Inhalation anthrax is a rare but acute infectious disease following adsorption of Bacillus anthracis spores through the lungs. The disease has a high fatality rate if untreated, but early and correct diagnosis has a significant impact on case patient recovery. The early symptoms of inhalation anthrax are, however, non-specific and current anthrax diagnostics are primarily dependent upon culture and confirmatory real-time PCR. Consequently, there may be a significant delay in diagnosis and targeted treatment. Rapid, culture-independent diagnostic tests are therefore needed, particularly in the context of a large scale emergency response. The aim of this study was to evaluate the ability of monoclonal antibodies to detect anthrax toxin proteins that are secreted early in the course of B. anthracis infection using a time-resolved fluorescence (TRF) immunoassay. We selected monoclonal antibodies that could detect protective antigen (PA), as PA83 and also PA63 and LF in the lethal toxin complex. The assay reliable detection limit (RDL) was 6.63 x 10-6muM (0.551ng/ml) for PA83 and 2.51 x 10-5muM (1.58ng/ml) for PA63. Despite variable precision and accuracy of the assay, PA was detected in 9 out of 10 sera samples from anthrax confirmed case patients with cutaneous (n=7), inhalation (n=2), and gastrointestinal (n=1) disease. Anthrax Immune Globulin (AIG), which has been used in treatment of clinical anthrax, interfered with detection of PA. This study demonstrates a culture-independent method of diagnosing anthrax through use of monoclonal antibodies to detect PA and LF in the lethal toxin complex.

Swine origin 2009 H1N1 influenza virus has spread globally to cause the first influenza pandemic of the 21(st) century. Serological studies can improve our understanding of the extent of human infection and risk factors associated with transmission of this pandemic virus. The "gold standard" for serodiagnosis of human influenza infection is the detection of seroconversion between acute and convalescent stage samples. However, timing of seroepidemiologic investigations often precludes collection of truly acute phase sera, requiring development of serologic criteria for evaluating convalescent phase sera that optimize detection of true positives and true negatives. To guide seroepidemiologic investigations into the spread of the novel 2009 pandemic H1N1 virus, we characterized serum antibody responses to 2009 H1N1 virus in 87 individuals with confirmed viral infection and 227 non-exposed U.S. individuals using microneutralization (MN) and hemagglutination-inhibition (HI) assays. Sensitivity and specificity were determined for each assay alone, and in combination, for detection of 2009 H1N1-specific antibodies in convalescent sera. Although the HI assay was more specific for detecting antibody to 2009 H1N1, the MN was more sensitive, particularly for detecting low titer seroconversions. A combination of titers (MN ≥40 and HI ≥20) provided highest sensitivity (90%) and specificity (96%) for individuals aged < 60 years and 92% specificity for adults aged ≥60 years for detection of serologically confirmed 2009 H1N1 infections in U.S. populations during the first pandemic waves. These studies provide an approach to optimize timely serologic investigations for future pandemics or outbreaks of novel influenza viruses among humans.

A two-stage, multilevel assay quality control (QC) system was designed and implemented for two high stringency QC anthrax serological assays; a quantitative anti-PA IgG enzyme-linked immunosorbent assay (ELISA) and an anthrax lethal toxin neutralization activity (TNA) assay. The QC system and the assays were applied for the congressionally mandated Centers for Disease Control and Prevention (CDC) Phase 4 human clinical trial of anthrax vaccine adsorbed (AVA, BioThrax). A total of 57,284 human serum samples were evaluated by anti-PA enzyme-linked immunosorbent assay (ELISA) and 11,685 samples by anthrax lethal toxin neutralization activity (TNA) assay. The QC system demonstrated overall sample acceptance rates of 86% for ELISA and 90% for the TNA assays respectively. Monitoring of multiple assay and test sample variables showed no significant long term trends or degradation in any of the critical assay reagents or reportable values for both assays. Assay quality control data establish the functionality of the quality control system and demonstrates the reliability of the serological data generated using these assays.