A dot-blot ELISA preliminary evaluation using PvMSP1-42 recombinant protein as antigen for serological diagnosis of Plasmodium vivax infection in Thailand

Plasmodium vivax is the most prevalent cause of malaria in Thailand and is predominant in malarial endemic areas worldwide. P. vivax infection is characterized by low parasitemia, latent liver-stage parasites, or asymptomatic infections leading to underreported P. vivax cases. These are significant challenges for controlling and eliminating P. vivax from endemic countries. This study developed and evaluated a dot-blot enzyme-linked immunosorbent assay (ELISA) using PvMSP1-42 recombinant antigen for serological diagnosis based on the detection of antibodies against P. vivax. The optimal PvMSP1-42 concentration and dilutions of anti-human IgG horseradish peroxidase (HRP)-conjugated antiserum were tested on 88 serum samples from P. vivax, Plasmodium falciparum and bacterial infection, including healthy individuals. A cut-off titer of 1:800 produced optimal values for sensitivity and specificity of 90.9 and 98.2%, respectively, with an accuracy of 95.5%. The positive and negative predictive values were 96.8 and 94.7% respectively. The results from microscopic examination and dot-blot ELISA showed strong agreement with the 0.902 kappa index. Thus, the dot-blot ELISA using PvMSP1-42 antigen provided high sensitivity and specificity suitable for serodiagnosis of P. vivax infection. The test is a simple and quick diagnostic assay suitable for field testing as it does not require specific equipment or particular skills.

A novel indirect ELISA for serodiagnosis of mucormycosis using antigens from Rhizopus arrhizus

BACKGROUND

Due to a delay in diagnosis by conventional techniques and high mortality, the development of a standardised and rapid non-culture-based technique is an unmet need in pulmonary, gastrointestinal, and disseminated forms of mucormycosis. Though limited studies have been conducted for molecular diagnosis, there are no established serologic tests for this highly fatal infection.

OBJECTIVE

To develop and evaluate an indirect in-house enzyme-linked immunosorbent assay (ELISA) utilising antigens of Rhizopus arrhizus for detecting anti-Rhizopus antibodies (IgG and IgM) in sera of patients with mucormycosis.

METHODS

We extracted both secretory and mycelial Rhizopus antigens using standardised protocols. Bradford assay was used for protein quantification. We then standardised an indirect ELISA using R. arrhizus mycelial and secretory antigens (10.0 μg/mL in bicarbonate buffer pH 9.2) for detecting anti-Rhizopus IgG and IgM antibodies in patient sera. We included patients with mucormycosis, other fungal infections, and healthy controls. Antibody index value (E-value) was calculated for each patient sample.

RESULTS

Asparagine broth culture filtrate utilising 85% ammonium sulphate salt fractionation and mycelial homogenate grown in yeast extract peptone dextrose (YPD) broth precipitated with trichloroacetic acid (TCA) yielded a large amount of good-quality protein for the assay. We included 55 patients with mucormycosis (rhino-orbito-cerebral mucormycosis [ROCM, n = 39], pulmonary [n = 15], gastrointestinal [n = 1]), 24 with other fungal infections (probable aspergillosis [n = 14], candidiasis [n = 10]), and healthy controls (n = 16). The sensitivity of the antibody test for diagnosing mucormycosis ranged from 83.6-92.7% for IgG and 72.7-87.3% for IgM, with a specificity of 91.7-92.5% for IgG and 80-82.5% for IgM. The sera from patients with other fungal infections and healthy individuals did not show significant cross-reactivity.

CONCLUSION

The detection of anti-Rhizopus IgG antibody performed significantly better in comparison to IgM-based ELISA for diagnosing both ROCM (sensitivity of 84.6% vs. 69.2%) and pulmonary cases (86.6% vs. 80.0%). More extensive studies are required to confirm our findings.

Accuracy improvement enzyme-linked immunosorbent assay using superparamagnetic/polyethylene glycol) nanoparticles for leishmaniasis diagnostic

Serodiagnosis methods have been used as platforms for diagnostic tests for many diseases. Due to magnetic nanoparticles' properties to quickly detach from an external magnetic field and particle size effects, these nanomaterials' functionalization allows the specific isolation of target analytes, enhancing accuracy parameters and reducing serodiagnosis time. Superparamagnetic iron oxide nanoparticles (MNPs) were synthesized and functionalized with polyethylene glycol (PEG) and then associated with the synthetic Leishmaniosis epitope. This nano-peptide antigen showed promising results. Regarding Tegumentary leishmaniasis diagnostic accuracy, the AUC was 0.8398 with sensibility 75% (95CI% 50.50 - 89.82) and specificity 87.50% (95CI% 71.93 - 95.03), and Visceral leishmaniasis accuracy study also present high performance, the AUC was 0.9258 with sensibility 87.50% (95CI% 63.98 - 97.78) and specificity 87.50% (95CI% 71.93 - 95.03). Our results demonstrate that the association of the antigen with MNPs accelerates and improves the diagnosis process. MNPs could be an important tool for enhancing serodiagnosis.

The Development of Toxoplasma gondii Recombinant Trivalent Chimeric Proteins as an Alternative to Toxoplasma Lysate Antigen (TLA) in Enzyme-Linked Immunosorbent Assay (ELISA) for the Detection of Immunoglobulin G (IgG) in Small Ruminants

This study presents an evaluation of seventeen newly produced recombinant trivalent chimeric proteins (containing the same immunodominant fragment of SAG1 and SAG2 of Toxoplasma gondii antigens, and an additional immunodominant fragment of one of the parasite antigens, such as AMA1, GRA1, GRA2, GRA5, GRA6, GRA7, GRA9, LDH2, MAG1, MIC1, MIC3, P35, and ROP1) as a potential alternative to the whole-cell tachyzoite lysate (TLA) used in the detection of infection in small ruminants. These recombinant proteins, obtained by genetic engineering and molecular biology methods, were tested for their reactivity with specific anti-Toxoplasma IgG antibodies contained in serum samples of small ruminants (192 samples of sheep serum and 95 samples of goat serum) using an enzyme-linked immunosorbent assay (ELISA). The reactivity of six recombinant trivalent chimeric proteins (SAG1-SAG2-GRA5, SAG1-SAG2-GRA9, SAG1-SAG2-MIC1, SAG1-SAG2-MIC3, SAG1-SAG2-P35, and SAG1-SAG2-ROP1) with IgG antibodies generated during T. gondii invasion was comparable to the sensitivity of TLA-based IgG ELISA (100%). The obtained results show a strong correlation with the results obtained for TLA. This suggests that these protein preparations may be a potential alternative to TLA used in commercial tests and could be used to develop a cheaper test for the detection of parasite infection in small ruminants.

Antibodies to Borrelia burgdorferi and Bartonella species in serum and synovial fluid from people with rheumatic diseases

Vector-borne infections may underlie some rheumatic diseases, particularly in people with joint effusions. This study aimed to compare serum and synovial fluid antibodies to B. burgdorferi and Bartonella spp. in patients with rheumatic diseases. This observational, cross-sectional study examined paired synovial fluid and serum specimens collected from 110 patients with joint effusion between October 2017 and January 2022. Testing for antibodies to B. burgdorferi (using CDC criteria) and Bartonella spp. via two indirect fluorescent antibody (IFA) assays was performed as part of routine patient care at the Institute for Specialized Medicine (San Diego, CA, USA). There were 30 participants (27%) with positive two-tier B. burgdorferi serology and 26 participants (24%) with IFA seroreactivity (≥1:256) to B. henselae and/or B. quintana. Both B. burgdorferi IgM and IgG were detected more frequently in synovial fluid than serum: 27% of patients were either IgM or IgG positive in synovial fluid, compared to 15.5% in serum (P = 0.048). Conversely, B. henselae and B. quintana antibodies were detected more frequently in serum than synovial fluid; overall only 2% of patients had positive IFA titers in synovial fluid, compared to 24% who had positive IFA titers in serum (P < 0.001). There were no significant associations between B. burgdorferi or Bartonella spp. seroreactivity with any of the clinical rheumatological diagnoses. This study provides preliminary support for the importance of synovial fluid antibody testing for documenting exposure to B. burgdorferi but not for documenting exposure to Bartonella spp.

IMPORTANCE

This study focuses on diagnostic testing for two common vector-borne diseases in an affected patient population. In it, we provide data showing that antibodies to B. burgdorferi, but not Bartonella spp., are more commonly found in synovial fluid than serum of patients with joint effusion. Since Lyme arthritis is a common-and sometimes difficult to diagnose-rheumatic disease, improving diagnostic capabilities is of utmost importance. While our findings are certainly not definitive for changes to practice, they do suggest that synovial fluid could be a useful sample for the clinical diagnosis of Lyme disease, and future prospective studies evaluating this claim are warranted.

Revisiting the antigen markers of vector-borne parasitic diseases identified by immunomics: identification and application to disease control

INTRODUCTION

Protein microarray is a promising immunomic approach for identifying biomarkers. Based on our previous study that reviewed parasite antigens and recent parasitic omics research, this article expands to include information on vector-borne parasitic diseases (VBPDs), namely, malaria, schistosomiasis, leishmaniasis, babesiosis, trypanosomiasis, lymphatic filariasis, and onchocerciasis.

AREAS COVERED

We revisit and systematically summarize antigen markers of vector-borne parasites identified by the immunomic approach and discuss the latest advances in identifying antigens for the rational development of diagnostics and vaccines. The applications and challenges of this approach for VBPD control are also discussed.

EXPERT OPINION

The immunomic approach has enabled the identification and/or validation of antigen markers for vaccine development, diagnosis, disease surveillance, and treatment. However, this approach presents several challenges, including limited sample size, variability in antigen expression, false-positive results, complexity of omics data, validation and reproducibility, and heterogeneity of diseases. In addition, antigen involvement in host immune evasion and antigen sensitivity/specificity are major issues in its application. Despite these limitations, this approach remains promising for controlling VBPD. Advances in technology and data analysis methods should continue to improve candidate antigen identification, as well as the use of a multiantigen approach in diagnostic and vaccine development for VBPD control.

Flow Cytometry-Based Measurement of Antibodies Specific for Cell Surface-Expressed Folded SARS-CoV-2 Receptor-Binding Domains

BACKGROUND

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has now become endemic and is currently one of the important respiratory virus infections regularly affecting mankind. The assessment of immunity against SARS-CoV-2 and its variants is important for guiding active and passive immunization and SARS-CoV-2-specific treatment strategies.

METHODS

We here devised a novel flow cytometry-based diagnostic platform for the assessment of immunity against cell-bound virus antigens. This platform is based on a collection of HEK-293T cell lines which, as exemplified in our study, stably express the receptor-binding domains (RBDs) of the SARS-CoV-2 S-proteins of eight major SARS-CoV-2 variants, ranging from Wuhan-Hu-1 to Omicron.

RESULTS

RBD-expressing cell lines stably display comparable levels of RBD on the surface of HEK-293T cells, as shown with anti-FLAG-tag antibodies directed against a N-terminally introduced 3x-FLAG sequence while the functionality of RBD was proven by ACE2 binding. We exemplify the usefulness and specificity of the cell-based test by direct binding of IgG and IgA antibodies of SARS-CoV-2-exposed and/or vaccinated individuals in which the assay shows a wide linear performance range both at very low and very high serum antibody concentrations. In another application, i.e., antibody adsorption studies, the test proved to be a powerful tool for measuring the ratios of individual variant-specific antibodies.

CONCLUSION

We have established a toolbox for measuring SARS-CoV-2-specific immunity against cell-bound virus antigens, which may be considered as an important addition to the armamentarium of SARS-CoV-2-specific diagnostic tests, allowing flexible and quick adaptation to new variants of concern.

Advances in diagnostic approaches to Fasciola infection in animals and humans: An overviews

Fasciolosis, caused by Fasciola hepatica and F. gigantica, is an impediment to the livestock industry’s expansion and has a massively negative socio-economic impact due to its widespread prevalence in livestock. It is a waterborne zoonosis affecting human populations in the countries where rural economies are associated with livestock rearing. Conventional diagnosis of Fasciola infection is done by detecting parasite eggs in the faeces of infected animals or by immunological methods. Accurate and quick immunodiagnosis of Fasciola infection in animals and humans is based on the detection of antibodies and specific antigens expressed in the prepatent stage of the parasite. Both molecular and serodiagnostic tests developed thus far have enhanced the reliability of Fasciola diagnosis in both man and animals but are not widely available in resource-poor nations. A pen-side diagnostic test based on a lateral flow assay or a DNA test like loop-mediated isothermal amplification (LAMP) would be simple, fast, and cost-effective, enabling clinicians to treat animals in a targeted manner and avoid the development of drug resistance to the limited flukicides. This review focuses on the recent advances made in the diagnosis of this parasite infection in animals and humans.

Evaluation of a minimal array of Treponema pallidum antigens as biomarkers for syphilis diagnosis, infection staging, and response to treatment

IMPORTANCE

This manuscript explores the host humoral response to selected antigens of the syphilis agent during infection to evaluate their potential use as diagnostic tests and markers for treatment.

Comparative analysis of a novel N-butanol-prepared antigen vs thermo-resistant and sonicated antigens for human leptospirosis detection

The diagnosis of human leptospirosis is mainly based on serological assays. Since the extraction by N-butanol has only been studied as an antigen for the diagnosis of cattle leptospirosis, this study aimed to investigate the feasibility of the N-butanol preparation for the diagnosis of human leptospirosis and compare it with sonicated and thermo-resistant antigens in IgM dot-blot test. Paired serum samples from 147 laboratory-confirmed leptospirosis cases were tested. The control group consisted of 148 serum samples from healthy individuals and nonleptospirosis cases. N-butanol antigens from serovar Copenhageni (ButC3) and serovar Patoc (ButP3) showed reactivity with antileptospiral antibodies from patients with confirmed leptospirosis. In the acute phase, sensitivities of IgM dot-blot assay with ButC3 and ButP3 antigens were 47.6% and 51.0%, respectively. In the convalescent phase, sensitivities were 95.9% (ButC3) and 93.2% (ButP3), and no significant differences were observed among the IgM dot-blot tests with other antigens. The specificity of the IgM dot-blot test with ButC3 antigen was good (92.6%), but with ButP3 (83.1%), it was significantly lower than with the other tests. The IgM dot-blot test described in this study is simple to perform and presents reliable visual results. Antigens prepared by N-butanol proved to be valuable diagnostic markers of leptospirosis.

Epitope Mapping of BmpA and BBK32 Borrelia burgdorferi Sensu Stricto Antigens for the Design of Chimeric Proteins with Potential Diagnostic Value

Lyme disease is a tick-borne zoonosis caused by Gram-negative bacteria belonging to the Borrelia burgdorferi sensu lato (s.l.) group. In this study, IgM- and IgG-specific linear epitopes of two B. burgdorferi sensu stricto (s.s.) antigens BmpA and BBK32 were mapped using a polypeptide array. Subsequently, two chimeric proteins BmpA-BBK32-M and BmpA-BBK32-G were designed to validate the construction of chimeras using the identified epitopes for the detection of IgM and IgG, respectively, by ELISA. IgG-ELISA based on the BmpA-BBK32-G antigen showed 71% sensitivity and 95% specificity, whereas a slightly lower diagnostic utility was obtained for IgM-ELISA based on BmpA-BBK32-M, where the sensitivity was also 71% but the specificity decreased to 89%. The reactivity of chimeric proteins with nondedicated antibodies was much lower. These results suggest that the identified epitopes may be useful in the design of new forms of antigens to increase the effectiveness of Lyme disease serodiagnosis. It has also been proven that appropriate selection of epitopes enables the construction of chimeric proteins exhibiting reactivity with a specific antibody isotype.

Antibody Cross-Reactivity in Serodiagnosis of Lyme Disease

Lyme disease is a tick-borne disease caused by spirochetes belonging to the Borrelia burgdorferi sensu lato complex. The disease is characterized by a varied course; therefore, the basis for diagnosis is laboratory methods. Currently, a two-tiered serological test is recommended, using an ELISA as a screening test and a Western blot as a confirmatory test. This approach was introduced due to the relatively high number of false-positive results obtained when using an ELISA alone. However, even this approach has not entirely solved the problem of false-positive results caused by cross-reactive antibodies. Many highly immunogenic B. burgdorferi s.l. proteins are recognized nonspecifically by antibodies directed against other pathogens. This also applies to antigens, such as OspC, BmpA, VlsE, and FlaB, i.e., those commonly used in serodiagnostic assays. Cross-reactions can be caused by both bacterial (relapsing fever Borrelia, Treponema pallidum) and viral (Epstein-Baar virus, Cytomegalovirus) infections. Additionally, a rheumatoid factor has also been shown to nonspecifically recognize B. burgdorferi s.l. proteins, resulting in false-positive results. Therefore, it is necessary to carefully interpret the results of serodiagnostic tests so as to avoid overdiagnosis of Lyme disease, which causes unnecessary implementations of strong antibiotic therapies and delays in the correct diagnosis.

Serodiagnosis of Abdominal Abscess Caused by Burkholderia pseudomallei: Case Report and Literature Review

Burkholderia pseudomallei, the causative agent of melioidosis can be responsible for a wide spectrum of clinical manifestations and heterogeneous prognoses, with a high mortality in the acute onset. We report a case of a deep abdominal abscess with sepsis secondary to melioidosis in a young farmer from a non-high-risk population. Emergency medical treatment was administered according to the detection of serum antibodies against Hcp1, the results of which provided etiological evidence of B. pseudomallei infection for the timely and properly antimicrobial therapy in the absence of direct evidence of melioidosis. To our knowledge, this is the first reported case of serodiagnosis of acute exacerbation of melioidosis in China.

Comparison of Three Serologic Tests for the Detection of Anti-Coxiella burnetii Antibodies in Patients with Q Fever

The performance of a commercial immunofluorescence assay (IFA commercial), an in-house immunofluorescence assay (IFA in-house) and an indirect enzyme-linked immunosorbent assay (ELISA) were evaluated in the detection of antibodies anti-C. burnetii in the serum of Q fever patients and persons without the disease. For the study, seropositive and seronegative samples for Q fever (n = 200) from a serum bank of the Instituto Adolfo Lutz in Brazil were used. Commercial IFA was considered in this study as the gold standard for diagnosing Q fever. The in-house IFA demonstrated good agreement with the commercial test, showing high sensitivity (91%) and specificity (97%) compared to the gold standard, with a Kappa coefficient of 0.8954. The indirect ELISA test showed lower agreement with the gold standard, showing low sensitivity (67%), although the specificity of the technique was high (97%) and the Kappa coefficient was moderate (0.6631). In-house IFA is an excellent alternative for diagnosing Q fever.

Development of a Novel Enzyme-Linked Immunosorbent Assay and Lateral Flow Test System for Improved Serodiagnosis of Visceral Leishmaniasis in Different Areas of Endemicity

Visceral leishmaniasis (VL) is caused by protozoan parasites of the Leishmania donovani complex and is one of the most prominent vector-borne infectious diseases with epidemic and mortality potential if not correctly diagnosed and treated. East African countries suffer from a very high incidence of VL, and although several diagnostic tests are available for VL, diagnosis continues to represent a big challenge in these countries due to the lack of sensitivity and specificity of current serological tools. Based on bioinformatic analysis, a new recombinant kinesin antigen from Leishmania infantum (rKLi8.3) was developed. The diagnostic performance of rKLi8.3 was evaluated by enzyme-linked immunosorbent assay (ELISA) and lateral flow test (LFT) on a panel of sera from Sudanese, Indian, and South American patients diagnosed with VL or other diseases, including tuberculosis, malaria, and trypanosomiasis. The diagnostic accuracy of rKLi8.3 was compared with rK39 and rKLO8 antigens. The VL-specific sensitivity of rK39, rKLO8, and rKLi8.3 ranged from 91.2% over 92.4% to 97.1% and specificity ranged from 93.6% over 97.6% to 99.2%, respectively. In India, all tests showed a comparable specificity of 90.9%, while the sensitivity ranged from 94.7% to 100% (rKLi8.3). In contrast to commercial serodiagnostic tests, rKLi8.3-based ELISA and LFT showed improved sensitivity and no cross-reactivity with other parasitic diseases. Thus, rKLi8.3-based ELISA and LFT offer improved VL serodiagnostic efficiency in East Africa and other areas of endemicity. IMPORTANCE Reliable and field suitable serodiagnosis of visceral leishmaniasis (VL) in East Africa has until now been a big challenge due to low sensitivity and cross-reactivity with other pathogens. To improve VL serodiagnosis, a new recombinant kinesin antigen from Leishmania infantum (rKLi8.3) was developed and tested with a panel of sera from Sudanese, Indian, and South American patients diagnosed with VL or other infectious diseases. Both prototype rKLi8.3-based enzyme-linked immunosorbent assay (ELISA) and lateral flow test (LFT) showed improved sensitivity and no cross-reactivity with other parasitic diseases. Thus, rKLi8.3-based ELISA and LFT offer substantially increased diagnostic efficiency for VL in East Africa and other areas of endemicity, compared to currently commercially available serodiagnostic tests.

Prospective Analysis of Antibody Diagnostic Tests and TTS1 Real-Time PCR for Diagnosis of Melioidosis in Areas Where It Is Endemic

Melioidosis is a tropical infectious disease caused by Burkholderia pseudomallei. Melioidosis is associated with diverse clinical manifestations and high mortality. Early diagnosis is needed for appropriate treatment, but it takes several days to obtain bacterial culture results. We previously developed a rapid immunochromatography test (ICT) based on hemolysin coregulated protein 1 (Hcp1) and two enzyme-linked immunosorbent assays (ELISAs) based on Hcp1 (Hcp1-ELISA) and O-polysaccharide (OPS-ELISA) for serodiagnosis of melioidosis. This study prospectively validated the diagnostic accuracy of the Hcp1-ICT in suspected melioidosis cases and determined its potential use for identifying occult melioidosis cases. Patients were enrolled and grouped by culture results, including 55 melioidosis cases, 49 other infection patients, and 69 patients with no pathogen detected. The results of the Hcp1-ICT were compared with culture, a real-time PCR test based on type 3 secretion system 1 genes (TTS1-PCR), and ELISAs. Patients in the no-pathogen-detected group were followed for subsequent culture results. Using bacterial culture as a gold standard, the sensitivity and specificity of Hcp1-ICT were 74.5% and 89.8%, respectively. The sensitivity and specificity of TTS1-PCR were 78.2% and 100%, respectively. The diagnostic accuracy was markedly improved if the Hcp1-ICT results were combined with TTS1-PCR results (sensitivity and specificity were 98.2% and 89.8%, respectively). Among patients with initially negative cultures, Hcp1-ICT was positive in 16/73 (21.9%). Five of the 16 patients (31.3%) were subsequently confirmed to have melioidosis by repeat culture. The combined Hcp1-ICT and TTS1-PCR test results are useful for diagnosis, and Hcp1-ICT may help identify occult cases of melioidosis.

rMELEISH: A Novel Recombinant Multiepitope-Based Protein Applied to the Serodiagnosis of Both Canine and Human Visceral Leishmaniasis

BACKGROUND

visceral leishmaniasis (VL) is a critical public health problem in over ninety countries. The control measures adopted in Brazil have been insufficient when it comes to preventing the spread of this overlooked disease. In this context, a precise diagnosis of VL in dogs and humans could help to reduce the number of cases of this disease. Distinct studies for the diagnosis of VL have used single recombinant proteins in serological assays; however, the results have been variable, mainly in relation to the sensitivity of the antigens. In this context, the development of multiepitope-based proteins could be relevant to solving such problem.

METHODS

a chimeric protein (rMELEISH) was constructed based on amino acid sequences from kinesin 39 (k39), alpha-tubulin, and heat-shock proteins HSP70 and HSP 83.1, and tested in enzyme-linked immunosorbent (ELISA) for the detection of L. infantum infection using canine (n = 140) and human (n = 145) sera samples.

RESULTS

in the trials, rMELEISH was able to discriminate between VL cases and cross-reactive diseases and healthy samples, with sensitivity and specificity values of 100%, as compared to the use of a soluble Leishmania antigenic extract (SLA).

CONCLUSIONS

the preliminary data suggest that rMELEISH has the potential to be tested in future studies against a larger serological panel and in field conditions for the diagnosis of canine and human VL.

Development and laboratory evaluation of a competitive ELISA for serodiagnosis of Nipah and Hendra virus infection using recombinant Nipah glycoproteins and a monoclonal antibody

Introduction

Nipah virus (NiV) and Hendra virus (HeV), of the genus Henipavirus, family Paramyxoviridae, are classified as Risk Group 4 (RG4) pathogens that cause respiratory disease in pigs and acute/febrile encephalitis in humans with high mortality.

Methods

A competitive enzyme-linked immunosorbent assay (cELISA) using a monoclonal antibody (mAb) and recombinant NiV glycoprotein (G) was developed and laboratory evaluated using sera from experimental pigs, mini pigs and nonhuman primates. The test depends on competition between specific antibodies in positive sera and a virus-specific mAb for binding to NiV-G.

Results

Based on 1,199 negative and 71 NiV positive serum test results, the cutoff value was determined as 35% inhibition. The diagnostic sensitivity and specificity of the NiV cELISA was 98.58 and 99.92%, respectively. When testing sera from animals experimentally infected with NiV Malaysia, the cELISA detected antibodies from 14 days post-infection (dpi) and remained positive until the end of the experiment (28 dpi). Comparisons using the Kappa coefficient showed strong agreement (100%) between the cELISA and a plaque reduction neutralization test (PRNT).

Discussion

Because our cELISA is simpler, faster, and gives comparable or better results than PRNT, it would be an adequate screening test for suspect NiV and HeV cases, and it would also be useful for epidemiological surveillance of Henipavirus infections in different animal species without changing reagents.

Evaluation of larval surface antigens from infective larvae of Strongyloides venezuelensis for the serodiagnosis of human strongyloidiasis

Serodiagnosis of strongyloidiasis is usually performed by ELISA for the detection of IgG antibodies due to its high sensitivity and practicality, but its main limitation is a constant source of S. stercoralis antigens. The use of S. venezuelensis as a heterologous source of antigens has facilitated several published studies on the serodiagnosis and epidemiology of human strongyloidiasis. The main objective of this study was to evaluate the diagnostic accuracy of surface cuticle antigens of infective larvae of S. venezuelensis extracted with CTAB detergent (L3-CTAB) in comparison with soluble somatic extracts (L3-SSE) using a panel of sera from immunocompetent and immunocompromised individuals, at three different cut-offs. ROC curve analysis showed that L3-CTAB had an AUC of 0.9926. At the first cut-off value (OD 450 nm = 0.214), sensitivity and specificity were 100% and 90.11%, respectively, with a diagnostic accuracy of 0.93. At a second cut-off value (OD 450 nm = 0.286), sensitivity and specificity were 70% and 100%, respectively, with a diagnostic accuracy of 0.91. However, at an alternative third cut-off value (OD 450 nm = 0.589), sensitivity and specificity were 95% and 97.8%, respectively, with a diagnostic accuracy of 0.97. Using L3-CTAB as an antigenic source, the seropositivity rate in immunocompromised patients was 28.13% (9/32) whereas a seropositivity rate of 34.38% (11/32) was found when L3-SSE was used in ELISA. Therefore, the L3-CTAB is simple and practical to obtain and was found to be highly sensitive and specific.

Point-of-Care Diagnostic for Trichomonas vaginalis, the Most Prevalent, Non-Viral Sexually Transmitted Infection

A point-of-care (POC) diagnostic is needed for both women and men to establish universal screening and surveillance for the number one, non-viral sexually transmitted infection (STI) caused by Trichomonas vaginalis. We developed a POC diagnostic for this STI using the MedMira Rapid Vertical Flow (RVF^®) Technology test cartridge with a membrane that includes a Vertical procedural/reagent control line (referred to as CVL) and spotted with 1 µg of a 72.4-kDa truncated version of α-actinin called ACT::SOE3. This protein is a specific diagnostic target for antibody in sera of individuals with trichomoniasis. Serum antibody to ACT::SOE3 is a positive reaction with the test spot. Specificity of ACT::SOE3 was revealed with monoclonal antibodies (MAbs) generated to ACT::SOE3. Addition of negative control serum with MAb 67B reactive to ACT::SOE3 shows detection of both ACT::SOE3 and the CVL. Only positive sera of individuals had antibody reactive with ACT::SOE3 and detected the presence of the spot and the CVL. Negative control sera were unreactive with ACT::SOE3 and only showed the presence of the CVL. Importantly, to show proof-of-principle for POC application, ACT::SOE3 was detected with the positive patient sera spiked with whole blood. Finally, packaged cartridges stored with desiccant packs at 37 °C for one year gave identical results with the positive and negative human sera. Our results show the validity of this new POC serodiagnostic for this STI.

Rapid Point-of-Care Tests Using Staphylococcal Protein A Can Detect Early IgM Responses in HIV-1 and Treponema pallidum Infections

Serological assays detecting IgM antibodies in addition to IgG antibodies have a diagnostic advantage in finding early infections. Staphylococcal protein A (SpA), widely used as an antibody-detecting reagent in various immunoassays, is considered to have a high binding affinity mainly to IgG, although its interaction with other classes of immunoglobulins has also been documented. Using 28 samples from 22 HIV-1 seroconversion panels, the present study demonstrated detection of early IgM antibodies by SpA-based rapid point-of-care tests, including DPP HIV 1/2, DPP HIV-Syphilis, STAT-PAK HIV 1/2, and Sure Check HIV 1/2. Samples with predominant IgM antibodies were identified by in-house IgM assays and confirmed by pretreatment with 0.1 M 2-mercaptoethanol. Likewise, the detection of treponemal IgM antibodies was shown by DPP HIV-Syphilis assay in eight samples collected at early syphilis infection. Direct interaction between IgM and SpA immobilized in solid phase or in solution was demonstrated with purified human polyclonal IgM. A strong correlation was found between the antibody levels detected by SpA and anti-IgM reagent in the early seroconversion samples, thus supporting the evidence for IgM binding by SpA. These assays demonstrated the ability to detect IgM antibodies, which may increase test sensitivity in early infections due to a reduced serodiagnostic window. IMPORTANCE Sexually transmitted infections, including HIV and syphilis, remain a global public health concern. The main laboratory testing approach for HIV and syphilis relies on serological assays. Detection of the IgM class of antibodies may have a diagnostic advantage in finding early infections. The present study using well-characterized HIV-1 and syphilis samples has demonstrated that staphylococcal protein A employed for antibody detection in rapid point-of-care tests, including DPP HIV 1/2, DPP HIV-Syphilis, STAT-PAK HIV 1/2, and Sure Check HIV 1/2, can capture IgM antibodies in addition to IgG antibodies. The findings strongly suggest that the ability to detect IgM antibodies by these immunoassays may facilitate the identification of acute-stage HIV and syphilis infections.

ELISA-based evaluation of antibody response to Leishmania in a region endemic for cutaneous leishmaniasis

Leishmaniasis includes several clinical forms. While routine diagnosis of cutaneous leishmaniasis (CL) is by microscopy, an antibody response to CL has been reported in several recent studies. This study evaluated anti-leishmanial immunoglobulin G (IgG) antibody responses as a biomarker of active leishmaniasis and a measure of exposure to Leishmania. Sera from 50 untreated CL patients, 140 patients under treatment and 280 healthy individuals residing in endemic regions collected as part of an epidemiological survey, was analysed with an enzyme-linked immunosorbent assay established in-house using receiver operator characteristic curve at optimized cut-off value. The assay showed high performance as a diagnostic tool in identifying exposure in endemic individuals (sensitivity: 98%, specificity: 90.3%). All patients showed lower antibody levels over time since onset of lesion/s. Antibody levels were higher (p ˂ .01) and persisted for a longer period in untreated patients. In patients under treatment, the level of anti-IgG antibodies was negatively correlated with the total duration the patient had been on treatment. The anti-leishmanial IgG response in Leishmania donovani-induced CL is transient and is unlikely to confer protective immunity. Optimized serological assays may be useful in endemic settings for diagnosis and monitoring the treatment response in CL.

Specificity of Immunoglobulin Response to Nontuberculous Mycobacteria Infection in People with Cystic Fibrosis

Nontuberculous mycobacteria (NTM) infections are increasingly prevalent in chronic lung diseases, including cystic fibrosis (CF). Mycobacterium abscessus is of particular concern due to relatively greater virulence and intrinsic antimicrobial resistance. Airway culture identification, the standard method for detecting pulmonary infection, is hindered by low sensitivity, long culture times, and reliance on sputum production or lavage. A culture-independent test for detecting NTM infection could complement, or replace, sputum culture, which is becoming more difficult to obtain with reduced sputum production by people with CF (pwCF) on highly effective modulator therapy. We describe an assay for the detection of plasma anti-M. abscessus antibodies of pwCF to antigens from M. abscessus lysates. Anti-M. abscessus IgG and IgA, but not IgM, discriminated with high specificity subjects infected with M. abscessus from those infected by M. avium complex, and from those with distant or no NTM infections. The IgG3 subclass predominated with minor contributions by other subclasses. Both aqueous and organic soluble antigens were recognized by plasma IgG. A validation cohort measuring IgG and IgG3 identified M. abscessus positive subjects, and elevated IgG was sustained over several years. These studies show the benefit of M. abscessus cell lysates to detect plasma IgG of subjects with CF and M. abscessus infections. Subclass analysis suggests that IgG3 is the predominant subtype in these subjects with chronic bacterial infections suggesting a defect in class maturation. Serodiagnosis could be useful to monitor M. abscessus group infections in chronic lung disease as an adjunct or alternative to culture. IMPORTANCE Lung infections with nontuberculous mycobacteria (NTM), and particularly Mycobacterium abscessus, a pathogen with high antibiotic resistance, are of great concern due to poor clinical outcomes and challenging detection in people with cystic fibrosis and other diseases. Standard detection methods are insensitive and increasingly difficult. We describe the measurement of NTM-specific antibodies from plasma to identify subjects infected with M. abscessus. The assay is sensitive and provides information on the immune response to NTM infections. This assay could be used to help identify subjects with NTM pulmonary infections and track disease progression, either alone or in conjunction with other tests.

Assessment of recombinant antigens Tp0100 and Tp1016 of Treponema pallidum for serological diagnosis of syphilis

Objective

To discover novel serodiagnostic candidates for the serological diagnosis of syphilis.

Methods

Two recombinant Treponema pallidum proteins Tp0100 and Tp1016 were expressed, purified, and identified by Western Blotting. A total of 600 clinical serum samples were tested with the Tp0100‐based ELISA, the Tp1016‐based ELISA, and the commercial LICA Syphilis TP kit (ChIVD, Beijing, China). The sensitivities were determined by testing 340 samples from individuals with clinically diagnosed primary, secondary, latent, and tertiary syphilis. The specificities were determined by screening 260 samples from healthy controls and individuals with potentially cross‐reactive infections, including leptospirosis, Lyme disease, hepatitis B, tuberculosis, rheumatoid arthritis, systemic lupus erythematosus. Kappa (κ) values were applied to compare the agreement between clinical syphilis diagnosis and the Tp0100‐based ELISA, the Tp1016‐based ELISA, or the LICA Syphilis TP test.

Results

Using clinical syphilis diagnosis as the gold standard, Tp0100 exhibited an overall sensitivity of 95.6% and specificity of 98.1% for testing IgG antibody while Tp1016 demonstrated only an overall sensitivity of 75.0% and specificity of 79.6%. In contrast, the LICA Syphilis TP test revealed an overall sensitivity of 97.6% and specificity of 96.2%. In addition, the overall percent agreement and corresponding κ values were 96.7% (95% CI 95.6%–97.8%) and 0.93 for the Tp0100‐based ELISA, 77.0% (95% CI 74.3%–79.7%) and 0.54 for the Tp1016‐based ELISA, and 97.0% (95% CI 96.0%–98.0%) and 0.94 for the LICA Syphilis TP test, respectively.

Conclusion

The recombinant T. pallidum protein Tp0100 shows promise as a novel diagnostic antigen in the serological tests for syphilis.

A High-Throughput Yellow Fever Neutralization Assay

Quick and accurate detection of neutralizing antibodies (nAbs) against yellow fever is essential in serodiagnosis during outbreaks for surveillance and to evaluate vaccine efficacy in population-wide studies. All of this requires serological assays that can process a large number of samples in a highly standardized format. Albeit being laborious, time-consuming, and limited in throughput, the classical plaque reduction neutralization test (PRNT) is still considered the gold standard for the detection and quantification of nAbs due to its sensitivity and specificity. Here, we report the development of an alternative fluorescence-based serological assay (SNTFLUO) with an equally high sensitivity and specificity that is fit for high-throughput testing with the potential for automation. Finally, our novel SNTFLUO was cross-validated in several reference laboratories and against international WHO standards, showing its potential to be implemented in clinical use. SNTFLUO assays with similar performance are available for the Japanese encephalitis, Zika, and dengue viruses amenable to differential diagnostics. IMPORTANCE Fast and accurate detection of neutralizing antibodies (nAbs) against yellow fever virus (YFV) is key in yellow fever serodiagnosis, outbreak surveillance, and monitoring of vaccine efficacy. Although classical PRNT remains the gold standard for measuring YFV nAbs, this methodology suffers from inherent limitations such as low throughput and overall high labor intensity. We present a novel fluorescence-based serum neutralization test (SNTFLUO) with equally high sensitivity and specificity that is fit for processing a large number of samples in a highly standardized manner and has the potential to be implemented for clinical use. In addition, we present SNTFLUO assays with similar performance for Japanese encephalitis, Zika, and dengue viruses, opening new avenues for differential diagnostics.

IgA Serological Response for the Diagnosis of Mycobacterium abscessus Infections in Patients with Cystic Fibrosis

The immunoglobulin A (IgA) status of cystic fibrosis (CF) patients, presenting with or without a non-tuberculous mycobacterial (NTM) infection, has to date not been fully elucidated toward two antigenic preparations previously described. We have chosen to determine the clinical values of an IgA ELISA for the diagnosis of NTM and/or Mycobacterium abscessus infections in CF patients. One hundred and 73 sera from CF patients, comprising 33 patients with M. abscessus positive cultures, and 31 non-CF healthy controls were assessed. IgA levels were evaluated by indirect ELISAs using a surface antigenic extract named TLR2eF for TLR2 positive extract and a recombinant protein, the phospholipase C (rMAB_0555 or rPLC). These assays revealed a sensitivity of 52.6% (95% CI = 35.8% to 69%) and 42.1% (95% CI = 26.3% to 59.2%) using TLR2eF and rPLC, respectively, and respective specificities of 92.6% (95% CI = 87.5% to 96.1%) and 92% (95% CI = 86.7% to 95.7%) for samples culture positive for M. abscessus. Overall sensitivity and specificity of 66.7% and 85.4%, respectively, were calculated for IgA detection in M. abscessus-culture positive CF patients, when we combine the results of the two used antigens, thus demonstrating the efficiency in detection of positive cases for these two antigens with IgA isotype. CF patients with a positive culture for M. abscessus had the highest IgA titers against TLR2eF and rPLC. The diagnosis of NTM infections, including those due to M. abscessus, can be improved by the addition of an IgA serological assay, especially when cultures, for example, are negative. Based on these promising results, a serological follow-up of a larger number of patients should be performed to determine if the IgA response may be correlated with an active/acute infection state or a very recent infection. IMPORTANCE Mycobacterium abscessus is currently the most frequently isolated rapid growing mycobacterium in human pathology and the major one involved in lung infections. It has recently emerged as responsible for severe pulmonary infections in patients with cystic fibrosis (CF) or those who have undergone lung transplantation. In addition, it represents the most antibiotic resistant mycobacterial species. However, despite its increasing clinical importance, very little is known about the use of M. abscessus parietal compounds and the host response. This has led to the development of serological tests to measure the antibody response in infected patients, and potentially to link this to the culture of respiratory samples. Herein, we describe an important analysis of the serological IgA response from CF patients, and we demonstrate the full diagnostic usefulness of this assay in the diagnosis of NTM infections, and more particularly M. abscessus, in CF patients.

Diagnostic value of recombinant nanoluciferase fused Toxoplasma gondii antigens in Luciferase-linked Antibody Capture Assay (LACA) for Toxoplasma infection in pigs

Toxoplasmosis is a widespread protozoan zoonosis. Since ingesting undercooked meat harboring Toxoplasma gondii cyst is considered one of the major transmission routes to humans, the screening of T. gondii in meat-producing animals can reduce the risk of food-borne toxoplasmosis in humans. Among serological diagnostic methods, Luciferase-linked Antibody Capture Assay (LACA) has been found to be a promising platform with high sensitivity and specificity. In this study, we aimed to evaluate recombinant nanoluciferase fused-T. gondii antigens (rNluc-GRA6, rNluc-GRA7, rNluc-GRA8 and rNluc-BAG1) for their potential use in LACA for pigs. As a result, the sensitivity of GRA6-, GRA7-, GRA8- and BAG1-LACA were 70.0%, 80.0%, 80.0% and 30.0% with specificity 87.0%, 81.5%, 74.1% and 50.0%, respectively. The cocktail LACA using a mixture of rNluc-GRA6, rNluc-GRA7 and rNluc-GRA8 indicated higher sensitivity (90.0%) and a similar specificity (96.3%) in comparison with the commercial ELISA kit. Compared to the Dye-Test as a reference test, cocktail LACA showed strong agreement (kappa value=0.811) when we assessed pig sera collected at the slaughterhouse. In addition, we also successfully established the rapid LACA format for the detection of Toxoplasma infection in pigs (called Rapid-LACA) in which the test could be performed within 30 min. In Rapid-LACA, the protein A pre-coated/blocked plates could be preserved at −30°C, 4°C or room temperature conditions for at least two months without compromising on the quality of assay.

Efficacy of LD Bio Aspergillus ICT Lateral Flow Assay for Serodiagnosis of Chronic Pulmonary Aspergillosis

Background: The diagnosis of CPA relies on the detection of the IgG Aspergillus antibody, which is not freely available, especially in resource-poor settings. Point-of-care tests like LDBio Aspergillus ICT lateral flow assay, evaluated in only a few studies, have shown promising results for the diagnosis of CPA. However, no study has compared the diagnostic performances of LDBio LFA in setting of tuberculosis endemic countries and have compared it with that of IgG Aspergillus. Objectives: This study aimed to evaluate the diagnostic performances of LDBio LFA in CPA and compare it with existing the diagnostic algorithm utilising ImmunoCAP IgG Aspergillus. Methods: Serial patients presenting with respiratory symptoms (cough, haemoptysis, fever, etc.) for >4 weeks were screened for eligibility. Relevant investigations, including direct microscopy and culture of respiratory secretions, IgG Aspergillus, chest imaging, etc., were done according to existing algorithm. Serums of all patients were tested by LDBio LFA and IgG Aspergillus (ImmunoCAP Asp IgG) and their diagnostic performances were compared. Results: A total of 174 patients were included in the study with ~66.7% patients having past history of tuberculosis. A diagnosis of CPA was made in 74 (42.5%) of patients. The estimated sensitivity and specificity of LDBio LFA was 67.6% (95% CI: 55.7−78%) and 81% (95% CI: 71.9−88.2%), respectively, which increased to 73.3% (95% CI: 60.3−83.9%) and 83.9% (95% CI: 71.7−92.4%), respectively, in patients with a past history of tuberculosis. The sensitivity and specificity of IgG Aspergillus was 82.4% (95% CI: 71.8−90.3%) and 82% (95% CI: 73.1−89%); 86.7% (95% CI: 75.4−94.1%) and 80.4% (95% CI: 67.6−89.8%), in the whole group and those with past history of tuberculosis, respectively. Conclusions: LDBio LFA is a point-of-care test with reasonable sensitivity and specificity. However, further tests may have to be done to rule-in or rule-out the diagnosis of CPA in the appropriate setting.

Development of a novel glycoprotein-based immunochromatographic test for the rapid serodiagnosis of bovine brucellosis

AIMS

Bovine brucellosis is a worldwide zoonotic disease that causes important economic losses and public health concerns. Because control of the disease depends on vaccination, serodiagnosis and isolation of the infected animals; affordable, rapid and accurate point of care (POC) tests are needed.

METHODS AND RESULTS

We developed and evaluated a novel glycoprotein-based immunochromatographic test for the detection of IgG antibodies against the O-polysaccharide of Brucella in bovine serum samples. Brucella GlycoStrip combines the power of immunochromatographic and bacterial glycoengineering technologies for the diagnosis of bovine brucellosis. The analysis of positive and negative reference samples indicated that the test has a diagnostic sensitivity and specificity of 96.9% (95% CI: 92.7-100.0%) and 100%, respectively.

CONCLUSIONS

Due to the recombinant glycoprotein-based antigen OAg-AcrA, which consists of the O-side chain of Brucella smooth lipopolysaccharide (sLPS) covalently linked to the carrier protein AcrA, the test is highly accurate, allows the differentiation of infected animals from those vaccinated with a rough strain or with a single dose of a smooth strain and fulfill the minimum diagnostic requirements established by the national and international regulations.

SIGNIFICANCE AND IMPACT OF STUDY

This strip test could provide a rapid (10 min) and accurate diagnosis of bovine brucellosis in the field contributing to the control of the disease.

PERFORMANCE EVALUATION OF SIX DIFFERENT SARS-CoV-2 ANTIBODY IMMUNOASSAYS: DISEASE SEVERITY AND SERUM SAMPLING TIME AFFECT THE SENSITIVITY

Comparative validation data and clinical performance data are essential for the reliable interpretation of SARS-CoV-2 antibody test results. This study aimed to assess the performance of six SARS-CoV-2 IgG immunoassays in different disease severity settings. Four automated chemiluminescence immunoassays Access (Beckman Coulter), Architect (Abbott), Atellica-IM (Siemens) and Elecsys (Roche) and two ELISA assays (SARS-CoV-2 IgG-S1-based and NCP IgG, Euroimmun) were evaluated in 143 patients and 50 pre-pandemic control sera. Accuracy and precision tests were performed for validation. Overall sensitivity differed between 73.38-88.65%, being higher in spike protein-based assays. Specificity was ≥ 98% in all immunoassays. IgG response was lower for the samples taken <20 days post-symptom onset (87.30%) than for the samples taken ≥20 days post-symptom onset (94.80%). Higher rate of antibody was detected in the clinically moderate disease group. In the asymptomatic and mild group more antibody positivity was detected with spike protein-based assays. Clinical performance of the immunoassays differs according to disease severity and antigen targeted; moderate disease leading to highest rate of IgG response. All the assays tested were eligible for the detection of SARS-CoV-2 IgG however, spike-based assays revealed relatively higher sensitivity than the nucleoprotein-based assays particularly in the asymptomatic and mild disease severity.

Peptide-Integrated Superparamagnetic Nanoparticles for the Identification of Epitopes from SARS-CoV-2 Spike and Nucleocapsid Proteins

The COVID-19 pandemic, caused by the fast transmission and spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is currently considered a serious health problem, requiring an effective strategy to contain SARS-CoV-2 dissemination. For this purpose, epitopes of the SARS-CoV-2 spike (S) and sucleocapsid (N) proteins were identified by bioinformatics tools, and peptides that mimic these epitopes were chemically synthesized and then conjugated to superparamagnetic nanoparticles (SPMNPs). Three peptides from S protein and three from N protein were used as antigens in a conventional enzyme-linked immunosorbent assay (ELISA) against serum samples from COVID-19-positive patients, or from healthy donors, collected before the pandemic. Three peptides were effective as antigens in conventional peptide-based ELISA, achieving 100% sensitivity and specificity, with high accuracy. The best-performing peptides, p2pS, p1pN, and p3pN, were associated with superparamagnetic nanoparticles (SPMNPs) and were used to perform nanomagnetic peptide-based ELISA. The p2pS-SPMNP conjugate presented 100% sensitivity and specificity and excellent accuracy (area under the curve (AUC) = 1.0). However, p1pN and p3pN peptides, when conjugated to SPMNPs, did not preserve the capacity to differentiate positive sera from negative sera in all tested samples, yet both presented sensitivity and specificity above 80% and high accuracy, AUC > 0.9. We obtained three peptides as advantageous antigens for serodiagnosis. These peptides, especially p2pS, showed promising results in a nanomagnetic peptide-based ELISA and may be suitable as a precoated antigen for commercial purposes, which would accelerate the diagnosis process.

Genetic drift in the genome of SARS COV-2 and its global health concern

The outbreak of the current coronavirus disease (COVID-19) occurred in late 2019 and quickly spread all over the world. The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) belongs to a genetically diverse group that mutates continuously leading to the emergence of multiple variants. Although a few antiviral agents and anti-inflammatory medicines are available, thousands of individuals have passed away due to emergence of new viral variants. Thus, proper surveillance of the SARS-CoV-2 genome is needed for the rapid identification of developing mutations over time, which are of the major concern if they occur specifically in the surface spike proteins of the virus (neutralizing analyte). This article reviews the potential mutations acquired by the SARS-CoV2 since the pandemic began and their significant impact on the neutralizing efficiency of vaccines and validity of the diagnostic assays.

Seroprevalence of Toxoplasma gondii infection from water buffaloes (Bubalus bubalis) in northeastern and southern Thailand

Toxoplasmosis is a parasitic disease resulting from infection with the apicomplexan Toxoplasma gondii (Nicolle et Manceaux, 1908), one of the world's most common parasites in warm-blooded animals, including humans. Sources of infection can be exposed to infected cat faeces, mother-to-child transmission during pregnancy, and notably, the consumption of undercooked contaminated meat of intermediate hosts. In Thailand, water buffaloes are highly valued for rice cultivation, traditional culture and meat production. Like several other mammalian species, these animals play a role as reservoirs of T. gondii, thus representing a threat to human health. The seroprevalence of T. gondii infection in swamp buffaloes was examined in southern and northeastern Thailand. In total, serum samples of 721 water buffaloes were collected from seven provinces (Ubon Ratchathani, Roi Et, Si Sa Ket, Surin, Buri Ram, Sakon Nakhon, and Songkhla) and examined for the presence of T. gondii infection using commercial latex agglutination test kits (TOXOCHECK-MT, Eiken Chemical Co., Tokyo, Japan). Of the 721 animals analysed, 49 (6.8%) were positive for T. gondii. Songkhla province had the highest seroprevalence (14.7%) among the seven provinces covered in this survey. There was a potential risk to local citizens of T. gondii infection identified by the present study, notably in northeastern Thailand, where despite lower seroprevalence consuming raw buffalo meat salad should be restricted to avoid the risk of zoonotic infections.

Development and Evaluation of a Fusion Polyprotein Based on HspX and Other Antigen Sequences for the Serodiagnosis of Tuberculosis

Background

The lack of suitable diagnostic tools contributes to the high prevalence of tuberculosis (TB) worldwide. Serological tests, based on multiple target antigens, represent an attractive option for diagnosis of this disease due to their rapidity, convenience, and low cost.

Methods

Measures to reduce non-specific reactions and thereby improve the specificity of serological tests were investigated, including blocking antibodies against common bacteria in serum samples and synthesizing polypeptides covering non-conserved dominant B-cell epitopes of antigens. In addition, a fusion polyprotein containing HspX and eight other antigen sequences was constructed and expressed to increase overall sensitivity of the tests.

Results

Inclusion of Escherichia coli lysate partially increased the specificity of the serological tests, while synthesis and inclusion of peptides containing non-conserved sequences of TB antigens as well as dominant B-cell epitopes reduced non-specific reactions without a decrease in sensitivity of the tests. A polyprotein fusing HspX and eight other antigen sequences was constructed and displayed 60.2% sensitivity, which was higher than that of HspX and the other individual antigen segments. Moreover, the specificity of the polyprotein was 93.8%, which was not significantly decreased when compared with HspX and the other individual antigen segments.

Conclusions

The roles of the fusion polyprotein in the humoral immune response against TB infection were demonstrated and provide a potential novel approach for the development of TB diagnostics.

Diagnostic accuracy of somatic and excretory-secretory antigens from Strongyloides venezuelensis infective larvae for the immunodiagnosis of human strongyloidiasis

To evaluate the diagnostic accuracy of three types of antigenic preparations from Strongyloides venezuelensis infective larvae for detection of serum IgG anti-Strongyloides antibodies by enzyme-linked immunosorbent assay (ELISA). Soluble somatic fractions (SSF) and membrane somatic fractions (MSF) and excretory−secretory (E/S) products from S. venezuelensis infective larvae were evaluated against 71 sera from individuals with strongyloidiasis, 105 sera from healthy individuals, and 84 sera from individuals with other helminth infections. Using an ELISA cut-off for 100% sensitivity, E/S products were 97.88% specific followed by MSF (93.12%) and then by SSF (85.2%). The occurrence of cross-reactivity with other helminths was 4.76% (4/84) with E/S products, 8.33% (7/84) with MSF, and 17.86% (15/84) with SSF. For a cut-off for 100% specificity, E/S products showed a sensitivity of 88.73% whereas MSF and SSF showed sensitivities of 59.15% and 53.52%, respectively. In conclusion, E/S products were the best antigenic option for the serodiagnosis of human strongyloidiasis.

Identification of Immunogenic Linear B-Cell Epitopes in C. burnetii Outer Membrane Proteins Using Immunoinformatics Approaches Reveals Potential Targets of Persistent Infections

Coxiella burnetii is a global, highly infectious intracellular bacterium, able to infect a wide range of hosts and to persist for months in the environment. It is the etiological agent of Q fever—a zoonosis of global priority. Currently, there are no national surveillance data on C. burnetii’s seroprevalence for any South American country, reinforcing the necessity of developing novel and inexpensive serological tools to monitor the prevalence of infections among humans and animals—especially cattle, goats, and sheep. In this study, we used immunoinformatics and computational biology tools to predict specific linear B-cell epitopes in three C. burnetii outer membrane proteins: OMP-H (CBU_0612), Com-1 (CBU_1910), and OMP-P1 (CBU_0311). Furthermore, predicted epitopes were tested by ELISA, as synthetic peptides, against samples of patients reactive to C. burnetii in indirect immunofluorescence assay, in order to evaluate their natural immunogenicity. In this way, two linear B-cell epitopes were identified in each studied protein (OMP-H_(51–59), OMP-H_(91–106), Com-1_(57–76), Com-1_(191–206), OMP-P1_(197–209), and OMP-P1_(215–227)); all of them were confirmed as naturally immunogenic by the presence of specific antibodies in 77% of studied patients against at least one of the identified epitopes. Remarkably, a higher frequency of endocarditis cases was observed among patients who presented an intense humoral response to OMP-H and Com-1 epitopes. These data confirm that immunoinformatics applied to the identification of specific B-cell epitopes can be an effective strategy to improve and accelerate the development of surveillance tools against neglected diseases.

A Multi-Epitope Fusion Protein-Based p-ELISA Method for Diagnosing Bovine and Goat Brucellosis

In recent years, the incidence of brucellosis has increased annually, causing tremendous economic losses to animal husbandry in a lot of countries. Therefore, developing rapid, sensitive, and specific diagnostic techniques is critical to control the spread of brucellosis. In this study, bioinformatics technology was used to predict the B cell epitopes of the main outer membrane proteins of Brucella, and the diagnostic efficacy of each epitope was verified by an indirect enzyme-linked immunosorbent assay (iELISA). Then, a fusion protein containing 22 verified epitopes was prokaryotically expressed and used as an antigen in paper-based ELISA (p-ELISA) for serodiagnosis of brucellosis. The multi-epitope-based p-ELISA was evaluated using a collection of brucellosis-positive and -negative sera collected from bovine and goat, respectively. Receiver operating characteristic (ROC) curve analysis showed that the sensitivity and specificity of detection-ELISA in diagnosing goat brucellosis were 98.85 and 98.51%. The positive and the negative predictive values were 99.29 and 98.15%, respectively. In diagnosing bovine brucellosis, the sensitivity and specificity of this method were 97.85 and 96.61%, with the positive and negative predictive values being identified as 98.28 and 97.33%, respectively. This study demonstrated that the B cell epitopes contained in major antigenic proteins of Brucella can be a very useful antigen source in developing a highly sensitive and specific method for serodiagnosis of brucellosis.

Identification of Anti-Premembrane Antibody as a Serocomplex-Specific Marker To Discriminate Zika, Dengue, and West Nile Virus Infections

Although transmission of Zika virus (ZIKV) in the Americas has greatly declined since late 2017, recent reports of reduced risks of symptomatic Zika by prior dengue virus (DENV) infection and increased risks of severe dengue disease by previous ZIKV or DENV infection underscore a critical need for serological tests that can discriminate past ZIKV, DENV, and/or other flavivirus infections and improve our understanding of the immune interactions between these viruses and vaccine strategy in endemic regions. As serological tests for ZIKV primarily focus on envelope (E) and nonstructural protein 1 (NS1), antibodies to other ZIKV proteins have not been explored. Here, we employed Western blot analysis using antigens of 6 flaviviruses from 3 serocomplexes to investigate antibody responses following reverse transcription-PCR (RT-PCR)-confirmed ZIKV infection. Panels of 20 primary ZIKV and 20 ZIKV with previous DENV infection recognized E proteins of all 6 flaviviruses and the NS1 protein of ZIKV with some cross-reactivity to DENV. While the primary ZIKV panel recognized only the premembrane (prM) protein of ZIKV, the ZIKV with previous DENV panel recognized both ZIKV and DENV prM proteins. Analysis of antibody responses following 42 DENV and 18 West Nile virus infections revealed similar patterns of recognition by anti-E and anti-NS1 antibodies, whereas both panels recognized the prM protein of the homologous serocomplex but not others. The specificity was further supported by analysis of sequential samples. Together, these findings suggest that anti-prM antibody is a flavivirus serocomplex-specific marker and can be used to delineate current and past flavivirus infections in endemic areas. IMPORTANCE Despite a decline in Zika virus (ZIKV) transmission since late 2017, questions regarding its surveillance, potential reemergence, and interactions with other flaviviruses in regions where it is endemic remain unanswered. Recent studies have reported reduced risks of symptomatic Zika by prior dengue virus (DENV) infection and increased risks of severe dengue disease by previous ZIKV or DENV infection, highlighting a need for better serological tests to discriminate past ZIKV, DENV, and/or other flavivirus infections and improved understanding of the immune interactions and vaccine strategy for these viruses. As most serological tests for ZIKV focused on envelope and nonstructural protein 1, antibodies to other ZIKV proteins, including potentially specific antibodies, remain understudied. We employed Western blot analysis using antigens of 6 flaviviruses to study antibody responses following well-documented ZIKV, DENV, and West Nile virus infections and identified anti-premembrane antibody as a flavivirus serocomplex-specific marker to delineate current and past flavivirus infections in areas where flaviviruses are endemic.

Eosinophilic meningomyelitis caused by Toxocara spp. in a migrant coming from La Reunion

A young man coming from La Reunion presented with headache, back pain, progressive urinary incontinence and gait instability. Blood cells count and cerebrospinal fluid (CSF) analysis showed eosinophilia. Magnetic resonance imaging (MRI) confirmed thoracic myelitis. CSF and serum serodiagnosis for Toxocara were both positive. Eosinophilic meningomyelitis secondary to a toxocariasis was diagnosed.

Comparison of the New Multiepitope Recombinant Peptide Antigen with Cyst Fluid Antigen in the Follow-up of Patients with Cystic Echinococcosis

Objective

The follow-up of patients with cystic echinococcosis (CE) offers the opportunity of evaluating the prognosis of the infection as well as detecting relapse. This study aimed to evaluate the performance of the new multiepitope recombinant peptide (recDipol) antigen in the follow-up of CE patients treated by surgery or percutaneous aspiration injection respiration.

Methods

A total of 137 blood samples from 28 patients were evaluated by IgG-ELISA method using recDipol and hydatid fluid (HF) antigens. The patients were simultaneously checked for recurrence by ultrasonography.

Results

The seropositivity rate of the 28 patients varied considerably during the follow-up. When the first blood of the patients was evaluated, 4 (14.28%) were seronegative by HF-ELISA and 9 (32.14%) were recDipol-ELISA. During the entire follow-up, only 1 (3.5%) and 6 (21.4%) patients were seronegative by HF-ELISA and recDipol ELISA, respectively.

Conclusion

We found that recDipol did not perform as expected in the follow-up due to the higher number of seronegative patients compared to HF-ELISA in the first blood and during the entire follow-up. Our results suggest that imaging methods are gold standards in the diagnosis and that, in parallel, longer-term patient follow-up is required with recombinant antigens that have an improved diagnostic performance.

Evaluation of The Diagnostic Algorithms for Serodiagnosis of Syphilis

We analyzed the performance parameters of the traditional and the reverse algorithms to find out which one is more convenient for serodiagnosis of syphilis. In total, 4789 serum samples were obtained in a cross-sectional study. Venereal Disease Research Laboratory (VDRL), Treponema pallidum Haemagglutination Assay (TPHA) and Chemiluminescent Microparticle Immunoassay (CMIA) tests were performed for every serum sample. In case of discordance between results, the TPHA was applied as a second treponemal test. Overall, 207 patients were serodiagnosed with syphilis. Among 4789 subjects tested, 125 (2.6%) and 206 (4.3%) were positive using the traditional algorithm and the reverse algorithm, respectively. The missed diagnosis rate of the traditional algorithm was 42.5%. The reverse algorithm had higher sensitivity than the traditional algorithm. Sensitivity levels of the traditional and the reverse algorithms were 57.49% and 99.85% respectively. The false positivity of the reverse algorithms was 0.02%.

Borrelia burgdorferi BmpA-BBK32 and BmpA-BBA64: New Recombinant Chimeric Proteins with Potential Diagnostic Value

Currently, the diagnosis of Lyme disease is based mostly on two-tiered serologic testing. In the new generation of immunoenzymatic assays, antigens comprise whole-cell lysates of members of the Borrelia burgdorferi sensu lato (s.l.) species complex, with the addition of selected recombinant proteins. Due to the high diversity of members of the B. burgdorferi s.l. genospecies and the low degree of conservation among the amino acid sequences of their proteins, serodiagnostic methods currently in use are not sufficient for the correct diagnosis of borreliosis. Two divalent chimeric proteins (BmpA-BBK32 and BmpA-BBA64) were expressed in Escherichia coli. Following purification by one-step metal-affinity chromatography, preparations were obtained containing milligram levels of chimeric protein exhibiting electrophoretic purity in excess of 98%. Reactivity of the new chimeric proteins with specific human IgG antibodies was preliminarily determined by Western blot. For this purpose, 20 negative sera and 20 positive sera was used. The new chimeric proteins were highly reactive with IgG antibodies contained in the serum of patients suffering from borreliosis. Moreover, no immunoreactivity of chimeric proteins was observed with antibodies in the sera of healthy people. These promising results suggest that new chimeric proteins have the potential to discriminate between positive and negative sera.

Immunological Cross-Reactivity of Proteins Extracted from the Oomycete Pythium insidiosum and the Fungus Basidiobolus ranarum Compromises the Detection Specificity of Immunodiagnostic Assays for Pythiosis

Pythiosis, a life-threatening disease caused by Pythium insidiosum, has been increasingly diagnosed worldwide. A recently developed immunochromatographic test (ICT) enables the rapid diagnosis of pythiosis. During the 3-year clinical implementation of ICT in Thailand, we collected the laboratory reports of 38 animals with suspected pythiosis and detected ICT false-positive results in three horses and a dog with basidiobolomycosis. P. insidiosum and Basidiobolus ranarum cause infections with indistinguishable clinical and microscopic features. This study investigated cross-reactive antibodies by probing P. insidiosum and B. ranarum crude extracts and cell-free synthesized I06 protein (encoded in P. insidiosum genome, not other fungi) against a panel of pythiosis, basidiobolomycosis, rabbit anti-I06 peptide, and control sera by Western blot analyses. ICT false-positive results occurred from the cross-reactivity of anti-B. ranarum antibodies to the 15, 50, 60, and 120 kDa proteins of P. insidiosum, not double infections caused by both pathogens. Notably, ICT could help to screen pythiosis, and the positive test requires confirmation by culture or molecular method. The detection specificity of ICT requires improvement. The crude extract containing multispecies antigens needs replacement with a refined P. insidiosum-specific protein. We proposed that the 55 kDa I06 protein is an excellent candidate for developing a more specific serodiagnostic test for pythiosis.

Strongyloides-Specific IgE Phage cDNA Clones and Development of a Novel ELISA for Strongyloidiasis

Strongyloidiasis, caused mainly by the nematode Strongyloides stercoralis, is prevalent worldwide and potentially fatal in immunosuppressed patients. We report on a new IgE biomarker to diagnose Strongyloides infection. Sera from two groups infected with Strongyloides served as positive samples: Group 1A, in which infection was confirmed by stool-microscopy and/or stool-polymerase chain reaction (PCR) and was seropositive by an IgG-enzyme linked immunosorbent assay (ELISA) and an IgG4 rapid test, and Group 1B in which infection was confirmed by stool-PCR but was seronegative. Negative samples (controls) comprised infections with other parasites (Group II) and healthy donors (Group III). Immunoscreenings of an S. stercoralis complementary DNA (cDNA) library were performed, and the cDNA clone with the highest diagnostic potential (clone A133) was selected for recombinant protein production and then evaluated using IgE Western blot and ELISA. The Western blot showed that the recombinant protein (rA133) was 100% reactive with Group IA (n = 10) and Group IB (n = 5), and 96% non-reactive with Groups II and III (n = 25). Subsequently, the IgE-ELISA was developed and showed 100% diagnostic sensitivity in Groups IA (n = 32) and IB (n = 11); and 99.3% specificity in Groups II and III (n = 144). In conclusion, this study has identified rA133 as a novel recombinant protein with potential diagnostic value, and that the IgE-ELISA incorporating this protein may be useful for patient diagnosis and epidemiological studies.

Use of a Latent Class Analysis in the Diagnosis of Chronic Chagas Disease in the Washington Metropolitan Area

BACKGROUND

The diversity of individuals at risk for Trypanosoma cruzi infection in the United States poses challenges for diagnosis. We evaluated the diagnostic accuracy of Food and Drug Administration (FDA)-cleared tests in the Washington Metropolitan area (WMA).

METHODS

In total, 1514 individuals were evaluated (1078 from Mexico, Central and northern South America [TcI-predominant areas], and 436 from southern South America [TcII/V/VI-predominant areas]). Optical density (OD) values from the Hemagen EIA and Chagatest v.3 Wiener, and categorical results of the IgG-TESA-blot (Western blot with trypomastigote excretory-secretory antigen), and the Chagas detect plus (CDP), as well as information of area of origin were used to determine T. cruzi serostatus using latent class analysis.

RESULTS

We detected 2 latent class (LC) of seropositives with low (LC1) and high (LC2) antibody levels. A significantly lower number of seropositives were detected by the Wiener, IgG-TESA-blot, and CDP in LC1 (60.6%, P < .001, 93.1%, P = .014, and 84.9%, P = .002, respectively) as compared to LC2 (100%, 100%, and 98.2%, respectively). LC1 was the main type of seropositives in TcI-predominant areas, representing 65.0% of all seropositives as opposed to 22.8% in TcII/V/VI-predominant areas. The highest sensitivity was observed for the Hemagen (100%, 95% confidence interval [CI]: 96.2-100.0), but this test has a low specificity (90.4%, 95% CI: 88.7-91.9). The best balance between positive (90.9%, 95% CI: 83.5-95.1), and negative (99.9%, 95% CI: 99.4-99.9) predictive values was obtained with the Wiener.

CONCLUSIONS

Deficiencies in current FDA-cleared assays were observed. Low antibody levels are the main type of seropositives in individuals from TcI-predominant areas, the most frequent immigrant group in the United States.

Development of Immunochromatographic Test Kit for Rapid Detection of Specific IgG4 Antibody in Whole-Blood Samples for Diagnosis of Human Gnathostomiasis

Human gnathostomiasis is a harmful food-borne zoonosis caused by roundworms of the genus Gnathostoma. The parasite can occasionally migrate to the central nervous system, causing life-threatening disease and death. Here, we report a new point-of-care (POC) test kit, the gnathostomiasis blood immunochromatographic test (GB-ICT) kit. The kit is based on recombinant Gnathostoma spinigerum antigen and detects specific IgG4 antibody in whole-blood samples (WBSs). The GB-ICT kit showed potentially high diagnostic values with simulated WBSs (n = 248), which were obtained by spiking patients’ sera with red blood cells. The accuracy, sensitivity, specificity, and positive and negative predictive values were 95.2%, 100%, 93.8%, 81.5%, and 100%, respectively. Ten WBSs from clinically suspected gnathostomiasis patients were all positive according to the GB-ICT kit, while 10 WBSs from healthy volunteers were negative. The GB-ICT kit is a simple and convenient POC testing tool using finger-prick blood samples: venous blood sampling and serum separation processes are not required. The GB-ICT kit can support clinical diagnosis in remote areas and field settings without sophisticated equipment facilities.

Recent advances in the diagnosis of COVID-19: a bird's eye view

INTRODUCTION

The COVID-19 pandemic is still escalating and has shaped an extraordinary and pressing need for rapid diagnostics with high sensitivity and specificity. Prompt diagnosis is the key to mitigate this situation. As several diagnostic tools for COVID-19 are already available and others are still under development, mandating a comprehensive review of the efficacy of existing tools and evaluate the potential of others.

AREAS COVERED

Currently explored platforms for SARS-CoV-2 diagnostics and surveillance centered on qRT-PCR, RT-PCR, CRISPR, microarray, LAMP, lateral flow immunoassays, proteomics-based approaches, and radiological scans are overviewed and summarized in this review along with their advantages and downsides. A narrative literature review was carried out by accessing the freely available online databases to encapsulate the developments in medical diagnostics.

EXPERT OPINION

An ideal detection method should be sensitive, specific, rapid, cost-effective, and should allow early diagnosis of the infection as near as possible to the point of care that could alter the current situation for the better. Medical diagnostics is a highly dynamic field as no diagnostic method available for SARS-CoV-2 detection offers a perfect solution and requires more attention and continuous R&D to challenge the present-day pandemic situation.

Enzyme-linked immunosorbent assays using virus-like particles containing mutations of conserved residues on envelope protein can distinguish three flavivirus infections

The recent outbreaks of Zika virus (ZIKV) in flavivirus-endemic regions highlight the need for sensitive and specific serological tests. Previously we and others reported key fusion loop (FL) residues and/or BC loop (BCL) residues on dengue virus (DENV) envelope protein recognized by flavivirus cross-reactive human monoclonal antibodies and polyclonal sera. To improve ZIKV serodiagnosis, we employed wild type (WT) and FL or FL/BCL mutant virus-like particles (VLP) of ZIKV, DENV1 and West Nile virus (WNV) in enzyme linked immunosorbent assays (ELISA), and tested convalescent-phase serum or plasma samples from reverse-transcription PCR-confirmed cases with different ZIKV, DENV and WNV infections. For IgG ELISA, ZIKV WT-VLP had a sensitivity of 100% and specificity of 52.9%, which was improved to 83.3% by FL/BCL mutant VLP and 92.2% by the ratio of relative optical density of mutant to WT VLP. Similarly, DENV1 and WNV WT-VLP had a sensitivity/specificity of 100%/70.0% and 100%/56.3%, respectively; the specificity was improved to 93.3% and 83.0% by FL mutant VLP. For IgM ELISA, ZIKV, DENV1 and WNV WT-VLP had a specificity of 96.4%, 92.3% and 91.4%, respectively, for primary infection; the specificity was improved to 93.7–99.3% by FL or FL/BCL mutant VLP. An algorithm based on a combination of mutant and WT-VLP IgG ELISA is proposed to discriminate primary ZIKV, DENV and WNV infections as well as secondary DENV and ZIKV infection with previous DENV infections; this could be a powerful tool to better understand the seroprevalence and pathogenesis of ZIKV in regions where multiple flaviviruses co-circulate.

Evaluation of the diagnostic potential of recombinant leptospiral OMP A-like protein (Loa22) and transmembrane (OmpL37) protein in latex agglutination test for serodiagnosis of leptospirosis in animals

Leptospirosis is a re-emerging zoonotic disease of animals and humans caused by pathogenic Leptospira, which has major public health concerns. The study is aimed to express the recombinant outer membrane protein (OMP) A-like protein (rLoa22) and transmembrane (rOmpL37) protein of Leptospira interrogans serovar Hardjo in the Escherichia coli and their evaluation as a diagnostic antigen in the latex agglutination test (LAT) to detect anti-leptospiral antibodies in the sera of animals. The Loa22 and OmpL37 genes lacking signal peptide coding sequences were individually amplified (522 and 963 bp), by polymerase chain reaction, and directionally cloned into a pETite N-His Kan vector for expression. The expressed purified proteins were characterized by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and immunoblot, which confirmed leptospiral specific reactive protein with a molecular weight of ~19 and 36 kDa, respectively. The sensitized latex beads coated with these OM proteins separately were evaluated in LAT using cattle sera of microscopic agglutination test (MAT) confirmed positive (n = 53) and negative (n = 52) cases of leptospirosis. The rLoa22 LAT and rOmpL37 LAT revealed the relative diagnostic sensitivity of 94·34 and 96·23%, diagnostic specificity of 92·31 and 96·15% and accuracy of 93·33 and 96·19%, with the excellent agreement of Cohen's kappa value of 0·87 and 0·92, respectively. After extensive evaluation, this rapid recombinant protein-based field diagnostic test can be applied as a screening test for the detection of anti-leptospiral antibodies in the sera of animals in the field conditions.