Antibody-mediated shift in the profile of glycoprotein A phenotypes observed in a mouse model of Pneumocystis carinii pneumonia

Francis Gigliotti, Beth A. Garvy, Allen G. Harmsen

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36 Scopus citations


It is well established that Pneumocystis carinii has the molecular capability for variation of a major surface antigen, glycoprotein A (gpA). However, the extent of expression of gpA variation among P. carinii organisms infecting a single host and whether this variation has any impact on host- parasite immunological interactions is unknown. Using a mouse model of P. carinii pneumonia, we were able to demonstrate the expression of more than one gpA phenotype in a closed population of infected mice. Administration of monoclonal antibody (MAb) 2B5, which is specific for one of the gpA phenotypes, resulted in a marked diminution in the frequency of this particular gpA phenotype in the population of organisms. This effect was due to a loss of trophozoites bearing the specific epitope recognized by MAb 2B5; cysts bearing the same epitope appeared unaffected. Interestingly, P. carinii was unable to introduce a new phenotype into the population to compensate for the loss of trophozoites bearing the epitope recognized by MAb 2B5. Discontinuing administration of MAb 2B5 allowed the MAb 2B5-binding phenotype to reemerge. This finding suggests that the phenotype recognized by MAb 2B5 was continually produced even when MAb 2B5 was present. Thus, although P. carinii exhibited a form of antigenic variation, it did not appear able to rapidly introduce new phenotypes into the population in response to destruction by antibodies.

Original languageEnglish
Pages (from-to)1892-1899
Number of pages8
JournalInfection and Immunity
Issue number6
StatePublished - Jun 1996

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases


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