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SUMMARYA four-component solid-phase capture enzyme immunoassay was set up to test for serum IgM antibody to respiratory syncytial (RS) virus and was compared with immunofluorescence assay (IFA).A total of 128 young children with acute respiratory infections were studied. Thirty-six were shown to be RS virus-positive by the detection of RS virus in nasopharyngeal secretions and 92 were RS virus-negative. A serum specimen was collected after admission to the hospital (days 0–4) and a further specimen was obtained during days 10–14. Out of 36 RS virus-positive patients, 28 (77·7%) were found to be positive for IgM by both capture-ELISA and IFA. Out of 92 RS virus-negative patients 5 (5·4%) were IgM-positive. Four false-positive results were obtained by IFA due to the presence of rheumatoid factor.The capture-ELISA was shown to be a reliable technique in detecting specific IgM antibody to RS virus.

Sera obtained from 34 men with Chlamydia trachomatis positive non-gonococcal urethritis, 34 men with C trachomatis negative non-gonococcal urethritis, 42 women with acute salpingitis, 38 healthy women, and 34 healthy men were studied for the presence of specific serum C trachomatis IgA and IgG antibodies. Serological results were correlated with C trachomatis isolation in cell culture. An enzyme linked immunosorbent assay (ELISA) for C trachomatis specific serum IgA was employed using highly purified elementary bodies of C trachomatis serotype L2 grown in LLC-MK2 cells. Results obtained for C trachomatis IgA antibody by the ELISA test were compared with results obtained for the same sera by a single antigen immunofluorescence technique. A good correlation (r = 0.91) was found between two methods. Serum IgG antibody was also determined in the same sera by the immunofluorescence technique. Patients with C trachomatis positive non-gonococcal urethritis had a significantly (p less than 0.0005) higher prevalence (94.1%) of serum IgA antibody by ELISA compared with patients with C trachomatis negative non-gonococcal urethritis (20.5%) or healthy men (5.9%). Similarly, women with acute salpingitis had a significantly (p less than 0.005) higher prevalence of serum IgA antibody (45.2%) compared with healthy controls (5.2%). Comparable results were obtained for C trachomatis serum IgA antibody using the immunofluorescence technique. The prevalence of C trachomatis IgG antibody was significantly higher in patients with C trachomatis positive non-gonococcal urethritis (97.0%) compared with those with C trachomatis negative non-gonococcal urethritis (33.3%) and healthy controls (23.5%). The importance of using specific C trachomatis serum IgA in the identification of chlamydial infection is discussed.

A technique using indirect immunoperoxidase antibody was developed for the detection of specific serum IgA antibody to Epstein-Barr virus capsid antigen and early antigen. The IgA technique was compared with an immunofluorescence antibody method. Epstein-Barr virus IgA antibody against viral capsid antigen was detected in all nine patients with Epstein-Barr virus associated undifferentiated nasopharyngeal carcinoma, in 13 (72.2%) of 18 patients with infectious mononucleosis, in 21 (28.3%) of 74 patients with acute lymphoblastic leukaemia, and in six (20%) of 30 patients who had recently had kidney transplants. Epstein-Barr virus IgA antibody against viral capsid antigen was also detected in four (10%) of 40 healthy subjects, but it was not found in any of 20 cord blood samples. Epstein-Barr virus IgA antibody to early antigen was detected in six (66.6%) patients with nasopharyngeal carcinoma and in two (2.7%) patients with acute lymphoblastic leukaemia. The immunoperoxidase assay for Epstein-Barr virus specific IgA was simple, reliable, and rapid and correlated well (r = 0.94) with the immunofluorescence antibody technique.

Antimicrobials are often used for prophylaxis and therapy of chlamydial infections. The large use of tetracycline has encouraged the selection of resistant organisms. The aim of this study was to evaluate the sensitivity to tetracycline of some Chlamydia suis strains isolated in Italy. The sensitivity of 14 C. suis isolates to doxycycline was tested and compared with the susceptibility to the same drug of the urethral Italian isolate GO86 of C. trachomatis serovar D, the reference strain 6BC of C. psittaci and three isolates of C. abortus, C. pecorum and C. felis, respectively. C. suis isolates were tested for the presence of the tet(C) resistance gene by a PCR assay amplifying a 525 base pair product of the tet(C) gene-coding region. As far as sensitivity to doxycycline is concerned, in comparison to the five strains of C. trachomatis, C. psittaci, C. abortus, C. pecorum and C. felis which were sensitive to doxycycline with MIC and MBC ranging from 0×03 to 0×125 µg/ml, respectively, the MIC and MBC values of doxycycline ranged from 4 to 8 µg/ml, respectively, in most swine isolates tested. All the C. suis isolates carried an identical nucleotide sequence that showed 100 per cent homology with those of the structural gene tet(C) described by Dugan and others (Gene Bank Accession AY428551). None of the other five chlamydial tetracycline sensitive strains carried the resistance gene tet(C).