Affiliation:
1. Departments of Microbiology and Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
Abstract
ABSTRACT
Nasopharyngeal colonization is the first step in the interaction between
Streptococcus pneumoniae
(the pneumococcus) and its human host. Factors that contribute to clearance of colonization are likely to affect the spread of the pneumococcus and the rate of pneumococcal disease in the population. To identify host and bacterial factors contributing to this process, we examined the time course of colonization using genetically modified mice and pneumococci. Severe combined immunodeficient mice remained persistently colonized (>6 weeks). Major histocompatibility complex II-deficient mice, but not μMT mice, were unable to clear colonization and showed a diminished T helper 1 response. Thus, CD4
+
T cells, rather than the generation of specific antibody, appear to be required for effective Th1-mediated clearance. In addition, the microbial pattern recognition receptor toll-like receptor 2 (TLR2), but not TLR4, was necessary for efficient clearance of colonization. In contrast, no role of complement component 3, inducible nitric oxide synthetase, interleukin 12 (IL-12), or IL-4 could be demonstrated. Expression of the pneumococcal toxin pneumolysin enhanced acute localized inflammatory responses and promoted clearance of colonization in a TLR4-independent manner. We conclude that both innate and CD4
+
T-cell-mediated immunity and proinflammatory bacterial factors, rather than a humoral adaptive immune response, are important for clearance of
S. pneumoniae
from the murine nasopharynx.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Reference67 articles.
1. ACIP. Prevention of pneumococcal disease: recommendations of the Advisory Committee on Immunization Practices (ACIP). 1997. Morb. Mortal. Wkly. Rep. Recomm. Rep.46(RR-8):1-24.
2. Akira, S., K. Takeda, and T. Kaisho. 2001. Toll-like receptors: critical proteins linking innate and acquired immunity. Nat. Immunol.2:675-680.
3. Austrian, R. 1986. Some aspects of the pneumococcal carrier state. J. Antimicrob. Chemother.18(Suppl. A):35-45.
4. Development of PCR-based hybridization protocol for identification of streptococcal species
5. Contribution of autolysin to virulence of Streptococcus pneumoniae