Evaluation of a novel fusion protein antigen for rapid serodiagnosis of tuberculosis

Recombinant multiepitope proteins expressed in Escherichia coli cells and their potential for immunodiagnosis

Recombinant multiepitope proteins (RMPs) are a promising alternative for application in diagnostic tests and, given their wide application in the most diverse diseases, this review article aims to survey the use of these antigens for diagnosis, as well as discuss the main points surrounding these antigens. RMPs usually consisting of linear, immunodominant, and phylogenetically conserved epitopes, has been applied in the experimental diagnosis of various human and animal diseases, such as leishmaniasis, brucellosis, cysticercosis, Chagas disease, hepatitis, leptospirosis, leprosy, filariasis, schistosomiasis, dengue, and COVID-19. The synthetic genes for these epitopes are joined to code a single RMP, either with spacers or fused, with different biochemical properties. The epitopes' high density within the RMPs contributes to a high degree of sensitivity and specificity. The RMPs can also sidestep the need for multiple peptide synthesis or multiple recombinant proteins, reducing costs and enhancing the standardization conditions for immunoassays. Methods such as bioinformatics and circular dichroism have been widely applied in the development of new RMPs, helping to guide their construction and better understand their structure. Several RMPs have been expressed, mainly using the Escherichia coli expression system, highlighting the importance of these cells in the biotechnological field. In fact, technological advances in this area, offering a wide range of different strains to be used, make these cells the most widely used expression platform. RMPs have been experimentally used to diagnose a broad range of illnesses in the laboratory, suggesting they could also be useful for accurate diagnoses commercially. On this point, the RMP method offers a tempting substitute for the production of promising antigens used to assemble commercial diagnostic kits.

Evaluation from a B-cell epitope-based chimeric protein for the serodiagnosis of tegumentary and visceral leishmaniasis

The diagnosis of leishmaniasis presents problems due to the variable sensitivity and/or specificity of tests. In addition, high levels of anti-parasite antibodies can remain after treatment, making it difficult to conduct a prognostic follow-up of patients. In this context, it is necessary to identify new candidates to be examined for the sensitive and specific diagnosis of the disease. In the present study, four Leishmania proteins, previously shown as antigenic for tegumentary leishmaniasis (TL), were evaluated, and their linear specific B-cell epitopes were predicted and used to generate a new gene codifying chimeric protein called ChimB, which was cloned, and the recombinant version was expressed, purified, and evaluated in ELISA (Enzyme-Linked Immunosorbent Assay) to diagnose TL and visceral leishmaniasis (VL). A total of 220 human serum samples were used, and, when ChimB was used, results showed sensitivity, specificity, and positive and negative predictive values of 100% for the diagnosis of both diseases; however, when using peptides, the sensitivity values reached from 28.0% to 57.3% and specificity varied from 16.3% to 83.7%. A soluble Leishmania extract (SLA) showed sensitivity and specificity values of 30.7% and 45.9%, respectively. The area under the curve (AUC) value for ChimB was 1.0, while for synthetic peptides, this value reached between 0.502 and 0.635, whereas for SLA, the value was of 0.589. Serological assays using sera samples collected before and after treatment showed significant reductions in the anti-ChimB antibody levels after therapy, suggesting a prognostic role of this recombinant antigen. In conclusion, preliminary data suggest the use from ChimB as a potential candidate for the diagnosis and prognosis of leishmaniasis.

Rational design and evaluation of the recombinant multiepitope protein for serodiagnosis of rubella

BACKGROUND

Rubella is an infection caused by rubella virus (RV) and is generally regarded as a mild childhood disease. The disease continues to be of public health importance mainly because when the infection is acquired during early pregnancy it often results in fetal abnormalities, which are classified as congenital rubella syndrome (CRS). An accurate diagnosis for rubella is thus of pivotal importance for proper treatment.

OBJECTIVE

To produce a recombinant multiepitope protein (rMERUB) for the diagnosis of rubella, based on conserved immunodominant epitopes of glycoprotein E1 and E2.

METHODS

A synthetic gene was designed and cloned into vector pET21a with a 6xHis tag at the C-terminal for affinity purification and overexpressed in Escherichia coli cells. Biophysical analysis of rMERUB was performed by circular dichroism. Biological activity was assessed using an in-house ELISA assay.

RESULTS

Expression in Escherichia coli showed a ~22 kDa protein that was purified and used to perform structural assays and an IgG ELISA. Structural analyses reveal rMERUB has a β leaf pattern that promotes the exposure of epitopes, thus allowing antibody recognition. Evaluation of 33 samples (22=positive; 11=negative) was performed using in-house ELISA and this was compared with a commercial kit. The sensitivity was 100% (95% CI: 85-100) and specificity 90.91% (95% CI: 62-99). Excellent agreement (Kappa index = 0.9) was obtained between ELISA assays.

CONCLUSIONS

The careful choice of epitopes and the high epitope density, coupled with simple-step purification, pinpoints rMERUB as a promising alternative for rubella diagnosis, with potential for the development of a diagnostic kit.

Serodiagnosis of canine leishmaniasis using a novel recombinant chimeric protein constructed with distinct B-cell epitopes from antigenic Leishmania infantum proteins

Visceral leishmaniasis (VL) is an important public health problem in the world, and control measures are insufficient to avoid the spread of this neglected disease. Dogs are important domestic reservoirs of Leishmania parasites in countries where VL is a zoonosis, representing a major source of infection between sand fly vectors and humans. In this context, a precise diagnosis of canine leishmaniasis (CanL) could help to reduce the number of human cases. Distinct approaches for the diagnosis of CanL have used recombinant proteins in serological assays. However, variable results of the antigens have been found, mainly to diagnosis asymptomatic cases. The present study used bioinformatics to select specific B-cell epitopes of four Leishmania infantum proteins, which had previously been proven to be antigenic in VL, aiming to produce a novel chimeric protein and to evaluate it for the diagnosis of CanL. Seven B-cell epitopes were identified and used to construct the chimera, which was analyzed in a recombinant format through an ELISA assay against a canine serological panel. A soluble Leishmania antigenic extract (SLA) was used as an antigen control. Results showed 100 % sensitivity and specificity for chimera, while when using SLA the values were 26.0 % and 96.4 %, respectively. The performance of chimera was compared with a commercial kit using asymptomatic and symptomatic dog sera, and the data showed that no false-negative result was found when the recombinant protein was used. However, when using the commercial kit, 40.0 % and 16.0 % of the false-negative results were found, respectively. In conclusion, the recombinant chimera showed an antigenic potential to be evaluated in new studies against a larger serological panel for the diagnosis of CanL.

Descriptive Comparison of ELISAs for the Detection of Toxoplasma gondii Antibodies in Animals: A Systematic Review

Toxoplasma gondii is the zoonotic parasite responsible for toxoplasmosis in warm-blooded vertebrates. This systematic review compares and evaluates the available knowledge on enzyme-linked immunosorbent assays (ELISAs), their components, and performance in detecting T. gondii antibodies in animals. Four databases were searched for published scientific studies on T. gondii and ELISA, and 57 articles were included. Overall, indirect (95%) and in-house (67%) ELISAs were the most used types of test among the studies examined, but the 'ID Screen® Toxoplasmosis Indirect Multi-species' was common among commercially available tests. Varying diagnostic performance (sensitivity and specificity) and Kappa agreements were observed depending on the type of sample (serum, meat juice, milk), antigen (native, recombinant, chimeric) and antibody-binding reagents used. Combinations of recombinant and chimeric antigens resulted in better performance than native or single recombinant antigens. Protein A/G appeared to be useful in detecting IgG antibodies in a wide range of animal species due to its non-species-specific binding. One study reported cross-reactivity, with Hammondia hammondi and Eimeria spp. This is the first systematic review to descriptively compare ELISAs for the detection of T. gondii antibodies across different animal species.

Designing fusion molecules from antigens of Mycobacterium tuberculosis for detection of multiple antibodies in plasma of TB patients

Tuberculosis (TB) is amongst the deadliest diseases worldwide. For effective control of TB a rapid, reliable and sensitive method for its diagnosis is essential. Serodiagnosis detecting multiple antibodies against antigens of Mycobacterium tuberculosis (Mtb) in blood samples could prove beneficial. Based on the epitope position in the molecule, two truncated variants of Rv1984c, i.e., Tn1Rv1984c and Tn2Rv1984c were expressed in Escherichia coli. Screening of the Rv1984c, Tn1Rv1984c and Tn2Rv1984c against 231 sera samples from the culture positive TB patients showed sensitivities of 34.2%, 49.4% and 26.8%, respectively. Another antigen Rv1352 was analyzed for the location of epitopes, which had not been reported before. A fusion molecule consisting of Tn1Rv1984c and Rv1352, expressed in E. coli, showed enhanced sensitivity of 62.8%. Joining another antigen Rv2031c to the N-terminus of Tn1Rv1984c-Rv1352, improved sensitivity to 71.4%. The fusion construct Rv2031c-Tn1Rv1984c-Rv1352 showed comparatively higher sensitivity of 73.4% in the male group as compared to 67% in the female group. Data derived for the secondary structure analysis through Circular Dichroism (CD) spectroscopy and prediction on the basis of molecular modelling was also in agreement. This construct can be a potential base for producing constructs with greater sensitivity through fusion of epitopes from additional Mtb antigens.

Gene design, optimization of protein expression and preliminary evaluation of a new chimeric protein for the serological diagnosis of both human and canine visceral leishmaniasis

Background

Visceral leishmaniasis (VL) is a major neglected disease, potentially fatal, whose control is still impaired by inefficient and/or expensive treatment and diagnostic methods. The most promising approach for VL diagnosis uses serological assays with recombinant proteins, since they are more efficient and easier to perform. Tests developed for the human form of the disease, however, have not been shown to be efficient for its diagnosis in the canine host, the major reservoir for the American VL.

Methodology/Principal findings

Here, we describe a systematic approach aimed at the production of a new chimeric protein potentially able to be used for both human and canine VL diagnosis and based both on in silico gene design and experimental data. Starting from the previous identification of Leishmania infantum recombinant antigens efficient for the diagnosis of either human or canine VL, three of the best performing antigens were selected (Lci2, Lci3 and Lci12). After a preliminary evaluation validating the chimeric approach, DNA fragments encoding predicted antigenic regions from each protein, enriched with repeats, were joined in various combinations to generate a total of seventeen chimeric genes optimized for prokaryotic expression. These were assessed for optimal expression and purification yield, with four chimeric proteins being efficiently produced. Their diagnostic potential was then evaluated through ELISA assays with sera from VL afflicted humans and dogs. After two rounds of gene design, the results showed high levels of sensitivity for the best chimeric protein, named Q5, in humans (82%) and dogs (100%) with 100% specificity in comparison with healthy controls. A single non-specific reaction was seen with serum from individuals with tegumentary leishmaniasis.

Conclusion

The newly described chimeric protein is potentially useful for the detection of both humans and dogs afflicted with VL, with its use in rapid tests necessary for validation as a new diagnostic tool.

Visceral leishmaniasis (VL) is a major neglected disease, potentially fatal, caused mainly by Leishmania infantum and L. donovani. Its control is still impaired by inefficient and/or expensive treatment and diagnostic methods. VL diagnosis is mostly dependent on serological assays made with bacterially expressed Leishmania proteins. Tests developed for the human form of the disease, however, are not efficient for its diagnosis in the canine host. Dogs are the major reservoir for the American VL and their infection also needs to be monitored, requiring a distinct diagnostic test. Here, we describe a new chimeric protein potentially able to be used for both human and canine VL diagnosis. Based on a systematic approach using three Leishmania proteins known to be efficient for the diagnosis of either human or canine VL, fragments of each were joined in various combinations. The diagnostic potential of different chimeric proteins was then evaluated with human and canine sera from VL afflicted individuals. The best protein showed high levels of sensitivity in humans and dogs with no relevant false positive results with healthy controls or humans with tegumentary leishmaniasis. It is then potentially useful for the detection of both humans and dogs afflicted with VL in novel diagnostic tests.

A Custom-Designed Recombinant Multiepitope Protein for Human Cytomegalovirus Diagnosis

BACKGROUND

The Human Cytomegalovirus (HCMV) has infected more than 90% of the world population and its prevalence can be related to the individuals geographical and socialeconomic status. Serological tests based on ELISA are pivotal for HCMV diagnosis. Due to the lack of standardization in the production/purification of antigens from viral preparations, ELISA tests are based on several recombinant proteins or peptides. As an alternative, multiepitope proteins may be employed.

OBJECTIVE

In this work, we developed a recombinant multiepitope protein (rMEHCMV) for HCMV diagnosis based on conserved and immunodominant epitopes derived from tegument (pp150, pp65 and pp28), glycoprotein gB (pp38) and DNA polymerase subunit (pp52) of HCMV.

METHODS

The rMEHCMV gene was synthesized de novo and overexpressed in Escherichia coli cells. The recombinant protein was purified to homogeneity using a Ni-NTA column. Biophysical analysis of recombinant protein was performed by circular dichroism. A preliminary biological activity test was performed using 12 positive human sera samples by using an in-house IgG ELISA. The following patents database were consulted: Espacenet, Google Patents and the National Institute of Intellectual Property (INPI, Brazil).

RESULTS

The recombinant multiepitope protein was successfully expressed in E. coli. The structural data obtained by circular dichroism spectroscopy showed that rMEHCMV is structurally disordered. An in-house IgG ELISA test with rMEHCMV was successfully used to recognized IgG from human serum samples.

CONCLUSION

Together, our results show that rMEHCMV should be considered as a potential antigenic target for HCMV diagnosis.

Expression and serological application of recombinant epitope-repeat protein carrying an immunodominant epitope of Newcastle disease virus nucleoprotein

Purpose

The aim of the present study was to develop a serodiagnostic test for differentiation infected from vaccinated animal (DIVA) strategy accompanying the marker vaccine lacking an immunodominant epitope (IDE) of nucleoprotein of Newcastle disease virus (NDV).

Materials and Methods

Recombinant epitope-repeat protein (rERP) gene encoding eight repeats of the IDE sequence (ETQFLDLMRAVANSMR) by tetra-glycine linker was synthesized. Recombinant baculovirus carrying the rERP gene was generated to express the rERP in insect cells. Specificity and sensitivity of an indirect enzyme-linked immunosorbent assay (ELISA) employing the rERP was evaluated.

Results

The rERP with molecular weight of 20 kDa was successfully expressed by the recombinant baculovirus in an insect-baculovirus system. The rERP was antigenically functional as demonstrated by Western blotting. An indirect ELISA employing the rERP was developed and its specificity and sensitivity was determined. The ELISA test allowed discrimination of NDV infected sera from epitope deletion virus vaccinated sera.

Conclusion

The preliminary results represent rERP ELISA as a promising DIVA diagnostic tool.

An evaluation of a recombinant multiepitope based antigen for detection of Toxoplasma gondii specific antibodies

BACKGROUND

The inefficiency of the current tachyzoite antigen-based serological assays for the serodiagnosis of Toxoplasma gondii infection mandates the need for acquirement of reliable and standard diagnostic reagents. Recently, epitope-based antigens have emerged as an alternative diagnostic marker for the achievement of highly sensitive and specific capture antigens. In this study, the diagnostic utility of a recombinant multiepitope antigen (USM.TOXO1) for the serodiagnosis of human toxoplasmosis was evaluated.

METHODS

An indirect enzyme-linked immunosorbent assay (ELISA) was developed to evaluate the usefulness of USM.TOXO1 antigen for the detection of IgG antibodies against Toxoplasma gondii in human sera. Whereas the reactivity of the developed antigen against IgM antibody was evaluated by western blot and Dot enzyme immunoassay (dot-EIA) analysis.

RESULTS

The diagnostic performance of the new antigens in IgG ELISA was achieved at the maximum values of 85.43% and 81.25% for diagnostic sensitivity and specificity respectively. The USM.TOXO1 was also proven to be reactive with anti- T. gondii IgM antibody.

CONCLUSIONS

This finding makes the USM.TOXO1 antigen an attractive candidate for improving the toxoplasmosis serodiagnosis and demonstrates that multiepitope antigens could be a potential and promising diagnostic marker for the development of high sensitive and accurate assays.

Novel recombinant multiepitope proteins for the detection of anti-Cryptococcus antibodies

AIM

To produce and test recombinant multiepitope proteins as an alternative assay for the serological diagnosis of cryptococcosis.

MATERIALS & METHODS

Previously, synthetic peptides were used to detect anti-Cryptococcus antibodies, and in silico analyses showed that the union of peptides would improve the results. Here, the coding sequences of these peptides were assembled into synthetic genes. Four genes have been cloned and expressed in Escherichia coli, producing recombinant multiepitope proteins: proteins A, B, C and D.

RESULTS

All constructs yielded good results; however, protein D showed the best results, with a sensitivity of 88.57% and specificity of 100%.

CONCLUSION

The multiepitope proteins were shown to be potential antigens for the diagnosis of cryptococcosis in an attempt to detect anti-Cryptococcus antibodies.

Evaluation of 5 Novel protein biomarkers for the rapid diagnosis of pulmonary and extra-pulmonary tuberculosis: preliminary results

Improved methods are required for the early and accurate diagnosis of tuberculosis, especially in the patients with smear-negative disease. Several biomarkers have been tried but most have shown poor sensitivity or specificity. In present study we aimed to evaluate the diagnostic utility of five novel antigens identified earlier by us. This is an initial study conducted on 250 subjects. The five recombinant antigens, named as rSS1 (Rv2145c), rSS2 (Rv0164), rSS3 (Rv1437), rSS4 (Rv1827) and rSS5 (Rv2970c), were expressed in pQE-30 expression vector, purified and their sero-diagnostic efficacy was evaluated in an unblinded manner using dot-blot and ELISA methods. The sensitivity and specificity of these novel antigens were compared with commercially available standard esat6 and 38 kDa antigens. Bacteriologically confirmed TB patients, non-TB disease controls and healthy individuals were included. which are based on novel antigen or novel technology, Area under curve (AUC) of the selected antigens were 0.98 (0.98-0.99) for rSS1, 0.88 (0.84-0.92) for rSS2, 0.88 (0.84-0.92) for rSS3, 0.95 (0.93-0.98) for rSS4 and 0.99 (0.98-1.0) for rSS5. Receiver operative characteristic (ROC) curve showed highly significant difference between TB and healthy subjects (p = <0.001). These initial findings, show that the recombinant antigens rSS1, rSS4 and rSS5 could be used as highly potential biomarkers for the serological diagnosis of active TB.

Influence of HLA-DRB1 Alleles on the Variations of Antibody Response to Tuberculosis Serodiagnostic Antigens in Active Tuberculosis Patients

Serology-based tests for tuberculosis (TB) diagnosis, though rapid, efficient and easily implemented, have so far shown unsatisfactory levels of sensitivity and specificity, probably due to variations of the antibody response in TB patients. The number and types of seropositive antigens vary from individual to individual. The person-to-person variations of antigen recognition may be linked to genetic polymorphisms of the human leukocyte antigen (HLA) class II alleles. In the present study, we find that there is a significant increase in the frequency of HLA-DRB1*14 (P = 2.5×10⁻⁴) among subjects with high antibody response levels compared to those with low antibody levels. HLA-DRB1*15, the most frequent allelic group in the studied active TB population, positively correlates with subjects with low antibody response levels rather than subjects with high antibody response levels (P = 0.005), which indicates the loss of relevant antigens for screening of patients with this allelic group. The potential association between HLA-DRB1 allelic group and individual antigens implies that TB diagnostic yield could be improved by the addition of antigens screened at the proteome scale in infected subjects from the HLA-DRB1*15 allelic group.

Fusion Molecules of Heat Shock Protein HSPX with Other Antigens of Mycobacterium tuberculosis Show High Potential in Serodiagnosis of Tuberculosis

Variable individual response against the antigens of Mycobacterium tuberculosis necessitates detection of multiple antibodies for enhancing reliability of serodiagnosis of tuberculosis. Fusion molecules consisting of two or more antigens showing high sensitivity would be helpful in achieving this objective. Antigens of M. tuberculosis HSPX and PE35 were expressed in a soluble form whereas tnPstS1 and FbpC1 were expressed as inclusion bodies at 37°C. Heat shock protein HSPX when attached to the N-termini of the antigens PE35, tnPstS1 and FbpC1, all the fusion molecules were expressed at high levels in E. coli in a soluble form. ELISA analysis of the plasma samples of TB patients against HSPX-tnPstS1 showed 57.7% sensitivity which is nearly the same as the expected combined value obtained after deducting the number of plasma samples (32) containing the antibodies against both the individual antigens. Likewise, the 54.4% sensitivity of HSPX-PE35 was nearly the same as that expected from the combined values of the contributing antigens. Structural analysis of all the fusion molecules by CD spectroscopy showed that α-helical and β-sheet contents were found close to those obtained through molecular modeling. Molecular modeling studies of HSPX-tnPstS1 and HSPX-PE35 support the analytical results as most of the epitopes of the contributing antigens were found to be available for binding to the corresponding antibodies. Using these fusion molecules in combination with other antigenic molecules should reduce the number of antigenic proteins required for a more reliable and economical serodiagnosis of tuberculosis. Also, HSPX seems to have potential application in soluble expression of heterologous proteins in E. coli.

A Novel Structurally Stable Multiepitope Protein for Detection of HCV

Hepatitis C virus (HCV) has emerged as the major pathogen of liver diseases in recent years leading to worldwide blood-transmitted chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Accurate diagnosis for differentiation of hepatitis C from other viruses is thus of pivotal importance for proper treatment. In this work we developed a recombinant multiepitope protein (rMEHCV) for hepatitis C diagnostic purposes based on conserved and immunodominant epitopes from core, NS3, NS4A, NS4B, and NS5 regions of the virus polyprotein of genotypes 1a, 1b, and 3a, the most prevalent genotypes in South America (especially in Brazil). A synthetic gene was designed to encode eight epitopes in tandem separated by a flexible linker and bearing a his-tag at the C-terminal end. The recombinant protein was produced in Escherichia coli and purified in a single affinity chromatographic step with >95% purity. Purified rMEHCV was used to perform an ELISA which showed that the recombinant protein was recognized by IgG and IgM from human serum samples. The structural data obtained by circular dichroism (CD) spectroscopy showed that rMEHCV is a highly thermal stable protein at neutral and alkaline conditions. Together, these results show that rMEHCV should be considered an alternative antigen for hepatitis C diagnosis.

Assessing humoral immune response of 4 recombinant antigens for serodiagnosis of tuberculosis

Serodiagnostic potential of four recombinant proteins (38 kDa[Rv0934], MPT64[Rv1980c], Adk[Rv0733], and BfrB[Rv3874]) was evaluated in Healthy control subjects (HCS), Healthy household contacts (HHC), Pulmonary tuberculosis patients (PTB), and Human immuno deficiency virus & Tuberculosis co-infected patients (HIV-TB). All the antigens tested individually for the detection of serum IgG by indirect ELISA. All the four antigens have a significantly higher antibody response in PTB compared to healthy controls (P < 0.05). The sensitivity of individual antigens ranged from 20% to 52.5% for the prefixed specificity of 95%. When results of all 4 antigens were combined the sensitivity was increased to 75% and specificity was reduced 89% in HCS. In smear- and culture-positive (S+C+) PTB, four antigen combination gives maximum sensitivity (89.6%) with 89% specificity. In smear negative culture negative (S-C+) PTB, three antigen combination (38 kDa with MPT64 and BfrB) gives maximum sensitivity (69.5%) and specificity (91.6%). In HIV-TB, 4 antigen combinations give the maximum sensitivity of 51.2% with 89% specificity. Combining serology (Four antigen combination) with smear was able to increase the sensitivity from 70% to 92.5% in culture positive PTB. So, we propose that this serology test can be used as adjunct test along with smear for rapid diagnosis of PTB.

Design and evaluation of a recombinant multi-epitope antigen for serodiagnosis of Toxoplasma gondii infection in humans

Background

Serological investigation remains the primary approach to achieve satisfactory results in Toxoplasma gondii identification. However, the accuracy of the native antigen used in the current diagnostic kits has proven to be insufficient as well as difficult to standardize, so significant efforts have been made to find alternative reagents as capture antigens. Consequently, multi-epitope peptides are promising diagnostic markers, with the potential for improving the accuracy of diagnostic kits. In this study, we described a simple, inexpensive and improved strategy to acquire such diagnostic markers. The study was aimed at producing novel synthetic protein consisting of multiple immunodominant epitopes of several T. gondii antigens.

Findings

To accomplish our goals, a single synthetic gene of approximately 456 bp, which encodes potential epitopes of T. gondii antigens, was successfully constructed using gene assembly PCR. The constructed gene was cloned into a pET32a expression vector and transformed into BL21 E. coli. The entire protein was successfully expressed and purified. Subsequently, the preliminary diagnostic performance of expressed protein was evaluated by developing IgG enzyme-linked immunosorbent assay (ELISA) and Western blot analysis using human sera. The results showed 100 % sensitivity and specificity.

Conclusion

A purified protein expressing multi-immunodominant epitopes of T. gondii was generated. Further studies are required to evaluate the immunogenicity in animal models and to verify the immuno-reactivity of USM.TOXO1 as a diagnostic antigen.

A recombinant multiepitope protein for hepatitis B diagnosis

Hepatitis B is a liver inflammation caused by hepatitis B virus (HBV) and can be diagnosed in clinical stage by hepatitis B core antibody from IgM class (anti-HBcIgM). Hepatitis B core antibody from IgG class (Anti-HBcIgG) appears quickly after IgM, reaching high titers in chronic hepatitis, and remains even after cure. Since hepatitis B core antibody (anti-HBc) is the first antibody identified and sometimes the only marker detected during the course of infection, it can be used both to indicate HBV acute infection (anti-HBc-IgM) and to identify individuals who have come into contact with the virus (anti-HBc-IgG). In this work we propose a recombinant hepatitis B core multiepitope antigen (rMEHB) to be used for diagnosis of hepatitis B. For this purpose, a synthetic gene coding for rMEHB was designed and cloned into vector pET21a with a 6xHis tag at the C-terminal. Time course induction in E. coli showed an induced protein with an apparent molecular mass of ~21 kDa. Protein purification was performed by a single step with affinity chromatography Ni-NTA. Circular dichroism spectroscopy indicated rMEHB as a thermal stable protein at pH 7.0 and 8.0. In these conditions rMEHB was successfully used to perform an enzyme linked immuno sorbent assay (ELISA) with positive and negative sera.

Identification of RD5-encoded Mycobacterium tuberculosis proteins as B-cell antigens used for serodiagnosis of tuberculosis

Comparative genomic studies have identified several Mycobacterium tuberculosis-specific genomic regions of difference (RDs) which are absent in the vaccine strains of Mycobacterium bovis BCG and which may be useful in the specific diagnosis of tuberculosis (TB). In this study, all encoded proteins from DNA segment RD5 of Mycobacterium tuberculosis, that is, Rv3117–Rv3121, were recombined and evaluated by enzyme-linked immunosorbent assays for antibody reactivity with sera from HIV-negative pulmonary TB patients (n = 60) and healthy controls (n = 32). The results identified two immunodominant antigens, that is, Rv3117 and Rv3120, both of which revealed a statistically significant antigenic distinction between healthy controls and TB patients (P < 0.05). In comparison with the well-known early-secreted antigen target 6 kDa (ESAT-6) (sensitivity 21.7%, specificity 90.6%), the higher detection sensitivity and higher specificity were achieved (Rv3117: sensitivity 25%, specificity 96.9%; Rv3120: sensitivity 31.7%, specificity 96.9%). Thus, the results highlight the immunosensitive and immunospecific nature of Rv3117 and Rv3120 and indicate promise for their use in the serodiagnosis of TB.