Uncoupling protein 2 (UCP2) uncouples respiration from oxidative phosphorylation and may contribute to obesity through effects on energy metabolism. Because basal metabolic rate is decreased in obesity, UCP2 expression is predicted to be reduced. Paradoxically, hepatic expression of UCP2 mRNA is increased in genetically obese (ob/ob) mice. In situ hybridization and immunohistochemical analysis of ob/ob livers demonstrate that UCP2 mRNA and protein expression are increased in hepatocytes, which do not express UCP2 in lean mice. Mitochondria isolated from ob/ob livers exhibit an increased rate of H ؉ leak which partially dissipates the mitochondrial membrane potential when the rate of electron transport is suppressed. In addition, hepatic ATP stores are reduced and these livers are more vulnerable to necrosis after transient hepatic ischemia. Hence, hepatocytes adapt to obesity by up-regulating UCP2. However, because this decreases the efficiency of energy trapping, the cells become vulnerable to ATP depletion when energy needs increase acutely.Obesity results from an imbalance between energy intake and energy expenditure (1). Uncoupling protein (UCP) 1 homologues uncouple mitochondrial respiration from oxidative phosphorylation, increasing thermogenesis while reducing the efficiency of ATP synthesis (2). While UCP1 is expressed exclusively in brown fat, UCP2 and UCP3 are also expressed in white fat and skeletal muscle (3). The tissue distribution of UCP2 and UCP3 has provoked speculation that these two proteins may be important regulators of energy homeostasis in adults (4), a possibility that is supported by evidence that the UCP2-UCP3 gene cluster maps to regions of human and murine chromosomes that have been linked to obesity (5).Because net energy expenditure is reduced in obese subjects, UCP2 and/or UCP3 expression or activity are predicted to be decreased. However, experimental evidence for this is relatively limited. A recent study of 6 lean and 6 obese, but otherwise healthy, men demonstrated a slight, but consistent, reduction in UCP2 mRNA levels in the abdominal muscle of the obese subjects (6). Polymorphisms of UCP2, but not UCP3, have been associated with decreased basal metabolic rate in young Pima Indian men, although UCP2 mRNA levels in skeletal muscle were not influenced (5). In mice, resistance to obesity induced by feeding high fat diets has been associated with an early, selective induction of UCP1 and UCP2 in brown and white fat, respectively, but not with changes in UCP3 expression (7).On the other hand, this evidence that decreased UCP2 may promote obesity is difficult to reconcile with observations that ob/ob and db/db obese mice have increased UCP2 mRNA levels in white adipose tissue (8), and that UCP2 mRNA levels in white fat are positively correlated with body mass index in humans (9). Also confusing are reports that caloric restriction, a situation that decreases resting energy expenditure, leads to increased UCP2-UCP3 mRNA expression in white fat and skeletal muscle in both obese and l...

Two recombinant Listeria monocytogenes (rLm) strains were produced that secrete the human papilloma virus-16 (HPV-16) E7 protein expressed in HPV-16-associated cervical cancer cells. One, Lm-E7, expresses and secretes E7 protein, whereas a second, Lm-LLO-E7, secretes E7 as a fusion protein joined to a nonhemolytic listeriolysin O (LLO). Lm-LLO-E7, but not Lm-E7, induces the regression of the E7-expressing tumor, TC-1, established in syngeneic C57BL/6 mice. Both recombinant E7-expressing rLm vaccines induce measurable anti-E7 CTL responses that stain positively for H-2Db E7 tetramers. Depletion of the CD8+ T cell subset before treatment abrogates the ability of Lm-LLO-E7 to impact on tumor growth. In addition, the rLm strains induce markedly different CD4+ T cell subsets. Depletion of the CD4+ T cell subset considerably reduces the ability of Lm-LLO-E7 to eliminate established TC-1 tumors. Surprisingly, the reverse is the case for Lm-E7, which becomes an effective anti-tumor immunotherapeutic in mice lacking this T cell subset. Ab-mediated depletion of TGF-β and CD25+ cells improves the effectiveness of Lm-E7 treatment, suggesting that TGF-β and CD25+ cells are in part responsible for this suppressive response. CD4+ T cells from mice immunized with Lm-E7 are capable of suppressing the ability of Lm-LLO-E7 to induce the regression of TC-1 when transferred to tumor-bearing mice. These studies demonstrate the complexity of L. monocytogenes-mediated tumor immunotherapy targeting the human tumor Ag, HPV-16 E7.

The presentation of antigenic peptides by major histocompatibility complex (MHC) class II molecules to CD4+ T cells is critical to the function of the immune system. In this study, we have utilized the sorting signal of the lysosomal-associated membrane protein LAMP-1 to target a model antigen, human papillomavirus 16 E7 (HPV-16 E7), into the endosomal and lysosomal compartments. The LAMP-1 sorting signal reroutes the antigen into the MHC class II processing pathway, resulting in enhanced presentation to CD4+ cells in vitro. In vivo immunization experiments in mice demonstrated that vaccinia containing the chimeric E7/LAMP-1 gene generated greater E7-specific lymphoproliferative activity, antibody titers, and cytotoxic T-lymphocyte activities than vaccinia containing the wild-type HPV-16 E7 gene. These results suggest that specific targeting of an antigen to the endosomal and lysosomal compartments enhances MHC class II presentation and vaccine potency.The presentation of antigenic peptides by major histocompatibility complex (MHC) class II molecules to CD4+ T cells is critical to the function of the immune system. CD4+ T cells are the major helper T-cell phenotype whose predominant function is to generate cytokines that regulate essentially all other functions of the immune response. CD4+ MHC class II restricted cells have also been shown to have cytotoxic capacity in a number of systems, including a response to fragments of the human immunodeficiency virus gpl20 protein (1). CD4+ cells have also been shown to be of great importance in immune responses against several different murine (2, 3) and human (4) solid malignancies. Several mouse tumors that were transfected with syngeneic MHC class II genes have become very effective vaccines against subsequent challenge with wild-type (wt) class II negative tumors (5). For these reasons, there has been increased interest in developing strategies that will most effectively activate CD4+ MHC class II restricted cells against a given specific antigen (6).Two major pathways by which antigens enter endosomal and lysosomal compartments for MHC class II presentation to CD4+ T cells have been described. The traditional pathway involves the phagocytosis or endocytosis of exogenous proteins into antigen-presenting cells (APCs), followed by degradation by acid proteases in the endosomal or lysosome-like compartments (7-9). A second pathway involves the processing of membrane proteins endogenously synthesized by APCs (1, 10). These membrane proteins are believed to enter endosomal and lysosomal compartments by internalization from the cell surface. In certain experimental systems, cytoplasmic proteins may also enter this endogenous MHC class II pathway (11, 12), but normally these antigens are preferentially routed for MHC class I presentation. In general, cytoplasmic or nuclear proThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to in...

Antigen-specific cancer immunotherapy and antiangiogenesis have emerged as two attractive strategies for cancer treatment. An innovative approach that combines both mechanisms will likely generate the most potent antitumor effect. We tested this approach using calreticulin (CRT), which has demonstrated the ability to enhance MHC class I presentation and exhibit an antiangiogenic effect. We explored the linkage of CRT to a model tumor antigen, human papilloma virus type-16 (HPV-16) E7, for the development of a DNA vaccine. We found that C57BL/6 mice vaccinated intradermally with CRT/E7 DNA exhibited a dramatic increase in E7-specific CD8 + T cell precursors and an impressive antitumor effect against E7-expressing tumors compared with mice vaccinated with wild-type E7 DNA or CRT DNA. Vaccination of CD4/CD8 double-depleted C57BL/6 mice and immunocompromised (BALB/c nu/nu) mice with CRT/E7 DNA or CRT DNA generated significant reduction of lung tumor nodules compared with wild-type E7 DNA, suggesting that antiangiogenesis may have contributed to the antitumor effect. Examination of microvessel density in lung tumor nodules and an in vivo angiogenesis assay further confirmed the antiangiogenic effect generated by CRT/E7 and CRT. Thus, cancer therapy using CRT linked to a tumor antigen holds promise for treating tumors by combining antigen-specific immunotherapy and antiangiogenesis.

Cancer of the uterine cervix is the second largest cause of cancer deaths in women, and its toll is greatest in populations that lack screening programmes to detect precursor lesions. Persistent infection with 'high risk' genotypes of human papillomavirus (HPV) is necessary, although not sufficient, to cause cervical carcinoma. Therefore, HPV vaccination provides an opportunity to profoundly affect cervical cancer incidence worldwide. A recently licensed HPV subunit vaccine protects women from a high proportion of precursor lesions of cervical carcinoma and most genital warts. Here we examine the ramifications and remaining questions that surround preventive HPV vaccines.Epidemiological and laboratory studies overwhelmingly support a necessary role for persistent human papillomavirus (HPV) infection and transcription in cervical carcinogenesis 1,2 (BOX 1). Importantly, HPV infection alone is not sufficient for cervical carcinogenesis, and additional steps occur over one or two decades. HPV is probably the most common sexually transmitted disease. It is estimated that the worldwide agestandardized prevalence of current HPV infection is 10.5% (95% CI 9.9-11.0) of women; the prevalence varies about 20-fold between different regions, from 1.4% (95% CI 0.5-2.2) in Spain to , although adenocarcinomas of the cervix are more challenging to detect with this approach. Progression to cancer can usually be prevented by the ablation or surgical removal of high-grade precursor lesions (HSIL or CIN2/3). In 2005, more than 60 million Pap smears were performed in the United States, and it is estimated that such screening programmes and intervention have reduced the incidence of cervical cancer by ~80% in the United States, but at a cost of more than US$6 billion a year.Despite this success, many women do not have access to screening. This problem is most acute in disadvantaged minorities in developed nations, in cultures that do not accept the screening process and in countries that are remote and lack the resources for screening programmes. Consequently, the impact of cervical cancer is greatest in these countries; the latest global estimates (from 2002) are 493,000 new cervical cancer cases each year, and 274,000 deaths, 80% of which occur in developing countries 8 .Vaccination traditionally represents the most cost-effective approach to combat infectious disease. Two approaches to vaccination, or a combination of both, can be considered: prophylactic (preventive) and therapeutic immunization. Prophylactic vaccination of healthy individuals against the aetiological agent protects against acquisition of the disease, but confers some risk to otherwise healthy patients and requires massive programmes to vaccinate a significant fraction of the population. Comprehensive prophylactic vaccination has historically proven most successful in disease reduction. The US Food and Drug Administration (FDA) approved a preventive HPV vaccine on 8 June 2006 for the immunization of women between 9-26 years of age 9 , and a second vacci...