Specific immunoglobulin A to Bordetella pertussis antigens in mucosal secretion for rapid diagnosis of whooping cough

The potential of saliva as an accessible and sensitive sample type for the detection of respiratory pathogens and host immunity

Despite its prominence in early scientific records, the usefulness of saliva as a respiratory specimen has been de-emphasised over the past century. However, due to its low cost and reliance on specific supply chains and the non-invasive nature of its collection, its benefits over swab-based specimens are again becoming increasingly recognised. These benefits were highlighted over the course of the COVID-19 pandemic, where saliva emerged as a more practical, clinically non-inferior sample type for the detection of SARS-CoV-2 and saw numerous saliva-based diagnostic tests approved for clinical use. Looking forward, as saliva uniquely contains both respiratory secretions and immunological components, it has potentially wide applications, ranging from clinical diagnostics to post-vaccine disease burden and immunity surveillance. This Personal View seeks to summarise the existing evidence for the use of saliva in detecting respiratory pathogens, beyond SARS-CoV-2, as well as detailing methodological factors that can influence sample quality and thus, clinical utility.

Oral fluid-based lateral flow point-of-care assays for pertussis serology

Introduction. Current serological diagnosis of pertussis is usually performed by ELISA, which is typically performed in larger diagnostic or reference laboratories, requires trained staff, and due to sample batching may have longer turnaround times.Hypothesis and Aim. A rapid point-of-care (POC) assay for pertussis serology would aid in both the diagnosis and surveillance of the disease.Methodology. A quantitative lateral flow (LF)-based immunoassay with fluorescent Eu-nanoparticle reporters was developed for the detection of anti-pertussis toxin (PT) and adenylate cyclase toxin (ACT) antibodies from oral fluid samples (N=100), from suspected pertussis cases with respiratory symptoms.Results. LF assay results were compared to those obtained with anti-PT IgG oral fluid ELISA. For an ELISA cut-off value of 50 arbitrary units, the overall agreement between the assays was 91/100 (91 %), the sensitivity was 63/70 (90 %) and the specificity was 28/30 (93 %). No ACT-specific antibodies were detected from oral fluid samples; however, the signal readout positively correlated to those patients with high anti-PT IgG antibodies.Conclusion. The developed LF assay was a specific, sensitive and rapid test for serological diagnosis of pertussis with anti-PT antibodies and is a suitable POC test using oral fluid samples.

Infant rhesus macaques as a non-human primate model of Bordetella pertussis infection

Background

The prevalent resurgence of pertussis has recently become a critical public health problem worldwide. To understand pertussis pathogenesis and the host response to both the pathogen and vaccines, a suitable pertussis animal model, particularly a non-human primate model, is necessary. Recently, a non-human primate pertussis model was successfully established with baboons. Rhesus macaques have been shown to be ideal animal models for several infectious diseases, but a model of infectious pertussis has not been established in these organisms. Studies on rhesus macaque models of pertussis were performed in the 1920s–1930s, but limited experimental details are available. Recent monkey pertussis models have not been successful because the typical clinical symptoms and transmission have not been achieved.

Methods

In the present study, infant rhesus macaques were challenged with Bordetella pertussis (B.p) using an aerosol method to evaluate the feasibility of this system as an animal model of pertussis.

Results

Upon aerosol infection, monkeys infected with the recently clinically isolated B.p strain 2016-CY-41 developed the typical whooping cough, leukocytosis, bacteria-positive nasopharyngeal wash (NPW), and interanimal transmission of pertussis. Both systemic and mucosal humoral responses were induced by B.p.

Conclusion

These results demonstrate that a model of pertussis was successfully established in infant rhesus macaques. This model provides a valuable platform for research on pertussis pathogenesis and evaluation of vaccine candidates.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06090-y.

Diagnosis of pertussis using nasopharyngeal IgA and polymerase chain reaction in specimens from outpatients in Australia

We assessed IgA antibodies and polymerase chain reaction (PCR) for diagnosis of pertussis in nasopharyngeal aspiration (NPA) samples from outpatients in Australia.   A total of 1700 patients (849 adults, 851 children) from Western Australia and the Northern Territory fulfilled the laboratory case definition for pertussis between 2004 and 2013: 732 specimens were positive by NPA IgA alone, 559 by PCR alone, and 409 by both tests. Overall, 968 cases (56.8%) were positive by PCR and 1141 cases (67.2%) by IgA [p < 0.00025]. Among pediatric patients, PCR was positive in 524 (61.3%) and IgA in 569 (67%). In 849 adult cases, the respective proportions were 52.3% and 67.4% [p < 0.00025].   The duration of cough in 507 patients was shorter in 262 pediatric cases (mean, 2.51 weeks; standard deviation [SD], 2.25) than 245 adult patients (3.27 weeks; SD, 2.79) [p = 0.0009]. PCR positivity showed a season-dependent variance (range, 5.6 to 85.9%) and peaked in the second week (71.7%) of illness. IgA antibodies peaked in the fifth week (89.5%) postinfection, and the positivity rate for NPA IgA was less variable (range, 38.3-97.2%).   Nasopharyngeal Bordetella pertussis-specific IgA antibodies are valuable in diagnosis of pertussis in Australia. Reliance on PCR alone misses a significant proportion of pertussis cases, especially those with a delayed presentation.

Saliva as a diagnostic medium

BACKGROUND

This is a review of current knowledge on the use of saliva, gingival cervical fluid and mucosal transudate in the detection of some oral and systemic diseases as well as drugs. Oral fluid is a diagnostic medium that can be easily collected and with minimal invasion but it has been neglected in the past. Today, saliva is being used more often to diagnose: HIV virus, oro-facial and systemic tumors, cardiovascular disease and in detecting addictive substances. Neutropil levels in saliva may also indicate successful bone marrow transplant. Oral fluid is now systematically being researched and oral fluid analysis is being compared with the analysis of other diagnostic media such as blood and urine. A number of recent studies have focused on oncogenic marker detection and its monitoring in saliva. The latest clinical and laboratory findings on diagnostic markers of oropharyngeal carcinoma in oral fluid could be the beginning of their wider use as a diagnostic medium. Oral fluid can also be also used to diagnose other malignancies such as breast cancer which was one of the first malignant tumors to be detected using genetic protein biomarkers. Raised levels of CA15-3 and the epidermal growth factor (EGF) receptor have been found in patients with breast cancer and elevated levels of CA 125 and the glycoprotein complex in the saliva of ovarian cancer patients.

CONCLUSION

Doubtless, the diagnostic value of saliva, aided by current technological development will increase rapidly in the near future.

Detection of anti-pertussis toxin IgG in oral fluids for use in diagnosis and surveillance of Bordetella pertussis infection in children and young adults

Bordetella pertussis infection is being increasingly recognized as a cause of prolonged, distressing cough (without whooping symptoms) in children and young adults. Diagnosis of infection in this population is important for treatment and surveillance purposes, and may also prove useful in reducing transmission to unvaccinated babies, for whom disease can be fatal. Serum IgG titres against pertussis toxin (PT) are routinely used as a marker of recent or persisting B. pertussis infection. However, collection of serum from young children is difficult, and compliance amongst these subjects to give samples is low. To circumvent these problems, an IgG-capture ELISA capable of detecting anti-PT IgG in oral fluid was devised. The assay was evaluated by comparison to a serum ELISA, using 187 matched serum and oral fluid samples from children (aged 5–16 years) with a history of prolonged coughing, whose serum anti-PT titre had already been determined (69 seropositive, 118 seronegative). The results showed that, using a cutoff of 70 arbitrary units (AU), the oral fluid assay detected seropositive subjects with a sensitivity of 79.7 % [95 % confidence interval (CI) 68.3–88.4] and a specificity of 96.6 % (95 % CI 91.5–99.1). Thus, oral fluid titres of ⩾70 AU would possess a positive predictive value of 76.2–93.2 % for pertussis amongst children with chronic coughs when used as a surrogate for the serum ELISA (assuming disease prevalence of 12–37 %). This oral fluid ELISA will greatly assist in the convenience of B. pertussis disease diagnosis and surveillance.

Oral diagnostics for the geriatric populations: current status and future prospects

Because it is a noninvasive technique, there is growing interest in replacing blood with oral-based methods of diagnostics. Oral diagnostics may be used for diagnosis and therapeutic drug monitoring of both oral diseases (eg, caries, periodontal disease,oral lesions, oral cancer) and systemic diseases (eg, infectious diseases, including HIV and AIDS, autoimmune diseases, cancer,and endocrine disorders). The authors address both existing techniques and oral-based diagnostics that will be applicable to the aging population in the future. They also highlight those techniques that are uniquely suited to point-of-care applications.

Molecular pathogenesis, epidemiology, and clinical manifestations of respiratory infections due to Bordetella pertussis and other Bordetella subspecies

Bordetella respiratory infections are common in people (B. pertussis) and in animals (B. bronchiseptica). During the last two decades, much has been learned about the virulence determinants, pathogenesis, and immunity of Bordetella. Clinically, the full spectrum of disease due to B. pertussis infection is now understood, and infections in adolescents and adults are recognized as the reservoir for cyclic outbreaks of disease. DTaP vaccines, which are less reactogenic than DTP vaccines, are now in general use in many developed countries, and it is expected that the expansion of their use to adolescents and adults will have a significant impact on reducing pertussis and perhaps decrease the circulation of B. pertussis. Future studies should seek to determine the cause of the unique cough which is associated with Bordetella respiratory infections. It is also hoped that data gathered from molecular Bordetella research will lead to a new generation of DTaP vaccines which provide greater efficacy than is provided by today's vaccines.

Oral fluids for the immunodiagnosis of Schistosoma mansoni infection

Saliva and oral transudate were evaluated for their potential as human specimens in the detection of IgG antibodies against soluble Schistosoma mansoni egg antigen (SEA). Preliminary laboratory testing of 49 subjects, 37 with parasitological proven infection and 12 negative controls, displayed 100% sensitivity in ELISA using serum and oral transudate and 94.6% using saliva. The specificity of the ELISA with serum was 100% versus 91.7% with both oral fluids. Significant Spearman rank correlations of anti-SEA IgG levels with egg counts were observed for serum, oral transudate and saliva (P < 0.05). The sensitivity of dot-ELISA was 100% for serum, 89% for transudate and 81% for saliva, and specificity was 100% for all 3 samples. The immunodiagnostic value of ELISA for the detection of anti-SEA IgG antibodies in oral transudate was further evaluated in 197 individuals from an endemic area of Brazil. The ELISA using serum and oral transudate showed sensitivities of 98.8% and 100% respectively and specificities of 67.8% and 64.3% respectively. Use of oral fluids for the diagnosis of S. mansoni infection was equivalent to sera with respect to test efficacy, offering an alternative to blood collection.

A nasal whole-cell pertussis vaccine can induce strong systemic and mucosal antibody responses which are not enhanced by cholera toxin

The immunogenicity of formaldehyde-inactivated Bordetella pertussis (Bp) delivered by the intranasal or colonic-rectal routes in BALB/c mice was studied by immunization four times at weekly intervals with Bp alone, or with Bp mixed with cholera toxin (CT) as a mucosal adjuvant. Mice given Bp subcutaneously, and untreated mice served as controls. Antibody responses in serum, saliva, bronchoalveolar lavage (BAL) fluids and extracts of faeces were measured by enzyme-linked immunosorbent assay. Nasal immunizations with Bp alone induced high levels of IgG antibodies to Bp in serum and BAL fluids, as well as IgA antibodies in serum, saliva, BAL fluids and extracts of faeces. The IgA responses were significantly reduced, and the IgG responses were not increased, when CT was given intranasally together with Bp. However, CT increased the IgA responses to Bp in faeces when both antigens were given rectally, while rectal administration of Bp alone did not induce significant serum or secretory antibody responses. However, when mixed with Bp, the CT itself induced antibodies to CT in serum and samples representing secretions after both nasal and rectal administrations. Thus, Bp is strongly immunogenic when applied intranasally, but not when presented into the intestinal lumen via the rectal route. It appears that CT, which is known to be a mucosal adjuvant and which in itself is a strong mucosal immunogen, will inhibit the immune responses of other strong immunogens when applied on the nasal mucosa.

The filamentous haemagglutinin, a multifaceted adhesion produced by virulent Bordetella spp

Filamentous haemagglutinin (FHA) is the major attachment factor produced by virulent Bordetella spp. Similar to the other virulence factors, its production is tightly regulated by a two-component system in response to environmental changes. Although of impressive size (c. 220 kDa), it is very efficiently released into the culture supernatant of Bordetella pertussis. Its biogenesis involves complex processing of a larger precursor with a calculated molecular mass of 370 kDa. Export of FHA into the culture medium depends on an outer membrane protein homologous to haemolysin accessory proteins. Purified extracellular FHA is able to increase the adherence of other pathogens to the host, which may contribute to super-infection in whooping cough. Although FHA- mutants colonize lungs as efficiently as the wild-type parent strains, immune responses against FHA appear to protect against colonization. Unlike many other adhesins, FHA expresses at least three different attachment activities, one specific for the CR3 integrins of macrophages, one involving a carbohydrate-binding site, specific for interactions with cilia, and a heparin-binding activity that may be important for interaction of B. pertussis with epithelial cells or extracellular matrices.

Salivary diagnosis: more than a lick and a promise

There is a growing appreciation for the use of oral fluid as an easily collected, non-invasive diagnostic medium in a variety of disease states and clinical situations. Dental applications include differential diagnosis of salivary gland disease, caries and periodontal disease activity and susceptibility tests, Candida monitoring and testing for HIV and hepatitis.

Evaluation of an improved DNA probe for diagnosis of pertussis

A Bordetella pertussis specific subclone, pRZ61, of a Bordetella genus-specific clone, pB23, was evaluated on nasopharyngeal aspirates of 179 patients with suspected pertussis. Hybridization was performed directly after spotting or after 1-3 days of preculture of the nylon membranes on solid culture medium. A direct comparison of the two probes was obtained by reprobing with the subclone the same membranes that had been hybridized with the parent probe. pRZ61 detected 50% of the serologically defined cases of pertussis, that is, had the same sensitivity as standard culture. Specificity as compared with serology was close to 100%. The increasing sensitivity and the corresponding decreasing specificity after preculture noted for pB23 was not seen with the subclone. The study showed that the improved probe represents a rapid diagnostic method in pertussis.

DNA probes for Bordetella species and a colorimetric reverse hybridization assay for the detection of Bordetella pertussis

Three oligonucleotide probe sequences were inferred from the 16S ribosomal ribonucleic acid (rRNA) and the 16S-23S rRNA spacer sequences of Bordetella pertussis ATCC 10380. These probes were used in hybridization tests with deoxyribonucleic acid from Bordetella species and other relevant bacterial taxa. A probe from the spacer region hybridized exclusively to the B. pertussis strains tested and not to strains from other species. Using a combination of three probes, B. pertussis, B. parapertussis/B. bronchiseptica and B. avium could be specifically identified and differentiated from other taxa. Differentiation between B. parapertussis and B. bronchiseptica was not possible with the probes used. Using the spacer probe, a colorimetric hybridization assay specific for B. pertussis was developed based on enzymatic amplification of the 16S-23S rRNA spacer and reverse hybridization in microtitre wells. As compared with results using agarose gel electrophoresis, and Southern and dot-spot hybridization with a 32P-labelled probe, this assay proved to be faster and easier to perform and was found to be at least as sensitive and specific.

Diagnostic value of clinical and bacteriological findings in pertussis

Clinical and bacteriological findings in the diagnosis of pertussis were evaluated in 300 consecutive patients with parental or the patient's own suspicion of the disease. Serology was used as a reference method. Of the 285 (95%) patients fully sampled, 163 (57%) were diagnosed as having pertussis while the remaining 122 patients constituted the non-pertussis control group. The clinical and epidemiological data were collected at the first visit made on median day seven of illness. In this population of mainly unimmunised children, the highest predictive values were obtained for the physician's diagnosis of pertussis (100%) and for the physician's diagnosis of some other illness (93%). The only clinical symptom with a high predictive value for pertussis was the report of whoops (92%). Among epidemiological data the highest predictive value (90%) was obtained for reported household exposure in unimmunised children more than 1 year of age. Culture of Bordetella pertussis was found to have an overall 50% sensitivity. Isolation of other bacteria had no predictive value in the differential diagnosis of pertussis.

DNA hybridization for diagnosis of pertussis

The aim of the present study was to evaluate a mixed phase DNA hybridization assay for detection of Bordetella pertussis and Bordetella parapertussis in nasopharyngeal aspirates from patients with suspected pertussis. Among 179 consecutive patients with own or parental suspicion of pertussis, the diagnosis was confirmed in 103 patients by serology and in 52/103 (50%) cases also by culture. The remaining 76 patients served as nonpertussis controls. Direct hybridization was positive in 38% samples with serology as reference method, a non-significant difference to the 50% sensitivity for culture. Preculture of samples on membranes for 24, 48 and 72 h gave a significantly higher sensitivity only with 72 h preculture, 69% vs 50% (P = 0.007). The 72h preculture gave, however, also a significant decrease of specificity, 87% vs 100% for routine culture (P = 0.001) and is not a more rapid diagnostic method. The result shows that rapid diagnosis by DNA hybridization can be achieved in a large proportion of pertussis cases. The presence of smaller numbers of bacteria in samples only positive after preculture indicate that DNA hybridization could be a highly sensitive diagnostic method with further development of more rapid amplification systems.

Immunoglobulin A antibodies to pertussis toxin and filamentous hemagglutinin in saliva from patients with pertussis

Immunoglobulin A (IgA) antibodies against pertussis toxin (PT) and filamentous hemagglutinin (FHA) in 181 saliva samples obtained during various stages of pertussis from 112 patients were determined. Saliva samples obtained within 5 days after the onset of symptoms did not have detectable IgA antibodies against either of the two antigens. Of the samples obtained between 6 and 50 days after the onset of symptoms, 72% had antibodies against FHA but only 40% had antibodies against PT. With few exceptions, saliva samples obtained more than 50 days after the onset of symptoms contained antibodies against both antigens. In the 59 patients from whom paired saliva samples were obtained at intervals of 2 to 5 weeks, a significant increase in the geometric mean FHA antibody titers but not PT antibody titers occurred. However, increases that were fourfold or greater were observed against FHA in only 19 patients and against PT in 14 patients. Thus, IgA antibodies against FHA and PT in saliva develop during pertussis, and the importance of secretory IgA antibodies for protection against infection and disease should be investigated. Determination of these antibodies in paired saliva samples is, however, of little value for the laboratory diagnosis of pertussis.

The diagnostic uses of saliva

It is becoming increasingly apparent to investigators and clinicians in a variety of disciplines that saliva has many diagnostic uses and is especially valuable in the young, the old and infirm and in large scale screening and epidemiologic studies. The highly sensitive test procedures that are now commonplace makes it practical to quantitate, despite very low concentrations, a large number of hormones and drugs in saliva. Indeed, all steroids of diagnostic significance in routine clinical endocrinology can now be readily measured in saliva. Drug monitoring can include abusive as well as therapeutic agents. The concordance between anti HIV antibodies in saliva and serum has stimulated application to various other antiviral antibodies as well as to viral antigens per se. Saliva has found use as a diagnostic aid in an increasing number of clinical situations and in systemic diseases that can affect salivary gland function and composition such as Sjögren's syndrome, cystic fibrosis and diseases of the adrenal cortex. The list keeps growing.

Use of a Chinese hamster ovary cell cytotoxicity assay for the rapid diagnosis of pertussis

A cytotoxicity assay with Chinese hamster ovary cells (CHO) capable of detecting 750 pg of pertussis toxin was assessed for use as a rapid test for the diagnosis of pertussis and compared with direct immunofluorescence (DFA). With pure bacterial cultures and simulated clinical specimens, the CHO assay detected as few as two colonies of Bordetella pertussis; no cytotoxicity occurred with other respiratory tract microorganisms. Next, nasopharyngeal aspirate secretions and nasopharyngeal cultures harvested after 72 h of incubation from 57 culture-positive and 201 culture-negative patients were examined. The CHO assay with nasopharyngeal secretions was positive in 25 (45%) of 55 culture-positive cases; DFA was positive in 15 (26%) of 57 cases (P = 0.05). The CHO assay with 72-h culture washes was positive in 42 (75%) of 57 culture-positive cases (P less than 0.001 compared with DFA). The CHO assay was more specific than DFA; all five CHO-positive, culture-negative cases were confirmed as true positives by serologic or toxin neutralization assays. In contrast, only 4 (36%) of 11 DFA-positive, culture-negative cases were confirmed as pertussis by serologic methods (P = 0.03). Combining the CHO assay with culture significantly decreased the delay in laboratory diagnosis of pertussis (3.30 versus 4.54 days; P = 0.01). The CHO assay is a sensitive and specific assay for the rapid diagnosis of pertussis.

Evaluation of culture, immunofluorescence, and serology for the diagnosis of pertussis

Nasopharyngeal culture, direct immunofluorescence, and serology of acute-phase and paired serum specimens were compared for the laboratory diagnosis of infections due to Bordetella pertussis in a community-based pediatric population with both high vaccine usage and high pertussis incidence. In 77 (37%) of 210 patients evaluated, one or more tests were positive for pertussis. A clinical illness compatible with pertussis was present in 52 (71%) of 73 pertussis test-positive and 42 (35%) of 119 test-negative patients (P less than 0.001). Nasopharyngeal culture was of low sensitivity (20 [26%] of 77 positive tests) but was most commonly confirmed by another positive pertussis test (85%). Direct immunofluorescence was both insensitive and nonspecific; only 6 (30%) of 20 cases positive by culture were positive by immunofluorescence, and only 4 (33%) of 12 of the culture-negative, immunofluorescence-positive cases could be confirmed by another positive pertussis test. Although serology by enzyme immunoassay proved to be the most sensitive of the laboratory tests (87%), this sensitivity could be achieved only by assaying both acute-phase and paired serum specimens and measuring immunoglobulin G (IgG), IgA, and IgM antibodies to two pertussis antigens (pertussis toxin and filamentous hemagglutinin). Loss of sensitivity occurred with any reduction in the number of these serologic assays performed. Optimal laboratory diagnosis of endemic pertussis in a pediatric population requires both nasopharyngeal culture and serology by enzyme immunoassay.