Investigation of preanalytical variables impacting pathogen cell-free DNA in blood and urine.
Journal of clinical microbiology
Peptide specific monoclonal antibodies of Leptospiral LigA for acute diagnosis of leptospirosis
2017; 7: 3250
Pathogen cell-free DNA (pcfDNA) in blood and urine is an attractive biomarker; however, the impact of preanalytical factors is not well understood.Blood and urine samples from healthy donors spiked with cfDNA from Mycobacterium tuberculosis, Salmonella enterica, Aspergillus fumigatus and EBV, and samples from tuberculosis patients were used to evaluate the impact of blood collection tube, urine preservative, processing delay, processing method, freezing and thawing, and sample volume on pcfDNA. PCR cycle threshold (CT) was used to measure amplifiable cfDNA.In spiked samples, median CT for M. tuberculosis, S. enterica, and EBV cfDNA was significantly lower in blood collected in K2EDTA than Streck and PAXgene blood collection tubes, and significantly lower in EDTA-urine than Streck-urine. Blood and urine samples from TB patients preserved with K2EDTA and Tris-EDTA, respectively, showed significantly lower median M. tuberculosis CT compared with Streck blood collection tube and urine preservative. Processing delay increased median pathogen CT for Streck and PAXgene but not K2EDTA blood samples, and for urine preserved with Streck reagent but not EDTA. Double spin compared with single spin plasma separation increased median pathogen CT regardless of blood collection tube. No differences were observed between whole urine and supernatant, and between fresh and thawed plasma and urine after 24 weeks at -80 °C. Larger plasma and urine volume in contrived and patient samples showed a significantly lower median M. tuberculosis CT. These findings suggest large volume single spin K2EDTA-plasma and EDTA-whole urine with up to 24-hour processing delay may optimize pcfDNA detection.
View details for DOI 10.1128/JCM.00782-19
View details for PubMedID 31511335
Leptospirosis is underdiagnosed due to low sensitivity, need of specialised equipment, and expensive reagents for serological and molecular diagnosis respectively. Considering the sensitivity, rapidity, inexpensive reagents and collection of clinical samples, the monoclonal antibody based antigen detection method from urine samples has been developed and evaluated. LigA (LK90) based B-cell specific epitopes were predicted and synthesised as peptides for the production of monoclonal antibody. LK90543: SNAQKNQGNA (amino acids: 543 to 552), and LK901110: DHHTQSSYTP (amino acids: 1110 to 1119) with VaxiJen score of 1.3719 and 1.2215, respectively were used. Thirty two and 28 urine samples from confirmed and seronegative healthy human subjects, respectively were included for the evaluation of MAb-based dot blot ELISA. The specificity of the evaluated MAbs, P1B1 and P4W2 were found to be in the range of ~93-96%. Moreover, the MAbs did not show cross-reactivity with other bacterial antigens as confirmed by IgG ELISA, further validating its specificity for leptospiral antigens. These findings suggest that the developed MAb based dot blot ELISA is a simple, rapid performed in less than 8 h, inexpensive with a ICER of $8.7/QALY, and affordable in developing countries and area where laboratory facilities are limited.
View details for DOI 10.1038/s41598-017-03658-0
View details for Web of Science ID 000403081900041
View details for PubMedID 28607384
View details for PubMedCentralID PMC5468321