Removal of nonspecific hemagglutination inhibitors, immunoglobulin G, and immunoglobulin A with streptococcal cells and its application to the rubella hemagglutination inhibition test

An Immunological System for the Detection of Pepper mild mottle virus in Soil from Green Pepper Fields

A reliable method, based on the double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), was developed for the extraction of viruses from soil and optimized for the detection of Pepper mild mottle virus (PMMoV) in soil taken from green pepper (Capsicum annuum) fields. When added to phosphate buffer, Tween 20 increases extraction efficiency and skim milk increases the specificity for PMMoV. Samples positive by DAS-ELISA were verified by inhibition testing using specific anti-PMMoV antibody, immuno-electron microscopy, reverse transcription-polymerase chain reaction, and inoculation tests on assay plants. Our system for detecting PMMoV in soil was successfully tested on samples from 22 infected and uninfected fields in Japan. When used before seedlings are planted, this method allows for the prediction of possible damage to cultivated plants by soil-borne PMMoV.

IgM neutralizing antibody responses to human herpesvirus-6 in patients with exanthem subitum or organ transplantation

The assay for detecting IgM neutralizing (NT) antibody activity to human herpesvirus-6 (HHV-6) was developed by using pretreatment of blood sample with staphylococcal protein A. The activity was mostly present in IgM fractions of serum but not in IgA fractions separated by ultracentrifugation. The assay was used for seroepidemiological studies for HHV-6 infection. In primary HHV-6 infection, IgM NT antibodies appeared 5 to 7 days after onset of exanthem subitum, reached maximum titers at 2 to 3 weeks, and tended to decline to undetectable levels after 2 months. In contrast, reactivation of HHV-6 observed in organ transplants showed somewhat greater degree of IgM NT antibody responses that persisted for 2 to 3 months and became undetectable 5 to 6 months after transplantation. The level and persistence of NT antibody titers measured by the conventional method was generally greater than those of the IgM titers. The prevalence of the IgM NT antibodies was examined in healthy individuals. The antibody was first detected at 4 to 7 months of age (5%), reached maximum level at 8 to 11 months (40%), and was detectable by 4 to 6 years (17%). A few (4 to 5%) of adolescents and adults were positive for the antibody.

Detection by polymerase chain reaction amplification of human herpesvirus 6 DNA in peripheral blood of patients with exanthem subitum

The polymerase chain reaction was used to detect human herpesvirus 6 (HHV-6) DNA in peripheral blood mononuclear cells from patients with exanthem subitum. Amplified products were detected by agarose gel electrophoresis and dot blot hybridization with a cloned DNA probe. No cross-hybridization with DNAs of five other human herpesviruses was observed in this system, and all HHV-6 strains gave positive reactions when the primer pairs were used. Immunoglobulin M antibody appeared about 5 days after the onset of disease, reaching a maximum after about 2 to 3 weeks and then decreasing to less than 1:10 1 month after the onset of disease in almost all patients. Mononuclear cells from seven patients with exanthem subitum all gave positive reactions in this system, and viral DNA was found in samples even during the convalescent phase of the disease. We conclude that this test, using polymerase chain reaction amplification, which takes only 1 to 2 days, is useful for the diagnosis of HHV-6 infection.