Development of a specific immunomagnetic capture-PCR for rapid detection of viable Mycoplasma agalactiae in sheep milk samples

Separation of spring viraemia of carp virus from large-volume samples using immunomagnetic beads

A method for separation of spring viraemia of carp virus (SVCV) from large-volume samples using immunomagnetic beads (IMBs) coated with a polyclonal antibody against SVCV was developed. The optimum amount of IMBs was 2 mg in 100 mL. After IMB treatment, the detection limit of SVCV in reverse transcription quantitative PCR (RT-qPCR) was 103 times the 50% tissue culture infectious dose per mL in 100-mL samples. The concentration of viral RNA extracted from SVCV that had been separated using IMBs was 5.18 × 103-fold higher than that of the unseparated SVCV. When fish samples were tested, the concordance rates of the IMBs/RT-qPCR and RT-qPCR were 100% and 67.5%, respectively.

Use of Immunomagnetic Separation tool in Leishmania promastigotes capture

Immunomagnetic Separation (IMS) assay has been used for isolation of viable whole organisms. The objective of our work is to produce anti-Leishmania magnetic beads and to assess the efficiency of the IMS technique on Leishmania promastigote capture in culture media. Polyclonal anti-Leishmania antibodies were produced by intravenous injection of viable metacyclic promastigotes of Leishmania (L.) major to rabbit. Purified anti-Leishmania IgG was assessed for their reactivity against both L. major and L. infantum promastigotes then covalently conjugated to magnetic beads and used for IMS. This latter was applied on either L. major promastigote cultures of known concentrations or early stage (24h, 48h, 72h) Novy-MacNeal-Nicolle (NNN) cultures of tissue fluid obtained from cutaneous leishmaniasis (CL) lesions. Promastigotes capture was assessed by either microscopy or qPCR after sample boiling. Indirect immunofluorescence assay showed that polyclonal antibodies reacted against both L. major and L. infantum promastigotes. In 50 µL solution, immunomagnetic beads were able to capture 5 live promastigotes out of 20 and 1050 out of 2500, giving an estimated efficiency of 25-42%. The efficiency of the IMS was lower for a lower number of parasites but still repeatable. On the other hand, IMS-qPCR applied to 14 NNN cultures of confirmed Leishmania lesions showed a higher sensitivity to detect live parasites than routine microscopy observation of promastigotes growth (93% positivity at 72h versus 50% positivity within 2-4 weeks incubation). The estimated number of captured parasites at 72h ranged from 1 to more than 100 parasites / 50 µL liquid phase of culture. These preliminary results open the way for interesting perspectives in the use of cultures for leishmaniasis diagnosis and also for other applications such as Leishmania detection in cultures taken from reservoir animals or sandflies.

Development of polyclonal-antibody-coated immunomagnetic beads for separation and detection of koi herpesvirus in large-volume samples

To separate and concentrate koi herpesvirus (KHV) from large-volume samples, a separation method based on immunomagnetic beads (IMBs) coated with polyclonal antibody directed against KHV was developed. After treatment with IMBs, viral DNA was extracted from samples and used as a template for quantitative PCR (qPCR). The results showed that the concentration of the template DNA extracted from the virus that had been separated using IMBs was 9.65-fold higher than that from virus not treated with IMBs. The detection limit of the IMBs/qPCR method was found to be at least 10 times lower than that of qPCR alone.

Development of loop-mediated isothermal amplification test for the diagnosis of contagious agalactia in goats

Contagious agalactia is a highly infectious disease affecting sheep and goats, mainly caused by Mycoplasma agalactiae. Although various tests are available for diagnosis of contagious agalactia, none of them is credited with the capacity to provide rapid and cost-effective diagnosis. This article reports the development of loop-mediated isothermal amplification (LAMP) test targeting the p40 gene of M. agalactiae, for the diagnosis of classical contagious agalactia. Optimum amplification was obtained at 58 °C in 70 min. The developed test was found to be 100-fold more sensitive than PCR and detected up to 20-fg level of DNA. The test was also superior to conventional PCR in detecting from artificially contaminated milk, i.e. 10(4)-fold more sensitive. The developed LAMP test could detect up to 10 cfu/ml of artificially contaminated milk, indicating its potential for being developed as a field test for rapid and sensitive diagnosis.