Evaluation of dried blood spot collection paper blotters for avian sexing by direct PCR

Effect of storage temperature and duration on direct PCR amplification of various feather types and DBS matrices

The use of direct PCR has been pioneered over the last decade for DNA analysis of biological specimens of distinct origins. The information on how longer these specimens can be stored and amplified by direct PCR is however scanty. Such a piece of information could expedite research and diagnostic studies without compromising the reliability of results. The current study was therefore designed to analyze the effect of storage temperature and duration on direct PCR amplification of biological specimens having either low quantity or high quantity of DNA. Whole blood, dried blood spots (DBS), and feathers from chicken were stored for five years at three different temperatures, viz. room temperature (∼25 °C), 4 °C, and -20 °C. These samples were subjected to crude DNA extraction by diluting them in PBS buffer and heating at 98 °C after 1 day, 7 days, 15 days, 1 month, 3 months, 6 months, 1 year, 3 years and 5 years of storage. The crude DNA was PCR-amplified with the use of DNA sexing primers as well as DNA barcoding primers. Incubation at 98 °C for 10 min of any type of sample in PBS buffer was sufficient for crude DNA extraction. There was irrelevant impact of feather type, DBS matrix nature and storage temperature on amplification success over the period of analysis. It was possible to successfully accomplish the amplification of 96 samples with the use of routine PCR reagents within 3.5-6.0 hrs. In short, economical and fast genetic analysis of commonly used avian samples is feasible after their storage for longer time at room temperature.

Dried Blood Spots technology for veterinary applications and biological investigations: technical aspects, retrospective analysis, ongoing status and future perspectives

Dried Blood Spots (DBS) technology has become a valuable tool in medical studies, however, in veterinary and biological research DBS technology applications are still limited. Up-to-date no review has comprehensively integrated all the evidence existing across the fields, technologies and animal species. In this paper we summarize the current applications of DBS technology in the mentioned areas, and provide a scope of different types of dried sample carriers (cellulose and non-cellulose), sampling devices, applicable methods for analyte extraction and detection. Mammals, birds, insects and other species are represented as the study objects. Besides the blood, the review considers a variety of specimens, such as milk, saliva, tissue samples and others. The main applications of dried samples highlighted in the review include epidemiological surveys and monitoring for infections agents or specific antibodies for disease/vaccination control in households and wildlife. Besides the genetic investigations, the paper describes detection of environmental contaminants, pregnancy diagnosis and many other useful applications of animal dried samples. The paper also analyses dried sample stability and storage conditions for antibodies, viruses and other substances. Finally, recent developments and future research for DBS technology in veterinary medicine and biological sciences are discussed.

Cultivation and characterization of primordial germ cells from blue layer hybrids (Araucana crossbreeds) and generation of germline chimeric chickens

The chicken (Gallus gallus) is one of the most common and widespread domestic species, with an estimated total population of 25 billion birds worldwide. The vast majority of chickens in agriculture originate from hybrid breeding programs and is concentrated on few commercially used high performance lines, whereas numerous local and indigenous breeds are at risk to become extinct. To preserve the genomic resources of rare and endangered chicken breeds innovative methods are necessary. Here, we established a solid workflow for the derivation and biobanking of chicken primordial germ cells (PGCs) from blue layer hybrids. To achieve this, embryos of a cross of heterozygous blue egg layers were sampled to obtain blood derived and gonadal male as well as female PGCs of different genotypes (homozygous, heterozygous and nullizygous blue-allele bearing). The total efficiency of established PGC lines was 45% (47/104) within an average of 49 days until they reached sufficient numbers of cells for cryopreservation. The stem-cell character of the cultivated PGCs was confirmed by SSEA-1 immunostaining, and RT-PCR amplification of the pluripotency- and PGC-specific genes cPOUV, cNANOG, cDAZL and CVH. The Sleeping Beauty transposon system allowed to generate a stable integration of a Venus fluorophore reporter into the chicken genome. Finally, we demonstrated that, after re-transfer into chicken embryos, Venus-positive PGCs migrated and colonized the forming gonads. Semen samples of 13 raised cell chimeric roosters were analyzed by flow cytometry for the efficiency of germline colonization by the transferred PGCs carrying the Venus reporter and their proper differentiation into vital spermatids. Thus, we provide a proof-of-concept study for the potential use of PGCs for the cryobanking of rare breeds or rare alleles.

Comparison of three filter paperbased devices for safety and stability of viral sample collection in poultry

General diagnosis of poultry viruses primarily relies on detection of viruses in samples, but many farms are located in remote areas requiring logistic transportation. Filter paper cards are a useful technology that offer an alternative for collecting and preserving samples without hazardous exposure. The goal of this study was to compare three filter papers: the Flinders Technology Associates filter (FTA®) card, dried blood spot (DBS) card and qualitative filter paper (FP) grade 2 to collect poultry samples. In particular, we have used Newcastle disease virus (NDV) to evaluate safety and a Marek's disease virus (MDV) attenuated vaccine (CVI988) to evaluate stability of viral DNA. This experiment was divided into two parts. The first part was to determine the DNA stability and detection limit of CVI988 in samples collected in different paper supports after four storage times (3, 7, 14 and 30 days post spot). The second part was to determine the safety of papers by evaluating the viral inactivation efficacy using NDV as a representative virus. Results showed that all papers could preserve CVI988 DNA at all times, with a detection limit of 0.5 PFU/5 µl for FTA® and DBS cards, and 5 PFU/5 µl for FP. Our results showed that the NDV remained viable and infectious on the DBS card and FP, while no viable virus was detected on the FTA® card, suggesting that the FTA® card was safest to use. Therefore, the use of the DBS card and FP for infectious sample collection should be discouraged and reconsidered. RESEARCH HIGHLIGHTS The detection limits of the FTA® card, DBS card and FP for CVI988 detection were 0.5, 0.5 and 5 PFU/5 µl, respectively. All three filter papers could preserve viral DNA for at least 30 days of post spot. The DBS card and FP are not suitable for collecting NDV samples, which is one of the major economical threats for the poultry industry worldwide.

Comparison of 25-hydroxyvitamin D concentration in chimpanzee dried blood spots and serum

BACKGROUND

Dried blood spots (DBS) are used in human medicine to measure total 25-hydroxyvitamin D (25-OHD) in the blood. However, this easy and affordable sampling technique has not been evaluated in primates to measure vitamin D concentrations.

OBJECTIVES

We aimed to compare 25-OHD measurements in chimpanzee serum at two different laboratories and determine the precision and accuracy of the DBS method by comparing DBS and serum results.

METHODS

Blood samples from 17 captive chimpanzees were collected, and 25-OHD₃ and 25-OHD₂ were measured in serum at two accredited laboratories using liquid chromatography-tandem mass spectrometry. The same analytes were measured on DBS cards, and results were compared with that of serum. Data were assessed using the Spearman correlation, Deming regression, and Bland-Altman analyses.

RESULTS

The correlation coefficient between the two measurements in serum was r_s  = .51 (P = .04), and the mean bias was -1.25 ± 14.83. When comparing 25-OHD concentrations measured in DBS and serum at the same laboratory, the r_s was 0.7 (P = .002), and the mean bias was 1.42 ± 14.58. Estimated intra-assay and inter-assay coefficients of variation for DBS results were 6% and 12.6%, respectively.

CONCLUSIONS

Although substantial analytical variability was found in 25-OHD measurements regardless of the sample type, the identification of both constant and proportional error and wider limits of agreement with the DBS technique makes the interpretation of DBS results challenging, especially for values close to clinical cut-off points. The DBS and serum methods were not interchangeable, and further studies are needed to validate DBS samples for vitamin D measurements in chimpanzees.

No evidence for a link between forest herbicides and offspring sex ratio in a migratory songbird using high-throughput molecular sexing

Many species that use or require early-successional forest are of conservation concern, including a number of songbirds that have experienced long-term population declines. In this study, our initial goal was to test whether herbicide application intensity was linked to offspring sex ratio in the White-crowned Sparrow (Zonotrichia leucophrys), a species that requires early-successional forest within forested landscapes. However, a rapid and accurate method using direct PCR to sex a large sample of birds (n > 1000 individuals) was unavailable, so our secondary goal was to develop a new approach for rapidly determine offspring sex. We obtained blood samples from sparrow young during the 2013-2014 breeding seasons in regenerating conifer plantations that were treated with one of four treatments (i.e. light, moderate, and intensive herbicide application, or no-spray control). We then optimized a protocol that used a commercially available, direct PCR kit to amplify sex-specific fragments of the CHD (chromo-helicase-DNA-binding) genes directly from whole blood stored in lysis buffer. Using this approach, we found no evidence that offspring sex ratio was linked to herbicide application intensity or to food availability across herbicide treatments. Our molecular sexing technique was 100% accurate when validated on known-sex adults, and 99.9% of our blood samples amplified successfully after being stored in lysis buffer stored for up to 3 years. The application of direct PCR for sexing birds eliminated the need for DNA extraction and substantially reduced sample processing time, cost, and the opportunity for errors during the extraction step. We conclude that forest herbicide application intensity does not influence sparrow offspring sex ratio in our study system, and that our approach provides a rapid, accurate, and tractable method for sexing birds that can facilitate studies that require processing of a large number of samples.

Strip-dried whole milk sampling technique for progesterone detection in cows by ELISA

New sampling format of whole cows' milk in strip-dried form was proposed. Few methodological issues of whole milk progesterone ELISA using samples dried on a membrane carrier in a form of strip were investigated and optimized: width of a strip, shape of punched/cut-off part of membrane, sample application method. It was shown that distribution of the hormone along narrow strip was even except the initial part of a strip (the first 0.5 × 0.5cm piece) where recovered concentration of progesterone was higher. Storage stability of progesterone in strip-dried whole cows' milk samples at 4°C, ambient temperature, 37°C and 60°C was investigated. Rising of the detected progesterone concentration over storage period at elevated temperatures was observed predominantly in milk samples with low hormone concentration (from non-pregnant cows). Strip-dried whole milk samples can be used for collection, transportation, storage and ELISA analysis of progesterone level which is correlated with reproductive status of cows.