Light and transmission electron microscopy of Vibrio campbellii infection in gnotobiotic Artemia franciscana and protection offered by a yeast mutant with elevated cell wall glucan.

Luminescent vibrios are amongst the most important pathogens in aquaculture, affecting almost all types of cultured organisms. Vibrio campbellii is one of these most important pathogens. In this study, the effects of feeding mnn9 yeast cell wall mutant and wild type yeast strain were investigated in the digestive tract of brine shrimp nauplii, Artemia franciscana, after experimental infection with V. campbellii (LMG 21363). Gnotobiotic A. franciscana nauplii were fed daily with dead Aeromonas hydrophila LVS3, and with either wild type strain of baker's yeast, Saccharomyces cerevisiae, or mutant strain mnn9, of which the cell wall contains elevated chitin and glucan and lower mannose levels. After three days of feeding, some nauplii were challenged with V. campbellii. Mean survival (%), individual length (mm) and total length (mm) at one day and two days after challenge were significantly higher in the group fed mnn9 than in the group fed wild type yeast (81 ± 1.50 and 63 ± 0.49, 1.56 ± 0.07 and 1.13 ± 0.02, 38.21 ± 3.11 and 21.26 ± 0.81 respectively for one day and 50 ± 2.37 and 20 ± 1.41, 2.33 ± 0.01 and 1.24 ± 0.04, 34.97 ± 5.56 and 7.45 ± 1.63 for two days after challenge). Histological examination revealed that the luminal diameter and enterocyte height of both mid- and hindgut were larger in the mnn9-fed group. Colonization of the gut lumen by V. campbellii could be observed by transmission electron microscopy for the group of nauplii fed with wild type yeast. Furthermore, it was observed that V. campbellii caused damage to the gut epithelium including shortening and disappearance of the microvilli, destruction of the apical cell membrane and cell lysis in the nauplii fed wild type yeast. The gut epithelium remained intact in challenged nauplii fed mnn9 yeast. The morphological findings of the present study further substantiate previous studies reporting a protective effect of this yeast cell wall mutant.

A method for the specific detection of resident bacteria in brine shrimp larvae.

In this study, we describe an easy but efficient method to specifically target the intestinal resident microbiota in brine shrimp larvae during DGGE analysis, hereby excluding the interference of both transient (luminal) bacteria and body surface bacteria. This effective technique has several advantages over alternative methods, with respect of ease of use and rapidity.

Herpes simplex virus type 1 penetrates the basement membrane in human nasal respiratory mucosa.

BACKGROUND: Herpes simplex virus infections are highly prevalent in humans. However, the current therapeutics suffer important drawbacks such as limited results in neonates, increasing occurrence of resistance and impeded treatment of stromal infections. Remarkably, interactions of herpesviruses with human mucosa, the locus of infection, remain poorly understood and the underlying mechanisms in stromal infection remain controversial. METHODOLOGY/PRINCIPAL FINDINGS: A human model consisting of nasal respiratory mucosa explants was characterised. Viability and integrity were examined during 96 h of cultivation. HSV1-mucosa interactions were analysed. In particular, we investigated whether HSV1 is able to reach the stroma. Explant viability and integrity remained preserved. HSV1 induced rounding up and loosening of epithelial cells with very few apoptotic and necrotic cells observed. Following 16-24 h of infection, HSV1 penetrated the basement membrane and replicated in the underlying lamina propria. CONCLUSIONS/SIGNIFICANCE: This human explant model can be used to study virus-mucosa interactions and viral mucosal invasion mechanisms. Using this model, our results provide a novel insight into the HSV1 stromal invasion mechanism and for the first time directly demonstrate that HSV1 can penetrate the basement membrane.