Performance of 14 rubella IgG immunoassays on samples with low positive or negative haemagglutination inhibition results.

BACKGROUND: Rubella IgG testing is routinely done in prenatal care and seroepidemiological studies. Recently concern was raised that seropositivity rates were decreasing questioning vaccination policies. Manufacturers of rubella IgG assays and authors of seroepidemiological studies use different cut-offs for the definition of seropositivity. As rubella virus circulation is reduced since many years, seronegativity rates might be overestimated using an inappropriate cut-off. OBJECTIVES: Using different cut-off definitions we compared fourteen current rubella IgG immunoassays for sensitivity and qualitative result concordance in samples with low positive or negative haemagglutination inhibition (HI) titre. STUDY DESIGN: 150 clinical samples from patients and health care workers were included in the study. All samples were measured in 14 different rubella IgG immunoassays. Seropositivity was defined using recombinant rubella IgG immunoblot as reference standard. RESULTS: The concordance of qualitative results using the manufacturers cut-off definitions was 56.4% if grey-zone results were analysed separately and 69.8% if grey-zone results were defined as positive. Using universal cut-offs of 10 IU/ml or 15 IU/ml the concordance was 70% and 61.4% respectively. Using the different cut-off definitions up to 71 out of the 124 immunoblot-positive samples tested negative in the immunoassays. The mean coefficient of variation (CV) of quantitative results in positive samples was 51% (range 19-113%). CONCLUSIONS: Determination of rubella immunity by measurement of rubella-IgG in a population with high vaccination coverage with current assays leads to a high number of false negative results. The value of routine rubella antibody testing in countries with high vaccination coverage should be discussed.

Detection of respiratory viruses using a multiplex real-time PCR assay in Germany, 2009/10.

The aim of this study was to determine the prevalence of respiratory viruses and to prospectively evaluate the performance of the fast-track diagnostics (FTD) respiratory pathogens multiplex PCR assay shortly after the 2009/10 influenza pandemic. Highly sensitive monoplex real-time PCR assays served as references. Discrepant results were further analyzed by the xTAG RVP Fast assay. A total of 369 respiratory samples from children and adults were collected prospectively in Germany from December 2009 until June 2010. The sensitivity and specificity of the FTD assay after resolution of discrepant results was 92.2 % and 99.5 %, respectively. Lowest specificity of the FTD assay was observed for human bocavirus. Multiple detections were recorded in 33/369 (8.9 %) of the samples by monoplex PCR and in 43/369 (11.7 %) using the FTD assay. The most prevalent viruses were respiratory syncytial virus and human metapneumovirus. Only pandemic influenza virus A/H1N1 (2009), and not seasonal influenza virus, was detected. Viruses other than influenza virus accounted for the majority of acute respiratory infections. The FTD assay can be easily implemented in general diagnostic laboratories and facilitate the optimization of patient-management schemes.

Persistence of human bocavirus DNA in immunocompromised children.

Human bocavirus is frequently detected in immunocompetent as well as in immunocompromised children. However, the course of infection in immunocompromised children is still poorly investigated. In the present study, we describe 4 cases of repeat human bocavirus detection in the presence of severe immunodeficiency. In the view of homologous viral sequences identified in serial samples, possible persistence and reactivation in these patients are discussed.

Human metapneumovirus induces more severe disease and stronger innate immune response in BALB/c mice as compared with respiratory syncytial virus.

BACKGROUND: Human metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are members of the Pneumovirinae subfamily of Paramyxoviridae and can cause severe respiratory disease, especially in infants and young children. Some differences in the clinical course of these infections have been described, but there are few comparative data on pathogenesis in humans and animal models. In this study, HMPV and RSV were compared for replication, pathogenesis and immune induction in BALB/c mice infected with equivalent inocula of either virus. METHODS: Viral titers in the lungs and in the nasal turbinates of mice were determined by plaque assay. Histopathological changes in the lungs as well as weight loss and levels of airway obstruction were monitored in the infected mice to record the severity of illness. Inflammatory cells recruited to the lungs were characterized by flow cytometry and by differential staining. In the case of natural killer cells, cytotoxic activity was also measured. Cytokine levels in the BAL were determined by cytometric bead array. RESULTS: RSV replicated to higher titers than HMPV in the lung and in the upper respiratory tract (URT), and virus elimination from the lungs was more rapid in HMPV-infected mice. Clinical illness as determined by airway obstruction, weight loss, and histopathology was significantly more severe after HMPV infection. A comparison of the cellular immune response revealed similar recruitment of T lymphocytes with a predominance of IFN-gamma-producing CD8+ T cells. By contrast, there were obvious differences in the innate immune response. After HMPV infection, more neutrophils could be detected in the airways and there were more activated NK cells than in RSV-infected mice. This correlated with higher levels of IL-6, TNF-alpha and MCP-1. CONCLUSION: This study shows important differences in HMPV and RSV pathogenesis and suggests that the pronounced innate immune response observed after HMPV infection might be instrumental in the severe pathology.

Systemic and mucosal immunity to respiratory syncytial virus induced by recombinant Streptococcus gordonii surface-displaying a domain of viral glycoprotein G.

A conserved fragment comprising amino acid residues 130-230 of the G glycoprotein of human respiratory syncytial virus subtype A was expressed in the commensal bacterium Streptococcus gordonii. Recombinant streptococci displaying the G domain at the cell surface were used to immunize mice via both parenteral and mucosal routes. Subcutaneous immunization induced respiratory syncytial virus-specific serum immunoglobin G (IgG) capable of partially controlling virus replication in the lungs. Intranasal immunization with live bacteria stimulated the production of IgA against both the whole virus and the G domain in serum and bronchoalveolar fluid. Upon challenge, immunized animals had significantly lower virus titres in the lungs than the controls. Our results show for the first time that the G domain-expressing S. gordonii strain elicits both systemic and mucosal immunity that reduced respiratory syncytial virus replication in the lungs of mice.

Novel human metapneumovirus sublineage.

In a pediatric surveillance network, 287 (5.1%) of 5,580 specimens from patients with acute respiratory infections tested positive for human metapneumovirus (HMPV). Phylogenetic analysis of N- and F-gene sequences of identified HMPV showed that 30% belonged to a novel phylogenetic cluster.

Generalized herpes simplex virus infection in an immunocompromised patient--report of a case and review of the literature.

Patients with immunodeficiency or treatment-related immunosuppression are at an increased risk of developing severe herpes simplex virus (HSV) infection. We present a fatal case of a generalized HSV-1 infection in a 22-year-old female afflicted by acute lymphoblastic leukemia who was treated with polychemotherapy. The terminal clinical course was characterized by abdominal pain, progressive hepatic failure, and disseminated intravascular coagulation. Autopsy revealed non-perioral herpetic skin lesions and mucosal ulceration of the esophagus and colon. Punctuated areas of yellow-tan necrosis with hyperemic rims were detected in the liver, spleen, and lung. Numerous petechiae were observed on the mucosal surface of the esophagus, jejunum, ileum, and colon. Microscopically, lesions demonstrated the cellular changes characteristic of herpetic infection. Immunohistochemistry for identification of the virus using monoclonal antibodies against HSV-1 and HSV-2 showed positive staining for HSV-1. Polymerase chain reaction and sequencing confirmed HSV-1 positivity. Emphasis must be placed on clinical awareness of a generalized HSV infection in immunocompromised patients. Absence of orofacial or genital lesions does not rule out the possibility of active HSV infection.