Mini-FLOTAC for counting Toxoplasma gondii oocysts from cat feces--comparison with cell counting plates

Is Immuno-PCR Better than ELISA Test for Detection of Toxoplasma gondii IgG Antibody?

INTRODUCTION

IgG antibodies against T. gondii persist for years, and can act as a reliable serological biomarker for the diagnosis of previous exposure to this parasite. Hence, the current investigation was designed to compare diagnostic power of immuno-polymerase chain reaction (iPCR) and enzyme-linked immunosorbent assay (ELISA) methods for detection of T. gondii IgG antibody.

METHODS

Immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against T. gondii were measured by the ELISA method in 81 participants. In addition, detection of acute and chronic toxoplasmosis was performed via the ELISA IgG avidity. The set-up of iPCR was carried out and then, serum IgG of subjects were detected using the iPCR method.

RESULTS

Of 81 samples, 4 (4.9%) and 30 (37%) cases were be found positive for IgM and IgG against T. gondii in the ELISA method, respectively. Moreover, of 81 specimens, 42 (51.9%) and 39 (48.1%) samples had low-avidity IgG and high-avidity IgG by the IgG avidity kit, respectively. While, 59 (72.8%) of 81 samples were detected positive using the iPCR technique. Kappa (κ) value coefficient, between the iPCR and ELISA (for IgG) showed a strong agreement (0.360, p value < 0.001). A value of 0.25 I.U./ml for serum IgG [area under curve (AUC) = 0.720 (CI = 0.613-0.827); p = 0.002] was the cut-off value to differentiating between positive and negative toxoplasmosis (with sensitivity 66.0% and specificity 60.0%).

CONCLUSION

Our findings indicated despite a strong agreement shown between iPCR and ELISA methods, the diagnostic power of iPCR technique was more sensitive than ELISA test for detection of T. gondii IgG antibody. However, more complementary investigations are widely needed in this regard.

Evaluation of immunogenicity and protection of the Mic1-3 knockout Toxoplasma gondii live attenuated strain in the feline host

Toxoplasmosis is a zoonotic disease caused by the parasite Toxoplasma gondii. Up to a third of the global human population is estimated to carry a T. gondii infection, which can result in severe complications in immunocompromised individuals and pregnant women. Humans and animals can become infected by ingesting either tissue cysts containing T. gondii bradyzoites, from raw or undercooked meat, or sporulated oocysts from environmental sources. T. gondii oocysts are released in the faeces of cats and other felids, which are the parasite's definitive hosts, leading to environmental contamination. Therefore, vaccination of the feline host against T. gondii is an interesting strategy to interrupt the parasitic life cycle and subsequently limit contamination of intermediate hosts. With this goal in mind, we tested in cats, an attenuated live strain of T. gondii deleted for the Mic1 and Mic3 genes (Mic1-3KO) that was previously shown to be an efficient vaccine candidate in mouse and sheep models. Subcutaneous or oral vaccination routes induced a high specific antibody titer in the cat sera, indicating that the Mic1-3KO strain is immunogenic for cats. To assess protection induced by the vaccine candidate strain, we followed oocysts shedding by vaccinated cats, after oral challenge with a T. gondii wild-type strain. Surprisingly, a high antibody titer did not prevent cats from shedding oocysts from the challenge strain, regardless of the vaccination route. Our results show that the Mic1-3KO vaccine candidate is immunogenic in the feline host, is well tolerated and safe, but does not confer protection against oocysts shedding after natural infection with wild type T. gondii. This result highlights the particular relationship between T. gondii and its unique definitive host, which indicates the need for further investigations to improve vaccination strategies to limit environmental and livestock contaminations.

An experimental genetically attenuated live vaccine to prevent transmission of Toxoplasma gondii by cats

Almost any warm-blooded creature can be an intermediate host for Toxoplasma gondii. However, sexual reproduction of T. gondii occurs only in felids, wherein fertilisation of haploid macrogametes by haploid microgametes, results in diploid zygotes, around which a protective wall develops, forming unsporulated oocysts. Unsporulated oocysts are shed in the faeces of cats and meiosis gives rise to haploid sporozoites within the oocysts. These, now infectious, sporulated oocysts contaminate the environment as a source of infection for people and their livestock. RNA-Seq analysis of cat enteric stages of T. gondii uncovered genes expressed uniquely in microgametes and macrogametes. A CRISPR/Cas9 strategy was used to create a T. gondii strain that exhibits defective fertilisation, decreased fecundity and generates oocysts that fail to produce sporozoites. Inoculation of cats with this engineered parasite strain totally prevented oocyst excretion following infection with wild-type T. gondii, demonstrating that this mutant is an attenuated, live, transmission-blocking vaccine.

The Mini-FLOTAC technique for the diagnosis of helminth and protozoan infections in humans and animals

This protocol is an extension to: Nat. Protoc. 5, 503-515 (2010); doi: 10.1038/nprot.2009.235; published online 25 February 2010The FLOTAC is a sensitive, accurate, and precise technique for the diagnosis of protozoan and helminth infections in humans and animals. However, it requires centrifugation, and hence might be out of reach in resource-constrained settings. As an extension of the original FLOTAC protocol, this protocol describes the Mini-FLOTAC technique, a logical evolution of FLOTAC conceived to perform multivalent, qualitative, and quantitative diagnosis of helminth and protozoan infections in human and animal feces, and urine. This has been found to be of most use in the processing of large numbers of samples with rapid laboratory workup, and for veterinary applications directly on-farm. In addition to the Mini-FLOTAC apparatus, we describe the use of the Fill-FLOTAC, a closed system used to facilitate the performance of the first four consecutive steps of the Mini-FLOTAC technique: fecal sample collection and weighing, homogenization, filtration, and filling of the Mini-FLOTAC chambers. Processing of an individual sample using this protocol requires ∼12 min.