Salivary antibody detection in epidemiological surveys: a pilot study after a mass vaccination campaign against rubella in São Paulo, Brazil

Use of traditional serological methods and oral fluids to assess immunogenicity in children aged 2-16 years after successive annual vaccinations with LAIV

Background

The UK introduced quadrivalent live attenuated influenza vaccine (qLAIV) for children in 2013/2014. The impact of annual vaccination on effectiveness and immunogenicity is being assessed.

Method

A phase III/IV open-label study of the immunogenicity of annual vaccination with qLAIV (Fluenz™) was conducted over three consecutive years (2014/15–2016/17) in 254, 249 and 162 children respectively. Serum responses to vaccine components were measured by Haemagglutination Inhibition (HAI) and anti-A(H1N1)pdm09 Neuraminidase (NAI) assays, stratified according to previous receipt of AS03_B-adjuvanted A(H1N1)pdm09 pandemic vaccine in 2009/10. Antibody levels to the A(H1N1)pdm09 and H3N2 vaccine components in oral fluids (OF) were explored using an ELISA.

Findings

More paired pre- and post-vaccination oral fluids (96%) than paired sera (87%) were obtained. Geometric mean titre rises using HAI assays were limited, with maximum rises seen in year one for both influenza B strains when 39% and 43% of subjects seroconverted (95% confidence interval 33–46% and 36–50%, respectively) and year two for influenza H3N2, when 40% (33–46%) individuals seroconverted. Prior pandemic vaccine receipt resulted in higher pre- and post-vaccination A(H1N1)pdm09 HAI titres and lower pre-and post-vaccination NAI (N1 neuraminidase) titres in all three years. OF results were congruent with HAI results; assay specificity compared to HAI was 88.1 and 71.6 percent, and sensitivity was 86.4 and 74.8 percent respectively for A(H1N1)pdm09 and H3N2.

Conclusion

In all three study years, vaccination with qLAIV resulted in poor antibody responses. However, OFs are an alternative specimen type that allows self sampling, can easily be obtained from children, and their analysis leads to similar conclusions as classic serology by HAI. Their suitability for seroprevalence studies should be investigated. We demonstrated a sustained effect from prior receipt of the AS03_B-adjuvanted A(H1N1)pdm09 vaccine, even after repeat vaccination with qLAIV indicating that early exposure to influenza antigens has a significant long lasting effect.

Application of Oral Fluid Assays in Support of Mumps, Rubella and Varicella Control Programs

Detection of specific viral antibody or nucleic acid produced by infection or immunization, using oral fluid samples, offers increased potential for wider population uptake compared to blood sampling. This methodology is well established for the control of HIV and measles infections, but can also be applied to the control of other vaccine preventable infections, and this review describes the application of oral fluid assays in support of mumps, rubella and varicella national immunization programs. In England and Wales individuals with suspected mumps or rubella, based on clinical presentation, can have an oral fluid swab sample taken for case confirmation. Universal varicella immunization of children has led to a drastic reduction of chickenpox in those countries where it is used; however, in England and Wales such a policy has not been instigated. Consequently, in England and Wales most children have had chickenpox by age 10 years; however, small, but significant, numbers of adults remain susceptible. Targeted varicella zoster virus (VZV) immunization of susceptible adolescents offers the potential to reduce the pool of susceptible adults and oral fluid determination of VZV immunity in adolescents is a potential means of identifying susceptible individuals in need of VZV vaccination. The main application of oral fluid testing is in those circumstances where blood sampling is deemed not necessary, or is undesirable, and when the documented sensitivity and specificity of the oral fluid assay methodology to be used is considered sufficient for the purpose intended.

Declining prevalence of hepatitis A virus antibodies among children from low socioeconomic groups reinforces the need for the implementation of hepatitis A vaccination in Brazil

Age-related seroprevalence studies that have been conducted in Brazil have indicated a transition from a high to a medium endemicity of hepatitis A virus (HAV) infection in the population. However, most of these studies have focused on urban populations that experience lower incidence rates of HAV infection. In the current study, the prevalence of anti-HAV antibodies was investigated in children with a low socioeconomic status (SES) that live on the periphery of three capital cities in Brazil. A total of 1,162 dried blood spot samples were collected from individuals whose ages ranged from one-18 years and tested for anti-HAV antibodies. A large number of children under five years old (74.1-90%) were identified to be susceptible to HAV infection. The anti-HAV antibody prevalence reached ≥ 50% among those that were 10-14 years of age or older. The anti-HAV prevalence rates observed were characteristics of regions with intermediate level of hepatitis A endemicity. These data indicated that a large proportion of children with a low SES that live at the periphery of urban cities might be at risk of contracting an HAV infection. The hepatitis A vaccine that is currently offered in Brazil is only available for high-risk groups or at private clinics and is unaffordable for individuals with a lower SES. The results from this study suggest that the hepatitis A vaccine should be included in the Brazilian National Program for Immunisation.

Brief report: a comparison of saliva collection methods with preschool children: the perspectives of children, parents, and childcare practitioners

Saliva offers developmental researchers and pediatric clinicians significant opportunities to measure numerous biological markers. However, many preschool-aged children refuse to participate in saliva collection. Identifying collection methods known to be acceptable to participants may help in maximizing participation. To this end, this study aimed to determine the relative acceptability of three different collection methods (passive drool, hydrocellulose microsponges, and polymer swabs) to children and their caregivers. Interviews were carried out with 15 preschool children (age range 32-66 months, M=43.65, SD=8.45), their parents, and childcare practitioners. Although children reported no overall preference for a specific method, parents and practitioners selected hydrocellulose microsponges most often as their preferred method.

Enzyme-linked immunosorbent assay using recombinant SAG1 antigen to detect Toxoplasma gondii-specific immunoglobulin G antibodies in human sera and saliva

Serologic detection of Toxoplasma gondii IgG antibodies is widely accepted as a means to determine immune status and susceptibility to Toxoplasma infection during pregnancy. However, current commercial kits present some drawbacks, such as a requirement for whole-parasite antigen preparation or interassay variability. To address these problems, the purpose of this study was to produce a whole sequence of the recombinant T. gondii SAG1 antigen (rSAG1) to assess its diagnostic performance in Toxoplasma IgG screening and to explore a saliva-based method as a noninvasive alternative to serum-based testing. rSAG1 was expressed in recombinant bacteria as inclusion bodies, purified through one-step affinity chromatography, and refolded in native form by dialysis. A large amount was obtained, and the specific antigen immunoreactivity was confirmed by immunoblotting. Two rSAG1-based enzyme-linked immunosorbent assays (ELISAs) applied to paired serum and saliva samples were designed. The rSAG1-based ELISA evaluation consisted of testing intrinsic sensitivity and specificity of 49 serum samples from patients immune to toxoplasmosis and 42 serum samples from nonimmune controls identified by routinely used kits. To assess agreement between serum-based and saliva-based tests, the positive percent agreement (PPA) and negative percent agreement (NPA) between the 2 tests were estimated. The rSAG1 serum-based ELISA detected specific IgG with 100% sensitivity and specificity. The PPA and NPA between the serum-based and saliva-based tests varied according to the selected optical density threshold in saliva. Thus, for a selected cutoff of 0.14, the PPA was 100% and the NPA was 88.1%, whereas for a selected cutoff of 0.29, the PPA was 67.3% and the NPA was 100%.

The use of dried blood spots for assessing antibody response to hepatitis A virus after natural infection and vaccination

During recent years, vaccination against hepatitis A has been implemented in several countries. It is expected that the increase in mass vaccination against hepatitis A will eventually result in a decreased prevalence of anti-HAV antibodies in the general population. For this reason, a suitable clinical sample for diagnosis of hepatitis A must be sufficiently sensitive to enable detection of lower antibodies titers. In this study, the feasibility of using dried blood spots (DBS) was assessed for the detection of anti-HAV antibodies after a natural infection and vaccination. Seventy-four DBS and paired plasma samples were obtained from a group of college students for a cross-sectional hepatitis A seroepidemiological study. Forty-six students seronegative for anti-HAV were selected randomly and immunized with an inactivated hepatitis A vaccine using an 0-6 month schedule. Seroconversion was monitored in paired plasma and DBS samples 6 months after the first dose followed by a period of 8 and 24 months after the second dose. A strong correlation between OD/CO rates of paired plasma and DBS samples for the detection of anti-HAV was observed. The sensitivity and specificity of the DBS compared with plasma for the detection of anti-HAV antibodies after natural infection was 100%. The sensitivity of DBS in samples collected 24 months after the second dose of hepatitis A vaccine was 95.4%. The results showed that DBS samples can be used for the detection of anti-HAV antibodies both after natural infection or vaccination.

The development of oral fluid-based diagnostics and applications in veterinary medicine

The purpose of this review was to discuss the history of the development and implementation of oral fluid diagnostics for infectious diseases of humans and domestic animals. The use of oral fluid for the assessment of health and diagnosis of disease in humans and animals has a surprisingly long history. As early as 1909, Pollaci and Ceraulo reported sensitive and specific agglutination of 'Micrococcus melitensis' (Brucella melitensis) by oral fluid from patients diagnosed with Malta Fever. A 1986 report of the detection of antibodies against human immunodeficiency virus (HIV) in oral fluid from patients with acquired immunodeficiency syndrome (AIDS) marked the start of a remarkably rapid series of developments in oral fluid-based assays. Cumulatively, the literature strongly supports implementation of oral fluid-based diagnostics in veterinary diagnostic medicine. Pathogen-specific IgA, IgM and IgG antibodies have all been demonstrated in oral fluid collected from diverse domestic animal species in response to infection. A variety of infectious agents, both local and systemic, are shed in oral fluid, including some of the most economically significant pathogens of production animals (e.g. foot-and-mouth disease virus, classical swine fever virus and porcine reproductive and respiratory syndrome virus) Ultimately, point-of-care rapid assays (i.e. cow-side, sow-side or pen-side tests) and access to real-time infectious disease data will revolutionize our delivery of health management services.

Immunodiagnosis of dengue virus infection using saliva

Keeping in view the complications and the case fatality associated with dengue virus, several serologic tests have been developed. However, the major drawback of these serologic tests is the need for a venous blood sample obtained by invasive venipuncture. As a noninvasive alternative, saliva provides a body fluid that contains antibodies of diagnostic importance. Hence, the detection of DEN-specific IgM and IgG antibodies in serum and saliva from 80 patients was compared. Salivary IgM antibodies were detected in 100% of the serum IgM-positive samples and in 30% of the serum samples that were negative for IgM antibodies. Salivary IgG antibodies were detected in 93.3% of the serum samples that were positive for anti-dengue IgG antibodies and in none of the serum IgG-negative cases. None of the specimens from the healthy controls showed the presence of IgM or IgG antibodies. The detection of both IgG and IgM antibodies in saliva correlated well with the serum IgG and IgM detection by the ELISA test (r = 0.6322 and r = 0.4227). Detection of salivary IgM antibodies by ELISA showed 100% sensitivity, 70% specificity, 90.9% positive predictive value, and 100% negative predictive value. The detection of IgG in saliva proved to be a promising tool as the sensitivity, specificity, positive predictive value, and negative predictive value were found out to be 93.3%, 100%, 100%, and 83.3%, respectively. Thus, from this study we conclude that the detection of DEN-specific salivary IgG and IgM antibodies are useful markers for dengue infection.

Validation of a modified commercial assay for the detection of rubella-specific IgG in oral fluid for use in population studies

Matching serum and oral fluid (saliva) samples were collected from 369 subjects in Tunisia in 2002, from a city in the north and a rural district in the south. Rubella-specific IgG was detected in sera by commercial ELISA (Dade Behring) and in matching oral fluids by two methods, a previously described IgG-capture ELISA (GACELISA) [J. Clin. Microbiol. 37 (1999) 391] and the Dade Behring ELISA with the assay protocol modified for use with oral fluids. Total IgG concentration of oral fluids was also measured. Rubella-specific IgG was detected in 289 (78.3%) sera overall. Differences in the age distribution of the study population in the north and south led to a higher prevalence being found in the north (86.2%) than in the south (71.8%). This difference was reflected in the oral fluid rubella-specific IgG results. With GACELISA, rubella-specific IgG was detected in 79.4% of oral fluids from the north and 69.7% from the south and with the modified Dade Behring assay, in 81.4% of oral fluids from the north and in 64.9% from the south. The sensitivity and specificity of GACELISA in comparison to results from the matching sera were 92.4 and 93.2%, respectively. The sensitivity and specificity of the modified Dade Behring ELISA were 89.8 and 92.0%, respectively. Total IgG concentration in oral fluid showed a weak correlation (r=0.19) with the modified Dade Behring results and with samples where total IgG was >7.5 mg/l, the sensitivity and specificity were 94.4 and 90.0%, respectively. Twenty-nine oral fluids, which gave false negative rubella-specific IgG results with the modified Dade Behring ELISA, had a lower mean total IgG concentration than 256 oral fluids which gave concordant positive results (7.0mg/l versus 15.8 mg/l, P<0.001). The study validated the modified Dade Behring ELISA, providing an alternative to the GACELISA for assessing levels of rubella immunity for population studies using oral fluid samples.

Diagnosis of dengue virus infection by detection of specific immunoglobulin M (IgM) and IgA antibodies in serum and saliva

To evaluate alternative approaches to the serological diagnosis of dengue virus (DEN) infection, the detection of DEN-specific immunoglobulin M (IgM) and IgA antibodies in serum and saliva specimens was assessed in 147 patients with symptoms of DEN infection seen at the Ministry of Health in Nicaragua. Seventy-two serum samples were determined to be positive for anti-DEN antibodies by IgM capture enzyme-linked immunosorbent assay, the routine diagnostic procedure. Serum and saliva specimens were obtained from 50 healthy adults as additional controls. IgM was detected in the saliva of 65 of the 72 serum IgM-positive cases, 6 of the 75 serum IgM-negative cases, and none of the control group, resulting in a sensitivity of 90.3% and a specificity of 92.0% and demonstrating that salivary IgM is a useful diagnostic marker for DEN infection. Detection of IgA in serum may be another feasible alternative for the diagnosis of DEN infection, with serum IgA found in 68 (94.4%) of the IgM-positive cases. In contrast, detection of IgA in saliva was not found to be a useful tool for DEN diagnosis in the present study. Further studies of the kinetics of antibody detection in another set of 151 paired acute- and convalescent-phase serum samples showed that DEN-specific IgA antibodies were detected in more acute-phase samples than were IgM antibodies. Thus, we conclude that DEN-specific IgA in serum is a potential diagnostic target. Furthermore, given that saliva is a readily obtainable, noninvasive specimen, detection of DEN-specific salivary IgM should be considered a useful, cheaper diagnostic modality with similar sensitivity and specificity to IgM detection in serum.

Diagnosis of rubella infection by detecting specific immunoglobulin M antibodies in saliva samples: a clinic-based study in Niterói, RJ, Brazil

This study was designed to investigate whether saliva could be a feasible alternative to serum for the diagnosis of recent rubella infection in a clinic setting. Forty-five paired blood and saliva samples collected 1 to 29 days after onset of illness were tested for specific immunoglobulin (Ig) M by antibody-capture radioimmunoassay (MACRIA). Rubella IgM was detected in all serum samples and in 38 (84.4%) saliva specimens. Forty-six serum and saliva samples from other patients with rash diseases were tested by MACRIA for control purposes and two saliva specimens were reactive. The saliva test had specificity of 96%. These results indicate that salivary IgM detection may be a convenient non-invasive alternative to serum for investigation of recent rubella cases, especially for disease surveillance and control programmes.

Detection of measles specific IgG in oral fluid using an FITC/anti-FITC IgG capture enzyme linked immunosorbent assay (GACELISA)

An IgG antibody capture enzyme linked immunosorbent assay (GACELISA) for the detection of measles specific IgG in oral fluid was developed using an FITC/anti-FITC amplification system. The GACELISA was evaluated by testing paired oral fluid and serum samples from 787 subjects in an epidemiological study of measles in rural Ethiopia. Oral fluids were tested by GACELISA and corresponding serum samples by a sensitive indirect ELISA for measles IgG (Behring Enzygnost). By comparison with the serum measles IgG assay, the oral fluid GACELISA had a sensitivity of 97.4% (95% confidence intervals: 95.9, 98.2) and a specificity of 90.0% (81.9, 94.3), with no significant differences observed by age group. Total IgG concentrations were measured on a subset of 160 oral fluids by an in-house ELISA. This showed that false negative GACELISA results tended to occur in samples with low concentrations of total IgG, although the trend was not statistically significant. It is concluded that the overall performance of the GACELISA was satisfactory, showing close agreement to the serum ELISA, and has potential to serve as an easily transferable tool for large scale epidemiological studies as required for the World Health Organisation's programme for the global control of measles.

Detection of antibodies against hepatitis A virus in eluates of blood spotted on filter-paper: a pilot study in Rio de Janeiro, Brazil

The validity of blood spotted on to filter-paper (BSOFP) eluates for the detection of antibodies against hepatitis A virus (HAV) was investigated in 718 individuals (children and adults) during a field study in a small area in Rio de Janeiro State, Brazil. Serum samples were considered the 'gold standard'. BSOFP eluates were analyzed by 2 different techniques: microplate competitive enzyme-linked immunosorbent assay (ELISA) of the whole study group and microparticle enzyme immune assay (MEIA) of a subsample of 59 individuals. For BSOFP eluates by ELISA, sensitivity and specificity were 89.6% (95% CI: 84.7-93.1) and 97.5% (95% CI: 95.6-98.7), respectively. For a seroprevalence of anti-HAV antibodies of 32%, the positive predictive value was 94.5% (95% CI: 90.3-97.0) and the negative predictive value was 95.2% (95% CI: 92.8-96.8). The test efficiency was 95.0% (95% CI: 93.1-96.4). Similar results were found for BSOFP eluates by MEIA. Agreement between the 2 techniques used for BSOFP (ELISA and MEIA) was also high (kappa = 0.93). These results encourage the more widespread application of BSOFP as a means of surveillance for large-scale epidemiological studies for hepatitis A.

Detection of rubella virus-specific immunoglobulin G in saliva by an amplification-based enzyme-linked immunosorbent assay using monoclonal antibody to fluorescein isothiocyanate

An immunoglobulin G (IgG)-capture enzyme-linked immunosorbent assay (ELISA) for rubella virus is described. The assay uses a fluorescein isothiocyanate (FITC)-anti-FITC amplification system. The detection limit of the ELISA was approximately 7 IU of rubella virus-specific IgG per ml of serum sample. For saliva samples the performances of the capture ELISA and previously described radioimmunoassay were assessed, and the results of those two assays were compared to the rubella virus-specific IgG result obtained by a commercial ELISA (Behring Enzygnost) with a panel of paired serum and saliva samples. This comparison showed that the capture ELISA with saliva was more sensitive than the radioimmunoassay and that the results correlated better with the serum IgG result than the results of the radioimmunoassay did, with an overall sensitivity of 82% and a rank correlation of 0.68, whereas the sensitivity and rank correlation for the radioimmunoassay were 74% and 0.45, respectively. For subjects of 10 years of age or younger, the ELISA with saliva had a sensitivity of 94% and a specificity of 100% compared to the results of the ELISA (Behring Enzygnost) for rubella virus-specific IgG with corresponding serum samples. The sensitivity was much lower for subjects ages 17 years or older. The assay may have wider epidemiological use with saliva specimens, particularly those from children.

Diagnosis of dengue infection by detecting specific immunoglobulin M antibodies in saliva samples

To investigate whether saliva could be used for diagnosis of recent dengue, serum and saliva samples were collected simultaneously from patients with suspected dengue infection. Sera (1:10 dilution) and saliva (undiluted) were tested by using an IgM capture enzyme linked immunosorbent assay (MAC-ELISA) with minor modifications (serum and saliva absorption for 3 h at 37 degrees C). The quality of saliva was evaluated by determining the IgG total concentration (enzyme immunoassay) which ranged from 2.7 to > 50 mg/l. Recent dengue infection was confirmed in 38 cases. Forty-six serum and saliva specimens were collected from these patients 1-30 days after the onset of symptoms. IgM was detected in 65.8% saliva samples. High rate of positivity ( > 80%) was observed for the saliva samples collected > or = 5 days after the onset of the disease. Fifty serum and saliva samples from other 32 patients with rash diseases were also tested and all the specimens were unreactive by MAC-ELISA. These results indicate that saliva may be a convenient non-invasive alternative to serum for diagnosis of recent dengue fever infection, especially for epidemiological studies during outbreaks of the disease.

Detection of specific antibodies in saliva during dengue infection

Saliva was collected prospectively from patients presenting with suspected dengue infection 4 to 8 days after the onset of symptoms and assayed by a commercial dengue immunoglobulin M (IgM) and IgG capture enzyme-linked immunosorbent assay (ELISA) (PanBio Dengue Duo ELISA). Laboratory diagnosis was based on virus isolation and on hemagglutination inhibition (HAI) assay and an in-house IgM and IgG capture ELISA. With a positive result defined as either salivary IgM or IgG levels above the cutoff value, an overall sensitivity of 92% was obtained for both primary- and secondary-dengue patients (22 of 24), while no patients with non-flavivirus infections (n = 11) and no healthy laboratory donors (n = 17) showed elevation of salivary antidengue antibody (100% specificity). Salivary IgG levels correlated well with serum HAI titer (r = 0.78), and salivary IgG levels could be used to distinguish between primary- and secondary-dengue virus infections.

Salivary diagnosis of measles for surveillance: a clinic-based study in Niterói, state of Rio de Janeiro, Brazil

This study was designed to investigate whether saliva could be a feasible alternative to serum for the diagnosis of recent measles infection in a clinic setting. Forty-two paired blood and saliva samples collected 1 to 16 days after onset of illness from 29 patients with clinical measles were tested for specific immunoglobulin (Ig) M by antibody-capture radioimmunoassay. Measles IgM was detected in all serum samples and in 39 (92.9%) saliva specimens. Between 1 and 3 weeks after illness onset, virus-specific IgM was detected in 100% of saliva samples. Measles IgM was also detected in 17 saliva specimens, not paired with blood samples, collected from study patients 5 days to 3 weeks after onset. Our results indicate that salivary IgM detection is a suitable non-invasive method for investigation of notified cases under conditions of routine clinic use.

An evaluation of oral-fluid collection devices for the determination of rubella antibody status in a rural Ethiopian community

We compared 3 different oral-fluid collection devices to assess their suitability for use in community studies of rubella antibody. Of 58 individuals enrolled from 13 households from a southern Ethiopian village, 38 provided a blood sample and oral fluids by the 3 devices: 2 proprietary, Omni-SAL and OraSure, and a third a polystyrene sponge swab (Sponge). The Sponge swab, used like a toothbrush, was most acceptable to survey staff and to participants of all ages, although it proved ill-adapted for fluid extraction. The other devices more often caused participant discomfort or anxiety, particularly in the young. Statistical comparison of rubella-specific immunoglobulin (Ig) G in oral fluid, measured by antibody-capture radioimmunoassay, and in serum, by indirect enzyme-linked immunosorbent assay, showed no clear differences between the devices in oral-fluid performance. Specificity range was 75-100% and sensitivity 73-85%, relative to serum. Specific-antibody levels declined with increasing age, with concomitant decreases in sensitivity, as previously documented. The relationship between specific IgG and total IgG in oral fluid differed by device. Specific IgG levels were highly correlated between paired samples using the Sponge device. We consider the Sponge device to be the most suitable for community survey work, although the extraction method requires improvement. Further work is needed to improve the sensitivity of antibody status determination in adults.

A comparison of oral fluid and serum for the detection of rubella-specific antibodies in a community study in Addis Ababa, Ethiopia

OBJECTIVE

To assess the utility of oral fluid compared with serum for the determination of age-prevalence of rubella-specific antibodies in an urban African community setting.

METHOD

Paired serum and oral fluid samples were collected from 439 individuals aged 0-49 years in Addis Ababa, Ethiopia, as part of a larger seroepidemiological survey in 1994. Oral fluid was sampled using a simple sponge device that was well accepted by subjects of all ages; venous blood was collected by Vacutainer system. We measured rubella-specific antibodies in serum by the Radial Haemolysis (RH) test, supported by two confirmatory assays, and in oral fluid by IgG antibody-capture radioimmunoassay (GACRIA).

RESULTS

Sensitivity and specificity of oral fluid results compared to serum were 89% and 76%, respectively. Sensitivity declined from 96% in age group 0-19 years to 90% in age group 20-29 and 78% in age group 30-49. Specificity was 86% in 0-9 year olds contrasting with 61% in older groups (10-49 years). The positive predictive value of an oral fluid sample was high in all age groups (range 92-100%), while the negative predictive value declined from > or =80% in those aged <10 years to <10% in those aged > or =30 years. Serum confirmatory tests suggested a proportion of false serum RH negatives, increasing with age, indicating a need to standardize serum as well as oral fluid tests.

CONCLUSION

In the community setting of a developing country, oral fluid surveys could be useful to estimate age-prevalence of rubella immunity and identify rubella-susceptible children for follow-up. Further work is required to simplify assays and sample processing, improve assay sensitivity and estimate assay specificity more precisely, and compare and standardise collection methods suitable for surveillance of a variety of childhood viral infections.

Population biology, evolution, and immunology of vaccination and vaccination programs

The purpose of prophylactic vaccination is to reduce morbidity and mortality in a population. Many questions related to the design of vaccines and vaccination programs require a population standpoint for their sharp formulation and laboratory and field studies to understand their immunologic background. Practical suggestions of the workshop included increased studies of age-specific immunity, better immunoepidemiologic surveillance, better design of efficacy studies, and more systematic sampling of parasite strains to study the evolutionary pressure exerted by vaccines. Theoretical immunology has much to contribute. One of the realizations of the workshop was the value of a strong interdisciplinary approach in vaccine development, utilizing relevant contributions from immunology, population biology, mathematical modeling, epidemiology, molecular biology, and virology.

Polypropylene fibre web, a new matrix for sampling blood for immunodiagnosis of schistosomiasis

Blood sampling on filter paper is widely used for immunodiagnostic and epidemiological purposes. However, elution of conventional filter papers impregnated with sera containing Schistosoma mansoni circulating anodic antigen (CAA) recovered only a small fraction of the antigen, thereby reducing the sensitivity of the assay. Polypropylene-based non-woven fibre web is a new sampling material with a low density of fibres and with a small surface area of contact. When it was impregnated with serum containing CAA, approximately 90% of the antigen could be extracted. The yield of antibodies against S. mansoni from the new sampling material did not differ from that from conventional filter papers.

Anti-Toxoplasma gondii immunoglobulins A and G in human saliva and serum

Paired human saliva and serum samples from 60 individuals were tested for specific IgA and IgG antibodies to Toxoplasma gondii. The study in both fluids was carried out by indirect immunoenzymatic assay (ELISA). Saline antigenic extract of T. gondii was used to coat plastic surfaces upon which the samples were then incubated; monospecific conjugates of anti-IgA and anti-IgG-peroxidase were then incubated with the samples after a washing procedure to separate the unbound antibodies. The enzymatic activity was measured and the results expressed in terms of ELISA index. Toxoplasma-specific IgG antibodies were detected in 43 of the serum samples (71.7%) and in 12 of the saliva samples (20.0%) whereas Toxoplasma-specific IgA antibodies were detected in 18 of the serum samples (30.0%) and in 12 of the saliva samples (20.0%). No association was observed when the Toxoplasma-specific IgG reactive and non-reactive serum samples were compared with the reactive and non-reactive saliva samples for this class of immunoglobulin. On the other hand, a significant association was observed when the Toxoplasma-specific IgA reactive and non-reactive serum samples were compared with the reactive and non-reactive saliva for this type of antibody. In conclusion, our results show that the detection of salivary IgA reflects the serum level of this isotype but salivary IgG does not. Moreover, the isolated detection of salivary IgG may not contribute to epidemiological studies of chronic toxoplasmic infections.

Detection of IgG antibody to Epstein-Barr virus viral capsid antigen in saliva by antibody capture radioimmunoassay

A 'G' antibody capture radioimmunoassay (GACRIA) to detect IgG to Epstein-Barr virus (EBV) viral capsid antigen (VCA) in saliva is described. The monoclonal antibody to EBV VCA used in the GACRIA bound non-specifically when testing saliva samples having a total IgG content of less than 2.0 mg/l, so giving false positive results. This problem was overcome by including 0.5% EBV-negative human serum in the monoclonal antibody diluent. The performance of the assay was then evaluated by comparing the GACRIA test on serum and saliva samples to indirect immunofluorescence assay (IFA) results on sera using a panel of paired serum/saliva samples. Compared to the corresponding serum IFA the saliva GACRIA had a sensitivity and specificity of 93.5 and 100%, respectively. Although less sensitive than IFA on serum samples, the saliva GACRIA is sufficiently sensitive to be used for epidemiological screening and will enable testing for anti-EBV VCA to be carried out easily and on a wide scale.

Potential for diagnosis of intestinal nematode infections through antibody detection in saliva

The present study was the first to investigate the potential of saliva in community diagnosis of the major human intestinal nematode infections, Trichuris trichiura, Ascaris lumbricoides, and the hookworms. Immunoglobulin G (IgG) antibodies specific to parasite antigens were quantified in saliva samples of 187 individuals (all ages) from a St Lucian community, and 120 school-aged children from Tanga region, Tanzania, and relationships with current infection status (determined by numbers of parasite eggs in stool) were examined. For T. trichiura infection, the age relationships of parasite-specific salivary IgG antibodies mirrored those of infection intensity at the community level. Within both areas, children with current T. trichiura infection exhibited significantly higher anti-T. trichiura salivary IgG responses than uninfected children. Similar trends were apparent for A. lumbricoides and hookworm infections, though not to a level of statistical significance. Comparison of mean T. trichiura infection levels and antibody responses in age-matched children from St Lucia and Tanzania suggested that measurement of parasite-specific salivary IgG may have potential as a marker of transmission intensity at the community level.

Diagnosis of parvovirus B19 infection by detection of specific immunoglobulin M antibody in saliva

Serum and saliva samples were simultaneously collected from patients with B19 infection. Specimens were collected in a period of 1 to 18 days after the onset of symptoms. Saliva samples were collected with a commercial device, OraSure. The quality of these samples was evaluated by determining the concentration of total immunoglobulin G (IgG) by an enzyme immunoassay. The concentration of IgG in these samples ranged from 4.8 to > 250 mg/liter. B19 infection was confirmed for 20 patients by testing sera in a 1: 100 dilution by an IgM capture enzyme immunoassay (MACEIA) and an IgM capture hemadherence test (MACHAT). Saliva samples from these IgM-positive patients were tested neat by MACEIA and MACHAT. IgM could be detected in 11 of 20 (55%) samples by MACEIA and in 15 of 18 (83%) samples by MACHAT. Serum and saliva samples from a further 17 patients with rash were also tested. All of these specimens were unreactive by both assays. These results show that saliva may be a convenient alternative to serum for the diagnosis of recent B19 infection.