Ilpo Kuronen

Diagnostic rapid tests for acute hantavirus infections: specific tests for Hantaan, Dobrava and Puumala viruses versus a hantavirus combination test.

Hantaviruses infecting humans in Eurasia include Hantaan, Seoul, Puumala and the closely related Dobrava and Saaremaa viruses. These viruses are causative agents of hemorrhagic fever with renal syndrome (HFRS), which is recognized as a severe health care problem in several countries. Diagnostics of hantavirus infections relies on serology, performed principally with enzyme immunoassay (EIA) or immunofluorescence assay (IFA). We developed four 5-min immunochromatographic IgM-antibody tests for diagnostics of acute Puumala, Dobrava and Hantaan virus infections and a similar combination test to detect all Eurasian pathogenic hantavirus infections. We evaluated the assays using 100 fingertip blood samples collected randomly from Finnish volunteers, 28 confirmed hantavirus IgM-negative sera, and 77 sera from patients with acute infections of various hantaviruses. The specificities and sensitivities of the Puumala-, Dobrava- and Hantaan virus -specific tests varied from 96 to 100%, whereas, the combination test showed 96% specificity and 80 to 93% sensitivity. Cross-reactions were observed commonly between the Dobrava and the Hantaan virus tests, but only rarely between the Puumala and the Hantaan virus, or the Puumala and the Dobrava virus, tests. Altogether, the rapid tests showed less cross-reactivity than the respective EIA tests. According to the results, the performance of these tests meets well the requirements for diagnostic use. Nevertheless, the specific one-antigen tests were markedly more sensitive than the combination test. However, if optimized, a combination test would be suitable for regions where several hantaviruses circulate.

New Immunochromatographic Rapid Test for Diagnosis of Acute Puumala Virus Infection

ABSTRACT A new immunochromatographic rapid test, POC PUUMALA (Erilab Ltd., Kuopio, Finland), for detection of acute-phase Puumala virus (PUUV) infection was developed based on a highly purified baculovirus-expressed PUUV nucleocapsid protein antigen and lateral immunodiffusion techniques. After addition of sample (5 μl of serum, plasma, or fingertip blood) and buffer, PUUV-specific immunoglobulin M (IgM) antibodies, if present, together with the gold-conjugated anti-human IgM, formed a specific colored line in 5 min. The sensitivity and specificity of the test were evaluated with 200 serum samples and 30 fingertip blood samples. The reference method for the serum samples was a μ-capture enzyme immunoassay (EIA) for IgM and an immunofluorescence assay (IFA) for IgG antibodies. The analytical sensitivity and specificity of the rapid test were 100 and 99%, respectively, for unfrozen serum samples (n = 103; 12 PUUV IgM-positive samples). When freeze-thawed serum samples were used, the sensitivity and specificity were each 97.1% (n = 70; 35 PUUV IgM-positive samples). The specificity of the test was 96.2% for 27 serum samples with nonspecific IgM antibodies or rheumatoid factor (RF). The fingertip blood samples (n= 30) were negative, but they gave clear positive results when spiked with IgM-positive sera (n = 20). The results were in good agreement with the standard diagnostic methods. The rapid performance, the lack of need for refined laboratory equipment, and the high specificity with fresh serum and fingertip blood samples indicate that the developed POC PUUMALA rapid test is a useful tool for fast diagnosis of acute PUUV infection.

Radiolabeling and in-vivo distribution of nanobacteria in rabbits

Nanobacteria are minute bacteria recently isolated from mammalian blood. They encapsulate themselves with apatite mineral. Cultured nanobacteria were radiolabeled with 99mTc, using a method which has been previously used for labeling red blood cells with 99mTc, and in vivo distribution of nanobacteria was followed with Single Photon Emission Computed Tomography (SPECT) imaging. The labeling yield was over 30%. Two rabbits were studied using dynamic planar imaging performed in the AP-position immediately after injection. Serial SPECT scans were acquired up to 24 h and one planar image was taken at 45 h. A control study was performed administering a similar dose of [99mTc] labeled albumin nanocolloids. Regional nanobacteria-to- nanocolloid ratios were calculated along with time and tissues (45 h) were analyzed for radioactivity and for nanobacteria. The main finding was that radiolabeled nanobacteria remained intact and showed a tissue specific distribution with a high accumulation in the kidneys and also in urine. Spleen, stomach, heart and intestine also showed increased uptake. Excretion into urine started 10 - 15 min after injection. These were live nanobacteria in the urine, which had better capabilities to penetrate into cells in vitro. The nanobacteria accessed the urine via tubular cells since nanobacteria were found in their cytoplasm and tubular surfaces. The results suggest that nanobacteria utilize endocytic transport of tubular cells and may be involved in the pathogenesis of mineral formation in mammalian kidney stones.

Hen Egg Yolk Antibodies Purified by Antigen Affinity under Highly Alkaline Conditions Provide New Tools for Diagnostics. Human Intact Parathyrin as a Model Antigen

Hen egg yolks have been recognized as convenient source for specific antibodies, although their utility in diagnostic applications has been hampered by the lack of efficient purification methods. In the present study, anti-human parathyrin antibodies were raised in rabbits, hens and mice using synthetic human parathyrin peptide (1-84) as an antigen. The antibodies were affinity purified with amino- (1-30) and carboxy- (49-89) terminal peptides of parathyrin under highly alkaline elution conditions, and were evaluated for their diagnostic value in different combinations in immunoenzymometric assay (IEMA) format. A pair of hen egg yolk antibodies were subjected to further methodological validation in the IEMA that was constructed with the N-terminal capture and C-terminal detection antibodies. The synthetic intact human parathyrin (1-84) peptide served as a standard. This within-day IEMA procedure turned out to be sensitive and it correlated well with the two independent intact parathyrin immunoradiometric assays. As shown in the present study, the immuno affinity purification with the highly alkaline elution conditions provides an efficient method for utilization of hen egg yolk antibodies. This is the first report on an application making use of a combination of two hen egg yolk antibody preparations in measuring a homogeneous protein in human serum.

Production of monoclonal and polyclonal antibodies against human osteocalcin sequences and development of a two-site ELISA for intact human osteocalcin

In this study we have raised polyclonal and monoclonal antibodies against human osteocalcin sequences coupled to bovine serum albumin (BSA). The antibodies were used for the development of a novel two-site ELISA on microtiter plates for intact human osteocalcin. The epitope, recognized by the monoclonal hybridoma product Os 31/2 that was used as the capture antibody, was located on the amino terminal sequence 1-29. The antibodies used for detection recognized the sequence 1-49. This method failed to detect any tryptic peptides derived from human osteocalcin sequence 1-49 nor did it detect peptide 1-29, thus demonstrating high specificity for the intact osteocalcin 1-49 only. This is a novel technique for the determination of intact osteocalcin. We have also validated the assay parameters for routine use. This direct and relatively simple procedure promises to be a powerful diagnostic and investigative tool.