Radioimmunoassay for the detection of virus-specific IgA antibodies in saliva

Saliva and viral infections

Over the last 10 years there have been only a handful of publications dealing with the oral virome, which is in contrast to the oral microbiome, an area that has seen considerable interest. Here, we survey viral infections in general and then focus on those viruses that are found in and/or are transmitted via the oral cavity; norovirus, rabies, human papillomavirus, Epstein‐Barr virus, herpes simplex viruses, hepatitis C virus, and HIV. Increasingly, viral infections have been diagnosed using an oral sample (e.g. saliva mucosal transudate or an oral swab) instead of blood or urine. The results of two studies using a rapid and semi‐quantitative lateral flow assay format demonstrating the correlation of HIV anti‐IgG/sIgA detection with saliva and serum samples are presented. When immediate detection of infection is important, point‐of‐care devices that obtain a non‐invasive sample from the oral cavity can be used to provide a first line diagnosis to assist in determining appropriate counselling and therapeutic path for an increasing number of diseases.

Application of salivary antibody immunoassays for the detection of incident infections with Norwalk virus in a group of volunteers

Norovirus infection is the most common cause of acute gastroenteritis in developed countries. Developing an assay based on a non-invasive biomarker for detecting incident norovirus infections could improve disease surveillance and epidemiological investigations. This project involved analysis of IgA and IgG norovirus-specific antibody responses in saliva samples from a Norwalk virus (Genogroup I, genotype 1 norovirus) challenge study involving infected and symptomatic, and non-infected asymptomatic individuals. Saliva was collected at the challenge, and two weeks and 40 days post-challenge. Samples were analyzed using the Luminex fluorometric and Meso Scale Discovery (MSD) electrochemiluminescence immunoassays. Recombinant P domains of Norwalk virus capsid protein, as well as similar recombinant proteins of two genogroup II noroviruses (VA387 and VA207) were used as antigens. Immunoconversions were defined as >4-fold increase in antibody responses to the norovirus antigens. Various sample pre-treatment options, buffers, saliva dilution ratios, and data adjustment approaches to control for sample-to-sample variability in saliva composition were compared using the Luminex assay. The results suggest that adjusting responses to the norovirus antigens for responses to the protein purification tag, glutathione-S-transferase (GST), significantly improved the odds of producing a correct immunoconversion test result. IgG-based tests were more accurate compared to IgA-based tests. At optimal conditions, both Luminex and MSD assays for Norwalk-specific IgG antibodies correctly identified all infected and non-infected individuals. There was no evidence of cross-reactivity of anti-Norwalk virus antibodies with genogroup II noroviruses. These results suggest that salivary antibody responses can be used for the detection of incident infections with Norwalk virus in prospective surveys.

Diagnosis of norwalk virus infection by indirect enzyme immunoassay detection of salivary antibodies to recombinant norwalk virus antigen

Simple diagnostic tests are needed for the detection of norovirus (NoV) outbreaks. Salivary antibody assays provide an attractive alternative to collecting and testing serum or stool samples. Antibodies to Norwalk virus (NV) in oral fluid samples were compared with NV antibodies in serum collected from 38 volunteers challenged with NV inoculum. Pre- and postchallenge (day 4, 8, 14, and 21) saliva and serum samples were examined by enzyme immunoassay (EIA) using recombinant NV antigen. Of 18 infected subjects (those who shed NV in stool or who demonstrated immunoglobulin G [IgG] seroconversion), 15 (83%) had > or =4-fold increases in NV-specific salivary IgA and 15 (83%) had > or =4-fold increases in NV-specific salivary IgG when prechallenge and postchallenge saliva samples were compared. When the results of the IgA and IgG assays were combined, all 18 infected subjects showed > or =4-fold increases in NV-specific salivary IgG or IgA postchallenge titers compared to their prechallenge titers. One of 19 uninfected subjects had a > or =4-fold increase in NV-specific salivary IgG. The sensitivity of the combined assay results was 100%, and the specificity was 95%. NV-specific salivary IgA titers peaked around 14 days postchallenge. NV-specific salivary IgG and serum IgG titers continued to rise through 21 days postchallenge. The application of this EIA to an elementary school outbreak indicated that 67% of the subjects with confirmed infections had >4-fold rises in anti-NoV IgA when an antigen in the same genetic cluster as the outbreak virus was used. This is the first documented mucosal antibody response to NoV in children. This EIA provides a useful approach for diagnosing NoV outbreaks.

The diagnostic applications of saliva--a review

This review examines the diagnostic application of saliva for systemic diseases. As a diagnostic fluid, saliva offers distinctive advantages over serum because it can be collected non-invasively by individuals with modest training. Furthermore, saliva may provide a cost-effective approach for the screening of large populations. Gland-specific saliva can be used for diagnosis of pathology specific to one of the major salivary glands. Whole saliva, however, is most frequently used for diagnosis of systemic diseases, since it is readily collected and contains serum constituents. These constituents are derived from the local vasculature of the salivary glands and also reach the oral cavity via the flow of gingival fluid. Analysis of saliva may be useful for the diagnosis of hereditary disorders, autoimmune diseases, malignant and infectious diseases, and endocrine disorders, as well as in the assessment of therapeutic levels of drugs and the monitoring of illicit drug use.

Human susceptibility and resistance to Norwalk virus infection

Infectious diseases have influenced population genetics and the evolution of the structure of the human genome in part by selecting for host susceptibility alleles that modify pathogenesis. Norovirus infection is associated with approximately 90% of epidemic non-bacterial acute gastroenteritis worldwide. Here, we show that resistance to Norwalk virus infection is multifactorial. Using a human challenge model, we showed that 29% of our study population was homozygous recessive for the alpha(1,2)fucosyltransferase gene (FUT2) in the ABH histo-blood group family and did not express the H type-1 oligosaccharide ligand required for Norwalk virus binding. The FUT2 susceptibility allele was fully penetrant against Norwalk virus infection as none of these individuals developed an infection after challenge, regardless of dose. Of the susceptible population that encoded a functional FUT2 gene, a portion was resistant to infection, suggesting that a memory immune response or some other unidentified factor also affords protection from Norwalk virus infection.

Neutralizing B cell response in measles

Co-evolving mechanisms of immune clearance and of immune suppression are among the hallmarks of measles. B cells are major targets cells of measles virus (MV) infection. Virus interactions with B cells result both in immune suppression and a vigorous antibody response. Although antibodies fully protect against (re)infection, their importance during the disease and in the presence of a potent cellular response is less well understood. Specific serum IgM appears with onset of rash and confirms clinical diagnosis. After isotype switching, IgG1 develops and confers life-long protection. The most abundant antibodies are specific for the nucleoprotein, but neutralizing and protective antibodies are solely directed against the two surface glycoproteins, the hemagglutinin and the fusion protein. Major neutralizing epitopes have been mapped mainly on the hemagglutinin protein with monoclonal antibodies, producing an increasingly comprehensive map of functional domains.

Detection of measles, mumps, and rubella antibodies in saliva using antibody capture radioimmunoassay

Antibody capture radioimmunoassays were developed for detecting virus specific IgM (MACRIA) and IgG (GACRIA) to measles, mumps, and rubella and used to investigate saliva as an alternative specimen to serum for diagnosis. Saliva was collected from 63 patients with measles, 19 with mumps, and 150 with rubella, which were all clinically diagnosed and serologically confirmed. Virus specific IgM was detected in 92% of measles, 75% of mumps, and 100% of rubella saliva samples collected during the first week of illness. Between 1 and 5 weeks after onset virus specific IgM was detected in 100% of saliva specimens. After the 5th week the proportion of reactive specimens declined. The specificity of the MACRIA tests was established by testing saliva samples collected from blood donors for measles (88), mumps (88), and rubella IgM (91). All of the saliva specimens tested for measles and rubella specific IgM were unreactive, 1/88 specimens tested for mumps specific IgM contained significant reactivity. Saliva specimens collected from acute cases of MMR were tested in all 3 MACRIAs. A small proportion of saliva samples contained detectable IgM of more than one virus infection. Rubella and measles specific IgG was detected in the saliva of all cases from the 4th or 5th day of illness, respectively. Detection of mumps specific IgG was less successful. We have demonstrated that virus specific IgM can be reliably detected in saliva samples collected from acute cases of measles, mumps, and rubella and identified 1-5 weeks after onset of illness as the optimum time for collection of samples.

Serum and salivary responses to oral tetravalent reassortant rotavirus vaccine in newborns

Serum and salivary responses of 95 infants to either a standard (4 x 10(4) plaque-forming units (PFU), 47 neonates) or a high dose (4 x 10(5) PFU, 48 neonates) of tetravalent reassortant rhesus rotavirus vaccine (administered at 2 days and at 6 weeks of age) were evaluated in a double-blind clinical trial. Serum and salivary IgA antibodies to the rotavirus group A common antigen were determined by ELISA and radioimmunoassay (RIA). Serum neutralizing antibodies to rhesus rotavirus were determined by fluorescent focus reduction assay. No significant differences in responses to the high versus standard dose were noted in serum or saliva. Response was influenced by cord blood antibodies. All infants who were cord blood-negative for rhesus rotavirus neutralizing antibodies (nine who received the standard dose and 20 who received the higher dose) had serum responses, compared with 42-70% of those who were cord blood-positive. The serum response rate recorded for babies with cord blood neutralizing titres > 1000 was 44%. Infants being bottle fed had a higher serum response rate than did babies being breast fed exclusively. If serum and salivary responses were combined, the response rate reached 80% for bottle fed infants. Thus, determination of serum responses alone underestimates vaccine 'take' in infants, and more so in highly endemic areas than in areas subject only to sporadic outbreaks. However, determination of salivary responses in newborn breastfed infants may be inaccurate, due to possible persistence of antibodies derived from colostrum or breast milk.

Antibodies in human tears during and after infection

The tear content of antibodies specific for various infectious agents has recently begun to be investigated. Important parameters of tear analysis with respect to antibody content are the method of tear collection and the laboratory techniques used to detect specific antibodies in the lacrimal fluid. Normal tears contain antibodies directed against both bacteria and viruses, and the antibody response in lacrimal fluid during immunization of animals and humans has been studied to some extent. This response has also been analyzed in humans during and after natural infection with certain viral and bacterial pathogens. It has become clear that local antibody synthesis takes place in the lacrimal gland, but at least some of these antibodies appear in tears because of lymphocyte sensitization in the common mucosal immune system. A certain degree of transudation of serum antibodies to tears is also often encountered, especially in severely inflamed eyes. Much of the data currently available needs to be confirmed, and more extensive studies need to be carried out for many pathogens. Potential benefits of such studies include development of new diagnostic techniques as well as a better understanding of when and how antibodies confer protection or may be potentially damaging.

Infection with the bacterium Streptococcus mutans and salivary IgA antibodies in mothers and their children

Salivary IgA-antibody titres against different streptococcal antigens were measured in 64 mothers and their first-born children. Their presence and the level of Streptococcus mutans had been monitored for several years. The children had carried this bacterium for various lengths of time and now had varying numbers of salivary Strep. mutans. The subjects had participated in a longitudinal study completed one and a half years before, concerning prevention of early colonization of the child's mouth by Strep. mutans through measures undertaken by the mother. Whole-saliva samples were collected from all subjects and analysed by ELISA techniques for total IgA, and for IgA antibodies to whole cells of Strep. mutans serotype c and d, whole cells of Strep. sanguis, purified polysaccharide and protein antigens of Strep. mutans serotype c and d; a pool of Escherichia coli antigens was used as a control. No significant differences were found in the level of any of the specific IgA antibodies in children with different levels of indigenous Strep. mutans. A tendency to higher IgA antibody activity was found in children who had levels of Strep. mutans first detectable after three years of age and who had carried the bacterium for six months or less. The IgA antibody activity to Strep. mutans specific serotype c antigen and to whole cells of Strep. mutans serotype c (JC 2) was significantly higher in children with no caries experience when compared to children with more than two df-surfaces. This study offers no clear evidence for a protective role of salivary IgA antibodies against Strep. mutans colonization.

The relationship between IgA antibodies to Streptococcus mutans antigens in human saliva and breast milk and the numbers of indigenous oral Streptococcus mutans

The influence of indigenous Streptococcus mutans on naturally-occurring levels of IgA antibodies was studied in 42 lactating females. Breast milk, parotid and whole-saliva samples were collected and analysed by the ELISA method for IgA antibodies, reacting with antigens from Strep. mutans. All salivas and breast milk showed IgA antibody activity to five antigenic preparations from Strep. mutans and to a pool of Escherichia coli antigens. No correlation was observed between the IgA antibody level in breast milk and that in saliva. The total IgA in breast milk was, however, considerably higher than in the salivas. In subjects with active caries and subjects with high DMFS scores, there was a tendency toward lower levels of IgA antibodies in whole saliva than in subjects with low caries experience. The levels of specific IgA antibodies in saliva did not reflect the amount of indigenous Strep. mutans present in the mouth at the time of sampling.

Studies on HSV specific IgA antibodies in lacrimal fluid from patients with herpes keratitis by solid phase radioimmunoassay

A highly sensitive solid phase radioimmunoassay (RIA) was adapted for determination of herpes simplex virus (HSV) specific IgA antibodies in lacrimal fluids. The RIA procedure was applied to examine HSV IgA antibodies in serial samples of lacrimal fluid and in sera from 14 patients with herpes keratitis. HSV-specific IgA antibodies were detected in the lacrimal fluid of the affected eye in 12 of the 14 patients. HSV IgA antibodies were also detected in the lacrimal fluid of the unaffected eye of 7 of these patients in titers lower than those found in the corresponding affected eye. Evidence for local HSV antibody production in lacrimal fluid in herpes keratitis was supported by examination for antibodies to the unrelated measles antigen. Detection of lacrimal fluid HSV IgA antibodies might be a useful adjunct in rapid diagnosis of herpes keratitis. The advantage of characterizing the local immune response as well as viral expression in the affected vs. the unaffected eye in the same individual as a model for understanding the factors leading to subclinical vs. clinical manifestations of recurrent ocular herpes virus infections will be discussed.