Determination of Immunoglobulin G in Bovine Colostrum and Milk Powders, and in Dietary Supplements of Bovine Origin by Protein G Affinity Liquid Chromatography: Collaborative Study

An AOAC collaborative study was conducted to evaluate an affinity LC procedure for measuring immunoglobulin G (IgG) in selected dairy powders. The powders were extracted with 0.15 M sodium chloride solution and the pH was adjusted to 4.6 to precipitate caseins, which would otherwise lead to an overestimation of IgG. The analyte was then bound to a commercially available Protein G affinity cartridge and selectively eluted with a glycine buffer at pH 2.5. Detection was at 280 nm and quantification was made against a calibration curve prepared from bovine serum IgG. The samples analyzed included the likely matrixes for which this assay will find commercial use, namely, high- and low-protein-content colostrum powders, tablets containing colostrum powder, and some IgG-containing dairy powders; milk protein isolate, whey protein concentrate, and skim milk powder. Eleven laboratories provided data for the study and assayed blind duplicates of six materials. The repeatability RSD values ranged from 2.1 to 4.2 and the reproducibility RSD values ranged from 6.4 to 18.5. The Protein G method with casein removal has adequate reproducibility for measuring IgG in colostrum-derived powders that are traded on the basis of IgG content as a colostral marker.

Determination of β-Carotene in Supplements and Raw Materials by Reversed-Phase High Pressure Liquid Chromatography: Collaborative Study

Twelve laboratories representing 4 countries participated in an interlaboratory study conducted to determine all-trans-β-carotene and total β-carotene in dietary supplements and raw materials. Thirteen samples were sent as blind duplicates to the collaborators. Results obtained from 11 laboratories are reported. For products composed as softgels and tablets that were analyzed for total β-carotene, the reproducibility relative standard deviation (RSDR) ranged from 3.35 to 23.09% and the HorRat values ranged from 1.06 to 3.72. For these products analyzed for trans β-carotene, the reproducibility relative standard deviation (RSDR) ranged from 4.28 to 22.76% and the HorRat values ranged from 0.92 to 3.37. The RSDr and HorRat values in the analysis of a beadlet raw material were substantial and it is believed that the variability within the material itself introduced significant variation in subsampling. The method uses high pressure liquid chromatography (LC) in the reversed-phase mode with visible light absorbance for detection and quantitation. If high levels of α-carotenes are present, a second LC system is used for additional separation and quantitation of the carotene species. It is recommended that the method be adopted as an AOAC Official Method.

Determination of immunoglobulin G in bovine colostrum and milk powders, and in dietary supplements of bovine origin by protein G affinity liquid chromatography: collaborative study

An AOAC collaborative study was conducted to evaluate an affinity LC procedure for measuring immunoglobulin G (IgG) in selected dairy powders. The powders were extracted with 0.15 M sodium chloride solution and the pH was adjusted to 4.6 to precipitate caseins, which would otherwise lead to an overestimation of IgG. The analyte was then bound to a commercially available Protein G affinity cartridge and selectively eluted with a glycine buffer at pH 2.5. Detection was at 280 nm and quantification was made against a calibration curve prepared from bovine serum IgG. The samples analyzed included the likely matrixes for which this assay will find commercial use, namely, high- and low-protein-content colostrum powders, tablets containing colostrum powder, and some IgG-containing dairy powders; milk protein isolate, whey protein concentrate, and skim milk powder. Eleven laboratories provided data for the study and assayed blind duplicates of six materials. The repeatability RSD values ranged from 2.1 to 4.2% and the reproducibility RSD values ranged from 6.4 to 18.5%. The Protein G method with casein removal has adequate reproducibility for measuring IgG in colostrum-derived powders that are traded on the basis of IgG content as a colostral marker.

The immune response to a DNA vaccine can be modulated by co-delivery of cytokine genes using a DNA prime-protein boost strategy

A large-scale DNA vaccination trial was performed in sheep to investigate whether co-delivery of the cytokine genes IL-4, IL-5, IL-15, GM-CSF or IFN-gamma could modulate the immune response generated to an antigen, in a DNA prime-recombinant protein boost regime. Vaccination with the recombinant EG95 protein has been shown to induce protection in sheep from Echinococcus granulosus infection, the causative agent of hydatid disease. Here we demonstrate that vaccination with DNA encoding EG95 effectively primed the humoral response, as judged by high IgG anti-EG95 titres detected one-week after a boost with the recombinant protein. However, by two weeks after protein-boost the titres in the control group had reached levels similar to the groups primed with EG95 DNA. Priming with two doses of DNA vaccine followed by boosting with recombinant protein induced a predominantly IgG1 response. In contrast, priming and boosting with the protein vaccine generated a strong IgG2 response. Co-delivery of the EG95 DNA vaccine with DNA encoding GM-CSF enhanced the antibody titre to EG95 while co-delivery of IFN-gamma or IL-4 encoding DNA appeared to reduce the ability of the DNA vaccine to prime an IgG antibody response. This study has demonstrated the efficacy of the co-delivery of cytokines to modulate immune responses generated in a DNA prime-protein boost strategy.

Determination of niacin in infant formula by solid-phase extraction and anion-exchange liquid chromatography

A peer-verified, solid-phase extraction (SPE)/anion exchange liquid chromatographic method is presented for the determination of niacin in milk-based and soy-based infant formula. Analysis is in 3 steps: test sample digestion, extraction/cleanup, and liquid chromatography (LC). Digestion uses a standard AOAC digestion procedure that involves autoclaving at 121 degrees C for 45 min in (1 + 1) H2SO4 to free endogenous niacin from protein and to convert added niacinamide to niacin. The digest solution is adjusted to pH 6.5 with 7.5M NaOH. Acidification to pH <1.0 with (1 + 1) H2SO4 precipitates the protein. The clarified solution is then filtered, and the filtrate is brought to volume. SPE of niacin is accomplished by passing an aliquot of the digest solution through an aromatic sulfonic acid-SPE (ArSCX-SPE) column. After the column is washed with methanol and water to remove extraneous material, the niacin is eluted with 0.25M sodium acetate/acetic acid buffer at pH 5.6. An anion-exchange polystyrene-divinylbenzene column with 0.1 M sodium acetate/acetic acid buffer at pH 4.0 is used for LC. Niacin is determined by UV detection at 260 nm. A standard curve is prepared by passing known amounts of niacin through the ArSCX-SPE columns used for niacin extraction. The following values for x and relative standard deviation (RSD) were obtained for National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1846 Infant Formula with a certified value for niacin of 63.3 +/- 7.6 microg/g: Submitting laboratory.-- x = 59.7 +/- 4.0 microg/g; RSD = >6.7%; confidence interval (CI) = +/- 1.4 microg/g; n = 27. Peer laboratory.--x = 56.6 +/- 6.6 microg/g; RSD = >11.7%; CI =+/- 4.1 microg/g; n = 8.

Inhibition of neutral endopeptidase, the degradative enzyme for natriuretic peptides, in rat kidney after oral SCH 42495

1. Inhibition of neutral endopeptidase (NEP), the degradative enzyme for atrial natriuretic peptide, was studied in vitro and in vivo using a previously characterized NEP inhibitor radioligand, 125I-labelled RB104. 2. SCH 42354, the active di-acid of the ethylester prodrug, SCH 42495, caused a concentration-dependent displacement of 125I-labelled RB104 from rat renal NEP. The concentration of SCH 42354 that displaced 50% of radioligand bound to the enzyme NEP (IC50) was 3.3 +/- 0.1 nmol/l (mean +/- SEM). Enalaprilat, an angiotensin converting enzyme inhibitor, did not displace 125I-labelled RB104 in concentrations up to 10 mumol/l. 3. In adult normotensive Sprague-Dawley rats, oral SCH 42495 (3-300 mg/kg) caused significant inhibition of renal NEP (P < 0.001). SCH 42495 had no effect on renal or plasma angiotensin converting enzyme activity, but high-dose SCH 42495 (300 mg/kg) caused a significant increase in plasma renin activity (P < 0.01). 4. In a time course study, oral SCH 42495 (30 mg/kg) caused rapid (within 30 min) and significant inhibition of renal NEP for up to 48 h (P < 0.001). No changes in plasma atrial natriuretic peptide or plasma angiotensin converting enzyme activity were seen. 5. These data provide evidence that short-term administration of the NEP inhibitor SCH 42495 results in inhibition of renal NEP and does not inhibit the circulating or the tissue renin-angiotensin system. The NEP inhibitor radioligand 125I-labelled RB104, is a useful tool to study tissue NEP inhibition after administration of NEP inhibitors.

Changes in plasma vitamin levels in the first 48 hours after onset of acute myocardial infarction

To establish whether plasma vitamin measurements made after acute myocardial infarction (AMI) can be used in case-control studies of coronary artery disease, the short-term effect of AMI on plasma concentrations of 25-hydroxyvitamin D3, beta-carotene, vitamin E and retinol was investigated. Sequential measures of these vitamins were made during the first 48 hours after AMI in 13 patients admitted to the hospital within 4 hours after the onset of symptoms. Plasma levels of 25-hydroxyvitamin D did not change significantly during the first 12 hours after onset of symptoms. Beta-carotene levels increased significantly (p less than 0.05) during the first 12 hours and then decreased, whereas levels of vitamin E and retinol progressively decreased during the first 48 hours by 26 and 25%, respectively. These results suggest that, of these vitamins, only plasma measurements of 25-hydroxyvitamin D3 collected within 12 hours of onset of symptoms may provide reliable information for case-control studies of AMI.