A Listeria vaccine and depletion of T-regulatory cells activate immunity against early stage pancreatic intraepithelial neoplasms and prolong survival of mice

BACKGROUND & AIMS

Premalignant lesions and early stage tumors contain immunosuppressive microenvironments that create barriers for cancer vaccines. Kras(G12D/+);Trp53(R172H/+);Pdx-1-Cre (KPC) mice, which express an activated form of Kras in pancreatic tissues, develop pancreatic intraepithelial neoplasms (PanIN) that progress to pancreatic ductal adenocarcinoma (PDA). We used these mice to study immune suppression in PDA.

METHODS

We immunized KPC and Kras(G12D/+);Pdx-1-Cre mice with attenuated intracellular Listeria monocytogenes (which induces CD4(+) and CD8(+) T-cell immunity) engineered to express Kras(G12D) (LM-Kras). The vaccine was given alone or in sequence with an anti-CD25 antibody (PC61) and cyclophosphamide to deplete T-regulatory (Treg) cells. Survival times were measured; pancreatic and spleen tissues were collected and analyzed by histologic, flow cytometry, and immunohistochemical analyses.

RESULTS

Interferon γ-mediated, CD8(+) T-cell responses were observed in KPC and Kras(G12D/+);Pdx-1-Cre mice given LM-Kras, but not in unvaccinated mice. Administration of LM-Kras to KPC mice 4-6 weeks old (with early stage PanINs), depleted of Treg cells, significantly prolonged survival and reduced PanIN progression (median survival, 265 days), compared with unvaccinated mice (median survival, 150 days; P = .002), mice given only LM-Kras (median survival, 150 days; P = .050), and unvaccinated mice depleted of Treg cells (median survival, 170 days; P = .048). In 8- to 12-week-old mice (with late-stage PanINs), LM-Kras, alone or in combination with Treg cell depletion, did not increase survival time or slow PanIN progression. The combination of LM-Kras and Treg cell depletion reduced numbers of Foxp3(+)CD4(+) T cells in pancreatic lymph nodes, increased numbers of CD4(+) T cells that secrete interleukin 17 and interferon γ, and caused CD11b(+)Gr1(+) cells in the pancreas to acquire an immunostimulatory phenotype.

CONCLUSIONS

Immunization of KPC mice with Listeria monocytogenes engineered to express Kras(G12D), along with depletion of Treg cells, reduces progression of early stage, but not late-stage, PanINs. This approach increases infiltration of the lesion with inflammatory cells. It might be possible to design immunotherapies against premalignant pancreatic lesions to slow or prevent progression to PDA.

Hepatotoxicity associated with dietary supplements containing anabolic steroids

BACKGROUND & AIMS

The aim of this article was to re-emphasize the hepatotoxicity associated with the use of anabolic androgenic steroids and to highlight the marketing and sale of anabolic androgenic steroids as dietary supplements.

METHODS

This was a case series of 2 patients who developed a cholestatic liver panel after consumption of anabolic androgenic steroids. A detailed Pubmed/Medline search was performed to research this topic.

RESULTS

We present 2 young men who developed significant cholestatic liver injury after consumption of anabolic androgenic steroids. This was associated with considerable morbidity, although both patients recovered without the need for a liver transplant. Both of these anabolic androgenic steroids were being marketed as dietary supplements.

CONCLUSIONS

Despite being classified as class III controlled substances, anabolic androgenic steroids are still a cause for serious hepatotoxicity in the United States. Some of these anabolic androgenic steroids are being marketed as dietary supplements. Although the Food and Drug Administration is making concerted efforts to regulate this, increased vigilance also is required from the medical profession.

The role of TNF-TNFR2 interactions in generation of CTL responses and clearance of hepatic adenovirus infection

Deficiency or inhibition of tumor necrosis factor (TNF) significantly prolongs hepatic expression of recombinant adenoviral vectors. To explore mechanisms responsible for this observation, the present studies examined the effects of TNF versus TNF receptor 1 (TNFR1) or TNFR2 deficiency on the course of antiviral-immune responses to a replication-deficient, beta-galactosidase-encoding recombinant adenovirus (AdCMV-lacZ). Clearance of AdCMV-lacZ was significantly delayed in TNF-deficient mice. Less pronounced but significant delays in AdCMV-lacZ clearance were observed in TNFR2-deficient but not TNFR1-deficient mice. Numbers of interferon-gamma expressing intrahepatic lymphocytes (IHL) were similar in AdCMV-lacZ-infected, TNF-deficient, TNFR1-deficient, TNFR2-deficient, and control mice. However, IHL isolated from AdCMV-lacZ-infected, TNF-deficient or AdCMV-lacZ-infected, TNFR2-deficient mice exhibited decreased levels of FasL expression and adenovirus-specific cytolytic T lymphocyte (CTL) activity. Similar defects in allo-specific killing of Fas-sensitive hepatocyte targets by TNF-deficient or TNFR2-deficient but not TNFR1-deficient CTL were also noted. No defects in generation of allo-specific cytotoxicity directed against perforin-sensitive target cells were noted in TNF-, TNFR1-, or TNFR2-deficient lymphocytes. These findings indicate that TNF/TNFR2 interactions facilitate generation of FasL-dependent CTL effector pathways that play an important role in in vivo antiviral-immune responses in the liver.

Experimental colitis decreases rat jejunal amino acid absorption: role of capsaicin sensitive primary afferents

Ulcerative colitis and experimental colitis are known to be associated with functional and structural abnormalities of the small intestine. The aim of this study was to determine whether experimental colitis in the rat has any effect on jejunal amino acid absorption and to investigate the neural mechanisms involved. In Sprague Dawley rats, colitis was induced by intracolonic administration of 0.1 ml of 6% iodoacetamide. Alanine absorption in the jejunum was measured using the single pass intraluminal perfusion technique in vivo and the three-compartment model in vitro. Experiments were done in normal and sham treated rats, as well as in rats that underwent neonatal capsaicin treatment, adult capsaicin treatment, or subdiaphragmatic vagotomy. Colitis was more severe in rats subjected to neonatal or adult capsaicin treatment, but was not affected by subdiaphragmatic vagotomy. In rats with colitis, jejunal alanine absorption was reduced by 2% (P>0.05), 28%, 40%, and 18% (P<0.001) at 1, 1.5, 2, and 3 days post rectal iodoacetamide administration. A rebound increase of 12% above baseline was noted at 4 days (P<0.05). Similar results were noted in vitro. In rats that received two consecutive injections of iodoacetamide, the decrease in jejunal alanine absorption occurred earlier, was more severe, and persisted for more than 30 days. Neonatal as well as adult capsaicin treatment aggravated both the colitis and the decrease in jejunal alanine absorption. On the other hand, subdiaphragmatic vagotomy attenuated the decrease in jejunal alanine absorption, but had no significant effect on colitis severity. It is concluded that iodoacetamide induced colitis impairs jejunal amino acid absorption and that this effect involves vagal efferents as well as capsaicin sensitive primary afferents.

Virally infected hepatocytes are resistant to perforin-dependent CTL effector mechanisms

Cell-mediated cytotoxicity plays an important role in the clearance of noncytopathic viruses from infected tissues. Perforin-dependent cytotoxic mechanisms have been noted to play an important role in the clearance of infections from multiple extrahepatic organs. In contrast, mice with defects in the Fas/Fas ligand (FasL)-mediated cytotoxicity pathway exhibit delayed clearance of adenovirus from the liver without apparent delay in the clearance of viral infections from extrahepatic organs. The present studies examined the role of cytotoxic effector mechanisms in intrahepatic immune responses to a replication-defective, recombinant beta-galactosidase-encoding adenovirus (AdCMV-lacZ). Delayed clearance of AdCMV-lacZ from the livers of FasL-defective B6.gld mice, but not perforin-deficient B6.pfp(-/-) mice, was noted despite no significant differences in initial hepatic CD8(+) T cell IFN-gamma or TNF responses or in activation of intrahepatic cytotoxic lymphocytes cells capable of killing AdCMV-lacZ-infected fibroblast targets. In contrast, AdCMV-lacZ-infected hepatocyte targets were far more sensitive to killing by intrahepatic cytotoxic lymphocytes from B6.pfp(-/-) than from B6.gld mice, and residual levels of virus-specific killing of hepatocyte targets by FasL-defective B6.gld CTL were blocked by TNF inhibition. These results suggest that inherent resistance of hepatocytes to cytotoxicity mediated by perforin-dependent mechanisms leaves Fas/FasL-dependent, cell-mediated cytotoxicity as the major pathway for CTL-mediated killing of virally infected hepatocytes and accounts for the more prominent role of perforin-independent anti-viral mechanisms in immune responses in the liver.