Validation of a modified commercial enzyme-linked immunoassay for detection of human immunodeficiency virus type 1 immunoglobulin G antibodies in saliva

Enzymatic Methods for Salivary Biomarkers Detection: Overview and Current Challenges

Early detection is a key factor in patient fate. Currently, multiple biomolecules have been recognized as biomarkers. Nevertheless, their identification is only the starting line on the way to their implementation in disease diagnosis. Although blood is the biofluid par excellence for the quantification of biomarkers, its extraction is uncomfortable and painful for many patients. In this sense, there is a gap in which saliva emerges as a non-invasive and valuable source of information, as it contains many of the biomarkers found in blood. Recent technological advances have made it possible to detect and quantify biomarkers in saliva samples. However, there are opportunity areas in terms of cost and complexity, which could be solved using simpler methodologies such as those based on enzymes. Many reviews have focused on presenting the state-of-the-art in identifying biomarkers in saliva samples. However, just a few of them provide critical analysis of technical elements for biomarker quantification in enzymatic methods for large-scale clinical applications. Thus, this review proposes enzymatic assays as a cost-effective alternative to overcome the limitations of current methods for the quantification of biomarkers in saliva, highlighting the technical and operational considerations necessary for sampling, method development, optimization, and validation.

Saliva SARS-CoV-2 Antibody Prevalence in Children

COVID-19 patients produce circulating and mucosal antibodies. In adults, specific saliva antibodies have been detected. Nonetheless, seroprevalence is routinely investigated, while little attention has been paid to mucosal antibodies. We therefore assessed SARS-CoV-2-specific antibody prevalence in serum and saliva in children in the Netherlands. We assessed SARS-CoV-2 antibody prevalence in serum and saliva of 517 children attending medical services in the Netherlands (irrespective of COVID-19 exposure) from April to October 2020. The prevalence of SARS-CoV-2 spike (S), receptor binding domain (RBD), and nucleocapsid (N)-specific IgG and IgA were evaluated with an exploratory Luminex assay in serum and saliva and with the Wantai SARS-CoV-2 RBD total antibody enzyme-linked immunosorbent assay in serum. Using the Wantai assay, the RBD-specific antibody prevalence in serum was 3.3% (95% confidence interval [CI]. 1.9 to 5.3%). With the Luminex assay, we detected heterogeneity between antibodies for S, RBD, and N antigens, as IgG and IgA prevalence ranged between 3.6 and 4.6% in serum and between 0 and 4.4% in saliva. The Luminex assay also revealed differences between serum and saliva, with SARS-CoV-2-specific IgG present in saliva but not in serum for 1.5 to 2.7% of all children. Using multiple antigen assays, the IgG prevalence for at least two out of three antigens (S, RBD, or N) in serum or saliva can be calculated as 3.8% (95% CI, 2.3 to 5.6%). Our study displays the heterogeneity of the SARS-CoV-2 antibody response in children and emphasizes the additional value of saliva antibody detection and the combined use of different antigens. IMPORTANCE Comprehending humoral immunity to SARS-CoV-2, including in children, is crucial for future public health and vaccine strategies. Others have suggested that mucosal antibody measurement could be an important and more convenient tool to evaluate humoral immunity compared to circulating antibodies. Nonetheless, seroprevalence is routinely investigated, while little attention has been paid to mucosal antibodies. We show the heterogeneity of SARS-CoV-2 antibodies, in terms of both antigen specificity and differences between circulating and mucosal antibodies, emphasizing the additional value of saliva antibody detection next to detection of antibodies in serum.

ELISA detection of SARS-CoV-2 antibodies in saliva

To facilitate containment of the COVID-19 pandemic currently active in the United States and across the world, options for easy, non-invasive antibody testing are required. Here we have adapted a commercially available, serum-based enzyme-linked immunosorbent assay (ELISA) for use with saliva samples, achieving 84.2% sensitivity and 100% specificity in a set of 149 clinical samples. This strategy will enable widespread, affordable testing for patients who experienced this disease, whilst minimizing exposure risk for healthcare workers.

Measurement of sexual health outcomes among people who inject drugs: pilot study in Catalonia, Spain and Barnaul, Russia

BACKGROUND

The main objective of this study was to test some of the draft sexual health indicators developed by the World Health Organization as part of a comprehensive indicator framework to monitor progress in universal access to reproductive health.

METHODS

Cross-sectional studies among people who inject drugs were conducted in Catalonia (n = 734) and Barnaul (n = 500). 'Sexual competency' was measured using three indicators: sexual satisfaction, sexual safety, and sexual autonomy. Individual social norms on sexuality were also collected. The construct validity of the sexual safety and sexual autonomy items were assessed. Multivariate logistic regression models explored factors associated with sexual dissatisfaction.

RESULTS

In Catalonia, sexual competency was higher among males than females who inject drugs (60.4% versus 33.3%). In both Catalonia and Barnaul, differences by sex in social norms on sexuality were seen. Mean scores on sexual safety (4.15 in Catalonia and 3.54 in Barnaul) were lower among participants who reported not using condoms. Mean scores on sexual autonomy (4.42 in Catalonia and 3.97 in Barnaul) were lower among those who had experienced some form of sexual assault. Perceived sexual safety, sexual autonomy, and social norms on sexuality were associated with sexual dissatisfaction.

CONCLUSIONS

The sexual health indicators tested are valid, feasible, and reliable tools to monitor and evaluate sexual health programs and activities. The results confirm that sexual satisfaction depends on safe sexual experiences, free from coercion and violence. Social norms and individual perceptions about sexual health need to be considered when developing national disease prevention programs.

Undiagnosed HIV and Hepatitis C infection in people who inject drugs: From new evidence to better practice

BACKGROUND

The objective of this study was to estimate the proportion of undiagnosed HIV or Hepatitis C virus (HCV) infection and to assess the risk factors associated with an undiagnosed infection.

METHODS

A questionnaire was distributed among people who inject drugs (PWID) in harm reduction centres in Catalonia, Spain 2008-2012 (n=2243). Self-report of HIV and HCV was compared to oral fluid tests to calculate the proportion of undiagnosed infection. Associations of undiagnosed HIV and HCV with age, origin, risk and protective factors of infection and services use were calculated using a Poisson regression model with robust variance.

RESULTS

The sensitivity of HIV self-report was 78.5% (75.2%-81.5%) and of HCV was 81.2% (79.1%-83.2%), being lower in younger and foreign-born PWID. Specificity for HCV was 55.9% (51.6%-60.1%). PWID who engaged in infection risk behaviors had lower risk of being undiagnosed. Being foreign-born and younger increased the risk of undiagnosed infection. PWID who had not accessed medical care in the last 6months had 1.46 (1.10-1.93) times more risk of undiagnosed HIV and 1.37 (1.11-1.70) times more risk of undiagnosed HCV.

CONCLUSION

Outreach programmes are essential to provide PWID, specially foreign-born and younger PIWD, access to HIV and HCV test.

High Prevalence and Incidence of HIV and HCV Among New Injecting Drug Users With a Large Proportion of Migrants--Is Prevention Failing?

OBJECTIVES

The aim of this study was to assess differences in the prevalence of HIV and HCV infection and associated risk factors between new (injecting for ≤5 years) and long-term injectors and to estimate HIV/HCV incidence among new injectors.

METHODS

Cross-sectional study among people who inject drugs (PWID) who attended harm reduction centers in Catalonia in 2010-11. Anonymous questionnaires and oral fluid samples were collected. Poisson regression models were applied to determine the association between HIV/HCV infection and risk factors.

RESULTS

Of the 761 participants, 21.4% were new injectors. New injectors were younger than long-term injectors (mean age = 31.6 vs. 37.8) and were more likely to be immigrants (59.0% vs. 33.4%). HIV and HCV prevalence was 20.6% and 59.4% among new injectors, and estimated HIV and HCV incidence 8.7 and 25.1 /100 person-years, respectively. Among new injectors, HIV infection was associated with homelessness (PR = 3.10) and reporting a previous sexually transmitted infection (PR = 1.79). Reporting front/backloading (PR = 1.33) and daily injection (PR = 1.35) were risk-factors for HCV infection. For long-term injectors, HIV risk factors were: having shared syringes (PR = 1.85), having injected cocaine (PR = 1.38), reporting front/backloading (PR = 1.30) and ever having been in prison (PR = 2.03).

CONCLUSION

A large proportion of PWID in Catalonia are new injectors, a subgroup with a high level of both sexual and parenteral exposure and a high incidence rate of HIV/ HCV infections. It is important to improve early diagnosis of these infections among this group, in particular among migrants. To identify and address risk factors for homelessness PWID should be a priority.

Cross-Sectional Study of Hepatitis A Virus Infection in the Pantanal Population before Vaccine Implementation in Brazil: Usage of Non-Invasive Specimen Collection

Population-based prevalence studies are essential tools for screening of hepatitis A and provide important data on susceptible groups. However, surveillance in isolated communities is difficult because of the limited access to these areas and the need for blood sample collection. This study aimed to determine the anti-HAV prevalence using oral fluid samples to provide an alternative tool for epidemiological studies that might be useful for vaccination-related decisions. The study population was composed of 224 volunteers from South Pantanal, aged 3 to 86 years old. This study was performed using oral fluids, previously standardized for anti-HAV antibody detection, which were collected using a ChemBio device. Eluates were tested using modified commercial EIA to detect anti-HAV antibodies. The overall prevalence was 79.1%, corresponding to 178 reactive EIA tests out of 224 samples. The age stratified data revealed a prevalence of 47.8% between 0–10 years, 84% in 11–20 years and 91.9% in subjects older than 21 years. Results indicate that hepatitis A prevalence was higher in adolescents and adults, corroborating the literature reports. Thus, oral fluid samples could replace serum in HAV epidemiological studies in isolated communities as they are efficient at detecting anti-HAV antibodies.

[Trends in HIV prevalence and associated risk behaviors in female sex workers in Catalonia (Spain)]

OBJECTIVES

To describe trends in HIV prevalence, sexual risk behaviors and other sexual health indicators in female sex workers (SW) from 2005 to 2011.

METHODS

Cross-sectional studies were conducted biennially among SW recruited in Catalonia (Spain) in the street, flats and clubs (n = 400). In addition to an anonymous questionnaire, oral fluid samples were collected to estimate HIV prevalence. Linear trends in proportions were assessed by the Mantel test.

RESULTS

The percentage of SW who used condoms inconsistently with clients (past 6 months) increased from 5.1% in 2005 to 9.9% in 2011 (p = 0.005); this percentage also increased with steady partners (86.2% in 2005 to 94.4% in 2011, p = 0.002). The prevalence of self-reported sexually transmitted infections (STI) increased from 14% in 2005 to 20.6% in 2011 (p = 0.001). The prevalence of HIV held constant over the years (about 2%), being higher in Spanish women (14.7% in 2011).

DISCUSSION

The prevalence of HIV in SW remained stable over the years, being higher in Spanish SW. The increase in unprotected sex and in the prevalence of self-reported STI among SW from 2005 to 2011 highlights a possible relaxation in preventive behaviors in this group. Interventions to reduce the transmission of these infections, as well as unwanted pregnancies, should continue in Catalonia in SW.

Using conventional HIV tests on oral fluid

There is need for more evaluations of non-invasive tests in order to broaden the reach of testing programs and to perform large scale epidemiological studies. In this study, three different human immunodeficiency virus (HIV) enzyme linked immunosorbent assays (ELISAs) and one line immunoassay were evaluated to detect HIV antibodies in oral fluid samples. Specimens were collected, after informed consent was obtained, with the Oracol (MMD, Worcester, England) device. A total IgG quantitation test was performed to demonstrate the quality of the sample. Assessment of a modified protocol of the Vironostika HIV Ag/Ab, Enzygnost Anti-HIV 1/2 Plus Genscreen HIV-1/2 Version 2 and a line immune confirmatory assay the INNO-LIA HIV I/II score was done, using oral fluid specimens of 325 HIV positive and negative individuals. For the ELISAs, the addition of an extra internal oral fluid control was evaluated as well as different cut-offs, time between sampling and testing and the effect of drinking water just before sampling. Finally, the confirmatory test and some testing algorithms and combination of tests were discussed. The results obtained from the oral fluid specimens were compared with the gold standard on paired serum specimens. Firstly, there was no significant difference observed between the use of the kit controls and the oral fluid controls. New protocols and calculation of cut-offs were defined for two of the three ELISAs. High sensitivities and specificities were obtained with all three ELISAs without any statistical difference between the three tests. Secondly, no statistically significant difference was observed when samples were stored for different time periods between sampling and testing, meaning that a period of seven days at room temperature before testing is still acceptable. Thirdly, drinking water before sample collection did not interfere with the testing, although lower optical densities were observed. None of the positive samples were missed. In addition, the line immunoassay INNO-LIA HIV I/II score test is a promising test for confirmation of reactive oral fluid specimen, but more samples need to be validated in order to adapt the interpretation rules specifically for oral fluid specimens. Different choices/algorithms adapted for the purpose of testing can be proposed. In conclusion, it can be said that the commercial ELISAs with adapted protocol and cut-off values are suitable tools for making HIV test performance accessible to people. With this non-invasive sampling method, more eligible individuals can and will be selected for further HIV test on blood.

Gender differences in HIV risk behaviours among intravenous drug users in Catalonia, Spain

OBJECTIVE

To describe gender differences in injection and sexual risks behaviours, and human immunodeficiency virus (HIV) and hepatitis C (HCV) prevalence among injecting drug users (IDU) in Catalonia, Spain.

METHODS

Cross-sectional studies in 2008-2009 (n=748) and 2010-2011 (n=597) in the network of harm reduction centres. Face to face interviews were conducted and oral fluid samples were collected to estimate HIV/HCV prevalence.

RESULTS

Female were more likely than male IDU to have had a steady sexual partner (68.2% versus 44.9%), to have had an IDU steady sexual partner (46.6% versus 15.1%) and to have exchanged sex for money or drugs in the last 6 months (25.5% versus 2.3%). There were no gender differences in injecting risk behaviours. HIV prevalence was 38.7% (91/235) in women and 31.5% (347/1103) in men (p=0.031). HIV prevalence among female IDU who reported having exchange sex for money or drugs was 53.3% (32/60). The prevalence of HCV was 67.4% (159/236) and 73.6% (810/1101) in female and male IDU, respectively (p=0.053). After adjustment by immigrant status, age and years of injection, differences among HIV/HCV prevalence by gender were not significant.

CONCLUSIONS

This study demonstrated differences in sexual risk behaviours between male and female IDU, but failed to find gender differences in injecting risk behaviours. Apart from that, the higher prevalence of HIV among women than among men, together with a lower prevalence of HCV, provides evidence that sexual transmission of HIV is important among female IDU. Additional studies are needed to analyze in-depth these specific risk factors for women in order to develop appropriate prevention and health education programs.

Saliva as a diagnostic fluid

Salivary diagnostics is a dynamic and emerging field utilizing nanotechnology and molecular diagnostics to aid in the diagnosis of oral and systemic diseases. In this article the author critically reviews the latest advances using oral biomarkers for disease detection. The use of oral fluids is broadening perspectives in clinical diagnosis, disease monitoring, and decision making for patient care. Important elements determining the future possibilities and challenges in this field are also discussed.

Importance of the cutoff ratio for detecting antibodies against hepatitis A virus in oral fluids by enzyme immunoassay

Multiple studies have examined the use of oral fluids in modified serum-based assays aiming to replace serum in antibody detection for hepatitis A. However, the reliable detection of HAV immunity in oral fluid requires an extremely sensitive assay; most immunoassays designed for serum antibody determination lack sufficient sensitivity for this purpose. Consequently, an "in-house" competitive enzyme immunoassay (EIA) designed specifically for use with oral samples collected using a ChemBio(®) device was developed to detect total anti-HAV antibodies (IgG and IgM). This system was compared to an in-house competitive EIA and a commercial EIA considered to be the "gold standard" using corresponding serum samples (n=225) to determine the accuracy of the assay and to evaluate the importance of the cutoff ratio for the detection of anti-HAV antibodies in oral fluids. When the median serum cutoff and the optimal oral fluid cutoff (ROC analysis) obtained from the in-house competitive EIA were compared, the oral fluid cutoff was found to be 28.8% higher than the serum cutoff. When different oral fluid cutoff values were compared, a reduction of about 17% was shown to be essential to increase test accuracy. At an oral fluid cutoff value of 0.351, sensitivity and specificity were higher, reaching 91.7% and 86.2% (p<0.001, AUROC=0.915), respectively. The convenience, accuracy and non-invasive nature of the developed method make it a useful alternative to serum-based assays for discriminating between HAV-immune and non-immune individuals.

Sexually transmitted infections and sexual practices among injecting drug users in harm reduction centers in Catalonia

BACKGROUND

The objectives of the study were to estimate the prevalence of Chlamydia trachomatis and Neisseria gonorrhoeae and sexual risk practices, and to identify factors associated with infection by C. trachomatis/N. gonorrhoeae.

METHODS

Injecting drug users were interviewed at harm reduction centers and biological samples were collected to estimate the prevalence of C. trachomatis and N. gonorrhoeae.

RESULTS

The prevalence of C. trachomatis was 2.3%, and this was higher among immigrants (3.6%); the prevalence of N. gonorrhoeae was 0.7% (no differences between Spanish-born and immigrants). Respondents aged ≤25 years had a higher risk of sexually transmitted infections (STIs) (OR 3.39), as did women (OR 3.08). Also associated with having an STI were not having registered employment (OR 4.70), injecting drugs daily (OR 4.21), and having unprotected sex with a stable partner (OR 3.37).

CONCLUSION

Although the prevalence of STIs observed is low, scant condom use makes it necessary for prevention programs to include messages related to sexual risk practices, especially among young people and women.

(C2) Saliva, breast milk, and mucosal fluids in HIV transmission

The oral environment has received various amounts of attention in association with HIV infection and pathogenesis. Since HIV infection occurs through mucosal tissue, oral factors-including tissue, fluids, and compartments-are of interest in furthering our understanding of the diagnosis, infectivity, transmission, and pathogenesis of disease. This report reviews: (1) HIV testing and diagnoses with oral fluids; (2) post-natal acquisition of HIV in association with breast-feeding from HIV-positive mothers; and (3) oral sex and HIV transmission. In the first, we examine how oral fluids are used to detect HIV infection and review current consensus on the role of salivary molecules as markers for immunosuppression. Second, lactation-associated HIV acquisition is reviewed, with special consideration of emerging issues associated with the impact of anti-retroviral therapies. Last, we consider current data on the risk of HIV infection in association with oral sex. Investigation of these diverse topics has a common goal: understanding how HIV presents in the oral environment, with an aim to rapid and accessible HIV diagnosis, and improved prevention and treatment of infection.

Determination of poliovirus-specific IgA in saliva by ELISA tests

This study describes three ELISA methods for detection of immunoglobulin A (IgA) specific to three types of Sabin strains of poliovirus in saliva taken from 70 children aged 6-7 years vaccinated with a full course of oral poliovirus vaccine (OPV). Of the three ELISA methods (conventional IgA ELISA and two new methods described in this communication, the alpha-capture ELISA and Inhibition ELISA), alpha-capture ELISA demonstrated the highest sensitivity, with all saliva samples testing positive for Sabin poliovirus strains specific IgA antibodies of 1-3 types. Of 62 available alpha-capture ELISA positive saliva samples, all were also positive by the inhibition ELISA, and a significant correlation was found between the results. Fifty-two available saliva samples were screened by the three ELISA tests with positive results, and a significant correlation was found between the alpha-capture ELISA and the IgA ELISA; the correlation between the IgA ELISA and inhibition ELISA was not significant. The results of this study suggest that determination of Sabin poliovirus-specific IgA in human saliva by the ELISA techniques (especially by the novel alpha-capture ELISA) can be used reliably for evaluation of mucosal immunity in large groups of people immunized with poliovirus vaccines and for epidemiological studies.

Detection of HCV antibodies in oral fluid

Although conventionally the detection of HCV antibodies is carried out on serum, the collection of oral fluid is non-invasive, safe and cost effective. In this study, the efficacy of the detection of HCV antibodies in oral fluid was assessed. 73 anti-HCV positive and 73 anti-HCV negative paired serum/oral fluid samples, drawn from patients visiting a Belgian academic hospital, were tested using the modified Ortho HCV 3.0 and LIA confirmation assay. Performing the test on oral fluid with the modified protocol, 61/73 anti-HCV positive samples were tested positive, while 73/73 anti-HCV negative samples were tested negative, giving a sensitivity and specificity of 83.6% (95% CI: 72.7-90.9%) and 100.0% (95% CI: 93.8-100.0%), respectively. Comparing S/CO of concordantly positive and negative samples, the cut-off point was lowered by 30% resulting in a sensitivity of 89.0% (95% CI: 79.0-94.8%) while the specificity remained 100.0% (95% CI: 93.8-100.0%). The confirmation assay was carried out as described by the manufacturer, diluting the oral fluid 1:10. Testing paired samples gave a concordance of 85.6% (125/146), yielding no more accurate results. These findings suggested that the modified ELISA method for anti-HCV detection in oral fluid can be used for epidemiological surveys.