Neutralizing antibodies (NAbs) are considered the primary mechanism of vaccine-mediated protection against human papillomaviruses (HPV), the causative agent of cervical cancer. However, the minimum level of NAb needed for protection is currently unknown. The HPV pseudovirion-based neutralization assay (PBNA) is the gold standard method for assessing HPV antibody responses but is time-consuming and labor-intensive. With the development of higher valency HPV vaccines, alternative serological assays with the capacity for multiplexing would improve efficiency and output. Here we describe a multiplex bead-based immunoassay to characterize the antibody responses to the seven oncogenic HPV types (HPV16/18/31/33/45/52/58) contained in the current licensed nonavalent HPV vaccine. This assay can measure antibody isotypes and subclasses (total IgG, IgM, IgA1-2, IgG1-4), and can be adapted to measure other antibody features (e.g., Fc receptors) that contribute to vaccine immunity. When tested with serum samples from unvaccinated and vaccinated individuals, we found high concordance between HPV-specific IgG using this multiplex assay and NAbs measured with PBNA. Overall, this assay is high-throughput, sample-sparing, and time-saving, providing an alternative to existing assays for the measurement and characterization of HPV antibody responses.

Toxoplasma gondii is a ubiquitous parasitic protozoan that may be an important cause of neurological and psychiatric diseases. The purpose of this case-control registry-based study was to evaluate the prevalence of T. gondii infection and related risk factors among subjects who attempted suicide by drug use and a control group at the Iranian National Registry Center for Toxoplasmosis in Mazandaran Province, northern Iran. Baseline data were collected from participants using a questionnaire, and a blood sample was taken from each individual. The plasma was prepared for serological analysis, whereas the buffy coat was used for molecular analysis. Out of 282 individuals (147 cases with suicide attempters [SA] and 135 controls), 42.9% of patients and 16.3% of control subjects were positive for anti-Toxoplasma immunoglobin G (IgG), but all participants were negative for T. gondii DNA and anti-Toxoplasma immunoglobin M. Based on multiple logistic regressions, IgG seropositivity in SA in the age group of 20-30 years was 3.22 times higher than that in the control group (p < 0.001). These findings suggest that latent T. gondii infection among SA is significantly higher than that in healthy individuals, indicating a potential association between latent toxoplasmosis and SA at least in the studied area. Further research is needed to shed light on the potential association between T. gondii and suicide among different populations and areas of the world.

Both viral infection and vaccination affect the antibody repertoire of a person. Here, we demonstrate that the analysis of serum antibodies generates information not only on the virus type that caused the infection but also on the specific virus variant. We developed a rapid multiplex assay providing a fingerprint of serum antibodies against five different SARS-CoV-2 variants based on a microarray of virus antigens immobilized on the surface of a label-free reflectometric biosensor. We analyzed serum from the plasma of convalescent subjects and vaccinated volunteers and extracted individual antibody profiles of both total immunoglobulin Ig and IgA fractions. We found that Ig level profiles were strongly correlated with the specific variant of infection or vaccination and that vaccinated subjects displayed a larger quantity of total Ig and a lower fraction of IgA relative to the population of convalescent unvaccinated subjects.

Whipple disease (WD) is a rare infection in genetically susceptible people caused by the bacterium Tropheryma whipplei. An indirect immunofluorescence serological assay (IFA), detecting patient antibodies to the bacterium, was developed using T. whipplei as antigen. We hypothesised that this assay could be used to rule out WD in patients in whom the diagnosis was being considered, based on high immunoglobulin (Ig) G titres to T. whipplei. In this study, 16 confirmed WD patients and 156 age-matched controls from across Australia were compared serologically. WD patients mostly underproduced IgG antibody to T. whipplei, with titres of ≤1:32 being common. While at an antibody titre of <1:64 the assay sensitivity for WD was only 69% [95% confidence interval (CI) 41-89%], its specificity for excluding WD was 91% (95% CI 85-95%). This specificity increased to 95% (95% CI 90-98%) at an antibody titre of <1:16. Patients with antibody titres of >1:64 were unlikely to have WD. At this titre, the seroprevalence of T. whipplei IgG antibody was 92% (223/242) in Australian blood donors. Unlike other serological assays, which are used to confirm a specific infection, this novel assay is designed to rule out WD infection with a specificity in Australia of 91%. Further validation of this assay, by trialling in other countries, should now be undertaken, as its usefulness is dependent on there being a high background seropositivity to T. whipplei in the general population at the location in which the assay is being used.

BACKGROUND: Tuberculosis is an infectious disease responsible for a significant cause of ill health. According to the WHO global tuberculosis report 2021. 9.9 million cases fell sick with TB in 2020. Significantly, the prevalence of tuberculosis in India is 25%.
OBJECTIVE: To analyze the prevalence of tuberculosis in the suburban areas of the metropolitan city in South India. To analyze the serological marker and prognosis of tuberculosis among males and females. To determine the importance of molecular testing - PCR confirmation on TB after AFB smear.
METHODS: A retrospective study to analyze 462 patients enrolled by the respiratory medicine department on suspecting pulmonary- 356 (M-264 & F-92) and extra-pulmonary-106 (M-73&F-33) patients and diagnosed Zhiel-Neelsen staining, Mantoux test, Chip-based RT-PCR test, Erythrocyte sedimentation rate, and analyzed serological test such as C-Reactive Protein, Chemiluminescence immune assay.
RESULTS: 23 patients were positive in Ziehl-Neelsen staining, 65 were positive in molecular True-Nat PCR test, Mantoux skin test induration in 10 patients, 98 TB Positive patients examined in the serological analysis, 1 & 3 patients reacted in HIV/HBsAg, and HBsAg test respectively, by chemiluminescence immunoassay, 8 PTB and 4 EPTB and 47 non-TB patients were positive in C-reactive protein, 46 TB and 94 non-TB patients detected abnormal values out of these 160 patients in ESR test.
CONCLUSIONS: The Prevalence of tuberculosis is significantly rising, especially in the middle-aged population. The rapid molecular diagnostics to detect TB are highly sensitive and specific. Serological markers are essential for the analysis of disease prognosis and need to focus on the guidance of DOTS and RNTCP to End TB.

Canine monocytic ehrlichiosis (CME) is the most common tick-borne disease affecting domestic dogs and other wild canids. It has a worldwide distribution and is associated with the presence of the brown dog tick. Few studies have been conducted in Mexico to identify and characterize Ehrlichia canis genetic variability. In the present study, 111 dogs of different sex, breed, and age from three geographic regions in Mexico were included. All of them had a previous history of tick infestation and/or the presence of one or more clinical signs compatible with CME. All dogs were tested by a commercial ELISA and nested PCR assay for the detection of E. canis. In addition, we analyzed the E. canis genetic diversity from the 16S rRNA gene sequences obtained in this study, along with 15 additional sequences described for E. canis in Mexico and obtained from GeneBank. Serological detection by commercial ELISA results showed overall infection rates of 85.58% (95/111), including 73.1% (30/41) in samples from Guerrero state; 75% (15/20) in Morelos; and 100% (50/50) in Chihuahua. On the other hand, molecular detection (nPCR assay) showed 31.5% (35/111) overall infection rate, with 41.4% (17/41) in Guerrero state; 55% (11/20) in Morelos; and 14% (7/50) in Chihuahua. We observed a high 16S rRNA gene sequence conservancy in most of the E. canis isolates in the three geographical areas from Mexico, including those analyzed in this research, suggesting a common geographic origin among isolates.

Current serological tests cannot differentiate between total immunoglobulin A (IgA) and dimeric IgA (dIgA) associated with mucosal immunity. Here, we describe two new assays, dIgA-ELISA and dIgA-multiplex bead assay (MBA), that utilize the preferential binding of dIgA to a chimeric form of secretory component, allowing the differentiation between dIgA and monomeric IgA. dIgA responses elicited through severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection were measured in (i) a longitudinal panel, consisting of 74 samples (n = 20 individuals) from hospitalized cases of coronavirus disease 2019 (COVID-19); (ii) a longitudinal panel, consisting of 96 samples (n = 10 individuals) from individuals with mild COVID-19; (iii) a cross-sectional panel with PCR-confirmed SARS-CoV-2 infection with mild COVID-19 (n = 199) and (iv) pre-COVID-19 samples (n = 200). The dIgA-ELISA and dIgA-MBA demonstrated a specificity for dIgA of 99% and 98.5%, respectively. Analysis of dIgA responses in the longitudinal panels revealed that 70% (ELISA) and 50% (MBA) of patients elicited a dIgA response by day 20 after PCR diagnosis with a SARS-CoV-2 infection. Individuals with mild COVID-19 displayed increased levels of dIgA within the first 3 weeks after diagnosis but responses appeared to be short lived, compared with sustained IgA levels. However, in samples from hospitalized patients with COVID-19 we observed high and sustained levels of dIgA, up to 245 days after PCR diagnosis. Our results suggest that severe COVID-19 infections are associated with sustained levels of plasma dIgA compared with mild cases.

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The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has been one of the most severe outbreaks of respiratory illness in history. The clinical symptoms of COVID-19 may be similar to flu, although they can be life-threatening, particularly in the elderly and immunocompromised population. Together with nucleic acid detection, serological testing has been essential for the diagnosis of SARS-CoV-2 infection but has been critically important for studying the epidemiology, serosurveillance, and for vaccine research and development. Multiplexed immunoassay technologies have a particular advantage as they can simultaneously measure multiple analytes from a single sample. xMAP technology is a multiplex analysis platform that can measure up to 500 analytes at the same time from the same sample. It has been shown to be an important tool for studying immune response to the various SARS-CoV-2 antigens, as well as for measuring host protein biomarker levels as prognostic indicators of COVID-19. In this chapter, we describe several key studies where xMAP technology was used for multiplexed analysis of SARS-COV-2 antibody responses and host protein expression in COVID-19 patients.

Diagnosis of Human T-cell Lymphotropic Virus (HTLV) types I and II infection requires sequencial testing with firstly a screening using an Enzyme immunoassay followed by a confirmatory test.
To compare the performances of the Alinity i rHTLV-I/II (Abbott®) and LIAISON® XL murex recHTLV-I/II serological screening tests to the ARCHITECT rHTLVI/II test followed if positive by HTLV BLOT 2.4, MP Diagnostics as the reference.
119 serum samples from 92 known HTLV-I infected patients and 184 from uninfected patients with HTLV were analyzed in parallel with, Alinity i rHTLV-I/II, LIAISON® XL murex recHTLV-I/II and ARCHITECT rHTLVI/II.
Alinity i rHTLV-I/II and LIAISON® XL murex recHTLV-I/II exhibited a total agreement with ARCHITECT rHTLVI/II for both positive and negative samples. Both tests are suitable alternatives for HTLV screening.