Future applications of oral fluid specimen technology

Detection of SARS-CoV-2 Antibodies in Oral Fluid Using a Magnetic Particle-Based Chemiluminescence Immunoassay - Beijing Municipality, China, 2021

Introduction

Oral fluids (OFs) have been broadly used as non-invasive samples for evaluating protective IgG antibodies from natural infection or vaccination, especially in pediatric populations.

Methods

Paired OF and serum were collected from both individuals who received a booster dose of the inactive coronavirus disease 2019 (COVID-19) vaccine as well as those who did not have a history of COVID-19 vaccination and infection (as the control group). The total human IgG antibody (HIgG) content was evaluated as a marker of OF sampling quality. An in-house adapted magnetic particle-based chemiluminescence immunoassay was used for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG antibody detection in the OF. The SARS-CoV-2 IgG antibody in the serum samples was detected using a commercial immunoassay.

Results

In total, 579 paired OF and serum samples were collected. An additional 172 OF samples were collected from preschool children. The results indicated that the HIgG concentration in qualified OF samples should be higher than 0.3 µg/mL. Compared to the serum assay, the in-house OF immunoassay for detecting IgG antibodies against SARS-CoV-2 had 95.06% accuracy, 95.03% sensitivity, and 100% specificity.

Conclusions

Overall, the in-house immunoassay for detecting SARS-CoV-2 IgG antibodies in OF showed high potential for application towards serological surveillance and immunization effect assessment after large-scale, inactive COVID-19 vaccination in China.

SARS Antibody Testing in Children: Development of Oral Fluid Assays for IgG Measurements

Seroepidemiological studies to monitor antibody kinetics are important for assessing the extent and spread of SARS-CoV-2 in a population. Noninvasive sampling methods are advantageous for reducing the need for venipuncture, which may be a barrier to investigations, particularly in pediatric populations. Oral fluids are obtained by gingiva-crevicular sampling from children and adults and are very well accepted. Enzyme immunoassays (EIAs) based on these samples have acceptable sensitivity and specificity compared to conventional serum-based antibody EIAs and are suitable for population-based surveillance. We describe the development and evaluation of SARS-CoV-2 IgG EIAs using SARS-CoV-2 viral nucleoprotein (NP) and spike (S) proteins in IgG isotype capture format and an indirect receptor-binding-domain (RBD) IgG EIA, intended for use in children as a primary endpoint. All three assays were assessed using a panel of 1,999 paired serum and oral fluids from children and adults participating in school SARS-CoV-2 surveillance studies during and after the first and second pandemic wave in the United Kingdom. The anti-NP IgG capture assay was the best candidate, with an overall sensitivity of 75% (95% confidence interval [CI]: 71 to 79%) and specificity of 99% (95% CI: 78 to 99%) compared with paired serum antibodies. Sensitivity observed in children (80%, 95% CI: 71 to 88%) was higher than that in adults (67%, CI: 60% to 74%). Oral fluid assays (OF) using spike protein and RBD antigens were also 99% specific and achieved reasonable but lower sensitivity in the target population (78%, 95% CI [68% to 86%] and 53%, 95% CI [43% to 64%], respectively). IMPORTANCE We report on the first large-scale assessment of the suitability of oral fluids for detection of SARS-CoV-2 antibody obtained from healthy children attending school. The sample type (gingiva-crevicular fluid, which is a transudate of blood but is not saliva) can be self collected. Although detection of antibodies in oral fluids is less sensitive than that in blood, our study suggests an optimal format for operational use. The laboratory methods we have developed can reliably measure antibodies in children, who are able to take their own samples. Our findings are of immediate practical relevance for use in large-scale seroprevalence studies designed to measure exposure to infection, as they typically require venipuncture. Overall, our data indicate that OF assays based on the detection of SARS-CoV-2 antibodies are a tool suitable for population-based seroepidemiology studies in children and highly acceptable in children and adults, as venipuncture is no longer necessary.

Evaluation of saliva collection devices for the analysis of proteins

BACKGROUND

Human saliva mirrors the body's health and can be collected non-invasively, does not require specialized skills and is suitable for large population based screening programs. The aims were twofold: to evaluate the suitability of commercially available saliva collection devices for quantifying proteins present in saliva and to provide levels for C-reactive protein (CRP), myoglobin, and immunoglobin E (IgE) in saliva of healthy individuals as a baseline for future studies.

METHODS

Saliva was collected from healthy volunteers (n=17, ages 18-33years). The following collection methods were evaluated: drool; Salimetrics® Oral Swab (SOS); Salivette® Cotton and Synthetic (Sarstedt) and Greiner Bio-One Saliva Collection System (GBO SCS®). We used AlphaLISA® assays to measure CRP, IgE and myoglobin levels in human saliva.

RESULTS

Significant (p<0.05) differences in the salivary flow rates were observed based on the method of collection, i.e. salivary flow rates were significantly lower (p<0.05) in unstimulated saliva (i.e. drool and SOS), when compared with mechanically stimulated methods (p<0.05) (Salivette® Cotton and Synthetic) and acid stimulated method (p<0.05) (SCS®). Saliva collected using SOS yielded significantly (p<0.05) lower concentrations of myoglobin and CRP, whilst, saliva collected using the Salivette® Cotton and Synthetic swab yielded significantly (p<0.05) lower myoglobin and IgE concentrations respectively.

CONCLUSIONS

The results demonstrated significantly relevant differences in analyte levels based on the collection method. Significant differences in the salivary flow rates were also observed depending on the saliva collection method. The data provide preliminary baseline values for salivary CRP, myoglobin, and IgE levels in healthy participants and based on the collection method.

Saliva as an analytical matrix: state of the art and application for biomonitoring

Analytical tests to measure chemicals in saliva can be employed for numerous analytes, endogenous compounds or xenobiotics. The objective was to determine which chemicals can be analysed with this matrix, which analytical methods are applicable, and what application is possible for biomonitoring. We reviewed the literature using three databases, MEDLINE, PubMed and Scopus, collecting articles on different kinds of analysis in saliva. Studies were principally about molecules of clinical interest, xenobiotics, especially drugs of abuse, and chemicals used at workplaces; some substances show no relevant correlation with exposure data while others seems to be of particular interest for systematic use for biomonitoring. Currently, saliva is used far less than other biological fluids but its use for biomonitoring of exposure to chemicals might open up new areas for research and would certainly simplify the collection of biological samples.

Antibody responses in oral fluid after administration of prophylactic human papillomavirus vaccines

We sought to determine whether oral fluid can be used to assess serum human papillomavirus (HPV) antibody status by enrolling women who had received a prophylactic HPV-16 vaccine in a new follow-up study. After the prophylactic HPV-6/11/16/18 vaccine was licensed in the United States, we administered it to consenting participants. With serologic findings used as the reference standard, The sensitivity of oral fluid was 49.6% (95% confidence interval [CI], 42.0%-57.3%) before and 100% (95% CI, 92.0%-100%) after administration of the quadrivalent vaccine. Oral fluid may have the potential to be used for monitoring of prophylactic HPV vaccines in the future.

Assessment of measles immunity among infants in Maputo City, Mozambique

Background

The optimum age for measles vaccination varies from country to country and thus a standardized vaccination schedule is controversial. While the increase in measles vaccination coverage has produced significant changes in the epidemiology of infection, vaccination schedules have not been adjusted. Instead, measures to cut wild-type virus transmission through mass vaccination campaigns have been instituted. This study estimates the presence of measles antibodies among six- and nine-month-old children and assesses the current vaccination seroconversion by using a non invasive method in Maputo City, Mozambique.

Methods

Six- and nine-month old children and their mothers were screened in a cross-sectional study for measles-specific antibodies in oral fluid. All vaccinated children were invited for a follow-up visit 15 days after immunization to assess seroconversion.

Results

82.4% of the children lost maternal antibodies by six months. Most children were antibody-positive post-vaccination at nine months, although 30.5 % of nine month old children had antibodies in oral fluid before vaccination. We suggest that these pre-vaccination antibodies are due to contact with wild-type of measles virus. The observed seroconversion rate after vaccination was 84.2%.

Conclusion

These data indicate a need to re-evaluate the effectiveness of the measles immunization policy in the current epidemiological scenario.

Feasibility of collecting oral fluid samples in the home setting to determine seroprevalence of infections in a large-scale cohort of preschool-aged children

Oral fluid is a non-invasive biological sample, which can be returned by post, making it suitable for large-scale epidemiological studies in children. We report our experience of oral fluid collection from 14 373 preschool-aged children in the UK Millennium Cohort Study. Samples were collected by mothers in the home setting following the guidance of trained interviewers, and posted to the laboratory. Samples were received from 11 698 children (81.4%). Children whose mothers were of Black Caribbean ethnicity and who lived in non-English-speaking households were less likely to provide a sample, and those with a maternal history of asthma more likely to provide a sample [adjusted risk ratio (95% CI) 0.85 (0.73-0.98), 0.87 (0.77-0.98) and 1.03 (1.00-1.05) respectively]. Collection of oral fluid samples is feasible and acceptable in large-scale child cohort studies. Formal interpreter support may be required to increase participation rates in surveys that collect biological samples from ethnic minorities.

Pilot of non-invasive (oral fluid) testing for HIV within a clinical setting

BACKGROUND

The objectives of the present study were: to determine the sensitivity and specificity of oral fluid testing compared with the performance of standard blood-based HIV enzyme immunoassay; to assess the feasibility of oral fluid specimen collection from clients for the purposes of HIV testing within a clinical setting; and to assess the clinical and laboratory impact regarding staffing, material resources, expertise and funding of oral fluid testing.

METHODS

A parallel comparative trial of oral fluid and blood testing was conducted among a group of HIV positive clients and a group of unknown HIV serostatus clients where each client was offered both tests. An ambulatory HIV clinic recruited 175 known HIV positive clients and 179 persons were recruited through an inner city sexual health clinic while attending for routine sexual health checks. Client responses to oral fluid collection were assessed. The sensitivity and specificity of oral fluid testing were calculated.

RESULTS

Of the 176 confirmed HIV reactive blood test results, the OraSure (OraSure Technologies, Beaverton, OR, USA) assay failed to detect only one of these, demonstrating a sensitivity of 99.4%. Of the 178 blood specimens that were tested as non-reactive by the AxSYM (Abbott Laboratories, Abbott Park, IL, USA) Combo system, OraSure recorded four of the corresponding oral fluid specimens as reactive (assumed to be false-positive), giving a specificity of 97.6%. Although evaluation of patients undergoing the test showed a large proportion (88.6%) preferred the OraSure test to conventional blood testing, a large minority of these (22.6%) made such a preference conditional on the OraSure test being as reliable as current blood testing.

CONCLUSIONS

This limited clinic based trial of oral fluid testing for HIV antibodies among an outpatient population has demonstrated the potential of oral fluid as a specimen for HIV testing. However, the lower performance of the test compared with current serum-based tests may limit the usefulness of OraSure to epidemiological studies or as an alternative screening tool in outreach settings among higher risk populations.

Implications for diagnostics in the biochemistry and physiology of saliva

Oral fluid mainly consists of a mixture of glandular salivas. In addition, it is contaminated by some crevicular fluid, containing serum constituents. The contribution of the various salivary glands shows a continuous variation, resulting in wide ranges of concentrations for all constituents of oral fluid. As a consequence, the collection of oral fluid for diagnostic purposes should be standardized. Oral fluid can be used to detect a number of diseases and recent use of illicit drugs. It can also be used to monitor therapeutic drug concentrations. The development of microchips for salivary components offers great possibilities to use oral fluid for point-of-care testing.

Paired, quantitative measurements of hepatitis B virus DNA in saliva, urine and serum of chronic hepatitis B patients

OBJECTIVES

Despite an abundance of epidemiological evidence for horizontal transmission of hepatitis B virus (HBV), the transmission route remains to be fully elucidated. In a new approach, we evaluated quantitative HBV DNA content in serum, saliva and urine as a first step in exploring possible modes of horizontal transmission.

METHODS

In an outpatient setting of an academic hospital, paired serum, saliva and urine samples were collected from 150 chronically infected HBV patients. A validated HBV DNA TaqMan assay was used to quantitatively measure HBV DNA.

RESULTS

Mean log HBV DNA in serum was 5.8 (range, undetectable to 10.0 log HBV DNA) copies/ml, 50% of the patients had an HBV DNA above 10 copies/ml in serum. Mean log HBV DNA level in saliva was 3.2 (range, undetectable to 7.5) copies/ml, 15% had an HBV DNA above 10 copies/ml in saliva. Mean log HBV DNA level in urine was 2.6 (range, undetectable to 5.4) copies/ml and 1% had an HBV DNA above 10 copies/ml in urine. A high, non-linear correlation was shown between HBV DNA in serum and saliva (Spearman's rho 0.82) and between serum and urine (Spearman's rho 0.74).

CONCLUSIONS

The significant amounts of HBV DNA found in saliva and urine in chronic HBV patients with high viraemia in serum may have implications for the understanding of hepatitis B epidemiology. The potential infectivity of these body fluids may provide an explanation for the 20% of cases of infection obtained through horizontal transmission for which the origin of infection is yet unknown.

Testosterone-mediated immune functions and male life histories

Recent advances in human life history theory have provided new insights into the potential selection pressures that were instrumental in the evolution of human and non-human primate males. However, gaps remain in our understanding of how primate males regulate and allocate energetic resources between survivorship and reproductive effort. Defense against parasitic infection is an important force shaping life history evolution. Proper performance of immunological responses against infection is influenced by many physiological systems, including metabolic, reproductive, and stress hormones. Because androgens influence and modulate immune, reproductive, and somatic metabolic functions, assessing changes in testosterone and immune factors during infection may yield insight into male physiological ecology. In this review, we examine male life history trade-offs between immune and reproductive endocrine functions as well as provide a comprehensive review of testosterone-immunocompetence relationships. Emphasis is placed on testosterone because it is a primary hormone shown to be crucial to energy-allocation processes in vertebrates. Non-primate species have been used more extensively in this research than humans or non-human primates, and therefore this extensive literature is organized and reviewed in order to better understand potential parallel relationships in primates, especially humans. Furthermore, we attempt to reconcile the many inconsistent results obtained from field studies on immune-endocrine interactions as well as detail various methodologies that may be used to forward this research in evolutionary anthropology.

Comparison of oral fluid collectors for use in a rapid point-of-care diagnostic device

Orally based diagnostic testing is emerging as an alternative, noninvasive method for analyzing a variety of analytes. These analytes include pathogens, antibodies, drugs, and nucleic acids. In the present study we developed a protocol for evaluation of collectors that could be used in orally based, point-of-care diagnostics. A performance comparison was carried out with a number of commercially available collectors, and their ability to deliver fluid, proteins, bacteria, and nucleic acid from pathogens compatible with PCR was assessed. The collectors were all capable of picking up and delivering test materials, albeit at various levels.

The IgG antibody profile to various antigen regions of hepatitis C virus differs in oral fluid and serum of patients with chronic hepatitis C

Antibodies to hepatitis C virus (HCV) can be detected not only in serum but also in oral fluid. The aim of the study was to determine IgG antibody reactivity directed to six antigen regions of HCV in oral fluid and to evaluate the significance of the antibody pattern in oral fluid compared to serum. Oral fluid and serum samples of 32 HCV viremic patients were collected to detect antibodies to six antigen regions incorporated as antigen bands into modified commercial updated third generation line immuno-assay. Compared to serum, a significantly lower cumulative antibody response and reactivity to five HCV antigens was found in oral fluid. The significantly highest prevalence of oral fluid reactivity was recorded with antigen C1 (78%), whereas in serum the most significantly frequent reactivity was detected with antigen NS3 (100%). The absence of antibody reactivity with antigen E2 was similar in both body fluids. The discrepancy in antibody pattern to HCV antigens between oral fluid and serum indicates the possible existence of local viral replication, viral mutants, viral inhibitors in oral cavity and, most probably, leakage of the muco-vascular barrier.

Human papillomavirus-specific antibody status in oral fluids modestly reflects serum status in human immunodeficiency virus-positive individuals

Serological assays are valuable tools for studies of the epidemiology of human papillomaviruses (HPVs). The efficacy of a less invasive oral-fluid assay for detection of HPV antibodies was examined. Matched serum, saliva, and oral mucosal transudate (OMT) specimens collected from 150 human immunodeficiency virus-seropositive patients were tested for immunoglobulin G antibodies against HPV-6 and HPV-11 combined (HPV-6/11) and HPV-16 capsids. Antibodies to HPV were detected in both types of oral specimens. Seroprevalence rates were 55% for HPV-6/11 and 37% for HPV-16, whereas oral prevalence rates were significantly lower (for HPV-6/11 in saliva, 31%, and in OMT, 19%; for HPV-16 in saliva, 19%, and in OMT, 17%). HPV antibody detection in OMT more accurately reflected the presence of antibodies in serum than did HPV antibody detection in saliva. More stringent saliva assay cutpoints yielded stronger associations between oropositivity and seropositivity; less stringent OMT cutpoints yielded stronger associations between oropositivity and seropositivity. Although HPV antibodies were detected in oral fluids, further optimization of the assay is necessary before oral-fluid testing can be implemented as a reliable alternative to serum testing for HPV.

Inhibitory effects of whole and parotid saliva on immunomodulators

Based on the presence of cytokines in whole saliva and their association with resistance and susceptibility to infectious disease, the present study was designed to evaluate the diagnostic potential of a large panel of cytokines and chemokines in saliva. Despite the endogenous presence of Th1/Th2 and pro-inflammatory cytokines and several chemokines in whole and parotid saliva of most individuals tested, the detection of known concentrations of several recombinant cytokines and chemokines was inhibited immediately following their addition to each type of saliva. In contrast, purified immunoglobulins were unaffected by either whole or parotid saliva. Further studies revealed that the inhibition of immunoreactivity involved sequestration of the majority of cytokines affected and degradation of chemokines. These results suggest that absolute concentrations of cytokines/chemokines may not be fully detectable in saliva. Therefore, the diagnostic value of any cytokine/chemokine is questionable and should be evaluated independently as such.

Saliva as a diagnostic fluid

In the last 10 years, the use of saliva as a diagnostic fluid has become somewhat of a translational research success story. Technologies are now available enabling saliva to be used to diagnose disease and predict disease progression. This review describes some important recent advances in salivary diagnostics and barriers to application and advancement. This review will also stimulate future research activity.

Human saliva as a diagnostic specimen

Human saliva can be easily obtained by noninvasive techniques and contains many analytes of interest for screening, diagnosis and monitoring. These include steroid and other nonpeptide hormones, therapeutic drugs, drugs of abuse and antibodies. Numerous studies in the past 40 y have shown correlations between serum and saliva levels. Both diurnal and monthly profiles of hormone levels parallel traditional serum patterns. Multiple specimens for steroid hormone analysis can be easily collected by the patient, at home, to monitor fertility cycles, menopausal fluctuations, stress and other diurnal variations. Drug doses can be monitored without inconvenient and costly visits to blood-drawing facilities. Antibody levels can be determined to screen for infectious diseases. Saliva can be collected directly by spitting into a tube or with one of several devices, each of which has its own special advantages and disadvantages. Salivary levels of steroid hormones and other analytes that are protein bound in serum reflect the unbound and active concentration of the hormone. Saliva can be used as a diagnostic specimen not only to obtain information more inexpensively and efficiently than serum, but also to provide information not readily available from serum testing.

A possible role for saliva as a diagnostic fluid in patients with chronic pain

OBJECTIVES

The focus of this review was on proteins and peptides found in saliva. Of greatest interest were those neuropeptides relevant to nociception and to the pathogenesis of chronic pain syndromes. An additional goal was to develop a standardized protocol to collect saliva for laboratory assessment.

METHODS

Data were obtained through discussion with experts at the medical schools in San Antonio and Heidelberg and a Medline literature search involving all relevant studies from 1966 to 1997. The literature search was based on the following key terms: saliva, serotonin, neuropeptide, substance P (SP), calcitonin gene-related peptide (CGRP), and nerve growth factor (NGF).

RESULTS

The mean concentration of SP in the saliva of healthy normal controls ranged from 9.6 to 220 pg/mL. Generally, the concentration of SP was approximately three times higher in saliva than in plasma. In a number of painful conditions, particularly tension headache, substantial elevations of salivary SP were found. Mean values for salivary CGRP in healthy controls were approximately 22 pmol/L and were significantly elevated in patients with migraine attacks or cluster headache. There were no data to indicate prior quantitative determination of NGF in human saliva.

CONCLUSIONS

After sampling and processing techniques have been standardized, measurement of neuropeptides in human saliva could provide a valuable tool for study of patients with chronic painful disorders such as rheumatoid arthritis, osteoarthritis, and even fibromyalgia syndrome.