Monoclonal and monospecific antibodies were used to characterize a major Mycoplasma pulmonis surface antigen complex, V-1. Heterogeneity of V-1 was detected among strains and a high frequency of variation was detected within subclones of single strains. Analysis of 18 different strains showed that no two displayed identical electrophoretic immunoblot patterns for V-1. Analysis of 50 filter clones from an individual strain (not previously filter cloned) revealed at least 10 different V-1 patterns. The two most frequently occurring patterns were expressed by 36% and 24%, respectively, of the total population. Serial subcloning (four separate series) of several of these original clones showed that the average rate of V-1 variation was 2 x 10-3 per cell per generation. Immunoblots with different anti-V-1 monoclonal antibodies demonstrated that there were both structurally and antigenically different forms of this antigen. Also, two-dimensional polyacrylamide gel analyses showed that different forms of V-1 could vary in charge. This potential for variability in a major surface antigen of mycoplasmas could have important implications as to how the organism interacts with its host.

Mycoplasma pneumoniae is an important etiologic agent of primary atypical pneumonia in children and adults. The diagnosis of M. pneumoniae infection is commonly confirmed through serologic testing. In this study, we used paired sera from 51 patients (all with confirmed M. pneumoniae infection and positive complement fixation [CF] titers) to compare the results of eight enzyme immunoassays (EIAs) available commercially in the United States. We compared two single-use EIAs and six plate-type EIAs. Results from acute-phase sera ranged from only 7 (14%) positive by ImmunoWELL (GenBio) immunoglobulin M (IgM) EIA to 23 (45%) positive by Zeus IgG EIA. When both the acute-phase and convalescent-phase serum samples were examined, positive results ranged from 20 (39%) by the ImmunoWELL (GenBio) IgM assay to 45 (88%) positive by the Remel IgG-IgM EIA. In this study, the single-use EIAs by Remel and Meridian were more reliable than were the plate-type EIAs. Among the plate-type EIAs, the Zeus and DiaSorin assays (which detect antibodies to protein antigens) were more sensitive than the ImmunoWELL assay (which detects antibodies to glycolipid antigens). In general, IgG EIAs on convalescent-phase sera were more concordant with one another than were IgM EIAs with one another. Scatter plot analysis of convalescent-phase sera showed that, as the CF titer dropped, the IgM assays identified fewer positive convalescent-phase sera. In contrast, the IgG assays provided fairly consistent positive results for convalescent-phase sera with CF titers of 64 and above. Results of individual tests and overall limitations of serodiagnostics for M. pneumoniae infections are discussed.Mycoplasma pneumoniae is an important etiologic agent of tracheobronchitis and primary atypical pneumonia in children and adults. It is responsible for 20% or more of communityacquired pneumonias overall (8) and can also be a significant cause of severe pneumonia requiring hospitalization in the elderly (12). Because they lack a cell wall, mycoplasmas do not respond to penicillins and other beta-lactams commonly used for the treatment of bacterial pneumonia. Laboratory diagnosis of M. pneumoniae infection is usually established through serological or molecular testing because the organism grows slowly and is difficult to isolate from clinical specimens (10,11,17). A reliable and sensitive serologic test for use in the early stages of M. pneumoniae infection is needed to confirm the clinical diagnosis and to ensure that the appropriate antibiotic therapy is used (5, 7).The detection of specific immunoglobulin M (IgM) antibody, which appears 7 to 10 days after infection and approximately 2 weeks before IgG antibody, has been shown previously to indicate a recent or current infection with M. pneumoniae (13,14). However, specific IgM in adults does not always indicate an acute infection because it can persist for up to a year after infection with M. pneumoniae (2, 4). In addition, an IgM response may be either minimal or undetectable when adults are reinfected (9, 15)...

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