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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The immunogenic potential of tetanus toxoid (TT) was compared when either adsorbed to aluminium hydroxide (TT-alum) or entrapped in microparticles consisting of poly(D,L-lactic-co-glycolic acid) (PLA:PGA, 55:45) derived polymers. Furthermore, the effect of administering the microparticles in an aqueous buffer or water-in-oil emulsion on the TT immunogenicity was also investigated. When mice were immunized with the different formulations, similar levels of anti-TT antibodies were observed during the primary IgG response. The choice of the carrier seemed to play an important role for both the level and maintenance of the secondary IgG response, attained as a consequence of a booster immunization with TT-alum. The strongest secondary antibody response was obtained by priming with TT-containing microparticles, resuspended in water-in-oil emulsions. As expected, incomplete Freund's adjuvant (IFA) proved to be a more potent adjuvant than peanut oil, whereas resuspension of the microparticles in aqueous solution induced a relatively less efficient antibody response. Overall, microencapsulated TT primed the mice more effectively, since the secondary antibody response was higher and persisted longer compared with TT-alum priming. These results indicate that in addition to TT maintaining its antigenicity after microencapsulation, the microparticles also potentiate its immunogenic properties. This approach should prove very useful for designing more effective vaccines.
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PMID:Parameters affecting the immunogenicity of microencapsulated tetanus toxoid. 152 81

Although CD4 antigen is expressed on monocytes (MO), its functional role is uncharacterized. In this study, isolated human MO were separated into CD4+ and CD4- MO subsets and assessed for presentation of tetanus toxoid. The CD4- MO subset had decreased antigen presenting cell (APC) capacity as well as increased PGE2 production when compared to the CD4+ MO subset. Addition of a cyclo-oxygenase inhibitor (Indomethacin) did not restore the CD4- MO subset's APC capacity to that of the similarly treated CD4+ MO subset, eliminating differential PGE2 production as the primary cause of differential APC capacity. Production of monokines such as IL-1 and plasminogen activator, which affect APC capacity, was similar in the CD4 MO subsets. However, tumor necrosis factor (TNF) production (IFN gamma plus MDP-induced) of the CD4+ MO subset was slightly greater than that of the CD4- MO. CD4- MO's lower APC capacity is not totally explained by their differential IL-1, TNF, or PGE2 production.
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PMID:Antigen presentation by the CD4 positive monocyte subset. 230 46

Dispersed cell cultures were established from 7- to 9-day postnatal mouse cerebellum. The fibrin slice method was used to obtain a localization of plasminogen activator production to specific cells. Fibrinolytically active cells were small (5- to 8-micrometer diameter), round, and occurred singly or in aggregates. Fibrinolysis was both plasminogen and time dependent, inhibitable by epsilon-aminocaproic acid and soybean trypsin inhibitor and did not occur when cells were fixed in formalin prior to the fibrin overlay. Strong fibrin degradation occurred only when granule neurons were abundant in the cultures. These plasminogen activator secreting cells were identified as granule neurons by cell separation methods, nuclear morphology, and their ability to bind tetanus toxin and rabbit antiserum against mouse cerebellum (anti-Cbl-1 antiserum). Plasminogen activator also could be quantified in fractionated tissue homogenates or in cell culture medium by the 125I-labeled fibrin plate assay. Fibrinolysis in cerebellar extracts was 95% dependent on the presence of added plasminogen; furthermore, the activity was greater in cerebellar extracts as compared to cerebral cortex of the same age. At the age examined, the cerebellum contains many migratory neurons, and plasminogen activator production may be involved in the process of cell movement.
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PMID:Plasminogen activator secretion by granule neurons in cultures of developing cerebellum. 695 Apr 20

Purified tetanus toxoid, a high-molecular-weight protein, was entrapped within poly(L-lactic acid) (PLA) and poly(D,L-lactic/glycolic acid) (PLGA) microspheres prepared by either a solvent extraction or a solvent evaporation method carried out in a multiple emulsion system (water-in-oil-in-water). The physical integrity and antigenicity of the protein treated under different processing conditions were investigated. A reduction of antigenicity that was related to the percentage of aggregated protein was noticed under some experimental conditions. This partial loss of antigenicity was associated with the lyophilization process and affected by the nature of the organic solvent. All types of microspheres prepared with different molecular weight PLA and PLGA displayed a high protein-loading efficiency (> 80%) but their size was strongly influenced by polymer molecular weight (3000 versus 100,000). Protein release pattern was influenced by both polymer molecular weight and composition (PLA versus PLGA). A constant release pattern after an induction period of 10 days was observed for microspheres composed of high-molecular-weight polymers (PLA and PLGA). The release rate was lower from PLA microspheres than from PLGA microspheres. In contrast, a continuously increasing release rate preceded by a burst was observed for low-molecular-weight (3000) PLGA microspheres. Microencapsulated tetanus toxoid was significantly more immunogenic in mice than fluid toxoid as determined by IgG anti-tetanus antibody levels and neutralizing antibodies. However, the magnitude and duration of the antibody response did not differ significantly from a similar dose of aluminium phosphate-adsorbed toxoid. We conclude that microencapsulated tetanus toxoid shows significant adjuvant activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Biodegradable microspheres as controlled-release tetanus toxoid delivery systems. 817 50

Controlled-release formulations based on poly(lactic) (PLA) and poly(lactic/glycolic) acid (PLGA) microspheres containing tetanus vaccine were designed. The polymers forming the microspheres were L-PLA of different molecular weights and DL-PLGA, 50:50. These microspheres were prepared by two solvent elimination procedures, both using a double emulsion, and were characterized for size, morphology, and toxoid release kinetics. The influence of formulation variables such as polymer type, vaccine composition, and vaccine/polymer ratio was also investigated. Both techniques yielded microspheres with similar size, morphology, and release properties. Microsphere size was dependent on the type of polymer and the presence of the surfactant L-alpha-phosphatidylcholine, which led to a reduction in microsphere size. On the other hand, the release kinetics of encapsulated protein were affected by the polymer properties (ratio lactic/glycolic acid and molecular weight) as well as by the vaccine composition, vaccine loading, and microsphere size. Moreover, for some formulations, a decrease in microsphere size occurred simultaneously, with an increase in porosity leading to an augmentation of release rate. The changes in the PLA molecular weight during in vitro release studies indicated that release profiles of tetanus toxoid from these microspheres were only marginally influenced by polymer degradation. A significant fraction of protein (between 15 and 35%) was initially released by diffusion through water-filled channels. In contrast, the decrease in the PLGA molecular weight over the first 10 days of incubation suggested that erosion of the polymer matrix substantially affects protein release from these microspheres. Among all formulations developed, two differing in microsphere size, polymer hydrophobicity, and release profile were selected for in vivo administration to mice.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Determinants of release rate of tetanus vaccine from polyester microspheres. 837 56

Various methods to determine loading of vaccine in biodegradable polymer microspheres encapsulating tetanus toxoid were evaluated. The microspheres were composed of poly (D-lactic acid) (PLA) and poly (DL-lactic-co-glycolic acid) (PLGA). Dissolution of microspheres in organic solvents such as methylene chloride, chloroform, or dimethyl sulfoxide and extraction of vaccine antigen or total protein with phosphate buffered saline gave variable results which depended upon the characteristics of the microspheres, such as type of polymer, excipients used in the microspheres and formulation conditions. Microspheres made from low molecular weight PLGA polymer and showing a large burst release exhibited up to 25% extraction of antigen whereas microspheres made from PLA microspheres with low burst release showed < 1% extraction. Extraction of total protein with 0.1 N NaOH and 5% sodium dodecyl sulfate showed results similar to those obtained with organic solvent extraction method. Partial digestion of microspheres with 6 N HCl at 60 degrees C for 20 h resulted in approximately 30% loss in TT protein by micro-bicinchoninic acid (BCA) assay. The major problem with this method was strong reactions in the micro-BCA assay of stabilizers, particularly sugars (glucose, sucrose) used in the microsphere formulations. Complete digestion of microspheres with 6 N HCl at 110 degrees C for 20 h or with 13.5 N NaOH at 121 degrees C for 1 h and quantitation of amino acids by a modified ninhydrin assay showed reproducible results on the protein loading in the microspheres. However, this method was affected by the presence of stabilizers, such as gelatin, which contain amino acids. Further, sucrose concentrations higher than 10% caused interference in the ninhydrin assay on samples hydrolyzed with 6 N HCl. In contrast, hydrolysis with 13.5 N NaOH did not show any interference by sucrose. Stabilizers used outside the microspheres for lyophilization purposes may be removed by washing the microspheres before loading determination or by dialysis but stabilizers used inside the microspheres would still cause interference. For reliable determination of total protein in the microspheres containing vaccines, we suggest complete digestion of microspheres with acid or base followed by amino acid analysis by colorimeteric assays such as ninhydrin method or using amino acid analyzers. The method needs to be optimized for each type of formulation to eliminate interference by the excipients. Alternatively, total protein nitrogen in the microspheres may be determined by the Kjel-dahl method if no amino acids or other nitrogen containing stabilizer is used inside the microspheres.
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PMID:Determination of protein loading in biodegradable polymer microspheres containing tetanus toxoid. 917 69

A theoretical model is outlined for predicting the time evolution of total mass, mean molecular weight, and drug release for the case of a spherical bulk-eroding microsphere, prepared by a double emulsification procedure and containing a hydrophilic drug, such as a protein or peptide. Explicit analytical formulae are derived for calculating the time evolution of measurable macroscopic characteristics, such as drug release or mean molecular weight. Microsphere hydration, polymer erosion, and drug release phases are each described. Results indicate that polymer degradation by only random-chain scission or only end scission (or unzipping) cannot explain experimentally observed kinetics of particle mass loss and molecular weight change; thus, a combined model (incorporating both random and end scission) is proposed. A general methodology for determining the microscopic transport coefficients (such as polymer degradation rate constant or drug diffusion coefficient) from erosion and release data is outlined. This paradigm is applied to the specific case of 50:50 poly(D,L-lactic-co-glycolic acid (PLGA) microspheres encapsulating glycoprotein 120 (gp 120), a candidate AIDS vaccine. Predictions permit comparisons with experimental data for mean weight- and number-averaged molecular weights, as well as for mass loss and protein release. Other comparisons are made with data appearing in the literature for release of tetanus toxoid from PLA and PLGA microspheres of variable molecular weight. Agreement between theory and experiment is observed.
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PMID:A theoretical model of erosion and macromolecular drug release from biodegrading microspheres. 942 63

The feasibility of biodegradable polyester microspheres (MS) for single injection vaccines will greatly depend on the toxoid stability within the MS exposed to in vivo conditions. This study examined the effects of polymer type and co-encapsulated additives on diphtheria (Dtxd) and tetanus (Ttxd) toxoid entrapment and stability. The co-encapsulated stabilizers influenced significantly the entrapment of Dtxd and Ttxd in PLA/PLGA MS. Typically, 5% BSA or trehalose decreased the amount of Dtxd entrapped in spray-dried MS, whereas BSA increased the entrapment in coacervated MS. Further, the entrapment of Dtxd decreased as a function of polymer hydrophobicity in spray-dried MS. Without additives, approx. 64, 43 and 16% entrapment efficiency of ELISA-reactive antigen was obtained for 14-17 kDa PLGA 50:50, PLGA 75:25 and PLA, respectively. The novel end-group stearylated 1-PLAs were only processed by coacervation. Satisfactory entrapment of 30-60% Dtxd was obtained. Here, albumin was a prerequisite for toxoid encapsulation, as BSA-free formulations produced strong toxoid precipitation. Furthermore, protein burst release increased with the more hydrophobic polymers, with Dtxd, Ttxd and the co-encapsulated BSA following a similar pattern and magnitude. This investigation also revealed that the method of protein extraction from the microspheres (O/W-partition or polymer hydrolysis) as well as the analytical methods (HPLC or ELISA) strongly influenced the determined amount of encapsulated toxoid and BSA. In conclusion, the study revealed the complexity of antigen microencapsulation when using different preparation and analytical techniques, as well as different types of materials.
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PMID:Diphtheria and tetanus toxoid microencapsulation into conventional and end-group alkylated PLA/PLGAs. 1038 3

The development of a single-dose tetanus vaccine based on Poly(Lactic acid) (PLA) or Poly(Lactide-co-Glycolide) (PLGA) microspheres has been complicated due to the instability of tetanus toxoid (TT) inside these systems. Herein we report an attempt to re-design PLGA microspheres by co-encapsulating TT in the dry solid state together with potential protein stabilizers, such as trehalose, bovine serum albumin, alginate, heparin, dextran or poloxamer 188 and by using an appropriate microencapsulation technique. These newly developed PLGA microspheres were able to release in vitro antigenically active TT for at least 5 weeks, the amount released being highly dependent on the stabilizing excipient used. More specifically, results showed that dextran and heparin provided a particularly stabilizing environment for TT inside the microspheres during the polymer degradation process. The efficacy of this strategy was demonstrated by the high, long lasting titers of neutralizing antibodies achieved after in vivo administration of dextran-containing microspheres with a small amount of alum-adsorbed TT, as compared to the commercial adsorbable tetanus vaccine. These findings suggest that future developments in the area of vaccinology depend on ability to combine a detailed knowledge of the microencapsulation technology with a rational choice of stabilizing excipient or combination of excipients.
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PMID:Formulation strategies for the stabilization of tetanus toxoid in poly(lactide-co-glycolide) microspheres. 1046 Sep 20

The aim of the present work was to evaluate if the presence of a polyethylenglycol (PEG) coating around PLA nanoparticles would affect their interaction with biological surfaces, following oral administration to rats. For this purpose, a model antigen, 125I-radiolabeled tetanus toxoid, was encapsulated in PLA and PLA-PEG nanoparticles by a modified water-in-oil-in-water solvent evaporation technique. Firstly, the stability of the nanoparticles in simulated gastrointestinal fluids was evaluated. Results showed an interaction between the nanoparticles and the enzymes of the digestive fluids, this interaction being considerably reduced by the PEG coating around the particles. On the other hand, the PLA forming the nanoparticles was found to be only slightly degraded (9% converted to lactate for PLA nanoparticles and 3% for PLA-PEG nanoparticles) and that the encapsulated tetanus toxoid remained mostly associated to the nanoparticles upon incubation in the digestive fluids for up to 4 h. Finally, the in vivo experiments showed that, after oral administration to rats, the levels of encapsulated radioactive antigen in the blood stream and lymphatics were higher for PLA-PEG nanoparticles than for PLA nanoparticles. In conclusion, the PLA-PEG nanoparticles have a promising future as protein delivery systems for oral administration.
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PMID:The role of PEG on the stability in digestive fluids and in vivo fate of PEG-PLA nanoparticles following oral administration. 1091 53


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