Vitamin D Antibodies in Systemic Sclerosis Patients: Findings and Clinical Correlations.

BACKGROUND: Vitamin D is a pivotal factor in calcium homeostasis and exerts immunomodulatory effects. Hypovitamin D has been demonstrated in systemic sclerosis (SSc) patients and may be related to more severe disease of longer duration and with extensive skin involvement. OBJECTIVES: To seek anti-vitamin D antibodies in SSc patients, as found by previous research in patients with systemic lupus erythematosus (SLE). METHODS: The study included 54 SSc patients and 41 volunteers. Immunoglobulin (Ig) G and IgM autoantibody levels against 25(OH)D and 1,25(OH)D were obtained from patients and controls and were compared. SSc patients were assessed for autoantibody profile and disease severity. RESULTS: Vitamin D antibodies were present in 87% of SSc patients and 42% of controls. Higher levels of anti-25(OH)D IgM antibodies were detected in SSc patients compared to controls (0.48 ± 0.22 vs. 0.29 ± 0.29, respectively, P = 0.002); however, IgG levels were lower in the SSc patients. No such discriminative. effect was found regarding anti-1,25(OH)D antibodies between SSc and controls. No correlation was found between,vitamin D antibodies and other autoantibodies, disease severity, or target organ damage. CONCLUSIONS: To the best of our knowledge; this is the first study of these novel, anti-vitamin D antibodies in SSc patients and the first time a correlation between IgM 25(OH) vitamin D antibodies and scleroderma has been identified. Further research on the pathophysiological significance and therapeutic potential of vitamin D is required.

Impact of assay design on test performance: lessons learned from 25-hydroxyvitamin D.

BACKGROUND: Current automated immunoassays vary significantly in many aspects of their design. This study sought to establish if the theoretical advantages and disadvantages associated with different design formats of automated 25-hydroxyvitamin D (25-OHD) assays are translated into variations in assay performance in practice. METHODS: 25-OHD was measured in 1236 samples using automated assays from Abbott, DiaSorin, Roche and Siemens. A subset of 362 samples had up to three liquid chromatography-tandem mass spectrometry 25-OHD analyses performed. 25-OHD2 recovery, dilution recovery, human anti-animal antibody (HAAA) interference, 3-epi-25-OHD3 cross-reactivity and precision of the automated assays were evaluated. RESULTS: The assay that combined release of 25-OHD with analyte capture in a single step showed the most accurate 25-OHD2 recovery and the best dilution recovery. The use of vitamin D binding protein (DBP) as the capture moiety was associated with 25-OHD2 under-recovery, a trend consistent with 3-epi-25-OHD3 cross-reactivity and immunity to HAAA interference. Assays using animal-derived antibodies did not show 3-epi-25-OHD3 cross-reactivity but were variably susceptible to HAAA interference. Not combining 25-OHD release and capture in one step and use of biotin-streptavidin interaction for solid phase separation were features of the assays with inferior accuracy for diluted samples. The assays that used a backfill assay format showed the best precision at high concentrations but this design did not guarantee precision at low 25-OHD concentrations. CONCLUSIONS: Variations in design among automated 25-OHD assays influence their performance characteristics. Consideration of the details of assay design is therefore important when selecting and validating new assays.

High vitamin D status in younger individuals is associated with low circulating thyrotropin.

BACKGROUND: Vitamin D is an immunomodulator and may affect autoimmune thyroid diseases. Vitamin D has also been shown to influence thyrocytes directly by attenuating thyrotropin (TSH)-stimulated iodide uptake and cell growth. However, it is unclear how vitamin D status is related to TSH at the population level. The goal of the present study was to investigate the relationship between vitamin D status and TSH levels according to thyroid autoantibodies in a population-based health survey in Thailand. METHODS: A total of 2582 adults, aged 15-98 years, were randomly selected according to the geographical region from the Thailand 4th National Health Examination Survey sample. By study design, the sexes were equally represented. Serum levels of 25-hydroxyvitamin D [25(OH)D], TSH, the thyroid peroxidase antibody (TPOAb), and the thyroglobulin antibody (TgAb) were measured in all subjects. RESULTS: The mean age was 55.0±0.4 (SE) years. In subjects positive for serum TgAb, serum TSH levels were higher, whereas total serum 25(OH)D levels were lower. In addition, the prevalence of vitamin D insufficiency in TgAb-positive subjects was significantly higher than that observed in TPOAb- and TgAb-negative subjects, whether based on cutoff values of 20 or 30 ng/mL: 8.3% vs. 5.6%, p<0.05; or 47.6% vs. 42.0%, p<0.05, respectively. However, vitamin D status was not associated with positive TPOAb and/or TgAb after controlling for sex and age. To explore the probable interaction between vitamin D status and age on serum TSH, analyses were performed according to age tertiles; it was found that higher 25(OH)D levels were independently associated with lower TSH, but only in subjects in the lowest age tertile. CONCLUSIONS: This population-based study showed that high vitamin D status in younger individuals is associated with low circulating TSH.

Toll-like receptor 8 ligands activate a vitamin D mediated autophagic response that inhibits human immunodeficiency virus type 1.

Toll-like receptors (TLR) are important in recognizing microbial pathogens and triggering host innate immune responses, including autophagy, and in the mediation of immune activation during human immunodeficiency virus type-1 (HIV) infection. We report here that TLR8 activation in human macrophages induces the expression of the human cathelicidin microbial peptide (CAMP), the vitamin D receptor (VDR) and cytochrome P450, family 27, subfamily B, polypeptide 1 (CYP27B1), which 1α-hydroxylates the inactive form of vitamin D, 25-hydroxycholecalciferol, into its biologically active metabolite. Moreover, we demonstrate using RNA interference, chemical inhibitors and vitamin D deficient media that TLR8 agonists inhibit HIV through a vitamin D and CAMP dependent autophagic mechanism. These data support an important role for vitamin D in the control of HIV infection, and provide a biological explanation for the benefits of vitamin D. These findings also provide new insights into potential novel targets to prevent and treat HIV infection.

Validation of the first automated chemiluminescence protein-binding assay for the detection of 25-hydroxycalciferol.

BACKGROUND: Measurement of 25-hydroxyvitamin D, 25(OH)D is the ideal parameter to indicate the access of the organism to vitamin D. Numerous studies have shown that serum levels of 25(OH)D are the best markers of vitamin D deficiency, normal vitamin D supply or vitamin D intoxication. The aim of the study was to validate a beta-site version of the first fully automated chemiluminescence protein-binding assay (CLPBA) for the detection of 25-hydroxycalciferol. METHODS: The newly developed CLPBA run on the Nichols Advantage Specialty Systems was compared to an inhouse radioimmunoassay (RIA), focussing on the major assay features such as imprecision, functional sensitivity, linearity, method comparison and suitability of serum or EDTA-plasma as well as establishing a preliminary reference range. RESULTS: Within-run imprecision is approximately 4.5% and total imprecision approximately 6% respectively (NCCLS protocol), functional sensitivity 6.8 microg/l. With mean recovery values of 96.9% and 98.7% for two diluted serum samples linearity is given over the measuring range. Due to different calibrations used for RIA and CLPBA the CLPBA reads approximately 70% lower (CLPBA = 0.321xRIA + 0.571, n = 469) but correlates well with the RIA (r = 0.9045). Method comparison with HPLC reveals a regression line of CLPBA = 0.8921xHPLC + 0.1358 (n = 54, r = 0.9117). Serum or EDTA-plasma is not equally suitable. Plasma samples read on average 5 microg/l higher than serum samples. The preliminary reference range is 11 microg/l to 84 microg/l (95% of all values). CONCLUSION: The validated 25(OH)D CLPBA is a very promising alternative to established commercially available 25(OH)D measurements and will, with its use on a fully automated platform, simplify the reliable quantification of 25-hydroxycalciferol significantly.