Vaccine-Induced Immunogenicity and Protection Against Pneumocystis Pneumonia in a Nonhuman Primate Model of HIV and Pneumocystis Coinfection.

Background: The ubiquitous opportunistic pathogen Pneumocystis jirovecii causes pneumonia in immunocompromised individuals, including human immunodeficiency virus (HIV)-infected individuals, and pulmonary colonization with P. jirovecii is believed to be a cofactor in the development of chronic obstructive pulmonary disease. There is no vaccine for P. jirovecii; however, most adults are seropositive, indicating natural immune priming to this pathogen. We have shown that humoral response to a recombinant subunit of the P. jirovecii protease kexin (KEX1) correlates with protection from P. jirovecii colonization and pneumonia.

Methods: Here we evaluated the immunogenicity and protective capacity of the recombinant KEX1 peptide vaccine in a preclinical, nonhuman primate model of HIV-induced immunosuppression and Pneumocystis coinfection.

Results: Immunization with KEX1 induced a robust humoral response remained at protective levels despite chronic simian immunodeficiency virus/HIV-induced immunosuppression. KEX1-immunized macaques were protected from Pneumocystis pneumonia, compared with mock-immunized animals (P= .047), following immunosuppression and subsequent natural, airborne exposure to Pneumocystis

Conclusions: These data support the concept that stimulation of preexisting immunological memory to Pneumocystis with a recombinant KEX1 vaccine prior to immunosuppression induces durable memory responses and protection in the context of chronic, complex immunosuppression.