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

Use of oral fluid samples for the investigation of outbreaks of human parvovirus B19 infection

The use of oral fluid (OF) samples for serological diagnosis of parvovirus B19 infection during outbreaks of erythema infectiosum had already been demonstrated, but the feasibility of using OF for the characterization of B19 genotypes circulating during outbreaks has not been described. The aim of this study was to assess the use of "in-house" PCR-based assays as a powerful tool for a rapid diagnosis and molecular characterization of B19 strains in OF samples during outbreaks. Paired serum and OF samples collected from anti-B19 IgM-positive patients, during two outbreaks of ertythema infectiosum (1999-2000 and 2004-2005), were tested by conventional (cPCR) and quantitative PCR (qPCR). qPCR was more sensitive than cPCR for detecting B19-DNA in both OF and serum. Overall, OF presented lower viral load (9.97 × 106 UI/mL) than serum (2.42 × 1010 UI/mL) and this difference was statistically significant. All OF samples obtained from patients in the age group < 14 years presented low viral load (< 104 IU/mL). No correlation was found between viral load and the number of days of onset of rash. Sequence analysis from PCR positive OF samples confirmed the circulation of subgenotype 1a (G1a) during these outbreaks. Our findings indicate that PCR-based assays may fail to detect B19-DNA in approximately 50% of OF compared to serum samples. Nevertheless, our study has shown for the first time that the genome sequence of the amplicon from non-invasive clinical sample is useful for molecular genotyping and may be a tool to clarify the genetic diversity of B19 strains circulating in distinct outbreaks.

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.

Comparison of available methods to elute serum from dried blood spot samples for measles serology

Six existing protocols for the extraction of serum from blood spots dried onto filter paper were compared. Assessment criteria included: detection of measles IgM and IgG by the Dade Behring Enzygnost immunoassays, volumes of recovered eluates, reproducibility, processing time and throughput, difficulty of protocol, equipment required, safety and estimated costs. Detection of measles IgM in eluates obtained by four of these protocols was as in serum, and significant differences were only observed in eluates from the two remaining protocols (p < 0.05). Significant differences were found between extraction protocols regarding measles-specific IgG detection when an IgG indeterminate DBS was analyzed (p < 0.05), but not when an IgG positive and negative DBS were studied. Sufficient eluate volumes were recovered for testing in the IgM Behring assay following all protocols but two. Sufficient eluate was recovered for testing in the IgG Behring assay following all six protocols. While all protocols were relatively easy to perform, only two protocols required less than 2h for completion. In general, compared protocols performed well on the extraction of antibodies from DBS for serology with differences being observed with eluate volume recovery, turn around time, required equipment and cost. An easy-to-implement protocol is proposed for the rapid extraction of serum for measles/rubella serology in outbreak situations for use in the World Health Organization Global Measles and Rubella Laboratory Network.