beta-defensin expression in immunocompetent and immunodeficient germ-free and Candida albicans-monoassociated mice

Defensins are important components of innate immunity and play a key role in the fight against infectious diseases; however, little is known about their role in resistance to fungal infection.

We examined gene expression of mouse beta -defensins (mBDs) 1-4 in orogastric tissues from germ-free (gf) and Candida albicans-monoassociated immunocompetent (C57BL/6) and immunodeficient (Tg epsilon 26 or gp91(phox-/-)/NOS2(-/-)) mice, using competitive reverse-transcriptase polymerase chain reaction.

The basal levels of beta -defensin gene expression in orogastric tissues from gf mice varied significantly between immunodeficient and immunocompetent mice and by the particular tissue analyzed. During gastric and lethal oroesophageal candidiasis, expression of mBD1, -3, and -4 was induced at the infection sites (stomach and tongue) and was concomitant with an induction of tumor necrosis factor- alpha expression in Tg epsilon 26 mice, compared with that in tissues from gf mice. Induction of mBD4 expression in response to gastric candidiasis, however, was dependent on the immune competency of the host. A C. albicans mutant that lacked key genes important for filamentation and virulence also significantly induced expression of mBD1, -3, and -4 in Tg epsilon 26 mice.

These data not only demonstrate quantitative and qualitative differences in beta -defensin expression in gf and gnotobiotic mice, they also suggest a role for these peptides in resistance to gastric and lethal oroesophageal candidiasis.