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F Zhou

Publications and source records attributed to F Zhou.

At least 145 records · Page 8Linked to original sources
PubMed1993

[Analysis of fatty acid composition of spotted fever group rickettsiae isolated in China by gas chromatography].

In present paper, fatty acid composition of seven Chinese isolates of SFG rickettsiae and six prototype strains of SFG rickettsiae were analyzed by GC-MS. Tested prototype strains of SFG rickettsiae were R. sibirica (strains 232 and 246), R. conorii (Simko), R. rickettsi (R), R. akari (Kaplan), R. australis (W58); Chinese isolates were An-84, Se-85, W-88 (human strain), MT-84, FT-84 (D. nuttalli strain), TO-85 (ova of nuttalli) and Chinese reference strain -JH-74 (D. nuttalli). They were propagated in yolk sacs of embryonated hen eggs and purified by centrifugation in a 30%-36%-42% discontinuous renografin density gradient. The fatty acid composition of selected strains of SFG rickettsiae was analyzed by gas chromatography, and then comparison being carried out by single linkage on mini-computer. Identification of the strains was performed based on the results obtained from GC-MS. Results showed that the fatty acid profiles of all the isolates from China were quantitatively similar to that of R. sibirica and quite different from other prototype strains of SFG rickettsiae.

China↗
PubMed1992

Prolonged survival of thymoma-bearing mice after vaccination with a soluble protein antigen entrapped in liposomes: a model study.

EG7-OVA cells are mouse thymoma EL4 cells stably transfected with the complementary DNA of chicken ovalbumin (OVA) and thus express OVA epitopes as a unique antigen. Cytotoxic T lymphocytes specific to OVA can be elicited by immunization of mice with OVA osmotically loaded into syngeneic splenocytes or entrapped in liposomes. Cytotoxic T lymphocytes thus induced can specifically cytolyse the EG7-OVA cells in vitro in an antigen-specific and major histocompatibility complex-restricted manner. In the present study, we have examined in this model system whether immunization with liposomal OVA can protect mice against tumors induced by EG7-OVA cells. Vaccination with OVA either entrapped in liposomes or osmotically loaded in the syngeneic splenocytes prolonged the survival of mice which had been challenged with EG7-OVA cells, but not those mice challenged with the parent EL4 cells. The antitumor effect was attributed to the induced OVA-specific cytotoxic T lymphocyte activity, since other forms of acquired immunity such as interaction of tumor cells with specific antibody could not be detected. Our results demonstrate that immunization with antigen incorporated in liposomes could be a useful means of inducing a protective antitumor response.

Animals↗
PubMed1992

Induction of cytotoxic T lymphocytes in vivo with protein antigen entrapped in membranous vehicles.

Intravenous administration of APC such as splenocytes loaded with a soluble protein Ag has been shown to prime for an Ag-specific CTL response. It is thought that the APC directly presents loaded Ag in a MHC-restricted manner. However, it is demonstrated in this study that allogeneic splenocytes, MHC-free RBC, and even synthetic lipid vesicles (liposomes) after loading with OVA can elicit an OVA-specific and MHC-restricted CTL response. Biodistribution studies of these Ag-associated vehicles showed that the liver, spleen, and lung were the major organs responsible to scavenge these carriers, suggesting that the monocyte-macrophage system was involved in the Ag presentation for CTL. Depletion of macrophages by a specific macrophage killer, Cl2MDP, containing liposomes, abolished the CTL induction by immunization with OVA Ag carried by these vehicles except the induction by syngeneic splenocytes. Thus, the syngeneic splenocytes present Ag directly to the T cells, but other membranous vehicles carry the Ag to the host APC including macrophages, which then present it to the T cells. These results indicate that formulation of an Ag in membranous/colloidal vehicles may be a way to prime for a CTL response.

Animals↗
PubMed1992

In vivo cytotoxic T lymphocyte induction with soluble proteins administered in liposomes.

The in vivo induction of a CTL response usually requires that Ag be endogenously synthesized so that appropriate processing can occur. In most of the few examples where successful CTL induction was reported with proteins and peptides, unacceptable adjuvants or means of Ag formulation were used. In the present report, liposomes were used to incorporate the soluble proteins OVA and beta-galactosidase. This simple and convenient to use approach, which requires minimal amounts of Ag, results in priming for a CD8+ CTL response and the establishment of immunologic memory. The liposome approach may not only prove a convenient means of inducing CTL responses in vivo but may also be useful to study the mechanisms of Ag processing.

Animals↗
PubMed1992

Soluble proteins delivered to dendritic cells via pH-sensitive liposomes induce primary cytotoxic T lymphocyte responses in vitro.

Effective immunity to many infectious agents, particularly viruses, requires a CD8+ cytotoxic T lymphocyte (CTL) response. Understanding how to achieve CTL induction with soluble proteins is important for vaccine development since such antigens are usually not processed appropriately to induce CTL. In the present report, we have demonstrated that a potent primary CTL response against a soluble protein can be achieved by delivering antigen in pH-sensitive liposomes to dendritic cells (DC) either in vivo or in vitro. Since the pH-sensitive liposome delivery system is efficient and easy to use, the approach promises to be valuable both in the study of basic mechanisms in antigen processing, and as a practical means of immunization.

Animals↗
PubMed1992

[Purification of the ninth component of human complement (C9)].

A large amount of human C9 was purified from plasma by the following procedures: 1) Polyethylene glycol precipitation; 2) Depletion of plasminogen by passing over an L-lys-sepharose column; 3) DEAE-sephadex A-50 chromatography; and 4) Hydroxylapatite (HA) chromatography. The method of C9 purification was improved by altering the column-elution conditions and by the establishment of a novel method for preparing high-flow-rate HA. As a result, the rate of recovery of C9 was high (28.2%) and no impurities were detected either on gel electrophoretic or immunochemical examination. The hemolytic activity of purified C9 was retained.

Chromatography↗
PubMed1992

[Biotransformation of zearalenone].

The conversion of Zearalenone by some strains of microorganisms was investigated. When the selective strains of Rhodotorula sp., Arthrobacter sp., Saccharomyces sp., and Candida sp. were incubated by shaking or standing at 28 degrees C for 72 h with an alcoholic solution of Zearalenone as the substrate at a concentration of 2-10 mg/ml ethanol (50-100 micrograms/ml medium), it was readily converted to give Zearalenols, consisting either mainly of the alpha-isomer (e.g. 96% in case of Rhodotorula sp. and 84% in case of Arthrobacter sp. as determined by HPLC) or beta-isomer (e.g. 91% and 92% in Saccharomyces sp. and Candida sp., respectively). The structure of the product was confirmed by 13C-NMR, MS and HPLC.

Arthrobacter↗
PubMed1991

An improved method of loading pH-sensitive liposomes with soluble proteins for class I restricted antigen presentation.

We have recently shown that ovalbumin (OVA) entrapped in pH-sensitive liposomes could sensitize mouse thymoma cells for lysis by MHC class I-restricted cytotoxic T lymphocytes (CTL) (Reddy et al. (1991) J. Immunol. Methods, 141, 157-163). The present studies were designed to optimize the antigen delivery system. A simple freeze-thaw method was developed to load OVA into pH-sensitive liposomes, and the protocol was optimized in terms of the choice of buffer, pH and ionic strength of the medium, lipid composition, lipid and OVA concentrations and the number of freeze-thaw cycles. Under optimized conditions, approximately 25% of OVA could be entrapped in pH-sensitive liposomes at 172 micrograms protein/mg lipid. This compares to only about 5% entrapment (70 micrograms protein/mg lipid) using the previous method. OVA loaded to pH-sensitive liposomes using the improved method led to a sensitive measure of CTL activity. The approach promises to be suitable to measure CTL against less available soluble antigens such as viral proteins.

Animals↗
PubMed1991

pH sensitive liposomes provide an efficient means of sensitizing target cells to class I restricted CTL recognition of a soluble protein.

Exogenous antigens are normally endocytosed and enter the class II pathway of processing and presentation. It had been shown earlier that soluble antigen could be introduced into the class I pathway of processing and presentation by osmotic loading. In this report, we have demonstrated that OVA containing liposomes that destabilize on exposure to low pH, referred to as pH sensitive liposomes, could sensitize target cells to lysis by class I MHC-restricted OVA-specific CTL. However, OVA-containing pH insensitive liposomes, native OVA, or OVA subjected to the same protocol as was used to make the liposomes, failed to sensitize targets to OVA-specific CTL lysis. The pH sensitive liposomal approach was less toxic and more efficient (about 20-fold) in delivering than the osmotic loading approach. The pH liposome approach may prove valuable to study CTL recognition characteristics of less available proteins such as viral proteins.

Animals↗