Nuclear localization signals (NLS) are generally short peptides that act as a signal fragment that mediates the transport of proteins from the cytoplasm into the nucleus. This NLS-dependent protein recognition, a process necessary for cargo proteins to pass the nuclear envelope through the nuclear pore complex, is facilitated by members of the importin superfamily. Here, we summarized the types of NLS, focused on the recently reported related proteins containing nuclear localization signals, and briefly summarized some mechanisms that do not depend on nuclear localization signals into the nucleus.

The attenuation and immunogenicity of two novel Salmonella vaccine strains, Salmonella enterica serovar Typhi (Ty2 ⌬aroC ⌬ssaV, designated ZH9) and S. enterica serovar Typhimurium (TML ⌬aroC ⌬ssaV, designated WT05), were evaluated after their oral administration to volunteers as single escalating doses of 10 7 , 10 8 , or 10 9 CFU. ZH9 was well tolerated, not detected in blood, nor persistently excreted in stool. Six of nine volunteers elicited anti-serovar Typhi lipopolysaccharide (LPS) immunoglobulin A (IgA) antibody-secreting cell (ASC) responses, with three of three vaccinees receiving 10 8 and two of three receiving 10 9 CFU which elicited high-titer LPS-specific serum IgG. WT05 was also well tolerated with no diarrhea, although the administration of 10 8 and 10 9 CFU resulted in shedding in stools for up to 23 days. Only volunteers immunized with 10 9 CFU of WT05 mounted detectable serovar Typhimurium LPS-specific ASC responses and serum antibody responses were variable. These data indicate that mutations in type III secretion systems may provide a route to the development of live vaccines in humans and highlight significant differences in the potential use of serovars Typhimurium and Typhi.

Destruction in intestinal barrier is concomitant with the intestinal diseases. There is growing evidence that tryptophan-derived intestinal bacterial metabolites play a critical role in maintaining the balance of intestinal mucosa. In this study, the Caco-2/HT29 coculture model was used to evaluate the effect of indole-3-propionic acid (IPA) on the intestinal barrier and explore its underlying mechanism. We found that IPA increased transepithelial electrical resistance and decreased paracellular permeability which was consistent with the increase in tight junction proteins (claudin-1, occludin, and ZO-1). Furthermore, IPA strengthened the mucus barrier by increasing mucins (MUC2 and MUC4) and goblet cell secretion products (TFF3 and RELMβ). Additionally, IPA weakened the expression of LPS-induced inflammatory factors. These discoveries provide new views for understanding the improvement of intestinal barrier by gut microbial metabolites of aromatic amino acids.

In-vitro proteinase production by oral Candida afbicans isolates from patients with and without HIV infection (18 isolates from each group) was assessed by image analysis of a plate assay, with bovine serum albumin (BSA) as a substrate. The effect of subminimal inhibitory concentrations (sub-MICs) of nystatin, amphotericin B, clotrimazole and miconazole on in-vitro proteinase production by these yeast isolates was also investigated. Proteinase production by C. albicans isolates from patients with HIV infection was significantly greater than production by those from individuals without infection. All 18 isolates from HIV-infected individuals produced proteinase, in comparison to 56% of isolates from uninfected individuals. Pre-exposure of C. albicans isolates (seven proteinase producers from each group) to 1/4 and 1/16 MICs of nystatin, amphotericin B, clotrimazole and miconazole resulted in decreased proteinase production in all isolates tested. However, after exposure to the four antimycotic agents, proteinase production was decreased to a significantly greater extent in isolates from uninfected individuals than in those with HIV disease. Furthermore, when the relative concentration effect of antimycotic agents on proteinase production was compared, C. albicans isolates from the HIV-free group demonstrated a salient dose-response relationship compared with the HIV-infected group. These results indicate that C. albicans from patients with HIV infection are significantly more proteolytic than those from individuals without the infection, and that polyenes and imidazoles curtail the proteolytic activity of all C. afbicans isolates, albeit to a lesser extent in those from HIVinfected patients. It appears that HIV disease favours oral colonisation by more proteolytic C. afbicans isolates, with resilient proteolytic activity.

We examined the production of secreted aspartyl proteinase (Sap), a putative virulence factor of Candida albicans, by a series of 17 isolates representing a single strain obtained from the oral cavity of an AIDS patient before and after the development of clinical and in vitro resistance to fluconazole. Isolates were grown in Sap-inducing yeast carbon base-bovine serum albumin medium containing 0, 0.25, 0.5, or 1 MIC of fluconazole, and cultures were sampled daily for 14 days to determine extracellular Sap activity by enzymatic degradation of bovine serum albumin. Extracellular Sap activity was significantly decreased in a dose-dependent manner for the most fluconazole-susceptible isolate (MIC, 1.0 g/ml) and significantly increased in a dose-dependent manner for the most fluconazole-resistant isolate (MIC, >64 g/ml). Enhanced extracellular Sap production could not be attributed to cell death or nonspecific release of Sap, because there was no reduction in the number of CFU and no significant release of enolase, a constitutive enzyme of the glycolytic pathway. Conversely, intracellular Sap concentrations were significantly increased in a dose-dependent manner in the most fluconazole-susceptible isolate and decreased in the most fluconazole-resistant isolate. Enhanced Sap production correlated with the overexpression of a gene encoding a multidrug resistance (MDR1) efflux pump occurring in these isolates. These data indicate that exposure to subinhibitory concentrations of fluconazole can result in enhanced extracellular production of Sap by isolates with the capacity to overexpress MDR1 and imply that patients infected with these isolates and subsequently treated with suboptimal doses of fluconazole may experience enhanced C. albicans virulence in vivo.

Porcine epidemic diarrhea virus (PEDV) infects the intestine of young pigs, but effective measures for prevention and treatment are lacking. N-Acetylcysteine (NAC) has been shown to reduce endotoxin-induced intestinal dysfunction. This study was conducted with the PEDV-infected neonatal piglet model to determine the effect of NAC supplementation on intestinal function. Thirty-two 7-day-old piglets were randomly allocated to one of four treatments in a 2 × 2 factorial design consisting of two liquid diets (0 or 50 mg/kg BW NAC supplementation) and oral administration of 0 or 10 TCID (50% tissue culture infectious dose) PEDV. On day 7 of the trial, half of the pigs (n = 8) in each dietary treatment received either sterile saline or PEDV (Yunnan province strain) solution at 10 TCID per pig. On day 10 of the trial, D-xylose (0.1 g/kg BW) was orally administrated to all pigs. One hour later, jugular vein blood samples were collected, and then all pigs were killed to obtain the small intestine. PEDV infection increased diarrhea incidence, while reducing ADG. PEDV infection also decreased plasma D-xylose concentration, small intestinal villus height, mucosal I-FABP and villin mRNA levels but increased mucosal MX1 and GCNT3 mRNA levels (P < 0.05). Dietary NAC supplementation ameliorated the PEDV-induced abnormal changes in all the measured variables. Moreover, NAC reduced oxidative stress, as indicated by decreases in plasma and mucosal HO levels. Collectively, these novel results indicate that dietary supplementation with NAC alleviates intestinal mucosal damage and improves the absorptive function of the small intestine in PEDV-infected piglets.

Lysozyme (muramidase) is a non-specific, antimicrobial protein ubiquitous in human mucosal secretions such as saliva. Although its antibacterial and antifungal activities are well recognised, there are no data on the specific concentrations necessary to affect the growth of Candida albicans or about the effect of lysozyme on the production of secreted aspartyl proteinase (Sap), a putative virulence factor of C. albicans. Five Sap-producing isolates of C. albicans were cultured in YCB-BSA medium with various concentrations of lysozyme to examine its effect on yeast cell growth, ultrastructural cellular topography and extracellular and intracellular Sap concentration and activity. Lysozyme was candidacidal at high concentrations and decreased significantly the extracellular Sap concentration at sublethal doses, accompanied by intracellular accumulation of the enzyme. At low concentrations of lysozyme (c. lOpg/ml), Sap activity decreased more than two-fold and Sap concentration decreased five-fold without any appreciable effect on cell growth or viability. Ultrastructural investigations showed ballooned cells and cells with invaginations (expecially present near bud scars), indicating that cell-wall components may be possible targets for this enzyme. All concentrations of lysozyme tested were well within physiologically attainable levels. These data suggest that lysozyme has, at least, a bimodal action on C. albicans, killing the organism at higher concentrations and modulating Sap metabolism at lower concentrations.

No abstract