Detecting the prevalence of bacterial colonization on tunneled cuffed hemodialysis catheters using quantitative PCR targeting 16S rRNA and scanning electron microscopy

BACKGROUND AND OBJECTIVES

Tunneled cuffed hemodialysis catheters (TCC) get colonized by microorganisms, increasing risk for catheter related bacteremia (CRB). Our objective was to detect the prevalence of bacterial colonization of TCC by using quantitative PCR (qPCR) targeting 16S rRNA and by determining the intraluminal adherent biological material (ABM) coverage.

METHODS

A total of 45 TCC were investigated. The 16S rRNA qPCR technique was used to detect bacterial colonization after scraping the intraluminal ABM. Proximal, middle, and distal TCC were evaluated by scanning electron microscopy (SEM) to determine the percentage (%) of intraluminal ABM coverage. All catheters were cultured following sonication.

RESULTS

A total of 45 TCC were removed: 7 due to CRB, 3 for suspected CRB and 35 were removed for non-infectious etiologies. Bacterial colonization was detected in 27 TCC by documenting 16S rRNA qPCR (+) results (60%). Seven of these 16S rRNA qPCR (+) catheters were removed due to CRB. There was no difference in demographic, clinical, or laboratory values between the 16S rRNA (+) versus (-) TCC. The 16S rRNA qPCR (-) outcome was highly associated with CRB-free status with negative predictive value of 100%. Bacterial colonization was documented in 10 TCC using catheter cultures (22%), which was significantly less compared to qPCR method (p = 0.0002). ABM were detected in all catheter pieces, with mean intraluminal surface coverage (ABMC) of 68.4 ± 26.1%. ABM was unlikely to be microbial biofilm in at least 36% of removed TCC as their 16S rRNA qPCR and catheter culture results were both negative.

CONCLUSIONS

Detecting bacterial colonization of TCC was significantly higher with 16S rRNA qPCR compared to catheter cultures. The 16S rRNA qPCR (-) cannot be predicted and was strongly associated with absence of CRB. Intraluminal ABM was not associated with microbial presence in about 1/3 of the TCC. These pieces of evidence may help to improve prophylactic strategies against CRB.

Educational intervention improves fruit and vegetable intake in young adults with metabolic syndrome components

The FRUVEDomics study investigates the effect of a diet intervention focused on increasing fruit and vegetable intake on the gut microbiome, and cardiovascular health of young adults with/at risk for Metabolic Syndrome (MetS). It was hypothesized the recommended diet would result in metabolic and gut microbiome changes. The 9-week dietary intervention adhered to the USDA Dietary Guidelines for Americans and focused on increasing fruit and vegetable intake to equal half of the diet. Seventeen eligible young adults with/or at high risk of MetS, consented and completed preintervention and postintervention measurements, including anthropometric, body composition, cardiovascular, complete blood lipid panel, and collection of stool sample for microbial analysis. Participants attended weekly consultations to assess food logs, food receipts, and adherence to the diet. Following intention-to-treat guidelines all 17 individuals were included in the dietary, clinical, and anthropometric analysis. Fruit and vegetable intake increased from 1.6 to 3.4 cups of fruits and vegetables (P < .001) daily. Total fiber (P = .02) and insoluble fiber (P < .0001) also increased. Clinical laboratory changes included an increase in sodium (P = .0006) and low-density lipoprotein cholesterol (P = .04). In the fecal microbiome, Erysipelotrichaceae (phylum Firmicutes) decreased (log2 fold change: −1.78, P = .01) and Caulobacteraceae (phylum Proteobacteria) increased (log2 fold change = 1.07, P = .01). Implementing a free living 9-week diet, with intensive education and accountability, gave young adults at high risk for/or diagnosed with MetS the knowledge, skills, and feedback to improve diet. To yield greater impact a longer diet intervention may be needed in this population.

Histologic and Immunologic Observations of Viral-Induced Rhinosinusitis in the Mouse

Viral upper respiratory infection is one of the most common diagnoses made in primary care offices. Although symptoms resolve within 1 week for many patients, a percentage develops rhinosinusitis, and many of these patients are treated with antibiotics. We have developed a model of viral rhinosinusitis using intranasal inoculation of reovirus into mice that were then killed on postinoculation days 2, 4, 7, 10, 14, or 21 and heads were embedded in paraffin for histological and immunohistochemical analyses. Reovirus-like immunoreactivity was noted in the septa and paranasal sinus mucosa in mice as early as day 2, with peak intensity seen on day 4, and scant staining seen on day 7. Complete absence of viral staining was seen by day 10, which corresponded with increased intracellular adhesion molecule 1 immunostaining in the nose. By day 10, a large mucosal influx of B cells was observed, with a moderate influx of macrophages and smaller influx of T cells. By day 14, there was a peak in the number of B cells with a corresponding, but less pronounced peak in T cells, while macrophages began to decline at this point. By day 21, the panel of immune markers returned to near normal levels. The results of this study suggest that the immune system continues to produce a response as long as 2 weeks after clearance of viral antigens. One proposed mechanism for this phenomenon is that local factors such as cytokines are released continually after infection, even in the absence of persistent viruses or bacteria.

Efficacy of nutritional interventions to lower circulating ceramides in young adults: FRUVEDomic pilot study

The 2010 USDA Dietary Guidelines for Americans (DGA) recommends a diet largely composed of fruit and vegetables. Consuming a diet high in fruit and vegetables and low in refined carbohydrates and saturated fat may reduce an individual's risk for type 2 diabetes, nonalcoholic fatty liver disease, low‐grade chronic inflammation, and metabolic syndrome (MetS). Several recent studies have implicated the bioactive sphingolipid ceramide as an associative and causative biomarker for the development of these conditions. Considering that the intake of fruit and vegetables is frequently inadequate in young adults, we performed a pilot investigation to assess the efficacy of a free‐living fruit and vegetable intervention on overall metabolic health, circulating ceramide supply, and inflammatory status in young adults. We discovered that adoption of the recommended DGA for fruit and vegetable intake for 8 weeks decreased waist circumference, systolic blood pressure, and circulating cholesterol. Lipidomics analysis revealed that nutritional intervention can lower circulating ceramides, including C24:0 ceramide, a known inhibitor of insulin signaling. Unexpectedly, we observed an increase in C16:0 ceramide, suggesting that this form of ceramide in circulation is not associated with metabolic disease in humans. We also observed an improved inflammatory status with enhanced fruit and vegetable intake that was correlated with ceramide concentrations. These data suggest that adopting the recommended DGA is associated with a reduction of many, but not all, ceramide species and may help to prevent or mitigate MetS. Future research needs to assess whether the ceramide‐lowering ability of nutritional intervention is associated with reduced risk of developing metabolic disease.

β-Elemene and taxanes synergistically induce cytotoxicity and inhibit proliferation in ovarian cancer and other tumor cells

β-Elemene, originally derived from plants, has been recently investigated as a new anticancer agent. The purpose of this study was to explore the efficacy and mechanisms of action of the combined use of β-elemene plus a taxane as an antitumor therapeutic strategy for ovarian cancer and other carcinomas. The interaction of β-elemene with paclitaxel or docetaxel produced additive to moderately synergistic effects against the platinum-resistant ovarian cancer cell line A2780/CP70 and its parental cell line A2780, and showed moderately synergistic activity against PC-3 prostate cancer cells. In addition, the co-administration of β-elemene and a taxane at low-micromolar concentrations dramatically increased the rate of micronucleus formation and the percentage of mitotic arrest in both ovarian cancer cell lines, as compared with treatment with either agent alone. The highest synergy towards the ovarian cancer cells was observed with β-elemene plus docetaxel. Consistent with these data, treatment of A2780/CP70 cells with β-elemene plus a taxane strikingly reduced cell viability and increased cell apoptosis, as assessed by annexin V binding. Moreover, β-elemene plus docetaxel induced elevated levels of caspase-9 and p53 proteins in A2780/CP70 cells, and the combination of β-elemene plus a taxane caused marked cell-cycle arrest at the G2/M phase in these cells. One possible mechanism to account for the enhanced cytotoxic efficacy of this combination treatment is a β-elemene-induced increase in taxane influx into cancer cells. These observations indicate that combination therapy with β-elemene and taxanes has synergistic antitumor activity against ovarian and prostate carcinomas in vitro. This promising new therapeutic combination warrants further pre-clinical exploration for the treatment of chemoresistant ovarian cancer and other types of tumors.

High throughput DNA sequencing to detect differences in the subgingival plaque microbiome in elderly subjects with and without dementia

Background

To investigate the potential association between oral health and cognitive function, a pilot study was conducted to evaluate high throughput DNA sequencing of the V3 region of the 16S ribosomal RNA gene for determining the relative abundance of bacterial taxa in subgingival plaque from older adults with or without dementia.

Methods

Subgingival plaque samples were obtained from ten individuals at least 70 years old who participated in a study to assess oral health and cognitive function. DNA was isolated from the samples and a gene segment from the V3 portion of the 16S bacterial ribosomal RNA gene was amplified and sequenced using an Illumina HiSeq1000 DNA sequencer. Bacterial populations found in the subgingival plaque were identified and assessed with respect to the cognitive status and oral health of the participants who provided the samples.

Results

More than two million high quality DNA sequences were obtained from each sample. Individuals differed greatly in the mix of phylotypes, but different sites from different subgingival depths in the same subject were usually similar. No consistent differences were observed in this small sample between subjects separated by levels of oral health, sex, or age; however a consistently higher level of Fusobacteriaceae and a generally lower level of Prevotellaceae was seen in subjects without dementia, although the difference did not reach statistical significance, possibly because of the small sample size.

Conclusions

The results from this pilot study provide suggestive evidence that alterations in the subgingival microbiome are associated with changes in cognitive function, and provide support for an expanded analysis of the role of the oral microbiome in dementia.

Evaluation of cisplatin in combination with β-elemene as a regimen for prostate cancer chemotherapy

Cisplatin is one of the most potent chemotherapeutic agents for the treatment of many types of solid tumours. Nevertheless, it is not the first-line drug for prostate cancer chemotherapy, because prostate tumour cells exhibit intrinsic and acquired resistance to cisplatin. We have previously demonstrated that β-elemene, a novel plant-derived anti-neoplastic with low toxicity, inhibits lung and ovarian carcinoma cell growth in vitro. In the present study, we explored the therapeutically chemosensitizing effect of β-elemene on cisplatin anti-tumour efficacy in androgen-independent prostate cancer cells as well as the underlying mechanism. β-Elemene significantly increased cisplatin cytotoxicity in the androgen-independent prostate carcinoma cell lines DU145 and PC-3. In addition, β-elemene markedly promoted cisplatin-induced apoptotic cell death in both cell lines, as determined by three different apoptosis assays. β-Elemene augmented the cisplatin-induced activation of caspase-3/7/10 and caspase-9, cleavage of caspase-3 and -9, suppression of Bcl-2 and Bcl-X(L) expression, and release of cytochrome c from mitochondria in these cells. Thus, β-elemene enhancement of cisplatin-induced apoptosis via mitochondrial activation of the caspase-mediated apoptotic pathway may account for the augmented anti-cancer potency of cisplatin in prostate cancer. Cisplatin combined with β-elemene as a chemosensitizer or adjuvant warrants further study and may be potentially useful as a first-line treatment of androgen-independent prostate carcinomas.

Use of 16S ribosomal RNA gene analyses to characterize the bacterial signature associated with poor oral health in West Virginia

BACKGROUND

West Virginia has the worst oral health in the United States, but the reasons for this are unclear. This pilot study explored the etiology of this disparity using culture-independent analyses to identify bacterial species associated with oral disease.

METHODS

Bacteria in subgingival plaque samples from twelve participants in two independent West Virginia dental-related studies were characterized using 16S rRNA gene sequencing and Human Oral Microbe Identification Microarray (HOMIM) analysis. Unifrac analysis was used to characterize phylogenetic differences between bacterial communities obtained from plaque of participants with low or high oral disease, which was further evaluated using clustering and Principal Coordinate Analysis.

RESULTS

Statistically different bacterial signatures (P<0.001) were identified in subgingival plaque of individuals with low or high oral disease in West Virginia based on 16S rRNA gene sequencing. Low disease contained a high frequency of Veillonella and Streptococcus, with a moderate number of Capnocytophaga. High disease exhibited substantially increased bacterial diversity and included a large proportion of Clostridiales cluster bacteria (Selenomonas, Eubacterium, Dialister). Phylogenetic trees constructed using 16S rRNA gene sequencing revealed that Clostridiales were repeated colonizers in plaque associated with high oral disease, providing evidence that the oral environment is somehow influencing the bacterial signature linked to disease.

CONCLUSIONS

Culture-independent analyses identified an atypical bacterial signature associated with high oral disease in West Virginians and provided evidence that the oral environment influenced this signature. Both findings provide insight into the etiology of the oral disparity in West Virginia.

Enteric reovirus infection stimulates peanut-specific IgG2a responses in a mouse food allergy model

IgE-mediated food allergies are an important cause of life-threatening hypersensitivity reactions. Orally administered peanut antigens mixed with the mucosal adjuvant cholera toxin (CT) induce a strong peanut extract (PE)-specific serum IgE response that is correlated with T-helper type 1 (Th1) and type 2 (Th2)-like T-cell responses. This study was conducted to determine if respiratory enteric orphan virus (reovirus), a non-pathogenic virus that induces robust Th1-mediated mucosal and systemic responses could modulate induction of PE-specific allergic responses when co-administered with PE. Young mice were orally exposed to PE mixed with CT, reovirus, or both CT and reovirus. As expected, CT promoted PE-specific serum IgE, IgG1, and IgG2a and intestinal IgA production as well as splenic Th1- and Th2-associated cytokine recall responses. Reovirus did not alter PE-specific serum IgE and IgG1 levels, but substantially increased the PE-specific IgG2a response when co-administered with PE with or without CT. Additionally, reovirus significantly decreased the percentage of the Peyer's patch CD8+ T-cells and Foxp3+CD4+ T-regulatory cells when co-administered with PE. These results demonstrate that an acute mucosal reovirus infection and subsequent Th1 immune response is capable of modulating the Th1/Th2 controlled humoral response to PE. The reovirus-mediated increase in the PE-specific IgG2a antibody response may have therapeutic implications as increased levels of non-allergenic PE-specific IgG2a could block PE antigens from binding to IgE-sensitized mast cells.

Bacterial- and viral-induced inflammation increases sensitivity to acetaminophen hepatotoxicity

Acetaminophen (APAP)-induced hepatotoxicity accounts for nearly half of acute liver failure cases in the United States. The doses that produce hepatotoxicity vary considerably and many risk factors have been proposed, including liver inflammation from viral hepatitis. Interestingly, inflammatory stress from another stimulus, bacterial endotoxin (lipopolysaccharide, LPS), renders the liver more sensitive to hepatotoxicity from numerous xenobiotic agents. The purpose of these studies was to test the hypothesis that inflammation induced by LPS or infection with reovirus increases sensitivity to APAP-induced liver injury. For LPS-induced inflammation, C57BL/6J mice were treated with either saline or LPS (44 x 10(6) EU/kg, ip) 2 h before treatment with APAP (100-400 mg/kg, ip) or saline. No elevation in serum alanine aminotransferase (ALT) activity was observed in mice that received vehicle or LPS alone. LPS co-treatment produced a leftward shift of the dose-response curve for APAP-induced hepatotoxicity and led to significantly greater tumor necrosis factor-alpha (TNF) production than APAP alone. Reovirus serotype 1 (10(8) PFU, iv) induced inflammation in Balb/c mice as evidenced by increases in hepatic mRNAs for macrophage inhibitory protein-2, interleukin-6, and TNF. Co-administration of reovirus and APAP at doses of 450 and 700 mg/kg (2 h after reovirus) led to increases in serum ALT activity, whereas neither reovirus nor APAP alone produced liver injury. Consistent with the increases in serum ALT activity, histopathologic examination revealed centrilobular necrosis with marked neutrophilic accumulation only in livers of mice treated with LPS/APAP or with reovirus/APAP. The results suggest that normally noninjurious doses of APAP are rendered hepatotoxic by modest inflammation, whether bacterial or viral in origin.

beta-Elemene, a novel plant-derived antineoplastic agent, increases cisplatin chemosensitivity of lung tumor cells by triggering apoptosis

beta-Elemene, a new plant-derived anticancer agent with low toxicity, has been reported to be effective in the treatment of leukemia and solid tumors. In the current study, we explored the therapeutic application of beta-elemene in sensitizing lung cancer cells to cisplatin. beta-Elemene considerably enhanced the inhibitory effect of cisplatin on cell proliferation in a time- and dose-dependent manner in the human non-small cell lung cancer (NSCLC) cell lines H460 and A549. Furthermore, this effect of beta-elemene on cisplatin activity occurred through the induction of apoptosis in NSCLC cells, as assessed by an ELISA-based assay, TUNEL assay and annexin V binding assay. Consistent with these results, the protein levels of Bax and phospho-Bcl-2 increased and those of Bcl-2 and XIAP decreased in cells treated with beta-elemene in combination with cisplatin, compared with the levels in cells treated with either agent alone. Finally, beta-elemene augmented the cisplatin-induced increases in caspase-3, -7, -9 and -10 activities and cleaved caspase-3, -9 and poly(ADP-ribose) polymerase levels in NSCLC cells. These observations suggest that beta-elemene sensitizes NSCLC cells to cisplatin via a mitochondria-mediated intrinsic apoptosis pathway involving Bcl-2 family proteins and IAPs (inhibitor of apoptosis proteins). Our data provide a rationale for developing a combination of beta-elemene and cisplatin as a regimen for the treatment of lung carcinoma and other cisplatin-resistant tumors.

In vitro combination characterization of the new anticancer plant drug beta-elemene with taxanes against human lung carcinoma

Beta-elemene has recently raised interest in P.R. China as a novel antitumor plant drug isolated from the Chinese medicinal herb Zedoary. To explore potentially useful combinations of beta-elemene with taxanes in the clinic, we characterized the effects of beta-elemene combined with taxanes in human lung cancer cells using a median effect analysis, micronucleus assay, apoptotic detection, and determination of gene expression in the signaling pathways of apoptosis. The synergistic analysis indicated that the interactions of beta-elemene with paclitaxel or docetaxel ranged from slight synergism to synergism. Combinations of beta-elemene with docetaxel induced much stronger synergistic interactions in p53 mutant H23 cells and p53 null H358 cells than in p53 wild-type H460 and A549 cells. Similar synergistic interactions were observed by micronucleus assay, apoptotic detection, and determination of apoptotic gene expression. Our findings indicate that the synergistic effects achieved with combinations of beta-elemene and taxanes are related to the augmented cytotoxic efficacy of taxanes owing to the action of beta-elemene. In H460 and A549 cells, dose-dependent upregulation of p53 protein expression was observed in cultures treated with docetaxel alone and with docetaxel plus beta-elemene, whereas no significant change in p53 expression was observed in any of the treatment groups in H23 cells. Fas revealed no alteration of expression with any of the treatments in this study. However, the combination treatments induced increased cytochrome c release from mitochondria, significant caspase-8 and -3 cleavage, and downregulation of Bcl-2 and Bcl-XL expression. These results suggest that, although p53 plays an important role in taxane-induced cell death, apoptosis induced by beta-elemene or in combination with docetaxel thereof seems to be initiated through a p53- and Fas-independent pathway via mitochondria in our lung cancer cells. The suppression of specific 'survival' gene expression appears to be the key action leading to the synergistic effect of combination treatments with beta-elemene and taxanes. Finally, the beta-elemene-induced alteration of cell membrane permeability, which has potential to result in enhanced cellular uptake of taxanes, may also contribute to the synergistic interactions of the combination treatments.

Deoxynivalenol Exacerbates Viral Bronchopneumonia Induced by Respiratory Reovirus Infection

The trichothecene mycotoxin deoxynivalenol (DON), a frequent contaminant of cereal grains, is known to dysregulate mucosal and systemic immunity. In this study, we tested the hypothesis that DON interferes with the murine immune response to viral respiratory infection. Female Balb/c mice (5 weeks old) were orally gavaged with DON (10 mg/kg body weight [bw]) or saline vehicle and then intranasally instilled with 10(7) plaque-forming units of reovirus serotype 1, strain Lang (T1/L). At 10-day postinstillation (PI), both viral titers and reovirus L(2) gene expression were 10-fold higher in lungs of DON-treated mice than in saline controls. The lowest observed effective DON dose that impaired viral clearance was 2 mg/kg bw. Although DON amplified reovirus-induced interferon (IFN)-beta and IFN-gamma mRNA responses in lung, the toxin suppressed mRNA expression for IFN-alpha, IFN-alphabeta receptor (IFNAR), and IFN-gamma receptor (IFNGR). DON also impaired induction of two type 1 IFN-dependent antiviral genes, double-stranded RNA activated protein kinase R (PKR) and oligoadenylate synthase 2 (OAS2). Respiratory reovirus infection caused a mild bronchopneumonia in mice which was markedly exacerbated by DON as evidenced by severe inflammatory cell infiltration, marked alveolar damage, and a higher volume density of intraepithelial mucosubstances in pulmonary airways. At 3- and 7-day PI, elevations in total protein, MCP-1, TNF-alpha, total cells, macrophages, neutrophils, and lymphocytes were observed in bronchoalveolar lavage fluid (BALF) of control mice infected with reovirus. DON markedly enhanced viral-induced elevations of protein, MCP-1, TNF-alpha, and inflammatory cells in the BALF at 3-day PI. DON exposure also upregulated induction of reovirus-specific immunoglobulin A (IgA) in BALF, fecal pellets, and serum. DON's effect on BALF IgA was preceded by elevated IL-6 expression and secretion in the lung. Taken together, the results suggest that DON compromised resistance to respiratory viral infection. Reduced expression of IFNAR and type 1 IFN-mediated genes in the lung might contribute to DON impairment of pulmonary reovirus clearance, whereas exacerbation of bronchopneumonia and IgA responses corresponded to increased MCP-1, TNF-alpha, and IL-6 expression.

Production of Alexa Fluor 488-labeled reovirus and characterization of target cell binding, competence, and immunogenicity of labeled virions

Respiratory enteric orphan virus (reovirus) has been used to study many aspects of the biology and genetics of viruses, viral infection, pathogenesis, and the immune response to virus infection. This report describes the functional activity of virus labeled with Alexa Fluor 488, a stable fluorescent dye. Matrix assisted laser desorption-time of flight analysis indicated that Alexa Fluor 488 labeled the outer capsid proteins of reovirus. Labeled virus bound to murine L929 fibroblasts as determined by flow cytometry and fluorescence microscopy, and the specificity of binding were demonstrated by competitive inhibition with non-labeled virus. Labeled reovirus induced apoptosis and cytopathic effect in infected L929 cells. Mice infected with labeled virus mounted robust serum antibody and CD8(+) T-cell responses, indicating that labeled virus retained immunogenicity in vivo. These results indicate that Alexa Fluor 488-labeled virus provides a powerful new tool to analyze reovirus infection in vitro and in vivo.

T-2 toxin impairment of enteric reovirus clearance in the mouse associated with suppressed immunoglobulin and IFN-gamma responses

Trichothecenes are exquisitely toxic to the gastrointestinal (GI) tract and leukocytes and thus are likely to impair gut immunity. The purpose of this research was to test the hypothesis that the Type A trichothecene T-2 toxin interferes with the gut mucosal immune response to enteric reovirus infection. Mice were exposed i.p. first to 1.75 mg/kg bw T-2 and then 2 h later with 3 × 10⁷ plaque-forming units of reovirus serotype 1, strain Lang (T1/L). As compared to vehicle-treated control, T-2-treated mice had dramatically elevated intestinal plaque-forming viral titers after 5 days and failed to completely clear the virus from intestine by 10 days. Levels of reovirus λ2 core spike (L2 gene) RNA in feces in T-2-treated mice were significantly higher at 1, 3, 5, and 7 days than controls. T-2 potentiated L2 mRNA expression in a dose-dependent manner with as little as 50 μg/kg of the toxin having a potentiative effect. T-2 exposure transiently suppressed induction of reovirus-specific IgA in feces (6 and 8 days) as well as specific IgA and IgG_2a in serum (5 days). This suppression corresponded to decreased secretion of reovirus-specific IgA and IgG_2a in Peyer's patch (PP) and lamina propria fragment cultures prepared 5 days after infection. T-2 suppressed IFN-γ responses in PP to reovirus at 3 and 7 days as compared to infected controls whereas IL-2 mRNA concentrations were unaffected. PP IL-6 mRNA levels were increased 2-fold 2 h after T-2 treatment, but no differences between infected T-2-exposed and infected vehicle-treated mice were detectable over the next 7 days. Overall, the results suggest that T-2 toxin increased both the extent of GI tract reovirus infection and fecal shedding which corresponded to both suppressed immunoglobulin and IFN-γ responses.

Regulation of polymeric immunoglobulin receptor expression by reovirus

Polymeric immunoglobulin receptor (pIgR) transcytoses dimeric IgA and IgA-coated immune complexes from the lamina propria across epithelia and into secretions. The effect of reovirus infection on regulation of pIgR expression in the human intestinal epithelial cell line HT-29 was characterized in this report. Both replication-competent and UV-inactivated reovirus at m.o.i. equivalents of 1-100 p.f.u. per cell upregulated pIgR mRNA by 24 h post-infection and intracellular pIgR protein was increased at 48 h following exposure to UV-inactivated virus. Binding of virus to HT-29 cells was required, as pre-incubating virus with specific antiserum, but not non-immune serum, inhibited reovirus-mediated pIgR upregulation. Endosomal acidification leading to uncoating of virus is a required step for pIgR upregulation, as ammonium chloride or bafilomycin A1 pre-treatment inhibited virus-induced pIgR upregulation. Inhibition experiments using the calpain inhibitor N-acetyl-leucyl-leucyl-norleucinal suggested that calpains are involved in reovirus-mediated pIgR upregulation. Upregulation of pIgR following virus infection appears to be an innate immune response against invading pathogens that could help the host clear infection effectively. Signalling induced by microbes and their products may serve to augment pIgR-mediated transcytosis of IgA, linking the innate and acquired immune responses to viruses.

Modulation of Murine Host Response to Enteric Reovirus Infection by the Trichothecene Deoxynivalenol

Based on the known capacity of deoxynivalenol (DON) to target gut lymphoid tissue and IgA production, it was hypothesized that this mycotoxin interferes with the immune response to enteric reovirus infection. When mice were orally gavaged, first with 25 mg/kg bw DON, and then with reovirus serotype 1, strain Lang (T1/L) 2 or 12 h later, viral titers in the GI tract were 10-fold higher than control mice after 5 days. Virus was almost completely cleared in both treatment and control groups from intestinal tissue after 10 days. Real-time PCR indicated that, in infected control mice, reovirus lambda2 core spike (L2 gene) RNA per g feces in infected mice that were pretreated with DON was significantly higher at 1, 3, and 5 days than in infected mice only. In reovirus-infected mice, DON at doses of 10 and 25 mg/kg bw but not 2 and 5 mg/kg bw increased fecal L2 RNA, whereas DON doses as low as 2 mg/kg potentiated L2 RNA levels in Peyer's patches (PP). Reovirus-specific IgA levels in feces of mice treated with DON were significantly elevated, as were specific IgA responses in lamina propria and PP fragment cultures. Similar effects were observed for serum IgA and IgG. DON suppressed IFN-gamma responses in PP to reovirus at 3 and 5 days as compared to infected controls, while IL-2 mRNA concentrations were unaffected. Although reovirus alone did not induce Th2 cytokine mRNAs in PP, DON exposure significantly elevated IL-4, IL-6, and IL-10 mRNA expression at various times during the infection. ELISPOT revealed that mRNA expression data corresponded to suppression of IFN-gamma- and enhancement of IL-4-producing cell responses in PP cultures from DON-treated mice. Taken together, these data suggest that DON transiently increased both severity of the reovirus infection and shedding in feces as well as elevated reovirus IgA responses. These effects corresponded to suppressed Th1 and enhanced Th2 cytokine expression.

Mucosal and systemic immunity to intestinal reovirus infection in aged mice

Systemic immunity is progressively impaired in aging, predisposing to morbidity and mortality from neoplasia and infectious disease. However, the effect of aging on mucosal immunity is controversial. To assess intestinal immunity in aging, young and aged mice were orally exposed to reovirus or cholera toxin (CT) and specific antibody and reovirus-specific cytotoxic T-cell (CTL) responses were assessed. As previously reported, aged mice immunized orally with CT mounted diminished intestinal IgA responses to CT compared to young mice. In contrast, aged mice yielded two to three-fold more reovirus-specific IgA-producing cells in the Peyers's patches (PP) compared to young mice, and higher titers of reovirus-specific IgA in fragment culture supernatants. Cytotoxicity and CTL frequencies from aged mice were not different from those of young mice. Together, these results suggest a diminished potential for systemic and intestinal immunity to orally applied protein antigens in aging, but an intact ability to respond to intestinal virus infection. Infection with a replicating virus may induce inflammatory mediators and innate immune factors that potentiate the priming of mucosal immunity; overcoming aging related deficits otherwise observed following oral immunization with non-replicating antigens, and suggests the importance of antigen replication to antigen-specific immunotherapy strategies in the elderly.

Role of interleukin-4 (IL-4) and IL-10 in serum immunoglobulin G antibody responses following mucosal or systemic reovirus infection

Mucosal and parenteral immunizations elicit qualitatively distinct immune responses, and there is evidence that mucosal immunization can skew the balance of T helper 1 and T helper 2 responses. However, a clear picture of the effect of the route of infection on the balance of the T helper responses has not yet emerged. Our laboratory previously demonstrated that oral reovirus infection elicits specific serum immunoglobulin G2a (IgG2a), while parenteral reovirus infection elicits the mixed production of specific serum IgG2a and IgG1 in mice of the H-2(d) haplotype. Knowing that IgG2a production is indicative of a T helper 1 response and IgG1 production is indicative of a T helper 2 response, we hypothesized that the route of infection influences the development of T helper 1 and T helper 2 responses. Using quantitative reverse transcription-PCR, we found that mRNA for the T helper 1 cytokines gamma interferon and interleukin-12 (IL-12) were expressed in draining lymphoid tissues following both oral and parenteral infections. However, we observed that mRNA for the T helper 2 cytokine IL-10 was suppressed in the Peyer's patches and mesenteric lymph nodes and IL-4 mRNA was suppressed in the mesenteric lymph nodes compared to noninfected controls, following oral infection. Using recombinant cytokines and cytokine knockout mice, we confirmed that IL-4 plays a major role in mediating the route-of-infection-dependent differences in serum IgG subclass responses. Therefore, the route of infection needs to be taken into consideration when developing vaccines and adjuvant therapies.

Influence of the route of infection on development of T-cell receptor beta-chain repertoires of reovirus-specific cytotoxic T lymphocytes

It is well established that the route of infection affects the nature of the adaptive immune response. However, little is known about the effects of the route of exposure on development of cytotoxic T-lymphocyte (CTL) responses. Alternative antigen-presenting cell populations, tissue-restricted expression of class I major histocompatibility complex-encoded molecules, and unique T-cell receptor (TCR)-bearing cells in mucosal tissues could influence the selection and expansion of responder T cells. This study addresses the question of whether the route of virus infection affects the selection and expansion of subpopulations of virus-specific CTLs. Mice were infected orally or in the hind footpads with reovirus, and the repertoires of TCR beta-chains expressed on virus-specific CD8(+) T cells in Peyer's patches or lymph nodes and spleens were examined. CD8(+) cells expressing the variable gene segment of the TCR beta-chain 6 (Vbeta6) expanded in the spleens of mice infected by either route and in CTL lines established from the spleens and draining lymphoid tissues. Adoptively transferred Vbeta6(+) CD8(+) T cells from orally or parenterally infected donors expanded in reovirus-infected severe combined immunodeficient recipient mice and mediated cytotoxicity ex vivo. Furthermore, recovered Vbeta6(+) cells were enriched for clones utilizing uniform complementarity-determining region 3 (CDR3) lengths. However, sequencing of CDR3beta regions from Vbeta6(+) CD8(+) cells indicated that Jbeta gene segment usage is significantly more restricted in CTLs from orally infected mice, suggesting that the route of infection affects selection and/or subsequent expansion of virus-specific CTLs.

Distinct mechanisms for cross-protection of the upper versus lower respiratory tract through intestinal priming

A main feature of the common mucosal immune system is that lymphocytes primed in one mucosal inductive site may home to distant mucosal effector sites. However, the mechanisms responsible for such cross-protection remain elusive. To address these we have used a model of local mucosal infection of mice with reovirus. In immunocompetent mice local duodenal priming protected against subsequent respiratory challenge. In the upper respiratory tract this protection appeared to be mainly mediated by specific IgA- and IgG2a-producing B cells, whereas ex vivo active effector memory CTL were found in the lower respiratory tract. In accordance with these findings, clearance of reovirus from the lower respiratory tract, but not from the upper respiratory tract, of infected SCID mice upon transfer of gut-primed lymphocytes depended on the presence of T cells. Taken together this study reveals that intestinal priming leads to protection of both the upper and lower respiratory tracts, however through distinct mechanisms. We suggest that cross-protection in the common mucosal immune system is mediated by trafficking of B cells and effector memory CTL.

Histologic and immunologic observations of viral-induced rhinosinusitis in the mouse

Viral upper respiratory infection is one of the most common diagnoses made in primary care offices. Although symptoms resolve within 1 week for many patients, a percentage develops rhinosinusitis, and many of these patients are treated with antibiotics. We have developed a model of viral rhinosinusitis using intranasal inoculation of reovirus into mice that were then killed on postinoculation days 2, 4, 7, 10, 14, or 21 and heads were embedded in paraffin for histological and immunohistochemical analyses. Reovirus-like immunoreactivity was noted in the septa and paranasal sinus mucosa in mice as early as day 2, with peak intensity seen on day 4, and scant staining seen on day 7. Complete absence of viral staining was seen by day 10, which corresponded with increased intracellular adhesion molecule 1 immunostaining in the nose. By day 10, a large mucosal influx of B cells was observed, with a moderate influx of macrophages and smaller influx of T cells. By day 14, there was a peak in the number of B cells with a corresponding, but less pronounced peak in T cells, while macrophages began to decline at this point. By day 21, the panel of immune markers returned to near normal levels. The results of this study suggest that the immune system continues to produce a response as long as 2 weeks after clearance of viral antigens. One proposed mechanism for this phenomenon is that local factors such as cytokines are released continually after infection, even in the absence of persistent viruses or bacteria.

Immunologic and histologic observations in reovirus-induced otitis media in the mouse

The goals of this study were to develop a mouse model for virally induced otitis media, and to study the immune response to infection. Intranasal inoculation of mice by reovirus was used to induce otitis media. Immunohistochemical evidence for the presence of reovirus in the nasopharynx, eustachian tubes, and middle ears and the amount of infiltrating B-cells and T-cells in those sites were serially evaluated by painlessly sacrificing animals over a 21 -day period. Reovirus antigen was detected in the middle ear mucosa by day 4 in 75% of infected animals, and histologic evidence for otitis media was found in 54% of all infected animals. A significant increase in B-cells in the nasopharynx and eustachian tubes was noted 7 to 10 days following infection. The number of infiltrating T-cells did not vary significantly from that in the control animals at any of the sites. These results provide a basis for further investigations of the immune response in otitis media.

T-Helper 1 and T-helper 2 cytokine responses in gut-associated lymphoid tissue following enteric reovirus infection

Enteric infection of mice with reovirus serotype 1 elicits antibody and cytotoxic T-lymphocytes in gut-associated lymphoid tissue (GALT). This led to the hypothesis that T-helper 1 (Th1) and T-helper 2 (Th2) responses develop in GALT. Reverse transcriptase-polymerase chain reactions on RNA from Peyer's patches (PP), intraepithelial lymphocytes (IEL), and lamina propria (LP) lymphocytes demonstrated that interferon (IFN)-gamma message was increased in PP and IEL, but not in LP following infection. No increase in mRNA for interleukin (IL)-4, IL-5, or IL-6 was detected. IFN-gamma, IL-5, and IL-6 were produced in in vitro cultures of PP 4-10 days postinfection. PP and spleen lymphocytes from infected mice produced IFN-gamma, but no IL-5 following in vitro restimulation. Infection also induced production of mRNA for the beta2 chain of the IL-12 receptor in PP. We conclude that reovirus induces robust Th1 and weak Th2 cell responses in GALT.

Enteric reovirus infection as a probe to study immunotoxicity of the gastrointestinal tract

The gastrointestinal (GI) tract contains a complex immune system that defends the host against a wide range of pathogens and toxins. The GI tract is also exposed to many environmental toxins that could adversely affect intestinal immunity, and few systems to study immunotoxicity of the GI tract have been described. We demonstrate that intestinal reovirus infection can be used as a system to assess the effects of toxins on intestinal and systemic immunity. Mice were given various doses of cyclophosphamide (CY) for 5 days at doses ranging from 100 to 500 mg/kg by the oral route or 200 mg/kg by the intraperitoneal route. On day 3 of dosing, mice were orally infected with reovirus serotype 1, strain Lang. The effects of CY on viral clearance, intestinal and systemic immune responses, and distribution of intestinal lymphocytes were assessed. Mice treated with CY failed to clear the virus in a dose-dependent manner, and serum anti-reovirus antibody titers were suppressed. Virus-specific IgA in cultures of intestinal tissue from CY-treated mice was significantly reduced compared to controls, although total IgA production was not affected. The virus-specific cytotoxic T-cell response in spleen was also suppressed in CY-treated animals. Cyclophosphamide treatment reduced the number and percentage of B-cells in Peyer's patches. Reovirus infection did not increase cellularity of Peyer's patches in CY-treated mice. Cyclophosphamide treatment also had little effect on the phenotype of intestinal intraepithelial lymphocytes. These data demonstrate that intestinal reovirus infection is useful in studying exposure of the GI tract to immunotoxic agents.

Enhanced mucosal and systemic immune responses to intestinal reovirus infection in beta2-microglobulin-deficient mice

Enteric infection of mice with respiratory enteric orphan virus (reovirus) type 1, strain Lang elicits both humoral and cellular immune responses. To investigate the role of CD8+, alpha/beta T-cell receptor (TCR)+ T cells in mucosal immunity to an enteric pathogen, we examined immune responses and viral clearance following enteric reovirus infection in C57BL/6, B6129F2, and beta2-microglobulin-deficient (beta2m-/-) mice. Analysis of Peyer's patch and lamina propria culture supernatants revealed a two- to threefold increase in levels of reovirus-specific immunoglobulin A in beta2m-/- mice compared to normal controls. These data corresponded to a similar increase in the frequency of virus-specific immunoglobulin A-producing cells in Peyer's patches and lamina propria and an increase in immunoglobulin G-producing cells in spleens from beta2m-/- mice compared to controls. These increased humoral immune responses were not due to a difference in B-cell populations because cell counts and flow cytometric analyses showed that beta2m-/- and control mice had similar numbers and percentages of B cells in mucosal and systemic tissues. Analysis of cytokine message by reverse transcriptase-PCR 5 and 10 days after infection revealed no difference in message level for transforming growth factor beta, gamma interferon, interleukin-4, interleukin-5, or interleukin-6 for all mouse strains. Virus tissue titers determined by plaque assay at 5 and 10 days after infection demonstrated that beta2m-/- mice cleared reovirus from the small intestines with the same efficiency as control mice. Collectively, these data suggest that CD8+, alpha/beta TCR+ T cells may regulate mucosal and systemic humoral immune responses to oral infection with reovirus.

Effects of the route of infection on immunoglobulin G subclasses and specificity of the reovirus-specific humoral immune response

Reovirus serotype 1, strain Lang (T1/L), a well characterized enteric virus, elicits humoral and cellular immune responses in mice. Although orally and intradermally induced infections generate comparable reovirus-specific serum antibody titers, little is known about the effects of the route of infection on the systemic immunoglobulin G (IgG) response. To assess whether the route of exposure affects virus-specific humoral immunity, we infected various strains of mice with reovirus T1/L by the oral or intradermal routes. At day 10 following infection, virus-specific serum antibody titers and IgG subclasses were determined by enzyme-linked immunosorbent assay. Serum IgG2a and IgG2b antibodies were detected in all mouse strains independent of the route of infection. Mice of the H-2d haplotype that received an intradermal infection also had high levels of reovirus-specific serum IgG1. This dichotomy of responses was not associated with differences in the types of cytokine produced by draining peripheral lymph nodes. However, peripheral lymph node lymphocytes from C3H mice produced significantly higher levels of gamma interferon than did BALB/c, C57BL/6, and B10.D2 mice. Additionally, peripheral lymph node lymphocytes from all strains of mice produced only low levels of interleukin-5, with no detectable level of interleukin-4 or interleukin-6. Analysis of specific antibody at inductive sites of the immune response showed that orally infected Peyer's patches produced predominantly IgA and intradermally infected peripheral lymph nodes produced predominantly IgG2a. Western blot (immunoblot) analysis showed that virus-specific IgA, IgG1, and IgG2a reacted with reovirus structural proteins. These data suggest that the route of infection affects the isotype and IgG subclasses, but not the antigen specificity, of the local antibody response. In addition, virus-specific IgG1 generated following an intradermally induced infection is linked to the H-2d major histocompatibility complex haplotype.

3,4-Dichloropropionanilide-induced atrophy of the thymus: mechanisms of toxicity and recovery

The herbicide 3,4-dichloropropionanilide (propanil) has several well-documented neurotoxic and immunotoxic effects on mice. We report here a detailed characterization of the effects of propanil exposure on the thymus. We found that at doses of 100-200 mg/kg, propanil induces significant thymic atrophy between 2 and 7 days postexposure. This atrophy is characterized by a decrease in thymus/body ratio and a decrease in cellularity. Flow cytometric analyses of thymuses from propanil- and vehicle-treated mice indicate that the CD4(+) CD8(+) population of immature cells, is most significantly decreased in propanil-exposed mice. We performed cell cycle analysis of thymocyte populations using two-color surface staining and the DNA binding dye 7-aminoactinomycin D to determine whether thymic atrophy was associated with changes in the percentages of cells in the S, G2, and M phases of the cell cycle. We found a high percentage of proliferating CD4(+)CD8(+) thymocytes 4 days after exposure. Thus, recovery of the thymus occurs following increases in thymocyte proliferation, most notably the immature CD4(+) CD8(+) thymocytes. We tested the hypothesis that glucocorticoids play a role in the observed atrophy by examining thymuses in adrenalectomized, propanil-treated mice. No atrophy was observed in those animals. These results suggest that propanil has an immunotoxic effect on the thymus that appears to be mediated, in part, by endogenous glucocorticoids.

Changes in primary and secondary lymphoid organ T-cell subpopulations resulting from acute in vivo exposure to propanil

Acute exposure to the herbicide propanil is immunotoxic for selected immune functions, as well as causing changes in the weights of the thymus and spleen. Although spleen cellularity and weight increase with propanil exposure, the thymus: body weight ratio decreases with increasing doses of propanil. The present study analyzes the thymocyte subpopulations in the thymus, spleen, and mesenteric lymph nodes. C57Bl/6 mice were treated with either 0, 100, 150, or 200 mg/kg propanil, and 7 d later thymocyte populations were analyzed by flow cytometry. In the thymus, propanil exposure resulted in a dose-dependent decrease in total numbers of T cells, as would be expected with its reduced weight. Determination of the thymocyte subpopulation distribution in the thymus showed a significant reduction in the number of CD3+CD4+CD8- (CD3+4+8-), CD3+CD4-CD8+ (CD3+4-8+), and CD3+CD4+CD8+ (CD3+4+8+) cells. Percent distribution of these thymic cell subpopulations showed similar decreases only with the highest dose. Apparent dose-related decreases in the numbers of CD3-CD4+CD8+ (CD3-4+8+) cells were also noted and were attributed to the general decrease in total thymus cells. The percentage of CD3- subpopulations showed an increasing trend with dose, which suggests that at 7 d postpropanil exposure there may be a specific effect on this most immature population. Although the size and cellularity of the spleen were increased, no change in CD4+ or CD8+ cell distribution was observed. Similarly, mesenteric lymph nodes showed no changes in the cell subpopulation distribution between propanil-treated and control animals.

Morphologic and functional alterations of mucosal T cells by cholera toxin and its B subunit

Despite the mucosal immunogenicity and adjuvanticity in vivo of cholera toxin (CT), both CT and CT B subunit are strong inhibitors of T cell activation in vitro. This study asked whether such T cell inhibition is relevant to the mucosal effects of CT in vivo. The activation of T cells pulsed in vitro for only 15 to 120 min with CT or CT B subunit, respectively, was inhibited, consistent with the expected short exposure times in vivo. Although both CD8+ and CD4+ T cells were inhibited in vitro, CD8+ T cells bound more toxin and were inhibited to a greater degree than were CD4+ T cells. Intestinal gavage of mice with 10 micrograms CT did not alter the overall composition of Peyer's Patch, mesenteric lymph node, or spleen but did cause a marked depletion of intraepithelial lymphocytes, mainly CD8+ T cells, and of lymphocytes in the dome epithelium over Peyer's Patch. To determine whether such inhibition of T cells was functionally relevant in vivo, T cells from mice fed keyhole limpet hemocyanin (KLH) were adoptively transferred into naive recipients, who were then parenterally immunized. T cells from mice fed KLH alone inhibited both the systemic IgG and secretory IgA anti-KLH response, but T cells from mice fed KLH plus CT did not, indicating that mucosally applied CT was able to abrogate the induction of this suppressor T cell. We conclude that one of the mechanisms of CT's mucosal effects in vivo is the inhibition of certain mucosal T cell functions and alteration of the regulatory T cell environment in gut-associated lymphoid tissue.

Morphologic and functional alterations of mucosal T cells by cholera toxin and its B subunit

Despite the mucosal immunogenicity and adjuvanticity in vivo of cholera toxin (CT), both CT and CT B subunit are strong inhibitors of T cell activation in vitro. This study asked whether such T cell inhibition is relevant to the mucosal effects of CT in vivo. The activation of T cells pulsed in vitro for only 15 to 120 min with CT or CT B subunit, respectively, was inhibited, consistent with the expected short exposure times in vivo. Although both CD8+ and CD4+ T cells were inhibited in vitro, CD8+ T cells bound more toxin and were inhibited to a greater degree than were CD4+ T cells. Intestinal gavage of mice with 10 micrograms CT did not alter the overall composition of Peyer's Patch, mesenteric lymph node, or spleen but did cause a marked depletion of intraepithelial lymphocytes, mainly CD8+ T cells, and of lymphocytes in the dome epithelium over Peyer's Patch. To determine whether such inhibition of T cells was functionally relevant in vivo, T cells from mice fed keyhole limpet hemocyanin (KLH) were adoptively transferred into naive recipients, who were then parenterally immunized. T cells from mice fed KLH alone inhibited both the systemic IgG and secretory IgA anti-KLH response, but T cells from mice fed KLH plus CT did not, indicating that mucosally applied CT was able to abrogate the induction of this suppressor T cell. We conclude that one of the mechanisms of CT's mucosal effects in vivo is the inhibition of certain mucosal T cell functions and alteration of the regulatory T cell environment in gut-associated lymphoid tissue.

Developmental relationship between cytotoxic alpha/beta T cell receptor-positive intraepithelial lymphocytes and Peyer's patch lymphocytes

Following intraduodenal priming of mice with reovirus, precursor cytotoxic T lymphocytes (pCTL) rapidly appear in intraepithelial lymphocytes (IEL) and Peyer's patches. These cells express CTL activity after secondary in vitro stimulation with reovirus-infected cells. Adoptive transfer of Peyer's patch lymphocytes from normal BALB/c mice into reovirus-infected CB.17 severe combined immunodeficiency mice results in the infection-dependent appearance of large numbers of both CD8+Thy-1+ and CD8-Thy-1+, IEL that express the alpha/beta T cell receptor (TcR). Phenotypic and functional characterization of IEL derived from conventionally reared, reovirus-infected mice also points to extensive similarities in the pCTL derived from Peyer's patches and IEL. As in the Peyer's patches, pCTL are persistent in the IEL compartment for up to 4 weeks after infection. A large percentage of IEL that are recovered from reovirus-primed mice after in vitro culture are CD8+Thy-1+ cells that express alpha/beta TcR. Furthermore, depletion experiments demonstrate that the CD8+Thy-1+ population mediates the virus-specific CTL activity. Using limiting dilution analyses, it was estimated that 7 days after intraduodenal infection the average frequency of virus-specific pCTL was 197/10(6) CD8+Thy-1+ IEL and 190/10(6) CD8+Thy-1+ Peyer's patch lymphocytes. Taken together, these observations provide evidence that specific cellular immunity to reovirus in IEL is mediated at least in part, by conventional cytotoxic T lymphocytes and that these cells are functionally and phenotypically similar to the pCTL derived from the Peyer's patches.

Viral gastrointestinal infections

Numerous disease-causing viruses of the gastrointestinal tract have been described. The diseases that they induce range from subclinical to fatal gastrointestinal or systemic organ infection. Recent advances in molecular biology and virus culture techniques, as well as improvements in animal models of these infections, have increased our understanding of pathologic processes associated with these viruses. Although our overall understanding of these viruses has improved to the extent that many more viruses can be identified as pathogens, we are still a long way from achieving a thorough understanding of the pathogenesis of viral infection and the mechanisms that mediate immunity.

Passive immunity to fatal reovirus serotype 3-induced meningoencephalitis mediated by both secretory and transplacental factors in neonatal mice

The role of passively acquired immunity to reovirus-induced meningoencephalitis in neonatal mice was examined. It was determined that female mice were capable of conferring protection against viral infection and meningoencephalitis in neonates depending on the route by which the dams were immunized and the serotype of the immunizing virus. Female mice immunized with homotypic virus via the oral route developed the most potent response. Infected neonates born and nursed by these females developed no signs of disease, and no virus was recoverable from their small intestines, livers, or brains following infection. Neonates born to females immunized with homotypic virus by the subcutaneous route manifested no evidence of meningoencephalitis or virus dissemination, yet virus was recovered from neonatal intestines. Mice immunized with heterotypic virus by either the subcutaneous or the oral route also conferred protection against disease; however, virus was recovered in small intestines and livers of infected neonates. Based on results from foster-nursing experiments, it appears that factors obtained both during suckling and by transplacental transfer contribute to protection. Passive transfer of reovirus-immune mouse serum also protected neonates from disease. These results demonstrate that passive immune mechanisms can mediate the protection of neonates against reovirus infection and provide further evidence of the importance of the mucosal immune response in protection against pathogens that invade the host via mucosal tissues.

A further characterization of Candida albicans-induced suppressor B-cell activity

We have previously established that components of the organism Candida albicans are capable of inducing suppressive activity in a population of B lymphocytes. The activity of this population is antigen non-specific. The proliferative response to T-cell, but not B-cell, specific mitogens is inhibited. In addition, the antibody response in vitro is suppressed. Since little is known about this relatively unique regulatory population, we have attempted to characterize both the expression and induction of activity of the Candida-primed cells. Our results show that both primary and secondary T-cell-dependent antibody responses are inhibited, whereas both type I and type II T-cell-independent antibody responses are not affected by the suppressor cell population. T-cell populations responsible for both interleukin-2 (IL-2) and cytolytic activity are also unaffected. These results suggest that while there is no antigen specificity for this population, the suppressive activity is extended to limited target cell populations. Results also suggest that both T cells and accessory cells are required for the induction of the suppressor cell activity, indicating that the Candida organism acts as a typical T-dependent antigen in the induction of regulatory cell activity.

The induction of T-suppressor cells with a soluble extract of Candida albicans

We have previously shown that whole cell preparations of Candida albicans are capable of inducing immunosuppressive B-cell activity both in vivo and in vitro. In an effort to characterize the components of the yeast which manifest this immunomodulatory activity, we have successfully generated a soluble extract with dithiothreitol which exerts immunosuppressive activity. This extract is capable of inducing antigen-nonspecific suppressor cells which inhibit the antibody response of normal cells in coculture. Both primary and secondary antibody responses are suppressed by these cells. Our results also show that the suppressor cell population is a member of the L3T4+ Ly-1+ Lyt-2- T-cell lineage. These results provide evidence that Candida extracts may possess clinically significant immunomodulatory activities.

Reoviruses as probes of the gut mucosal T cell population

Reovirus, serotype 1, causes a transient, asymptomatic infection of the murine intestine when given intraduodenally or orally. However, this infection markedly perturbs both B- and T- cell populations in Peyer's patches (PP) resulting in: 1) a rapid and persistent increase in specific precursors for cytotoxic T cells (pCTL) and a gradient of frequencies highest in PP and lowest in distal lymphoid tissue; 2) a similar increase in memory B cells committed to IgA; 3) the transient appearance of a subset of germinal center B cells identified by MAb, GC-T; 4) the appearance of pCTL among intraepithelial lymphocytes; and 5) the antigen non-specific alteration in Ig isotype potential of B cells previously primed and found in PP. The pCTL appearing upon acute gut mucosal infection with reovirus are Thyl+, Lyt2+, virus-specific, viral serotype non-specific, class I MHC haplotype restricted and occur within the subset of T cells which newly appears also identified by MAb GC-T. Infections of both neonatal and severe-combined immunodeficient mice indicate that the elements of the immune system may operate at many levels to resist, limit, contain, and resolve viral infection.

Induction of suppressor cells in vitro by Candida albicans

Normal splenocytes cultured with Formalin-killed Candida albicans were shown to acquire significant suppressor cell activity in a period of 3 days. These cells were found to suppress both the phytohemagglutinin-induced mitogen response as well as the anti-sheep erythrocyte antibody response. Experiments were carried out to determine the nature of the suppressor cell population. Results showed that these cells were not susceptible to treatment with anti-Thy 1 antibody and complement. Panning experiments showed that the suppressor cells were not plastic-adherent or Mac-1 antigen-positive. The suppressor cells were, however, adherent to anti-mouse immunoglobulin (F(ab')2-fragment)-coated dishes. Additional experiments showed that the suppressor cell activity was susceptible to treatment with monoclonal anti-Lyb 2.1 antibody and complement. These results suggest that the suppressor cell induced in vitro by Candida is a member of the B-lymphocyte lineage.