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We previously reported that infection of KB cells by echoviruses (EV) was inhibited by a KB-derived EV receptor murine monoclonal antibody (mAb 143). This antibody enabled the identification of a cellular receptor common to all echoviruses (with the exception of EV-22 and -23) and coxsackievirus (CV) A9, but different from the receptor of other picornaviruses. We now present results of cell protection assays conducted with human and simian cell lines different from the KB cell line used for production of mAb 143. When human embryonic lung fibroblasts were pretreated with 150 micrograms/ml of mAb 143, EV-11 and CV-A9 were completely inhibited (more than a 2-log difference compared to untreated cells). When the cell protection experiments were performed with Vero cells, the same results were observed with EV-33, but not with EV-22. The protection afforded human fibroblast cells by mAb 143 persisted for at least 5 days after 2-h exposure to 100 TCID50 of EV-11. These results suggest that EV receptors can be effectively blocked for prolonged periods in susceptible cells.

A panel of 68 serum specimens from 41 subjects exhibiting various immunological patterns to Mycoplasma pneumoniae as determined by detection of a 180 kDa protein in immunoblotting was used to compare five commercially available tests based on different methods: complement fixation test (CFT), microparticle agglutination (MAG), indirect immunofluorescence assay (IFA), enzyme-linked immunosorbent assay (Elisa), and latex agglutination (LA). The tests were performed according to the manufacturers' instructions. For the determination of immunity to M pneumoniae, the five tests were in good accordance with immunoblotting: sensitivity was 100% for all the five assays, specificity ranged from 95.6% (MAG) to 82.6% (Elisa) and overall agreement ranged from 98.2% (MAG) to 92.8% (Elisa). The comparisons of antibody rates obtained by the four quantitative tests (CFT, MAG, IFA, Elisa) showed correlation coefficients ranging from 0.87 (CFT-IFA) to 0.67 (CFT-Elisa). Six significant antibody rises demonstrated by immunoblotting patterns were detected by all the tests but Elisa in one case. As a whole, the commercial assays gave satisfactory results for routine determination of immune status to M pneumoniae: CFT was the cheapest test and MAG and LA were the easiest to perform.

Competition binding studies between viruses are usually performed with radiolabelled probes. In this report, a cytofluorimetric method using biotinylated echovirus (EV) 11 is described for the study of competition of enteroviruses for a common cell receptor site. An N-hydroxysuccinimide ester biotin spacer arm was used for biotinylation of CsSO4-purified EV 11. Biotinylation did not change the infectivity of the virus (attachment to and replication in susceptible cells). With the exception of EV 22 and EV 23, all the echovirus serotypes and also coxsackievirus A9 (CA 9) were able to inhibit the absorption of biotinylated EV 11 onto cells. The taxonomic implications of these findings are discussed.