Mycoplasma pneumoniae is a significant human respiratory pathogen that causes high morbidity worldwide. No vaccine to prevent M. pneumoniae infection currently exists, since the mechanisms of pathogenesis are poorly understood. To this end, we constructed a P30 cytadhesin mutant (P-130) with a drastically reduced capacity for binding to erythrocytes and an inability to glide on glass substrates. This mutant was determined to be avirulent and cannot survive in the lungs of BALB/c mice. We also ascertained that the previously identified P30 gliding motility mutant II-3R is avirulent and also cannot be recovered from the lungs of mice after infection. Mutant P130 was then assessed for its efficacy as a live attenuated vaccine candidate in mice after challenge with wild-type M. pneumoniae. After vaccination with the P-130 P30 mutant, mice showed evidence of exacerbated disease upon subsequent challenge with the wild-type strain PI1428, which appears to be driven by a Th17 response and corresponding eosinophilia. Our results are in accordance with other reports of vaccine-induced disease exacerbation in rodents and emphasize the need to better understand the basic mechanisms of M. pneumoniae pathogenesis.
Mycoplasma pneumoniae is a chronic human pathogen and the etiological agent of many cases of bronchitis and community-acquired pneumonia. Infection with this bacterium can also cause and/or exacerbate other diseases including asthma, myocarditis, sickle cell disease, and encephalitis. Outbreaks are common at such institutions as military bases, schools, and hospitals, where individuals are in close contact for long periods of time, reflecting the community-acquired nature of infections. Diagnosis is difficult as most medical laboratories do not screen for this pathogen, since quick and inexpensive tests are not readily available. Common first-line -lactam antibiotics are ineffective treatments since mycoplasmas lack a cell wall; consequently, this pathogen is often overlooked during diagnosis of affected individuals, and common treatments do not target the source of the disease. This results in considerable economic and societal hardships due to lost and ineffective work/school time, making this pathogen a burden to public health (1, 42).Several virulence determinants of M. pneumoniae have been previously identified and characterized. This bacterium is thought primarily to exploit an extracellular niche and requires a complex tip structure to attach to its host's mucosal epithelium. The tip structure is also involved in gliding motility and cell division. Densely clustered on the surface of the tip structure are the major cytadhesins P1 and P30 and cytadherence-accessory proteins B/C, which are supported by a framework of interdependent cytoskeletal proteins, including HMW1, HMW2, HMW3, P200, P65, P41, and P24 (reviewed in reference 2). Cytadhesin protein P30 has been shown to be critical for both attachment (11, 32) and gliding motility, although its requirements for each are distinguishable (18). Thus, mutant II-...