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Cryptococcus neoformans is resistant to surfactant protein A mediated host defense mechanisms.

Giles SS, Zaas AK, Reidy MF, Perfect JR, Wright JR - PLoS ONE (2007)

Bottom Line: Using in vitro binding assays we confirmed that SP-A does not directly bind to a fully encapsulated strain of C. neoformans (H99).We found that the immune response assessed by cellular counts, TNFalpha cytokine production, and fungal burden in lungs and bronchoalveolar lavage fluids during early stages of infection were equivalent.Our results suggest that unlike a variety of bacteria, viruses, and other fungi, progression of disease with an inhalational challenge of C. neoformans does not appear to be negatively or positively affected by SP-A mediated mechanisms of pulmonary host defense.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America.

ABSTRACT
Initiation of a protective immune response to infection by the pathogenic fungus Cryptococcus neoformans is mediated in part by host factors that promote interactions between immune cells and C. neoformans yeast. Surfactant protein A (SP-A) contributes positively to pulmonary host defenses against a variety of bacteria, viruses, and fungi in part by promoting the recognition and phagocytosis of these pathogens by alveolar macrophages. In the present study we investigated the role of SP-A as a mediator of host defense against the pulmonary pathogen, C. neoformans. Previous studies have shown that SP-A binds to acapsular and minimally encapsulated strains of C. neoformans. Using in vitro binding assays we confirmed that SP-A does not directly bind to a fully encapsulated strain of C. neoformans (H99). However, we observed that when C. neoformans was incubated in bronchoalveolar fluid, SP-A binding was detected, suggesting that another alveolar host factor may enable SP-A binding. Indeed, we discovered that SP-A binds encapsulated C. neoformans via a previously unknown IgG dependent mechanism. The consequence of this interaction was the inhibition of IgG-mediated phagocytosis of C. neoformans by alveolar macrophages. Therefore, to assess the contribution of SP-A to the pulmonary host defenses we compared in vivo infections using SP-A mice (SP-A-/-) and wild-type mice in an intranasal infection model. We found that the immune response assessed by cellular counts, TNFalpha cytokine production, and fungal burden in lungs and bronchoalveolar lavage fluids during early stages of infection were equivalent. Furthermore, the survival outcome of C. neoformans infection was equivalent in SP-A-/- and wild-type mice. Our results suggest that unlike a variety of bacteria, viruses, and other fungi, progression of disease with an inhalational challenge of C. neoformans does not appear to be negatively or positively affected by SP-A mediated mechanisms of pulmonary host defense.

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C. neoformans infection appears to progress equivalently in SP-A-/- and wild-type mice.(A.) Three days post infection the fungal burdens of lung tissue and BALs from wild-type (n = 4 and n = 7, respectively) and SP-A-/- (n = 3 and n = 8, respectively) mice were equivalent. (B.) A similar trend was observed at day seven post infection; no difference between groups were observed. (C.) Quantitative differentials showed no differences in the numbers of macrophages, polymorphonuclear neutrophils or lymphocytes present in BALs collected from wild-type (n = 3) and SP-A-/- (n = 3) mice seven days post infection. (D.) There were also no differences in the numbers of macrophages from SP-A-/- (n = 3) and wild-type mice (n = 3) that had phagocytosed C. neoformans. TNFα levels (measured by ELISA) in the lungs of wild-type and SP-A-/- mice at day three (n = 8 and n = 7, respectively) and seven (n = 16 and n = 17, respectively) post infection were equivalent (P>0.05). Results represent the mean plus or minus the standard error of the mean for the indicated number of experiments. (AM, alveolar macrophage; PMN, polymorphonuclear neutrophils; Lymphs, lymphocytes; BAL, bronchoalveolar fluid)
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pone-0001370-g004: C. neoformans infection appears to progress equivalently in SP-A-/- and wild-type mice.(A.) Three days post infection the fungal burdens of lung tissue and BALs from wild-type (n = 4 and n = 7, respectively) and SP-A-/- (n = 3 and n = 8, respectively) mice were equivalent. (B.) A similar trend was observed at day seven post infection; no difference between groups were observed. (C.) Quantitative differentials showed no differences in the numbers of macrophages, polymorphonuclear neutrophils or lymphocytes present in BALs collected from wild-type (n = 3) and SP-A-/- (n = 3) mice seven days post infection. (D.) There were also no differences in the numbers of macrophages from SP-A-/- (n = 3) and wild-type mice (n = 3) that had phagocytosed C. neoformans. TNFα levels (measured by ELISA) in the lungs of wild-type and SP-A-/- mice at day three (n = 8 and n = 7, respectively) and seven (n = 16 and n = 17, respectively) post infection were equivalent (P>0.05). Results represent the mean plus or minus the standard error of the mean for the indicated number of experiments. (AM, alveolar macrophage; PMN, polymorphonuclear neutrophils; Lymphs, lymphocytes; BAL, bronchoalveolar fluid)

Mentions: We began by first investigating whether SP-A deficiency affected the colonization of the lungs by C. neoformans. Bronchoalveolar lavage fluid and lung tissue were collected from SP-A-/- (n = 3 and n = 8, respectively) and wild-type (n = 4 and n = 7, respectively) mice at days three and seven post infection. We found that SP-A deficiency did not affect the colonization of the lungs by C. neoformans (Figure 4A). At day seven post infection a significantly greater (P<0.001) number of yeast were present in the lung tissue of both mouse strains, as compared to the bronchoalveolar lavage fluid (Figure 4B), suggesting that C. neoformans had equally invaded the pulmonary parenchyma of both strains.


Cryptococcus neoformans is resistant to surfactant protein A mediated host defense mechanisms.

Giles SS, Zaas AK, Reidy MF, Perfect JR, Wright JR - PLoS ONE (2007)

C. neoformans infection appears to progress equivalently in SP-A-/- and wild-type mice.(A.) Three days post infection the fungal burdens of lung tissue and BALs from wild-type (n = 4 and n = 7, respectively) and SP-A-/- (n = 3 and n = 8, respectively) mice were equivalent. (B.) A similar trend was observed at day seven post infection; no difference between groups were observed. (C.) Quantitative differentials showed no differences in the numbers of macrophages, polymorphonuclear neutrophils or lymphocytes present in BALs collected from wild-type (n = 3) and SP-A-/- (n = 3) mice seven days post infection. (D.) There were also no differences in the numbers of macrophages from SP-A-/- (n = 3) and wild-type mice (n = 3) that had phagocytosed C. neoformans. TNFα levels (measured by ELISA) in the lungs of wild-type and SP-A-/- mice at day three (n = 8 and n = 7, respectively) and seven (n = 16 and n = 17, respectively) post infection were equivalent (P>0.05). Results represent the mean plus or minus the standard error of the mean for the indicated number of experiments. (AM, alveolar macrophage; PMN, polymorphonuclear neutrophils; Lymphs, lymphocytes; BAL, bronchoalveolar fluid)
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Related In: Results  -  Collection

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pone-0001370-g004: C. neoformans infection appears to progress equivalently in SP-A-/- and wild-type mice.(A.) Three days post infection the fungal burdens of lung tissue and BALs from wild-type (n = 4 and n = 7, respectively) and SP-A-/- (n = 3 and n = 8, respectively) mice were equivalent. (B.) A similar trend was observed at day seven post infection; no difference between groups were observed. (C.) Quantitative differentials showed no differences in the numbers of macrophages, polymorphonuclear neutrophils or lymphocytes present in BALs collected from wild-type (n = 3) and SP-A-/- (n = 3) mice seven days post infection. (D.) There were also no differences in the numbers of macrophages from SP-A-/- (n = 3) and wild-type mice (n = 3) that had phagocytosed C. neoformans. TNFα levels (measured by ELISA) in the lungs of wild-type and SP-A-/- mice at day three (n = 8 and n = 7, respectively) and seven (n = 16 and n = 17, respectively) post infection were equivalent (P>0.05). Results represent the mean plus or minus the standard error of the mean for the indicated number of experiments. (AM, alveolar macrophage; PMN, polymorphonuclear neutrophils; Lymphs, lymphocytes; BAL, bronchoalveolar fluid)
Mentions: We began by first investigating whether SP-A deficiency affected the colonization of the lungs by C. neoformans. Bronchoalveolar lavage fluid and lung tissue were collected from SP-A-/- (n = 3 and n = 8, respectively) and wild-type (n = 4 and n = 7, respectively) mice at days three and seven post infection. We found that SP-A deficiency did not affect the colonization of the lungs by C. neoformans (Figure 4A). At day seven post infection a significantly greater (P<0.001) number of yeast were present in the lung tissue of both mouse strains, as compared to the bronchoalveolar lavage fluid (Figure 4B), suggesting that C. neoformans had equally invaded the pulmonary parenchyma of both strains.

Bottom Line: Using in vitro binding assays we confirmed that SP-A does not directly bind to a fully encapsulated strain of C. neoformans (H99).We found that the immune response assessed by cellular counts, TNFalpha cytokine production, and fungal burden in lungs and bronchoalveolar lavage fluids during early stages of infection were equivalent.Our results suggest that unlike a variety of bacteria, viruses, and other fungi, progression of disease with an inhalational challenge of C. neoformans does not appear to be negatively or positively affected by SP-A mediated mechanisms of pulmonary host defense.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States of America.

ABSTRACT
Initiation of a protective immune response to infection by the pathogenic fungus Cryptococcus neoformans is mediated in part by host factors that promote interactions between immune cells and C. neoformans yeast. Surfactant protein A (SP-A) contributes positively to pulmonary host defenses against a variety of bacteria, viruses, and fungi in part by promoting the recognition and phagocytosis of these pathogens by alveolar macrophages. In the present study we investigated the role of SP-A as a mediator of host defense against the pulmonary pathogen, C. neoformans. Previous studies have shown that SP-A binds to acapsular and minimally encapsulated strains of C. neoformans. Using in vitro binding assays we confirmed that SP-A does not directly bind to a fully encapsulated strain of C. neoformans (H99). However, we observed that when C. neoformans was incubated in bronchoalveolar fluid, SP-A binding was detected, suggesting that another alveolar host factor may enable SP-A binding. Indeed, we discovered that SP-A binds encapsulated C. neoformans via a previously unknown IgG dependent mechanism. The consequence of this interaction was the inhibition of IgG-mediated phagocytosis of C. neoformans by alveolar macrophages. Therefore, to assess the contribution of SP-A to the pulmonary host defenses we compared in vivo infections using SP-A mice (SP-A-/-) and wild-type mice in an intranasal infection model. We found that the immune response assessed by cellular counts, TNFalpha cytokine production, and fungal burden in lungs and bronchoalveolar lavage fluids during early stages of infection were equivalent. Furthermore, the survival outcome of C. neoformans infection was equivalent in SP-A-/- and wild-type mice. Our results suggest that unlike a variety of bacteria, viruses, and other fungi, progression of disease with an inhalational challenge of C. neoformans does not appear to be negatively or positively affected by SP-A mediated mechanisms of pulmonary host defense.

Show MeSH
Related in: MedlinePlus