Deletion of the E3-6.7K/gp19K region reduces the persistence of wild-type adenovirus in a permissive tumor model in Syrian hamsters

A partial deletion of the adenovirus E3 region, comprising the overlapping 6.7K/gp19K genes, has been described for the incorporation of therapeutic genes in 'armed' oncolytic adenoviruses. This deletion allows the insertion of up to 2.5 kb genetic material into the virus and ensures strong expression of transgenes without reducing the replication and cytolytic potency of viruses in vitro. E3-gp19K and 6.7K proteins are involved in avoiding recognition and elimination of infected cells by the host immune system. Therefore, we have studied the effect of this deletion on the replication and transgene expression of the virus in immunocompetent models based on Syrian hamsters. Tumors were established by intrahepatic injection of pancreatic cancer cells with moderate (HaP-T1, HP-1) or low (H2T) permissivity for adenovirus replication. The wild-type human adenovirus 5 (Ad5) or a modified version containing the luciferase gene in the E3-6.7K/gp19K locus (Ad-WTLuc) were injected intratumorally. We found that elimination of Ad-WTLuc was faster than Ad5 in HaP-T1 and HP-1 tumors. In contrast, no differences were observed when the same tumor was established in severely immunocompromised NOD-scid IL2Rgamma(null) mice. In addition, virus-mediated luciferase expression was more stable in these animals. These results suggest that the lack of E3-6.7K/gp19K genes may accelerate the clearance of oncolytic adenoviruses in some immunocompetent tumor models.

Decreased splenic mRNA expression levels of TNF-alpha and IL-6 in diet-induced obese animals

Obesity could be considered as a systemic low-grade inflammatory condition affecting inflammation markers. Adipose tissue synthesizes cytokines whose degree of elevation may depend on the obesity status. Recently, new information is collected on the cross-talking between immune system and adipose tissue in obesity. We report hereby that tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) gene expression in spleen of diet-induced obese animals were markedly decreased (more than 50%) as a consequence of the high fat feeding during five weeks. Interestingly, a very significant negative correlation was found between splenic TNF-alpha mRNA levels and total fat pads (r = -0.806, p = 0.000). These findings support the hypothesis that TNF-alpha gene expression may follow different trends in obese animals adipocytes and splenocytes.

Effects of a beta3-adrenergic agonist on the immune response in diet-induced (cafeteria) obese animals

Molecules with affinity for beta3-adrenoceptors are not only effective anti-obesity agents in rodent models, but may play a role in the regulation of the immune response. The aim of the current investigation was to analyse the effects of trecadrine on the immune response in diet-induced (cafeteria) obese rats. Male Wistar rats were divided into 2 groups, the control group (C, n=9) was fed with the standard pelleted chow laboratory diet, while the other group was fed with a high-fat (cafeteria) diet. Cafeteria-fed rats were divided into two new subgroups (n=9 each), which received either i.p. saline (obese, O) or trecadrine (1mg/kg/day) (obese+trecadrine, O+T) daily for 5 weeks. Lymphocyte subpopulations and the proliferative response were determined by validated procedures. The administration of trecadrine was able to prevent the onset of obesity in cafeteria-fed rats. Trecadrine-treatment to obese animals appeared to improve the number of lymphocyte subpopulations (CD4+ and CD8+) as compared to those animals only receiving the high-fat diet, being the values of the trecadrine-treated animals on the high-fat diet similar to the control rats. However, the lymphoproliferative response when stimulated with several mitogens was markedly reduced by the cafeteria intake and was further decreased by the beta3-adrenergic administration. The spleen mRNA expression level of UCP2, PPARgamma and Ob-Rb were not affected by the trecadrine treatment. Summing up, at the immune system level, trecadrine administration increased the proportion of CD4+ spleen lymphocytes, although it was not able to restore the lymphocyte proliferative response which was depressed.

NF-kappa B-binding activity in an animal diet-induced overweightness model and the impact of subsequent energy restriction

An impaired immune function linked to obesity has been shown in both human and animal studies. The purpose of this work was to analyse the hypothesis that PPAR gamma 1 participates in the inhibition of the immune response by affecting the DNA-binding ability of the NF-kappa B complex and whether the SREBP-1 expression can regulate PPAR gamma 1 expression in spleen. Diet-induced overweight rats showed higher PPAR gamma 1 (p<0.05) and lower SREBP-1 (p<0.01) mRNA expression levels with an inhibition of the DNA-binding ability of NF-kappa B compared to control rats as determined by gel-shift analysis. On the other hand, energy restriction decreased SREBP-1 (p<0.01) mRNA expression with no differences in PPAR gamma 1 mRNA expression compared to non-restricted rats, which was accompanied by a restoration in the DNA-binding ability of NF-kappa B as shown by gel-shift analysis. These results suggest that PPAR gamma 1 may be involved in the altered immune response through changes in the activity of NF-kappa B.

Obesity and immunocompetence

The increasing worldwide prevalence of obesity is a major health problem since excessive body weight constitutes a risk factor in a number of chronic diseases. It has been reported that obese individuals are more susceptible to infection than lean subjects; however, the underlying factors are not fully understood. Limited and often controversial information exists comparing immunocompetence in obese and nonobese subjects as well as the cellular and molecular mechanisms involved, although much evidence supports a link between adipose tissue metabolism and immunocompetent cell functions. The complexity and heterogeneity of nutritional status and immune system interactions require an integral study of the immunocompetent cells, their subsets and products, as well as specific and non-specific inducer/regulatory systems in situations of human obesity. Additional research is needed to determine the clinical implications of these alterations on immunity and whether various interventions such as weight loss, exercise or nutrient supplementation could help to ameliorate them.