Measurement of Nutritional and Inflammatory Biomarkers in Dry Plasma Spots (DPS) (P10-097-19)

Objectives

Conduct time and temperature stability experiments on Nutritional Biomarkers (NBs) and inflammation markers extracted from ViveBio Dry Plasma Spots (DPS).

Methods

Blood samples of 3 hematocrits (20, 30 and 45%) were created by combining purchased red blood cells (RBC) and sera. Blood samples of 35 µL were loaded onto ViveBio plasma separators. The underlying pads with plasma were stored at 45°, 23°, 4°, -20° and -70°C. Samples were tested on days 0, 1, 3, 7, 14, 28, 84 and 168.

Ferritin, Retinol Binding Protein (RBP4), soluble Transferrin Receptors (sTfR), Thyroglobulin (Tg), α-acid Glycoprotein (AGP), and C-Reactive Protein (CRP) were measured using the Quansys Biosciences, Q-Plex Micronutrient Array (Q-Plex). Values measured in the liquid sera were used as reference values for the DPS.

Red blood cell (RBC) folates and serum vitamin B12 were measured using a 96 well plate microbiological assay (ALPCO-Immundiagnostik AG).

25OH-Vitamin D3, Retinol, Methylmalonic acid (MMA) and Homocysteine (HCY) were measured using LC-MS/MS.

The Q-Plex was compared at 3 independent laboratories using a group of 80 whole blood samples, non-spiked and spiked with AGP, CRP, HRP2 and sTfR. Liquid plasma and extracted plasma from ViveBio pads were generated and stored at -80°C four weeks prior to assay.

Results

Overall, the measured values for Ferritin, RBP4, Tg, AGP, CRP, 25OH-D, Retinol and MMA decrease with increasing storage temperature and length of storage. Ferritin and Tg exhibited the best stability at 16.8% and 8.0% over a 6 month period. Vitamin B12 exhibited very poor stability declining to below the LOQ within day 3. Most of the NBs at 1 month correlated well with liquid plasma values (r2 = 0.42 to 0.99) (AGP at 23°C, r2 = 0.428; at -70°C r2 = 0.990 Ferritin stored at 23°C, r2 = 0.854; at -70°C r2 = 0.992; Thyroglobulin at 23°C, r2 = 0.916; at -70°C r2 = 0.830).

Conclusions

We have demonstrated that NBs can be analyzed in low volumes of DPS generated by the ViveBio plasma separator. The Q-Plex performed reproducibly on split samples among 3 labs. These tools offer great potential to improve nutritional assessment in population studies.

Funding Sources

Funding provided by the Bill and Melinda Gates foundation.

Measurement of micronutrient deficiency associated biomarkers in dried blood spots using a multiplexed immunoarray

Simplifying blood collection is often critical when collecting specimens in remote and/or austere settings. The use of dried blood spots (DBS) offers a practical collection method suitable for a wide variety of analytes. A small volume of whole blood can be obtained rapidly through a minimally invasive heel- or finger-stick using a disposable safety lancet. Once dried, the samples require no further processing, are stable for months or longer, pose minimal risk of disease transmission, and are easy to ship. DBS are often used in demographic health surveys to assess infectious disease status in vulnerable populations. These samples can be used to screen biomarkers of micronutrient deficiency (MND) and inflammation. We recently described a multiplexed immunoarray, the Q-plex human micronutrient array, which can simultaneously quantify seven biomarkers related to MND, inflammation and malarial antigenemia using plasma (alpha-1-acid glycoprotein, C-reactive protein, ferritin, histidine-rich protein 2, retinol binding protein, soluble transferrin receptor, and thyroglobulin). In this work, we present a protocol for preparing eluates from DBS samples and their measurement using a modified protocol for this new tool. We evaluated the concordance of analyte concentrations (excluding ferritin) from a panel ninety samples of DBS prepared from anticoagulated venous blood and paired K2-EDTA plasma. The results show high correlation between DBS eluates and wet plasma for five of the six analytes screened, suggesting the Q-plex human micronutrient array can be used with DBS samples, but also highlighting that anticoagulants can have a negative effects on some test components.

Simultaneous assessment of iodine, iron, vitamin A, malarial antigenemia, and inflammation status biomarkers via a multiplex immunoassay method on a population of pregnant women from Niger

Deficiencies of vitamin A, iron, and iodine are major public health concerns in many low- and middle-income countries, but information on their status in populations is often lacking due to high costs and logistical challenges associated with assessing micronutrient status. Accurate, user-friendly, and low-cost analytical tools are needed to allow large-scale population surveys on micronutrient status. We present the expansion of a 7-plex protein microarray tool for the simultaneous measurement of up to seven biomarkers with relevance to the assessment of the key micronutrients iron, iodine, and vitamin A, and inflammation and malaria biomarkers: α-1-acid glycoprotein, C-reactive protein, ferritin, retinol binding protein 4, soluble transferrin receptor, thyroglobulin, and histidine-rich protein II. Assay performance was assessed using international reference standards and then verified by comparing the multiplexed and conventional immunoassay results on a training panel of plasma samples collected from US adults. These data were used to assign nominal concentrations to the calibrators of the assay to further improve performance which was then assessed by interrogating plasma samples from a cohort of pregnant women from Niger. The correlation between assays for each biomarker measured from this cohort was typically good, with the exception of thyroglobulin, and the sensitivity ranged from 74% to 93%, and specificity from 81% to 98%. The 7-Plex micronutrient assay has the potential for use as an affordable tool for population surveillance of vitamin A, iron, and iodine deficiencies as well as falciparum malarial parasitemia infectivity and inflammation. The assay is easy-to-use, requires minimal sample volume, and is scalable, rapid, and accurate—needing only a low-cost reader and basic equipment present in most reference laboratory settings and so may be employed by low and middle income countries for micronutrient surveillance to inform on status in key populations. Micronutrient deficiencies including iron, iodine, and vitamin A affect a significant portion of the world’s population. Efforts to assess the prevalence of these deficiencies in vulnerable populations are challenging, partly due to measurement tools that are inadequate for assessing multiple micronutrients in large-scale population surveys. We have developed a 7-plex immunoassay for the simultaneous measurement of seven biomarkers relevant to assessing iodine, iron, and vitamin A status, inflammation and Plasmodium falciparum parasitemia by measuring levels of thyroglobulin, ferritin, soluble transferrin receptor, retinol binding protein 4, α-1-acid glycoprotein, C-reactive protein, and histidine-rich protein II. This 7-plex immunoassay technique has potential as a rapid and effective tool for use in large-scale surveys and assessments of nutrition intervention programs in low- and middle-income countries.

Pathogenesis of pulmonary aspergillosis. Granulocytopenia versus cyclosporine and methylprednisolone-induced immunosuppression

Patients with chemotherapy-induced granulocytopenia for neoplastic diseases and those receiving cyclosporin A plus corticosteroids for prevention and treatment of organ transplant rejection are two immunologically distinct patient populations with high risks for development of invasive pulmonary aspergillosis. In order to compare the pathogenesis of aspergillosis in these two high-risk populations and to further characterize the role of cyclosporin A in development of pulmonary aspergillosis, we studied the patterns of infection and inflammation in two clinically applicable rabbit models of invasive pulmonary aspergillosis. There were striking differences in the patterns of infection and inflammation of invasive pulmonary aspergillosis according to the type of underlying immune defect. Among rabbits challenged with the same intratracheal inoculum, there was a 100% mortality for invasive pulmonary aspergillosis in profoundly granulocytopenic rabbits in comparison with a 100% mortality for invasive pulmonary aspergillosis in profoundly granulocytopenic rabbits in comparison with a 100% survival in rabbits immunosuppressed with cyclosporin A plus methylprednisolone (CsA+MP). Lesions of pulmonary aspergillosis in granulocytopenic rabbits consisted predominantly of coagulative necrosis, intraalveolar hemorrhage, and scant mononuclear inflammatory infiltrate. By comparison, pulmonary foci in rabbits immunosuppressed by CsA+MP consisted mainly of neutrophilic and monocytic infiltrates, inflammatory necrosis, and scant intraalveolar hemorrhage. There was extensive infiltration by hyphae with angioinvasion in granulocytopenic rabbits, whereas conidia in various stages of germination predominated in CsA+MP treated animals in which there was a paucity of hyphae or angioinvasion. Extrapulmonary disease predominated in granulocytopenic rabbits. Methylprednisolone was the major immunosuppressive drug in rabbits treated with CsA+MP. Cyclosporin A alone did not increase the progression of pulmonary aspergillosis and did so only when used chronically with methylprednisolone.

Antifungal effects of the nonlinear pharmacokinetics of cilofungin, a 1,3-beta-glucan synthetase inhibitor, during continuous and intermittent intravenous infusions in treatment of experimental disseminated candidiasis

Cilofungin (LY-121019) is a fungicidal cell wall-active 1,3-beta-glucan synthetase inhibitor with a short plasma half-life and saturable nonlinear plasma pharmacokinetics. To optimize the in vivo efficacy of this compound, we studied the effects of its linear and nonlinear pharmacokinetics during continuous versus intermittent intravenous infusion of cilofungin in the treatment of experimental disseminated candidiasis in persistently granulocytopenic rabbits. Six groups of rabbits were studied, untreated controls (n = 32) and five cilofungin dosage regimen groups consisting of the following: 25 mg/kg of body weight intravenously twice daily (VLoINT) (n = 9); 50 mg/kg twice daily (LoINT) (n = 9); 90 mg/kg twice daily (HiINT) (n = 11); 5 mg/kg/h for 18 h/day (LoCI) (n = 7); and 10 mg/kg/h for 18 h/day (HiCI) (n = 7). All regimens achieved plasma concentrations exceeding the MIC for Candida albicans (0.25 microgram/ml). In vitro timed kill assays found that the fungicidal activity and rate of kill by cilofungin above the MIC for C. albicans was concentration dependent. At the lower dosage regimens (VLoINT, LoINT, and LoCI), cilofungin followed linear plasma pharmacokinetics, whereas at higher doses (HiCI and HiINT), nonlinear kinetics consistent with a saturated elimination pathway(s) were observed. Only HiCI and HiINT produced a 10(3)- to 10(4)-fold reduction in CFU per gram in candidiasis of the brain (P less than or equal to 0.001). HiCI and HiINT also significantly reduced infection in the choroid (P less than or equal to 0.05). All regimens, except VLoInt, significantly (P less than or equal to 0.01) reduced tissue infections in lung, liver, spleen, and kidney. However, only the regimens with nonlinear saturation kinetics (HiCI and HiINT) produced a 10(6) reduction in the spleen and a > 10(5) reduction of C. albicans in the kidney and liver. A simple doubling of the dosage from LoCI to HiCI resulted in tissue concentrations that were 10 times higher and a 10(2)- to 10(4)-fold-greater antifungal effect. There was a direct correlation (r2 = 0.83) between tissue concentrations of cilofungin and antifungal activity. Thus, continuous and intermittent infusion dosage regimens that elicit nonlinear saturation plasma pharmacokinetics of cilofungin were associated with increased antifungal activity against experimental disseminated candidiasis.

Tobramycin-furosemide interaction

A 70-year-old, 75-kg white female with a history of congestive heart failure was admitted with a two-week episode of progressive shortness of breath, increased abdominal distension, and ankle edema. Sputum Gram stains revealed gram-negative bacilli, and the patient was started on a loading dose of tobramycin 150 mg (2 mg/kg) over 30 minutes. The peak tobramycin level was 3.7 micrograms/ml drawn 45 minutes after the infusion was completed. Seven hours after the loading dose infusion, a trough level of 1.5 micrograms/ml was obtained. Based on the Sawchuk-Zaske method, the patient was started on a regimen of tobramycin 180 mg iv q8h. The following day, the patient received furosemide 120 mg iv. The trough and peak levels drawn 30 minutes before and after the fourth dose of tobramycin were 5.3 micrograms/ml and 16.2 micrograms/ml, respectively. The half-life of tobramycin remained relatively constant, while the volume of distribution decreased 40 percent after the administration of furosemide. This case illustrates that moderate doses of furosemide, administered to edematous patients receiving tobramycin, may cause an increase in both peak and trough levels, thus increasing the chances of ototoxicity and nephrotoxicity.