IFN-alpha induces MxA gene expression in cultured human corneal fibroblasts.

Treatment of certain human cells with Interferon-alpha (IFN-alpha) induces the synthesis of a 76 kDa protein designated MxA that is involved in resistance to viral infection. We have used a specific cDNA clone and monoclonal Ab to show that MxA is induced in IFN-alpha treated human corneal fibroblast cultures. Mx RNA was increased 23-fold and 45-fold after 5 and 9 h of IFN-alpha treatment, respectively. The MxA protein was detectable by immunoblotting at 5 hr after IFN treatment and peaked at 17 hr. Concentrations of IFN-alpha as low as 1 U/ml induced detectable amounts of MxA, and expression was maximal at 1 x 10(3) U ml-1. These results confirm that MxA synthesis is induced in human corneal fibroblasts treated with IFN-alpha.

Interferon-alpha and interferon-gamma induced modulation of proteins in human corneal fibroblasts.

Little is known about the effects of interferon (IFN) on cell function in the eye. We have analyzed the effect of INF-alpha and IFN-gamma on the expression of proteins in cultured human corneal fibroblasts. Treatment with IFN-alpha increased the synthesis of proteins of 84, 76, 52, and 28 kD and decreased the synthesis of a 72-kD protein. Treatment with IFN-gamma increased the synthesis of proteins of 83, 66, 64, 54, and 47 kD. The effect of IFN-alpha and IFN-gamma were first detected at 5-9 h and 9 h, respectively, after the addition of the IFNs and were maximal at 17 and 24 h, respectively. Most of the changes were seen at doses of 1 x 10(1) to 1 x 10(2) U/ml of IFN-alpha or IFN-gamma and were maximal at 1 x 10(2) to 1 x 10(3) U/ml. Thus, each IFN induced distinct proteins based on apparent molecular weight and isoelectric point. These results show that IFN-alpha and IFN-gamma affect the synthesis of small groups of distinct proteins in human corneal fibroblasts.

Enhanced inhibition of herpes simplex virus type 1 growth in human corneal fibroblasts by combinations of interferon-alpha and -gamma.

Trials testing the topical treatment of herpes simplex virus (HSV) ocular infections with single interferons (IFN) have provided mixed results. To determine if combination therapy with IFN may be more effective, the ability of combinations of IFN-alpha and IFN-gamma to inhibit HSV growth in human corneal fibroblasts (HCF) was assessed. Virus yields were reduced 282-fold and 37-fold, respectively, in HCF treated with either IFN-alpha or IFN-gamma (10(3) units/mL each). In cells treated with a combination of IFN-alpha and IFN-gamma (10(3) units/mL each), an average reduction of 5.1 x 10(5)-fold in the yield of infectious virus was achieved. Combinations of IFN-alpha and IFN-gamma considerably enhanced the antiviral effect in HCF, suggesting that combination treatment may be efficacious against ocular HSV infections; these findings provide a possible explanation at the cellular level for the poor results achieved in previous clinical trials.

Colonization and pathogenesis of Cryptococcus neoformans in gnotobiotic mice.

Congenitally immunodeficient nude (nu/nu) mice and their immunocompetent littermates (nu/+) were used to determine whether the absence of thymus-matured T cells would alter the capacity of Cryptococcus neoformans to colonize their mucosal surfaces or enhance their susceptibility to systemic cryptococcosis, or both, following oral challenge. We present data demonstrating that an encapsulated strain of C. neoformans serotype A colonized the alimentary tracts of germfree, conventional, and antibiotic-treated conventional nu/nu mice. Scanning electron microscopy showed that C. neoformans adhered to the epithelial surfaces of the oral cavities, esophagi, and gastrointestinal tracts of monoassociated nu/nu and nu/+ mice, and culture data showed that there were more viable C. neoformans cells in the alimentary tracts of nu/nu mice than of nu/+ mice. Tetracycline-treated conventional nu/nu, but not nu/+, mice were also colonized with C. neoformans following intragastric challenge. C. neoformans-monoassociated and tetracycline-treated conventional nu/nu mice succumbed to disseminated cryptococcosis with cerebral involvement 3 to 4 weeks after oral challenge, whereas no mortality was observed for similarily challenged nu/+ mice. These results demonstrate that an encapsulated strain of C. neoformans can colonize mucosal surfaces and cause systemic cryptococcosis in immunodeficient nu/nu mice, suggesting that the alimentary tract can be a portal of entry for C. neoformans in an immunodeficient host. These data also indicate that functional T cells play an important role in resistance to systemic cryptococcosis of endogenous origin.

Colonization of congenitally athymic, gnotobiotic mice by Candida albicans.

Colony counts, scanning electron microscopy, and light microscopy were used to assess the capacity of Candida albicans to colonize (naturally) and infect the alimentary tract of adult and neonatal (athymic [nu/nu] or heterozygous [+/nu] littermates) germfree BALB/c mice. When exposed to yeast-phase C. albicans, the alimentary tract of adult germfree mice (nu/nu or +/nu) is quickly (within 24 to 48 h) colonized with yeast cells. Neither morbidity nor mortality was evident in any mice that were colonized with a pure culture of C. albicans for 6 months. Yeast cells of C. albicans predominated on mucosal surfaces in the oral cavities and vaginas of adult athymic and heterozygous mice. In both genotypes, C. albicans hyphae were observed in keratinized tissue on the dorsal posterior tongue surface and in the cardial-atrium section of the stomach. Conversely, neonatal athymic or heterozygous mice, born to germfree or C. albicans-colonized mothers, do not become heavily colonized or infected with C. albicans until 11 to 15 days after birth. Although yeast cells adhered to some mucosal surfaces in vivo, neither widespread mucocutaneous candidiasis, i.e., invasion of mucosal surfaces with C. albicans hyphae, nor overwhelming systemic candidiasis was evident in neonatal (nu/nu or +/nu) mice. Thus, even in the absence of functional T-cells and a viable bacterial flora, athymic and heterozygous littermate mice (adult or neonatal BALB/c) that are colonized with a pure culture of C. albicans manifest resistance to extensive mucocutaneous and systemic candidiasis.

Bladder mucin: a scanning electron microscopy study in experimental cystitis.

Scanning electron microscopy has been used to assess surface mucin changes following an induced Escherichia coli urinary tract infection in the rat bladder. The principal changes seen following bacterial challenge were bacterial adherence to the urothelium, swelling of epithelial folds, disruption of the mucin layer, and increased adherence of bacteria to the sub-surface epithelium. The bladder mucin before infection appeared as an even, whitish, viscous layer which covered epithelial cells and cell junctions. Bacteria appeared to become enmeshed in mucin strands after infection and this process may facilitate bacterial washout from the bladder. A recovery phase showed reversal of the scanning electron microscopy changes. These findings support other studies in suggesting that mucin may play a role in protecting the bladder from invading and adhering bacteria.