Multiplexed bead-based assay for the simultaneous quantification of human serum IgG antibodies to tetanus, diphtheria, pertussis toxin, filamentous hemagglutinin, and pertactin

BackgroundLuminex bead-based assays offer multiplexing to test antibodies against multiple antigens simultaneously; however, this requires validation using internationally certified reference standards. Therefore, there is an urgent need to characterize existing reference standards for the standardization of multiplex immunoassays (MIAs). Here, we report the development and validation of an MIA for the simultaneous estimation of levels of human serum immunoglobulin G (IgG) antibodies for pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (PRN), diphtheria toxoid (DT), and tetanus toxoid (TT).MethodsThe MIA was assessed using a panel of human serum samples and WHO reference standards. The WHO reference standards were also studied for suitability in the MIA. Purified antigens (PT, FHA, PRN, DT, and TT) were coupled to the spectrally unique magnetic carboxylated microspheres. The method was validated in accordance with the United States Food and Drug Administration (US FDA), European Medicines Agency (EMA), and the International Committee of Harmonization Multidisciplinary (ICH M10) guidelines, and parameters such as precision, accuracy, dilutional linearity, assay range, robustness, and stability were assessed. Method agreements with commercially available IgG enzyme-linked immunosorbent assay (ELISA) assays were also evaluated. In addition, the study assessed the level of correlation between the IgG levels estimated by the MIA and the cell-based neutralizing antibody assays for PT and DT.ResultsWe identified that an equimix of WHO international standards (i.e., 06/142, 10/262, and TE-3) afforded the best dynamic range for all the antigens in the MIA. For all five antigens, we observed that the back-fitted recoveries using the four-parameter logistic (4-PL) regression fits ranged between 80% and 120% for all calibration levels, and the percentage coefficient of variation (% CV) was < 20%. In addition, the difference in mean fluorescence intensity (MFI) between the monoplex and multiplex format was < 10% for each antigen, indicating no crosstalk among the beads. The MIA also showed good agreement with conventional and commercially available assays, and a positive correlation (> 0.75) with toxin neutralization assays for PT and DT was observed.ConclusionThe MIA that was calibrated in accordance with WHO reference standards demonstrated increased sensitivity, reproducibility, and high throughput capabilities, allowing for the design of robust studies that evaluate both natural and vaccine-induced immunity

Predictors of bisexual behaviour among MSM attending intervention sites may help in prevention interventions for this bridge to the heterosexual epidemic in India: data from HIV sentinel surveillance.

Indian cultural tradition demanding marriage, many MSM howsoever they self-identify are likely to be married or have sex with women. To consolidate India's HIV prevention gains, it is important to understand and address the interaction between the MSM and heterosexual epidemics in India and create specific interventions for bisexual MSM. The challenge is to identify and intervene this hard to reach population. Data from HIV Sentinel Surveillance 2011 among MSM in four Indian states were analyzed to assess predictors and prevalence of bisexual behaviour in MSM.Between March-May 2011, 4682 men (15-49 years) who had anal/oral sex with a male partner in the past month, attending intervention sites and consenting for an un-linked anonymous survey answered an 11- item questionnaire and provided blood for HIV test by finger stick at 19 designated surveillance sites.Of 4682 MSM tested overall, 5% were illiterate, 51% reported only receptive anal intercourse, 21% only penetrative and 28% both. 36% MSM had ever received money for sex. Overall 6.8% were HIV infected. 44% MSM were bisexual in the last six months. On multivariate analysis, 'being bisexual' was found to be independently associated with 'older age': 26-30 years [AOR = 3.1, 95% CI(2.7, 3.7)], >30 years [AOR = 6.5, 95% CI(5.5, 7.7)]; 'reporting penetrative behaviour alone' with other men [AOR = 5.8, 95% CI(4.8, 7.0), p<0.01] and 'reporting both penetrative and receptive behaviour' [AOR = 2.7, 95% CI(2.3, 3.1) p<0.01]. Those who both paid and received money for sex [AOR = 0.49, 95% CI (0.38, 0.62)] were significantly less likely to be bisexual.A substantial proportion of men receiving services from Targeted Intervention programs are bisexual and the easy opportunity for intervention in this setting should be capitalised upon. Focusing on older MSM, as well as MSM who show penetrative behaviour with other men, could help in reaching this population

Demographic and socio-economic characteristics of MSM in states in west-central India (Year 2011).

<p>Note: MSMO: Men having Sex with Men Only, MSMW: Men having Sex with Men and Women, IDU: Injecting Drug Use, *Approx. 0.3%–1.3% data on these variables is missing overall.</p><p>Demographic and socio-economic characteristics of MSM in states in west-central India (Year 2011).</p

Predictors of HIV infection among MSM in west-central India (Year 2011).

<p>Note: Column 2: Denominators for percentages are respective figures in 1st column. OR: Odds Ratio; AOR: Adjusted Odds Ratio; IDU: Injecting Drug Use. * ‘Received Money’ = Only sold sex, ‘Paid’ = Only bought sex; ‘Received+Paid’ =  Bought and sold sex.</p><p>Predictors of HIV infection among MSM in west-central India (Year 2011).</p

Predictors of bisexual behaviour among MSM in west-central India (Year 2011).

<p>Note: Column 2: Denominators for percentages are respective figures in 1st column. OR: Odds Ratio; AOR: Adjusted Odds Ratio. * Missing information about bisexuality for 32 records; IDU: Injecting Drug Use, MSMW: Men having Sex with Men and Women. * ‘Received Money’ =  Only sold sex, ‘Paid’ = Only bought sex; ‘Received+Paid’ =  Bought and sold sex.</p><p>Predictors of bisexual behaviour among MSM in west-central India (Year 2011).</p