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Biomedical subjects

J Alsenz

Publications and source records attributed to J Alsenz.

At least 19 recordsLinked to original sources
PubMed1998

Active apical secretory efflux of the HIV protease inhibitors saquinavir and ritonavir in Caco-2 cell monolayers.

PURPOSE: To investigate in vitro the mechanisms involved in the gastro-intestinal absorption of the HIV protease inhibitor, saquinavir mesylate (Invirase), whose oral bioavailability is low, variable, and significantly increased by co-administration with ritonavir, also an HIV protease inhibitor but with higher oral bioavailability. METHODS: Confluent epithelial layers of human Caco-2 cells mimicking the intestinal barrier. RESULTS: Both saquinavir and ritonavir showed polarized transport through Caco-2 cell monolayers in the basolateral to apical direction (secretory pathway), exceeding apical to basolateral transport (absorptive pathway) by factors of 50-70 and 15-25, respectively. Active efflux was temperature dependent, saturable and inhibited by verapamil and cyclosporin A. Saquinavir and ritonavir decreased each other's secretory permeability and hence elevated their net transport by the absorptive pathway. CONCLUSIONS: Saquinavir and ritonavir are both substrates for an efflux mechanism in the gut, most likely P-glycoprotein, which acts as a counter-transporter for both drugs. Together with sensitivity to gutwall metabolism by cytochrome P-450 3A, this may partially account for the low and variable oral bioavailability of saquinavir in clinical studies and for its increased bioavailability after co-administration with ritonavir.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Estimation of permeability by passive diffusion through Caco-2 cell monolayers using the drugs' lipophilicity and molecular weight.

A recently developed, new theoretical absorption model for passive diffusion through biological membranes describing the dependency of membrane permeability on lipophilicity and molecular size, predicts different sigmoid-hyperbolic permeability-lipophilicity relationships for different molecular weight ranges. This model has been tested with experimental in vitro cultured epithelial cell (Caco-2) permeability data for structurally diverse drugs differing in lipophilicity, ionization state and molecular size. These data were pooled with literature values. Using this simple physicochemical approach, the permeability of a compound through Caco-2 cells by passive diffusion can be predicted from the compounds' distribution coefficient in 1-octanol/water (log D(oct)) and its molecular weight (MW). Deviations from this expected behaviour may point to the involvement of biological components in the transport process, which may require further investigations.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed1997

Development and use of enzyme-linked immunosorbent assays (ELISA) for the detection of protein aggregates in interferon-alpha (IFN-alpha) formulations.

PURPOSE: Protein aggregates are thought to be involved in the immunogenicity of recombinant proteins in humans. To probe human IFN-alpha formulations for the presence of soluble protein aggregates, enzyme-linked immunosorbent assays (ELISA) were developed. METHODS: For the detection of IFN-alpha-IFN-alpha and HSA-IFN-alpha aggregates, sandwich ELISAs were developed using a monoclonal anti-IFN-alpha antibody as a capture antibody and the same anti-IFN-alpha antibody and an anti-human serum albumin (HSA) antibody (HRP-labeled), respectively. RESULTS: Marketed freeze-dried, HSA-containing IFN-alpha-formulations tested in the ELISAs all contained IFN-alpha-IFN-alpha and/or HSA-IFN-alpha protein aggregates, although in varying amounts. These aggregates were predominantly IFN-alpha dimers and 1:1 conjugates of HSA with IFN-alpha. Test formulations revealed that aggregation of IFN-alpha was strongly affected by the presence of pharmaceutical excipients, pH of the formulation, lyophilisation procedure, and storage temperature and time. CONCLUSIONS: The ELISAs are rapid, highly specific for aggregates in the presence of both IFN-alpha and HSA monomers and allow the direct detection of both types of aggregates in formulations in the nanogram range. The new assays will assist the monitoring of the aggregate-inducing processes during IFN-alpha formulation and storage in an early phase and the development of aggregate-free IFN-alpha formulations.

Drug Storage↗
PubMed1997

Protein aggregates seem to play a key role among the parameters influencing the antigenicity of interferon alpha (IFN-alpha) in normal and transgenic mice.

PURPOSE: During long-term treatment of various malignant or viral diseases with IFN-alpha up to 20% of patients develop anti-IFN-alpha antibodies for as yet unknown reasons. METHODS: To address this issue, a mouse model using Balb/C mice was established and the relevance of several potentially anti-IFN-alpha antibodies inducing factors was studied. RESULTS: The model revealed that both a higher frequency of injections and a higher dosage of IFN-alpha were more immunogenic and that the route of administration affected the antibody response to IFN-alpha. The intrinsic immunostimulatory activity of IFN-alpha itself also enhanced the immune response. IFN-alpha protein aggregates (IFN-alpha-IFN-alpha and human serum albumin (HSA)-IFN-alpha aggregates), which were recently identified in all marketed IFN-alpha products, were significantly more immunogenic than IFN-alpha monomers. These aggregates broke the tolerance against human IFN-alpha monomers in human IFN-alpha transgenic mice. CONCLUSIONS: Based on these animal studies it is proposed that the immune response to IFN-alpha in humans is most probably elicited by a combination of several factors among which IFN-alpha protein aggregates seem to play a key role.

Adjuvants, Immunologic↗
PubMed1997

Interferon immunogenicity: preclinical evaluation of interferon-alpha 2a.

A preclinical evaluation of the immunogenicity of various preparations of interferon-alpha (IFN-alpha) was performed with in vitro and in vivo animal models. The distribution of genes for IFN-alpha 2a, IFN-alpha 2b, and IFN-alpha 2c in various cell populations and the response of human T cell clones to IFN-alpha peptides were investigated. The immunogenicity of IFN-alpha in IFN-alpha 2b transgenic mice and factors that influence the immunogenicity of IFN-alpha in normal mice were also studied. The genes for IFN-alpha 2a and IFN-alpha 2b were found in KG-1 cells, whereas IFN-alpha 2b and IFN-alpha 2c genes were present in Namalwa cells. No difference in proliferation of human T cells, T cell lines, or T cell clones could be obtained with IFN-alpha peptides. In transgenic mice bearing the human IFN-alpha 2b gene, no antibody response was obtained following immunization with either IFN-alpha 2a or IFN-alpha 2b. Normal mice immunized with either IFN-alpha 2a or IFN-alpha 2b produced equivalent titers of antibodies, which cross-reacted with both IFNs. Studies evaluating the relative immunogenicity of IFN-alpha in normal mice demonstrated that a number of treatment and host variables can modulate immunogenicity of IFN-alpha preparations.

Amino Acid Sequence↗
PubMed1993

Third component of trout complement. cDNA cloning and conservation of functional sites.

Of the 30 distinct complement proteins recognized to date, C3 is probably the most versatile and multifunctional molecule known, interacting with at least 20 different proteins. It plays a critical role in both pathways of complement activation and participates in phagocytic and immunoregulatory processes. Structural and functional analysis of C3 from different species, in addition to phylogenetic information, provides insights into the structural elements mediating the various functions. This study describes the cDNA cloning of one of two isoforms of the third complement component, C3-1, of rainbow trout (Salmo gairdneri) and the analysis of its functional sites. By screening a trout liver lambda gt11 library with anti-trout C3 chain-specific antibodies and polymerase chain reaction we have determined the cDNA sequence of trout C3-1. The obtained sequence is in complete agreement with the protein sequence of several tryptic peptides, corresponding to different regions of trout C3-1. C3-1 consists of 1640 amino acids with a calculated molecular mass of 181,497 Da. The sequence contains two potential N-glycosylation sites, one on each chain of C3. The deduced protein sequence showed 44.1, 43.3, 44.2, 44.9, 43.1, 43.8, 45.9, 29.9, and 33.1% amino acid identities to human, mouse rat, guinea pig, rabbit, cobra, frog, hagfish, and lamprey C3, whereas the identities to human C4, C5, and alpha 2M are 30.4, 28, and 22.9%, respectively. The trout C3 amino acid sequence shows clusters of high and low similarity to C3 from other species. In the regions of high similarity belong the C3 domains that contain the thiolester site and the properdin binding sites, whereas the regions that correspond to regions of human C3 where CR1 and CR2 bind show low amino acid sequence similarity. The deduced amino acid sequence shows that the C3 convertase cleavage site (Arg-Ser) is conserved in trout C3, whereas the factor I cleavage sites are Arg-Ala and Arg-Thr instead of Arg-Ser, which is found in the C3 of other species. Protein sequencing of the trout C3 fragments fixed on zymosan during complement activation confirmed the cleavage of trout C3 by trout C3 convertase and factor I at Arg-Ser and Arg-Thr, respectively.

Amino Acid Sequence↗
PubMed1992

Segment spanning residues 727-768 of the complement C3 sequence contains a neoantigenic site and accommodates the binding of CR1, factor H, and factor B.

CR1, CR2, DAF, MCP, factor H, C4bp, factor B, and C3 are members of a family of structurally related molecules, the majority of which belong to the complement system. Several of these molecules also share functional features such as cofactor and decay/dissociation activity and compete with one another in binding to C3b. Since factor H appears to bind to multiple sites in C3, we investigated the relationship between the factor H- and CR1-binding sites in C3b. Factor H binding to C3b is inhibited by either the C3c or C3d fragments, and addition of both fragments together augments this inhibition. One monoclonal anti-C3c antibody, anti-C3-9, which recognizes a neoantigenic epitope expressed upon cleavage to C3 to C3b, inhibited both factor H and CR1 binding to EC3b cells. This monoclonal antibody (MoAb) also inhibited factor B binding to EC3b. Two observations further supported our hypothesis that these molecules bind to proximal sites in C3b. First, a synthetic peptide spanning this region of C3b (C3(727-768)) inhibited factor H binding. Second, antibodies raised against this peptide inhibited binding to CR1, factor H, and factor B to C3b. These data show that H binds to at least two sites in C3b: the site in the C3c fragment is within the identified CR1-binding domain while the site in the C3d fragment surrounds the CR2-binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Evidence for multiple sites of interaction in C3 for complement receptor type 2 (C3d/EBV receptor, CD21).

Multivalent but not monovalent CR2 ligands are required to elicit Raji cell proliferation as well as other B cell responses. It has been reported (C. Servis and J. D. Lambris, J. Immunol. 1989. 142: 2207) that the tetrameric peptide T-(C31202-1214)4, which represents the CR2-binding site in C3d, was able to support Raji cell growth. We show here that the tetrameric peptide T-(gp350(19-30)4, which contains the CR2-binding site in gp350 protein of EBV also induces Raji cell growth and this effect is inhibited by the monomeric peptides gp350(19-30) and C3(1201-1214). We also investigated the nature of the interaction between C3 fragment and CR2 in order to explain the Raji cell growth-supporting effect exerted by C3. The following findings suggest that there are multiple sites in the C3 molecule able to interact with CR2: (1) both C3c and C3d immobilized on microspheres are able to bind to Raji cells through CR2. (2) soluble C3d inhibits to a greater extent the binding of CR2 to fixed C3d than to fixed C3b, which suggests the existence of additional CR2-binding sites within C3b not present in the C3d portion of the molecule; (3) synthetic peptides C3(1187-1214), C3(741-757) and C3(295-307) which represents regions of similarity in the C3 molecule bind specifically to CR2 on Raji cells and compete with each other for binding to the receptor and (4) preincubation of microtiter plate-fixed C3b with monoclonal or polyclonal anti-peptide antibodies (C3-9, anti-C3(727-768) recognize the N terminus of the alpha chain of C3 (including residues 741-757) inhibited CR2 binding. Therefore, these data suggest that the N terminus of the alpha chain of C3 is involved in binding to CR2.

Amino Acid Sequence↗
PubMed1989

Cell surface proteins reacting with activated complement components.

The biologic activities mediated by the products of complement activation include cellular, bacterial, and viral lysis, inflammation, phagocytosis, and immunoregulation. These responses are achieved through the interaction of the activated forms of several of the complement proteins with cell membrane proteins. This report reviews aspects of the structure, ligand specificity, and function of the various complement receptors with particular emphasis on those receptors which bind to the activated fragments of C3. In addition, we briefly summarize the surface proteins on foreign particles that bind C3 and their possible role in the pathogenesis of these organisms.

Animals↗
PubMed1989

Acquired C1 inhibitor (C1-INH) deficiency type II. Replacement therapy with C1-INH and analysis of patients' C1-INH and anti-C1-INH autoantibodies.

The response of two patients with autoantibody-mediated C1-inhibitor (C1-INH) deficiency to replacement therapy with C1-INH was studied over a period of 3 d. In patient 1 an acute attack of angioedema was successfully managed by infusion of 1,000 U of C1-INH concentrate. C1-INH function returned to normal levels within 30 min, while CH50 and C4 peaked after 6-7 h and C1 hemolytic activity reached 50-60% of normal after 3 d. Immediately after the injection an increase in C1-INH-anti-C1-INH complexes was observed. Based on NH2-terminal sequence analysis of the patients' Mr 96,000 C1-INH, it is concluded that this fragment is generated after cleavage of C1-INH in its active site by one of its target proteases without generating a covalent C1-INH-enzyme complex. In a second patient with a four to five times higher anti-C1-INH antibody titer, the infusion of 500 ml of plasma or of 2,000 U of C1-INH concentrate influenced neither the severity of the patient's angioedema nor the tested parameters, except for an increase in the amount of C1-INH-anti-C1-INH complexes. Analysis of patients' anti-C1-INH antibodies revealed that the antibodies recognize different epitopes within the C1-INH. This suggests that patients with acquired angioedema type II are a heterogenous group with respect to the C1-INH autoantibodies.

Amino Acid Sequence↗
PubMed1989

The acquired C1-INH deficiencies with autoantibodies (AAE type II).

A new type of acquired C1-inhibitor (C1-INH) deficiency has been recognized (AAE type II) which is characterized by the presence of autoantibodies to C1-INH and by a circulating 96 KD C1-INH molecule. The clinical manifestations and biochemical abnormalities of this novel autoimmune disease resemble those found in the other forms of acquired C1-INH deficiency (AAE type I), including recurrent angioedema and low serum levels of C2, C4, C1, C1q and C1-INH activity. However, in contrast to AAE type I, AAE type II is not associated to other diseases. Evidence has been provided that the anti-C1-INH antibodies play a major role in the development and maintenance of AAE type II. These autoantibodies seem to impede C1-INH activity, thus allowing unopposed activation of the complement and/or contact system and to induce the generation of the 96 KD C1-INH species in the patients' plasma.

Angioedema↗
PubMed1988

A rapid and simple ELISA for the determination of duplicate monoclonal antibodies during epitope analysis of antigens and its application to the study of C1(-)-INH.

A rapid and simple ELISA has been developed for identifying the specificities of two monoclonal antibodies recognizing either similar or distinct epitope(s) of an antigen. The method utilizes microtiter plates coated with one of the monoclonal antibodies either by direct adsorption of the purified antibody to the plastic or by immobilization of the antibody from ascites or hybridoma supernatants via immobilized polyclonal anti-mouse immunoglobulin antibodies. After preincubation of the antigen with the second monoclonal antibody, the mixture is added to the surface-immobilized first antibody. The amount of antigen bound to the first antibody is subsequently measured by rabbit polyclonal antibodies to the antigen and peroxidase-conjugated anti-rabbit immunoglobulin antibodies. Binding of antigen to the first antibody is only observed when the second monoclonal antibody binds to a distinct epitope. The major advantages of this procedure are its simplicity, rapidity and independence of radioisotopes. Using this method a library of monoclonal antibodies against human C1(-)-INH has been tested and several duplicate monoclonal antibodies have been identified. Furthermore, the above analytical procedure was capable of detecting conformational changes of the C1(-)-INH molecule induced either by binding of a monoclonal antibody to C1(-)-INH or by enzymatic cleavage of C1(-)-INH.

Antibodies, Monoclonal↗
PubMed1987

Autoantibody-mediated acquired deficiency of C1 inhibitor.

During the past 25 years, three forms of deficiency of the inhibitor of the first component of complement (C1 inhibitor) with angioedema have been recognized; two forms are hereditary and one is acquired. As compared with hereditary angioedema, the syndrome of acquired C1-inhibitor deficiency is rare, and it is usually associated with lymphoproliferative diseases. We report another type of acquired C1-inhibitor deficiency with angioedema. Two patients with recurrent angioedema but no associated diseases were found to have IgG1 autoantibodies against C1 inhibitor. The anti-C1-inhibitor antibodies prevented binding of C1 inhibitor to activated C1s. Both patients had 60 to 70 percent of normal levels of C1 inhibitor, but it was functionally inactive, with a molecular weight of 96,000 (normal C1 inhibitor, 105,000). In vitro studies of the patients' serum revealed degradation of 125I-labeled 105,000-dalton C1 inhibitor into the inactive 96,000-dalton molecule, caused by activated C1s and not found in normal human serum. We conclude that these cases of acquired C1-inhibitor deficiency resulted from a blockade of C1-inhibitor function by the anti-C1-inhibitor antibodies and from subsequent inactivation of C1 inhibitor by the now uncontrolled enzyme, activated C1s. As in other forms of C1-inhibitor deficiency, the unopposed activation of the complement system led to angioedema.

Adult↗
PubMed1987

[Formation of IgG antibodies to C1 inhibitor as the cause of life-threatening angioedema].

A clinical picture with recurrent (in some cases potentially fatal) edema of skin and internal organs based not on a hereditary C1 inhibitor deficiency, but an acquired loss of C1 inhibitor activity due to antibodies is described for the first time in two patients. The clinical symptoms commenced in middle age patients between 40 and 46 years old. Anti C1 antibodies of the IgG were found in both patients. Quantitatively, these C1 inhibitor protein was in the lower range of normal, whereas no inhibitor activity could be demonstrated functionally. The function of the complement components C1, C2 and C4 was greatly reduced. The therapeutic use of C1 inhibitor concentrate at a high doses (6 X 500 U) as well as administration of high-dose corticosteroids in several emergency situations was unsuccessful.

Adult↗
PubMed1987

Simplified methods for the purification, quantitation, and functional estimation of human complement C-1-inhibitor (C-1-INH) with a monoclonal anti-C-1-INH antibody.

New methods have been developed for the isolation, quantitative detection, and functional measurement of human complement C-1-inhibitor (C-1-INH). The two-step purification procedure for C-1-INH from human plasma or serum employs affinity chromatography with a monoclonal anti-C-1-INH antibody coupled to CNBr-activated Sepharose 4B followed by fractionation on a FPLC Mono Q HR 5/5 column. It yields functionally active, homogeneous C-1-INH with about 40% recovery. For quantitative estimation of C-1-INH an ELISA was performed. ELISA plates were coated with a polyclonal anti-C-1-INH antibody, serum or plasma was added and bound C-1-INH was detected with the monoclonal anti-C-1-INH antibody. The method has a sensitivity of 0.4 ng C-1-INH per assay corresponding to 20 ng/ml. For the detection of functionally active C-1-INH an ELISA was developed using C1-s-coated microtiter plates. After incubation with serum or plasma, C1-s-bound C-1-INH was monitored with the monoclonal anti-C-1-INH antibody. With this method it is possible to measure as little as 0.3 ng of functionally active C-1-INH in 20 microliter of a biological sample. All methods described in the present paper are easy to perform, rapid, sensitive, and highly reproducible.

Animals↗