Development and evaluation of a rapid immunochromatographic test for mumps-specific IgM in oral fluid specimens and use as a matrix for preserving viral nucleic acid for RT-PCR

Rapid immunochromatographic test for detection of anti-factor XIII A subunit antibodies can diagnose 90 % of cases with autoimmune haemorrhaphilia XIII/13

Autoimmune haemorrhaphilia XIII/13 (AH13) is an acquired lifethreatening bleeding disorder due to anti-factor XIII (FXIII) autoantibodies (auto-Abs). AH13 patients may die of haemorrhage without correct diagnosis and proper treatment because of lack of awareness and the absence of rapid easy-to-use tests specific for this disease. Currently, the definitive diagnosis is established by cumbersome and time-consuming laboratory tests such as dot-blot assays and enzymelinked immunosorbent assays (ELISA), and therefore these tests are generally not carried out. To save AH13 patients’ lives, there is an urgent necessity for developing a rapid test for FXIII auto-Abs. We first generated and characterised mouse monoclonal antibodies (mAb) against human FXIII A subunit (FXIII-A), and then developed a rapid immunochromatographic test (ICT) for detection of anti-FXIII-A auto- Abs using one mAb with a dissociation constant of 9.3 × 10-11 M. The auto-Ab-FXIII-A complex was captured by the mAb on a nitrocellulose membrane and visualised by Au-conjugated anti-human IgG Ab. Mixing with healthy control plasma improved the detection of auto-Abs in patients having extremely low levels of FXIII-A. The specificity and sensitivity of the ICT were 87% and 94%, respectively. We also detected auto-Abs against activated FXIII (FXIIIa) in three patients by pre-converting FXIII to FXIIIa by thrombin treatment. ICT values were significantly inversely correlated with FXIII activity levels, indicating an association between the quantity of anti-FXIII autoantibodies and AH13. This reliable rapid ICT assay can be applied to a point-of-care test to detect anti-FXIII-A auto-Abs, and will contribute to early diagnosis and treatment of AH13.

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 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.

Investigation of a measles outbreak in Zimbabwe, 2010: potential of a point of care test to replace laboratory confirmation of suspected cases

Blood and oral fluid (OF) samples were collected from 103 suspected measles cases between February and November 2010 during a nationwide measles outbreak in Zimbabwe. Siemens measles IgM enzyme immunoassay (EIA) on serum, Microimmune measles IgM capture EIA on OF, real-time haemagglutinin (H) gene PCR and nested nucleocapsid (N) gene PCR on OF were performed, confirming 75 measles cases. These samples were then used to evaluate a newly developed point of care test (POCT) for measles and determine its potential for identifying measles cases in outbreaks. After performing POCTs on OF samples, nucleic acid was extracted from the used test strips and the measles H and N genes amplified by RT-PCR. The sensitivity, specificity, positive and negative predictive values of the POCT for IgM in OF was 75·0% [95% confidence interval (CI) 63·4-84·5], 96·2% (95% CI 80·4-99·9), 98·2% (95% CI 90·3-100) and 58·1% (95% CI 42·1-73·0), respectively. The N gene sequences showed high level of agreement between original OF and corresponding POCT strips. Measles genotype B3 was identified in all cases. We conclude that the measles POCT has the potential to be used, at the point of contact, in outbreak situations and provide molecular characterization of the virus at a later date.

Measles

Measles is a highly contagious disease caused by measles virus and is one of the most devastating infectious diseases of man--measles was responsible for millions of deaths annually worldwide before the introduction of the measles vaccines. Remarkable progress in reducing the number of people dying from measles has been made through measles vaccination, with an estimated 164,000 deaths attributed to measles in 2008. This achievement attests to the enormous importance of measles vaccination to public health. However, this progress is threatened by failure to maintain high levels of measles vaccine coverage. Recent measles outbreaks in sub-Saharan Africa, Europe, and the USA show the ease with which measles virus can re-enter communities if high levels of population immunity are not sustained. The major challenges for continued measles control and eventual eradication will be logistical, financial, and the garnering of sufficient political will. These challenges need to be met to ensure that future generations of children do not die of measles.

A point-of-care test for measles diagnosis: detection of measles-specific IgM antibodies and viral nucleic acid

OBJECTIVE

To evaluate the performance of a newly developed point-of-care test (POCT) for the detection of measles-specific IgM antibodies in serum and oral fluid specimens and to assess if measles virus nucleic acid could be recovered from used POCT strips.

METHODS

The POCT was used to test 170 serum specimens collected through measles surveillance or vaccination programmes in Ethiopia, Malaysia and the Russian Federation: 69 were positive for measles immunoglobulin M (IgM) antibodies, 74 were positive for rubella IgM antibodies and 7 were positive for both. Also tested were 282 oral fluid specimens from the measles, mumps and rubella (MMR) surveillance programme of the United Kingdom of Great Britain and Northern Ireland. The Microimmune measles IgM capture enzyme immunoassay was the gold standard for comparison. A panel of 24 oral fluids was used to investigate if measles virus haemagglutinin (H) and nucleocapsid (N) genes could be amplified by polymerase chain reaction directly from used POCT strips.

FINDINGS

With serum POCT showed a sensitivity and specificity of 90.8% (69/76) and 93.6% (88/94), respectively; with oral fluids, sensitivity and specificity were 90.0% (63/70) and 96.2% (200/208), respectively. Both H and N genes were reliably detected in POCT strips and the N genes could be sequenced for genotyping. Measles virus genes could be recovered from POCT strips after storage for 5 weeks at 20-25 °C.

CONCLUSION

The POCT has the sensitivity and specificity required of a field-based test for measles diagnosis. However, its role in global measles control programmes requires further evaluation.

Saliva as a diagnostic fluid

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