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Respir Res. 2018 Sep 25;19(1):187. doi: 10.1186/s12931-018-0895-8.

PrtA immunization fails to protect against pulmonary and invasive infection by Streptococcus pneumoniae.

Author information

1
Department of Pediatrics, Chi Mei Medical Center, Tainan, Taiwan.
2
Taipei Medical University, Taipei, Taiwan.
3
Kaohsiung Medical University, Kaohsiung, Taiwan.
4
Chung Shan Medical University, Taichung, Taiwan.
5
Cheng Hsin General Hospital, Taipei, Taiwan.
6
Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei, Taiwan.
7
Department and Graduate Institute of Microbiology and Immunology, National Defense Medical Center, Taipei, Taiwan.
8
Department of Emergency Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
9
Graduate Institute of Injury Prevention and Control, College of Public Health and Nutrition, Taipei Medical University, Taipei, Taiwan.
10
Division of Cardiology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
11
National Institute of Infectious Diseases and Vaccinology, National Health Research Institutes, Miaoli, Taiwan.
12
Department and Graduate Institute of Microbiology and Immunology, National Defense Medical Center, Taipei, Taiwan. ypchuang@mail.ndmctsgh.edu.tw.

Abstract

BACKGROUND:

Streptococcus pneumoniae is a respiratory pathogen causing severe lung infection that may lead to complications such as bacteremia. Current polysaccharide vaccines have limited serotype coverage and therefore cannot provide maximal and long-term protection. Global efforts are being made to develop a conserved protein vaccine candidate. PrtA, a pneumococcal surface protein, was identified by screening a pneumococcal genomic expression library using convalescent patient serum. The prtA gene is prevalent and conserved among S. pneumoniae strains. Its protective efficacy, however, has not been described. Mucosal immunization could sensitize both local and systemic immunity, which would be an ideal scenario for preventing S. pneumoniae infection.

METHODS:

We immunized BALB/c mice intranasally with a combination of a PrtA fragment (amino acids 144-1041) and Th17 potentiated adjuvant, curdlan. We then measured the T-cell and antibody responses. The protective efficacy conferred to the immunized mice was further evaluated using a murine model of acute pneumococcal pneumonia and pneumococcal bacteremia.

RESULTS:

There was a profound antigen-specific IL-17A and IFN-γ response in PrtA-immunized mice compared with that of adjuvant control group. Even though PrtA-specific IgG and IgA titer in sera was elevated in immunized mice, only a moderate IgA response was observed in the bronchoalveolar lavage fluid. The PrtA-immunized antisera facilitated the activated murine macrophage, RAW264.7, to opsonophagocytose S. pneumoniae D39 strain; however, PrtA-specific immunoglobulins bound to pneumococcal surfaces with a limited potency. Finally, PrtA-induced immune reactions failed to protect mice against S. pneumoniae-induced acute pneumonia and bacterial propagation through the blood.

CONCLUSIONS:

Immunization with recombinant PrtA combined with curdlan produced antigen-specific antibodies and elicited IL-17A response. However, it failed to protect the mice against S. pneumoniae-induced infection.

KEYWORDS:

Curdlan; IL-17A; PrtA; Streptococcus pneumoniae

PMID:
30253765
PMCID:
PMC6157060
DOI:
10.1186/s12931-018-0895-8
[Indexed for MEDLINE]
Free PMC Article

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