Immunological Characterization of Apolipoprotein AI from Normal Human Plasma: Mapping of Antigenic Determinants

Milthorp, Peter; Weech, Philip K.; Milne, Ross W.; Marcel, Yves L.

doi:10.1007/978-1-4615-9474-1_12

Cited by 3 publications

(3 citation statements)

References 35 publications

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“…The conformation of the apoA-I molecule on the different LpA-I complexes was evaluated by competitive solid-phase radioimmunometric assay with a panel of 16 antibodies specific for epitopes that range from the N terminus to the C terminus of the apoA-I molecule (24,(39)(40)(41). Competitive binding curves were parallel for all mAbs; therefore, ED 50 values were determined and are presented in Fig.…”

Section: Effect Of the Apoa-ii Content Of Lpa-i/a-ii Complexes On Thementioning

confidence: 99%

Apolipoprotein A-II regulates HDL stability and affects hepatic lipase association and activity

Boucher

Ramsamy

Braschi

et al. 2004

Journal of Lipid Research

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The effect of apolipoprotein A-II (apoA-II) on the structure and stability of HDL has been investigated in reconstituted HDL particles. Purified human apoA-II was incorporated into sonicated, spherical LpA-I particles containing apoA-I, phospholipids, and various amounts of triacylglycerol (TG), diacylglycerol (DG), and/or free cholesterol. Although the addition of PC to apoA-I reduces the thermodynamic stability (free energy of denaturation) of its ␣ -helices, PC has the opposite effect on apoA-II and significantly increases its helical stability. Similarly, substitution of apoA-I with various amounts of apoA-II significantly increases the thermodynamic stability of the particle ␣ -helical structure. ApoA-II also increases the size and net negative charge of the lipoprotein particles. ApoA-II directly affects apoA-I conformation and increases the immunoreactivity of epitopes in the N and C termini of apoA-I but decreases the exposure of central domains in the molecule (residues 98-186). ApoA-II appears to increase HL association with HDL and inhibits lipid hydrolysis. ApoA-II mildly inhibits PC hydrolysis in TG-enriched particles but significantly inhibits DG hydrolysis in DG-rich LpA-I. In addition, apoA-II enhances the ability of reconstituted LpA-I particles to inhibit VLDL-TG hydrolysis by HL. Therefore, apoA-II affects both the structure and the dynamic behavior of HDL particles and selectively modifies lipid metabolism.

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Section: Effect Of the Apoa-ii Content Of Lpa-i/a-ii Complexes On Thementioning

confidence: 99%

Apolipoprotein A-II regulates HDL stability and affects hepatic lipase association and activity

Boucher

Ramsamy

Braschi

et al. 2004

Journal of Lipid Research

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“…3 ' * Although these seven distinct antigenic determinants are distributed between residues 1 to 148 on the apo A-l sequence, the predicted secondary structure of apo A-l indicates that this region of the molecule is densely packed, increasing the probability that these determinants may be spatially close to one another; 4 however, we have found them to be differentially affected by a previously unknown phenomenon that modifies the antigens during storage.…”

Section: Discussionmentioning

confidence: 67%

“…These phenomena have been observed in different degrees with monoclonal antibodies from Series 1, obtained following immunization and screening with purified apo A-l, 3 ' 4 and from Series 2, obtained following immunization and screening with native HDL. 4 …”

mentioning

confidence: 99%

Immunochemical characterization of apolipoprotein A-I from normal human plasma. In vitro modification of apo A-I antigens.

Milthorp¹,

Weech²,

Milne³

et al. 1986

Arteriosclerosis

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Two series of monoclonal antibodies (MAB) directed against apolipoprotein A-I (apo A-I) reacted differentially with freshly prepared sera or plasma. MAB from Series 1 were obtained after immunization and screening with purified apo A-I, while those from Series 2 were obtained by immunization with high density lipoprotein (HDL) and screening with both HDL and apo A-I. Series 2 MAB 5F6, 3G10, and 4F7 reacted significantly better with fresh material than material stored at 4 degrees C for longer than 1 month. Conversely, Series 1 MAB 3D4, and 6B8, and Series 2 MAB 2F1 reacted more strongly with the stored preparations. Series 2 MAB 4H1 reacted equally with stored or fresh material. The inability of 3D4 and 6B8 to react with fresh sera or plasma was not due to an inhibitor in the fresh material. Preparation of HDL from serum or plasma and delipidation of this material had no effect on the above phenomena, which appears related directly to apo A-I and not to the interaction of apo A-I with lipids. The variation of immunoreactivity with storage at 4 degrees C was also shown to be unrelated to proteolysis of apo A-I. Alkaline treatment of freshly prepared sera, HDL, or apo HDL with sodium hydroxide simulated the effect of storage, allowing this material to react strongly with MAB 3D4, 6B8. As expected, there was a decrease in the reactivity of MAB 5F6 with alkali-treated fresh material compared to untreated fresh material. However, further investigation showed that alkaline treatment does not completely mimic the effect of storage. MAB 2F1, which reacts poorly with fresh material, reacted very poorly with alkali-treated fresh material, and MAB 3G10 and 4F7, which react well with fresh material, reacted even better with alkali-treated fresh material. While isoelectric focusing of apo HDL prepared from stored serum showed a redistribution of apo A-I toward more acidic isoforms compared to fresh serum, alkaline treatment of apo HDL resulted in partial cleavage of apo A-I and in the generation of isoforms more acidic than known apo A-I isomorphs. Therefore, alkaline treatment of serum is only a partial model for antigenic modification of apo A-I upon storage. These results demonstrate that in vitro conditions (storage or alkaline treatment) selectively modify certain antigenic sites of apo A-I, but not others. This phenomenon, which is probably related to deamidation, may affect apo A-I immunoassays with either monoclonal or polyclonal antibodies.

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Factors Affecting the Expression of Apolipoprotein A-I Epitopes and Screening for Mutants

Marcel

Leblond

Raffai

et al. 1989

Human Apolipoprotein Mutants 2

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Immunological Characterization of Apolipoprotein AI from Normal Human Plasma: Mapping of Antigenic Determinants

Cited by 3 publications

References 35 publications

Apolipoprotein A-II regulates HDL stability and affects hepatic lipase association and activity

Apolipoprotein A-II regulates HDL stability and affects hepatic lipase association and activity

Immunochemical characterization of apolipoprotein A-I from normal human plasma. In vitro modification of apo A-I antigens.

Factors Affecting the Expression of Apolipoprotein A-I Epitopes and Screening for Mutants

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