ELISA protein G for the diagnosis of contagious agalactia in small ruminants

Comparison of commercial enzyme-linked immunosorbent assays for diagnosis of contagious agalactia caused by Mycoplasma agalactiae

Introduction

Contagious agalactia (CA) is a disease affecting small ruminants with worldwide distribution and caused by several mycoplasmas, especially M. agalactiae. The main option for systematic diagnosis under monitoring control programmes is the enzyme-linked immunosorbent assay (ELISA) test.

Material and Methods

This study was designed to appraise the performance of two commercial indirect ELISA tests using M. agalactiae p48 protein and one using total protein, for antibody detection in small ruminants after natural infection with different M. agalactiae strains. We carried out the test evaluation using sera of confirmed M. agalactiae-positive goats with clinical signs. In addition, test agreement was assessed by kappa between the three commercial ELISA tests.

Results

All three ELISA tests showed high validity scores (Youden’s J: 72.9–84%). The sensitivity values for the P48 protein-based tests were 76.9% and 84.6%, and was 79% for the total protein-based test. The specificity of all tests was 100%. In addition, between the total protein-based ELISA test and the other two ELISA tests based on the P48 protein, the agreement was substantial (kappa: 0.762–0.763) and the agreement between the latter two tests was almost perfect (kappa: 0.93).

Conclusion

The validity parameters for all tests allowed their application for diagnostic purposes in lactating goats excreting M. agalactiae in milk and presenting clinical signs. The agreements show that any of these ELISA tests could be equally well used for diagnosis in programmes against CA.

Identification of conserved Mycoplasma agalactiae surface antigens by immunoproteomics

Contagious agalactia represents one of the most relevant infectious diseases of dairy sheep, with Mycoplasma agalactiae being the primary etiological agent. The early, sensitive, and specific identification of infected animals, as well as the development of efficient prophylactic tools, remain challenging. Here, we present a comprehensive characterization of M. agalactiae antigens focusing on those shared among different isolates. Leveraging on previous proteomic data obtained on individual strains, we adopted a strategy entailing sample pooling to optimize the identification of conserved proteins that induce an immune response. The liposoluble proteins from previously characterized field isolates and the type strain PG2^T were enriched by Triton X-114 fractionation, pooled, analysed by one-dimensional (1D) and two-dimensional (2D) electrophoresis, and subjected to western immunoblotting against sheep sera collected during natural infection with M. agalactiae. Immunodominant antigens were identified by Matrix-Assisted Laser Desorption-Time-Of-Flight-Mass Spectrometry (MALDI-TOF-MS). This combined immunoproteomic approach confirmed the role of several known immunogens, including P80, P48, and P40, and most variable surface proteins (Vpmas), and unveiled novel immunodominant, conserved antigens, including MAG_1000, MAG_2220, MAG_1980, phnD, MAG_4740, and MAG_2430. Genomic context, functional prediction, subcellular localization, and invariable expression of these proteins in all isolates suggest their possible involvement in bacterial pathogenicity and metabolism. Moreover, most of the identified antigens elicit a host humoral response since the early stages of infection, persisting for at least 270 days. The immunodominant, conserved antigen panel identified in this work supports the development of effective vaccines and diagnostic tools with higher sensitivity and specificity in all the natural infection stages.

Seroprevalence and associated risk factors of Mycoplasma agalactiae and investigation of coinfection with the caprine lentivirus in Rio Grande do Norte, Brazil

Contagious agalactia is a disease caused by Mycoplasma agalactiae that leads to a reduction or complete stop of milk production. Caprine arthritis encephalitis (CAE) is an infectious disease caused by a lentivirus of the Retroviridae family, member of the small ruminant lentivirus (SRLV) group. Although these diseases are caused by distinct pathogens, the clinical presentation is similar. Hence, this study aimed to perform a serological investigation, as well as to assess correlation between both diseases and risk factors associated in two mesoregions of Rio Grande do Norte, Brazil. Enzyme-linked immunosorbent assay (ELISA) was used for contagious agalactia and western blot for CAE. A total of 538 serum samples were used in this study that were collected from goats and sorted from a blood bank of the Brazilian Agricultural Research Corporation. Seroprevalence of M. agalactiae in flocks from Rio Grande do Norte was 7.8% (42/538). In both regions that were investigated, 25.9% (14/54) of farms had positive animals. CAE results revealed that 3.9% (21/538) of animals and 42.6% (23/54) of farms had this disease. Concerning risk factors, only sex and animal category presented significant relevance (P < 0.05) for contagious agalactia, in which females presented higher frequency of seropositive individuals (10.1%; 39/387). In the animal category, 4.3% (14/326) and 11.1% (36/323) of female breeders were positive for CAE and contagious agalactia, respectively, and significance was identified only in the latter (P < 0.05). In conclusion, there was no correlation between the investigated diseases, considering that no animal demonstrated antibodies for both pathogens.

Mycoplasma agalactiae in semen and milk of goat from Pernambuco state, Brazil

In goat and sheep flocks, mycoplasmosis is a disease that may cause severe economical losses associated with polyarthritis, mastitis, agalactia, conjunctivitis, pneumonia and reproductive failure. The latter may involve repeat breeding, granular vulvovaginitis, infertility and abortions. The aim of the present study was to assess the occurrence of Mycoplasma agalactiae (Ma) in semen and milk samples from naturally infected goat in the semiarid region from Pernambuco State, Northeast from Brazil. Thirty-nine semen samples and 81 milk samples were submitted to DNA extraction using a commercially available kit and following the manufacturer's instructions. The polymerase chain reaction (PCR) was then performed in accordance with protocols described in the literature. The results of the present study revealed the presence of Ma in the DNA of 17.9% (7/39) of the semen samples and 3.7% (3/81) of the milk samples. The results obtained in the present study confirm the elimination of the DNA of Ma in the semen and milk samples. The presence of this agent in goat flocks is considered very risky in terms of reproductive disorders and contagious agalactia outbreaks in the Northeast region of Brazil.

Efficiency of inactive vaccines against contagious agalactia in Brazil

This paper aims to evaluate the efficiency of three inactive vaccines against contagious agalactia prepared with samples of Mycoplasma agalactiae isolated in Brazil and different adjuvants. Vaccine 1 adsorbed with aluminum hydroxide was administered in 23 goats (Gc1) and 13 sheep (Gov1); vaccine 2 containing Montanide IMS-2215-VG was administered in 22 goats (Gc2) and 12 sheep (Gov2) and vaccine 3, containing Montanide Gel-01 was administered in 22 goats (Gc3) and 12 sheep (Gov3). All animals were negative for Ma at indirect ELISA and received two doses of 2mL each, subcutaneously, within a 21 day interval. Five animals from each species were used as control. Seventy-five days after the booster, four animals from each vaccinated group and two from the control group were challenged with 5mL of Ma culture containing 10(7)cfu/mL, orally and through immersion of the female's udder in lactation. The serological response was analyzed during vaccination days (0 and 21) and at 51, 81, 111, 141 and 171 days after vaccination. The collection and analysis of the challenged animals were conducted at the day of the challenge (D0) and 7, 14, 21, 28, 35, 42, 49 and 56 days after the challenge. The three vaccines induced the production of antibodies, having no significant statistical difference (p<0.05). Animals from groups Gc1, Gc2 and Gov2 developed higher levels of antibodies, with significant statistical difference compared to the other vaccinated group and control group (p<0.05). After the challenge, the animals from the control presented an increase in regional lymph nodes and conjunctivitis, mastitis and arthritis. In four vaccinated animals, discrete conjunctivitis and congestion of the episcleral veins was observed. It is concluded that vaccines 1 and 2 induced levels of protective antibodies in goats and sheep, sufficient for clinical protection of the animals submitted to the experimental infection, indicating its use on the prevention of contagious agalactia.

Resposta imunológica em caprinos vacinados contra agalaxia contagiosa

Este trabalho teve como objetivo avaliar a eficiência de duas vacinas inativadas contra agalaxia contagiosa contendo adjuvante oleoso e aquoso. Para tanto, foram utilizados 73 caprinos, agrupados em dois experimentos. No experimento I, para avaliar a inocuidade das vacinas, foram utilizados 15 caprinos, subdivididos em três grupos de cinco animais cada, sendo que o grupo A1 foi imunizado com a vacina aquosa, o grupo B1 com a vacina oleosa e o grupo C não imunizado, foi o controle. No experimento II, para avaliar a resposta imune foram utilizados 58 caprinos, subdivididos em dois grupos, sendo o grupo A2, com 28 animais imunizados com a vacina aquosa e o grupo B2, com 30 animais imunizados com a vacina oleosa. Os animais do experimento II receberam uma terceira dose, 180 dias após a segunda dose vacinal. Os níveis de anticorpos foram determinados por ELISA indireto, realizado no dia de cada vacinação e 30 dias após a segunda dose (experimento I) e 30 dias após a terceira dose vacinal (experimento II). Os animais do grupo B1 e B2 (vacina oleosa) apresentaram níveis de anticorpos estatisticamente superiores (P<0,05) quando comparados aos dos grupos A1 e A2 (vacina aquosa) nos dois experimentos.

Comparative assessment of two commonly used commercial ELISA tests for the serological diagnosis of contagious agalactia of small ruminants caused by Mycoplasma agalactiae

Background

Contagious agalactia (CA) of sheep and goats caused by Mycoplasma agalactiae is a widely occurring economically important disease that is difficult to control. The ELISA is commonly used for the serological detection of CA but it has some limitations and the performance of the available tests have not been properly evaluated.

Two commercial ELISA kits are widely used, one involving a fusion protein as target antigen and the other a total antigen. The objectives were to compare these tests by evaluating:

i. Their diagnostic sensitivity and specificity, the relevance of the recommended cut-off points, the correlation between the two tests, and, the correlation between serology data and the milk shedding of M. agalatiae;

ii. The influence of extrinsic factors such as the targeted animal species, geographical origin of the samples, intra-specific variability of M. agalactiae and concurrent mycoplasma infections.

A sample of 5900 animals from 211 farms with continuous CA monitoring for 20 years and no prior vaccination history was used. The infection status was known from prior bacteriological, epidemiological and serological monitoring with a complementary immunoblotting test.

Results

The average diagnostic sensitivity was 56% [51.8–59.8] for the fusion protein ELISA and 84% [81.3–87.2] for the total antigen ELISA, with noteworthy flock-related variations. The average diagnostic specificity for the fusion protein ELISA was 100% [99.9–100], and for the total antigen ELISA differed significantly between goats and sheep: 99.3% [97.4–99.9] and 95.7% [93.8–97.2] respectively.

Experimental inoculations with different M. agalactiae strains revealed that the ELISA kits poorly detected the antibody response to certain strains. Furthermore, test performances varied according to the host species or geographical origin of the samples.

Finally, the correlation between milk shedding of M. agalactiae and the presence of detectable antibodies in the blood was poor.

Conclusions

These serological tests are not interchangeable. The choice of a test will depend on the objectives (early detection of infection or disease control program), on the prevalence of infection and the control protocol used. Given the variety of factors that may influence performance, a preliminary assessment of the test in a given situation is recommended prior to widespread use.

IgG-detection devices for the Tus-Ter-lock immuno-PCR diagnostic platform

The number of new Immuno-PCR technologies and applications is steadily growing as a result of a general need for more sensitive immunoassays for early detection of diseases. Although Immuno-PCR has been demonstrated to be superior to its immunoassay counterpart, it is still regarded as a challenging technology due to various problems arising from its increased detection power, such as high background noise as well as substantial batch-to-batch reproducibility issues. Current efforts have intensified to produce homogeneous universal protein-DNA conjugates to simplify this technology and render it more robust. We have recently developed a new quantitative Immuno-PCR (qIPCR) technology using the Tus-Ter-lock (TT-lock) interaction to produce homogeneous protein-DNA conjugates that can detect very small numbers of disease-related antibodies. We now report the further development of the TT-lock Immuno-PCR platform for the quasi universal quantitative detection of antigens and mammalian IgG. For this, Tus was fused to various IgG-binding proteins--i.e. protein G, protein L and their LG chimera--and self-assembled to the TT-lock-T template. These detection devices were then evaluated and applied in various direct and indirect Immuno-PCR formats. The direct TT-lock qIPCR could detect goat anti-GFP IgG at concentrations as low as 0.3 pM and total human IgG in serum samples with great sensitivity. Further indirect TT-lock qIPCR systems were developed that could detect 1 pM of GFP and 10 pM of measles nucleoprotein. In all cases, the superiority of the TT-lock Immuno-PCR was demonstrated in terms of sensitivity over an analogous Protein G-Peroxidase ELISA.