given in association with HSV-antigen gD in an antigen-specific mode did it exhibit an enhanced protective effect against the sublethal dose of genital HSV-2 challenge.(ABSTRACT TRUNCATED AT 250 WORDS)

Adjuvants, Immunologic↗
PubMed1994

Differential disposition of soluble and liposome-formulated human recombinant interleukin-7: effects on blood lymphocyte population in guinea pigs.

The effects of liposome formulation on interleukin-7 (IL-7)-dependent lymphopoietic activity was investigated based on the pharmacokinetics and tissue distribution profile of soluble and liposome-formulated recombinant human IL-7. Using 125I-IL-7, we determined the role of liposome formulation on in vivo IL-7 disposition by analyzing injection site, blood, tissue, and urinary kinetics. Following a 30- to 40-microgram subcutaneous dose of soluble IL-7, most of the IL-7 was eliminated through urinary excretion within 24 hr. An equivalent subcutaneous dose of liposome-encapsulated IL-7 resulted in a peak level less than one-tenth that seen with soluble drug but produced sustained blood and urinary levels for 5 days. The bioavailability of liposome-encapsulated IL-7 was comparable to that of soluble IL-7, as determined by both blood and urinary data. Kinetic analysis of IL-7 at the subcutaneous injection site indicated that liposome encapsulation significantly reduced the rate of disappearance at the injection site. Studies with a mixture of 40% liposome-encapsulated and 60% soluble IL-7 gave an intermediate response between that of soluble IL-7 and that of liposome-encapsulated IL-7. Characterization of blood cells from IL-7-treated animals indicated that treatment with two weekly doses of mixed IL-7 liposomes (40% liposome encapsulated IL-7) significantly increased the total numbers of lymphocytes by day 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Comparison of rates of intracellular metabolism of zidovudine in human and primate peripheral blood mononuclear cells.

3'-Azido-3'-deoxythymidine (AZT) is a drug of choice for the treatment of AIDS. On the basis of pharmacokinetic data, the nonhuman primate Macaca nemestrina has been shown to be a suitable animal model for use in the study of the disposition of AZT. However, since AZT is activated to its metabolite, the AZT triphosphate (AZTTP), intracellularly, we investigated the intracellular activation of AZT in peripheral blood mononuclear cells (PBMCs) of healthy and simian immunodeficiency virus-infected macaques and compared it with that in PBMCs obtained from human volunteers. At 5 microM extracellular AZT, both human and macaque PBMCs rapidly convert AZT to AZT monophosphate (AZTMP) (84% of total phosphorylated products) in 4 h. Increases in AZTMP levels of 7.7- and 12-fold were observed in human and macaque PBMCs, respectively, when the extracellular AZT concentration increased from 0.45 to 14.4 microM. Similar ratios of AZT metabolites, AZT diphosphate (AZTDP)/AZTTP (0.7 to 1.4), AZTMP/AZTDP (3 to 14), and AZTMP/AZTTP (3 to 19), over the same AZT concentration range were observed in both human and macaque PBMCs, suggesting that these cells have similar capacities to phosphorylate AZT. Simian immunodeficiency virus-infected macaque PBMCs showed a fivefold increase in intracellular AZT and AZTMP levels and a twofold increase in AZTDP and AZTTP levels (picomoles per 10(7) cells) when compared with those in the uninfected cells (at 4 h with 0.9 microM extracellular concentration). This increase in AZT metabolite levels has also been reported for human immunodeficiency virus-infected PBMCs. Collectively, given the similarities in phosphorylation profiles between healthy and infected human and macaque PBMCs, we conclude that the macaque is a suitable animal model for use in the study of factors that can effect the in vivo phosphorylation of AZT.

Animals↗
PubMed1994

Antinociception and side effects of liposome-encapsulated alfentanil after spinal delivery in rats.

We investigated the spinal antinociceptive and supraspinally mediated side effects of intrathecal (IT) alfentanil after delivery in saline or when encapsulated in liposomes of different lipid constituencies in rats. Rats prepared with chronic IT catheters received IT injections of alfentanil (1, 3, 10, 30, or 50 micrograms) prepared in either saline or in one of three liposome formulations (dipalmitoyl phosphatidyl choline [DPPC], DPPC containing 20% by weight of dipalmitoyl phosphatidyl glycerol [DPPC-DPPG], or DPPC containing 20 weight percent of cholesterol [DPPC-CHOL]). Antinociception was measured by hot-plate (HP) test (52.5 degrees C). In separate groups of halothane-anesthetized rats, plasma alfentanil concentrations were measured (2-120 min) after 50 micrograms IT alfentanil given in either saline or liposomes. Antinociception was measured by tail withdrawal upon its immersion in water 52.5 degrees C. Supraspinal side effects of the drug were tested by measuring catalepsy and the eye blink evoked by touching the cornea. IT alfentanil in saline produced a dose-dependent increase in the HP response latency and this effect was accompanied by a similar dose-dependent increase in the incidence of catalepsy and blockade of corneal responses, indicating a rapid supraspinal redistribution. The HP dose-response curve for IT alfentanil delivered in liposomes was shifted slightly to the right, as compared to saline vehicle, but liposome encapsulation totally abolished the side effects that were otherwise observed at the highest IT alfentanil dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Alfentanil↗
PubMed1994

Effect of MTP-PE liposomes and interleukin-7 on induction of antibody and cell-mediated immune responses to a recombinant HIV-envelope protein.

We investigated the ability of human recombinant interleukin-7 (IL-7) to enhance the immune responses of mice vaccinated with either the alum-associated or liposome-formulated recombinant human immunodeficiency virus (HIV)-envelope protein, env-2-3SF2 (a nonglycosylated denatured gp 120 of HIV-1SF2 produced in genetically engineered yeast). Pathogen-free (C3H) mice were vaccinated on days 0, 14, and 28 with 10 micrograms of either the alum-associated env-2-3SF2 or liposome-formulated env-2-3SF2, both containing a lipophylic muramyl tripeptide, MTP-PE. Liposome-formulated IL-7 (5 micrograms/mouse) or empty liposomes were given on days 7, 14, 21, and 28. Antibody response against the immunized antigen, evaluated on day 21 and day 35 or 42, showed that liposome-formulated antigen induced higher antibody titer than did alum-associated antigen, and these antibody responses can be enhanced by concurrent administration of IL-7 liposomes. Spleen cells were harvested on day 21 and day 35 or 42 to evaluate cytotoxic T lymphocyte responses directed against autologous cells infected with vaccinia virus-expressing HIV-envelope protein. Mice treated with liposome-formulated antigen expressed the highest cytotoxic t-lymphocyte (CTL) activity, regardless of whether IL-7 liposome was given as an immune potentiator. In contrast, spleen cells from mice vaccinated with alum-associated antigen exhibited minimal CTL response, which was enhanced by concurrent IL-7 liposome treatment. Collectively, IL-7 liposome treatment enhanced the antibody production of the alum-associated or liposome-formulated env-2-3SF2, whereas its enhancement of CTL activity was detected only in mice vaccinated with alum-associated antigen.

AIDS Vaccines↗
PubMed1993

Effect of zidovudine on human placental trophoblast and Hofbauer cell functions.

We have optimized a procedure to isolate placental trophoblasts and Hofbauer cells simultaneously in a quantity sufficient for short-term cultures and then used these placental cells to investigate the effects of zidovudine (ZDV) on trophoblast and Hofbauer cell functions. Of more than 10 term placentas tested, ZDV inhibits DNA synthesis of trophoblasts in a concentration-dependent manner with half the maximal inhibitory concentration (IC50) of 9.88 +/- 1.35 microM. Of the hormones evaluated, production of progesterone by trophoblasts is most sensitive to ZDV (IC50 = 3.65 +/- 0.29 microM). The inhibitory effect of ZDV on the secretion of placental lactogen and choriogonadotropin by the trophoblasts was detected only at a much higher concentration (> or = 60 microM). ZDV does not affect trophoblast or Hofbauer cell protein synthesis. Collectively, our results indicate that at clinically relevant concentrations (< or = 10 microM), ZDV significantly inhibits both the DNA synthesis of placental trophoblasts and their production of progesterone, while having a minimal effect on protein synthesis of both types of placental cells.

Cells, Cultured↗
PubMed1992

Liposome-formulated interleukin-2 as an adjuvant of recombinant HSV glycoprotein gD for the treatment of recurrent genital HSV-2 in guinea-pigs.

The use of interleukin-2 (IL-2) as an adjuvant to enhance an antigen-induced immunotherapeutic effect was investigated using guinea-pigs with established HSV-2 infection. Animals treated with four weekly doses of liposome-formulated IL-2 (2.7 x 10(5) U kg-1 dose) overlapping two biweekly doses of an HSV-recombinant glycoprotein D (rgD) treatment demonstrated approximately 70% reduction in HSV-2 recurrent disease compared with placebo (p less than 0.005). Combination therapy rgD plus liposome-formulated IL-2 exhibited approximately 30% greater therapeutic effect than either agent alone (p less than 0.05). Liposome formulation of IL-2 was essential to elicit the adjuvant effect. Identical biweekly dosing or more frequent daily dosing of soluble IL-2 did not produce additional therapeutic effects, suggesting the role of liposome targeting to lymph nodes. Although rgD plus liposome-formulated IL-2 induced a marginal early antibody response to rgD, there was no significant increase in overall antibody response. Combination therapy increased the frequency of minimally positive HSV lymphoproliferative response.

Animals↗
PubMed1991

Antiviral activity and dose optimum of recombinant macrophage colony-stimulating factor on herpes simplex genitalis in guinea pigs.

The antiviral activity of recombinant human macrophage CSF (M-CSF) against genital herpes simplex virus type-2 (HSV-2) infection in guinea pigs was investigated. M-CSF stimulates proliferation of human and guinea pig peripheral blood monocytes, specifically the plastic adherent esterase-positive mononuclear cells. When anti-HSV-2 activity of M-CSF was evaluated in guinea pigs by 6 daily injection (s.c.) of M-CSF at various doses (5 x 10(5) to 7 x 10(7) U/kg), we found 2 x 10(6) U/kg to be the optimum dose for protective efficacy against primary HSV-2 infection. Either at a lethal, 5 x 10(5) pfu, or sublethal 5 x 10(4) pfu of virus challenge, animals treated with the optimum regimen of M-CSF exhibited lower herpetic lesion scores (p less than 0.005), and lower mortality (p less than 0.025) than animals in placebo group. M-CSF treatment increased the HSV-infected cell killing activities of plastic-adherent mononuclear cells, indicating that in vivo administration of M-CSF may activate the antiviral effects of guinea pig macrophages that may play a role in protection against severity and mortality of herpetic disease.

Animals↗
PubMed1990

Physical and biological characterization of antigen presenting liposome formulations: relative efficacy for the treatment of recurrent genital HSV-2 in guinea pigs.

Antigen presenting liposomes (APLs) containing both liposome encapsulated (44%) and free (56%) recombinant glycoprotein D of herpes simplex virus type-2 (rgD-2) were characterized with respect to the interaction of the antigen with the lipid bilayer and the biological activities provided by each form of rgD-2. We found that free rgD-2 added externally to empty liposomes exhibited some biological activities both in vitro and in vivo, although we could not detect any significant adsorption and/or insertion of this form of rgD-2 into the lipid bilayer. Compared to APLs containing both forms of rgD-2, purified liposomes containing only encapsulated rgD-2 gave only 50% of the relative activity in vitro as measured by their ability to stimulate rgD-2 specific lymphocyte proliferation, and 67% of the relative activity in vivo as measured by their immunotherapeutic effect on recurrent genital HSV-2 disease in guinea pigs (P less than 0.05). These data indicate that while liposome encapsulated rgD-2 is essential for the elicitation of immunogenic responses, the free soluble rgD-2 in the APL formulation also acts in concert to generate an optimum immunotherapeutic efficacy.

Animals↗