[Frontiers in Bioscience E4, 651-661, January 1, 2012]

SP-A and SP-D in host defense against fungal infections and allergies

Hrishikesh Pandit1, Shanmuga P. Madhukaran2, Annapurna Nayak2, Taruna Madan1

1National Institute for Research in Reproductive Health, Mumbai, India, 2Centre for Infection, Immunity and Disease Mechanisms, Biosciences, School of Health Sciences and Social Care, Brunel University, London, UK.

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. Structure of SP-A and SP-D
4. Interactions with fungal pathogens
4.1. Opportunistic fungal pathogens:
4.1.1. Aspergillus fumigatus
4.1.2. Candida albicans
4.1.3. Cryptococcus neoformans
4.1.4. Pneumocystis carinii
4.2 .Primary fungal pathogens:
4.2.1. Blastomyces dermatitidis
4.2.2. Coccidiodes immitis and Coccidiodes posadasii
4.2.3. Histoplasma capsulatum
5. Interactions with fungal allergens
6. Levels of SP-A and SP-D during infection and allergy
7. Polymorphisms in genes encoding SP-A and SP-D
8. Perspectives and Conclusions
9. Acknowledgment
10. References

1. ABSTRACT

Innate immunity mediated by pattern recognition proteins is relevant in the host defense against fungi. SP-A and SP-D are two such proteins belonging to the class of collagen domain containing C-type lectins, or collectins. They bind to the sugar moieties present on the cell walls of various fungi in a dose dependent manner via their carbohydrate recognition domain (CRD). SP-A and SP-D directly interact with alveolar macrophages, neutrophils, lymphocytes. We review these roles of SP-A and SP-D against various clinically relevant fungal pathogens and fungal allergens. SP-A and SP-D gene deficient mice showed increased susceptibility/ resistance to various fungal infections. Patients of fungal infections and allergies are reported with alterations in the serum or lung lavage levels of SP-A and SP-D. There are studies associating the gene polymorphisms in SP-A and SP-D with alterations in their levels or functions or susceptibility of the host to fungal diseases. In view of the protective role of SP-D in murine models of Aspergillus fumigatus infections and allergies, therapeutic use of SP-D could be explored further.