Reduced cholesterol accumulation by leptin deficient (ob/ob) mouse macrophages.

OBJECTIVE: Although presenting many aspects of the metabolic syndrome, leptin deficient (ob/ob) mice do not spontaneously develop atherosclerosis. To examine the role of leptin in foam cell formation we analyzed ob/ob leukocyte inflammation markers and macrophage cholesterol accumulation. METHODS: Resident and thioglycollate (TG) elicited peritoneal cells of ob/ob and wildtype mice were studied. Activation markers, scavenger receptors (SR) and cholesterol accumulation were analyzed using flow cytometry and Taqman analysis. Cytokines, haptoglobin, adiponectin and amyloid A levels were analyzed with ELISA. RESULTS: Macrophages of ob/ob mice had reduced expression of MHC class II, CD11b, CD40, SR-A and CD36 and reduced cholesterol accumulation in vitro. Plasma haptoglobin was increased and T-cell IFNgamma was reduced in ob/ob mice. Peritoneal TG instillation induced an unexpectedly weak inflammatory response in ob/ob mice. CONCLUSIONS: The ob/ob mice had a reduced inflammatory response and reduced macrophage cholesterol accumulation in vitro. The data suggest decreased foam cell formation and atherosclerosis development in ob/ob mice.

Peptides spanning the junctional region of both the abl/bcr and the bcr/abl fusion proteins bind common HLA class I molecules.

The Philadelphia (Ph) chromosome, resulting from the t(9;22) translocation, is characteristic of chronic myeloid leukemia (CML). As a result of this translocation, two novel chimeric genes are generated and the bcr/abl and abl/bcr fusion proteins expressed. The bcr/abl fusion mRNA is present in all CML patients, whereas the reciprocal abl/bcr fusion mRNA is detectable in about 80% of the Ph+ CML patients. These fusion proteins may undergo enzymatic degradation in the cytosol and give rise to MHC class I restricted peptide epitopes originating from the junctional regions of the translocation products, which thus may serve as novel tumor specific antigens. Previously, other groups have tested peptides corresponding to the junctional region of the bcr/abl protein for their binding capacity to HLA class I molecules and have identified a few candidate epitopes. Peptides originating from the abl/bcr fusion protein have on the other hand so far been neglected, for no apparent reason. We have now extended these studies to include also the reciprocal abl/bcr translocation product by testing a large panel of synthetic peptides corresponding to the junctional regions of both the abl/bcr and the bcr/abl fusion proteins for their ability to stabilize HLA class I molecules. We find that the abl/bcr translocation product may be an even more important source of CML specific peptide antigens and together the junctional sequences of both these proteins contain peptide sequences which bind efficiently to a number of HLA molecules (HLA-A1, -A2, -A3, -A11, -B7, -B27, -B35) and thus may serve as candidate CML specific tumor antigens.

Susceptibility to polyoma virus tumorigenesis in X-linked immunodeficient (XID) and B-cell deficient (microMT) mice is not increased.

Polyoma virus induced tumorigenesis is controlled by T-cells, while B-cells clear virus infection. In order to study if T-cells can override the tumorigenic effect of a long term disseminated viral infection, the tumorigenicity and persistence of polyoma virus in antibody deficient adult and newborn infected X-linked immunodeficient (XID) and microMT mice was followed. In newborn infected XID and CBA control mice (sensitive to tumorigenesis), the frequency of tumor development was similar, and viral DNA was persistent at least 10 months p.i. In polyoma-infected newborn and adult microMT, and control C57BL/6 mice (resistant to tumorigenesis) as well as in adult XID and CBA control mice, no polyoma tumors were observed. Nevertheless, viral DNA was detected in most tissues in all microMT mice throughout the 5-7 month observation period, whereas in the remaining groups of mice persistent viral infection was limited or not detected. We suggest that the tumorigenic potential of an extensive persistent polyoma virus infection can be overcome as long as a functional T-cell system is present.

Adult X-linked immunodeficiency (XID) mice, IGM-/- single knockout and IGM-/- CD8-/- double knockout mice do not clear polyomavirus infection.

The importance of antibodies for elimination of polyomavirus infection and the prevention of virus induced oncogenesis was studied, X-linked immunodeficiency (XID) mice, IgM-/- single knockout and IgMI-/- CD8-/- double knockout mice, all defective in antibody production, and normal control mice were infected with polyomavirus as adults. The mice were followed for presence of polyoma DNA with a polyoma specific polymerase chain reaction (PCR) over 6 weeks post infection (p.i.), a time point at which polyomavirus DNA is no longer detected in normal adult infected mice. As expected, virus DNA was not detected in normal mice 6 weeks p.i. In both IgM-/- single knockout and IgM-/- CD8-/- double knockout mice a disseminated infection was still observed by 6 weeks p.i. and the latter group of mice succumbed around two months p.i. In XID mice, only one third of the mice were still positive for viral DNA 6 weeks p.i. No polyomavirus induced tumors were observed in any of the mice during the 2-4 month observation period.

Polyoma tumor development in neonatally polyoma-virus-infected CD4-/- and CD8-/- single knockout and CD4-/-8-/- double knockout mice.

CD4-/- or CD8-/- single knockout as well as CD4-/-8-/- double knockout mice were infected with polyoma virus as newborns or 1 week after birth. The animals were followed for tumor development and virus persistence. Double knockout mice developed tumors at a higher incidence (29%) than either the CD8-/- or CD4-/- single knockout mice (11% and 2%, respectively). Persistence of polyoma virus was examined by PCR in one third of all animals included in the study. Seven of the 17 CD4-/-8-/- double knockout mice gave positive evidence of virus persistence up to 6 months p.i. where virus DNA was present in most organs. Corresponding tests in single knockout mice gave positive results of persistent viral DNA in 2 of the 19 CD8-/-and 2 of the 7 CD4-/-mice. In the single knockout mice polyoma DNA could only be detected in a more limited variety of organs compared to the double knockouts.

A short peptide eluted from the H-2Kb molecule of a polyomavirus-positive tumor corresponds to polyomavirus large T antigen peptide at amino acids 578 to 585 and induces polyomavirus-specific immunity.

A short peptide in complex with the H-2Kb molecule on PyRMA, a polyomavirus transfectant of the mouse lymphoma cell line RMA, was identified as a polyomavirus tumor-specific transplantation antigen. The peptide was obtained by affinity chromatography, acidic extraction, and reverse-phase high-pressure liquid chromatography (HPLC). In one HPLC fraction, a peptide sequence in which 5 of 8 amino acids, GKxGLxxA, corresponded to residues 578 to 585 of polyomavirus large T antigen was identified. In tumor rejection assays, we therefore tested three related synthetic peptides, corresponding to the octapeptide LT 578-585, GKTGLAAA; the nonapeptide LT 578-586, GKTGLAAAL; and the decapeptide LT 578-587, GKTGLAAALI. The octapeptide was found to give the most effective immunization against the outgrowth of the polyomavirus DNA-positive PyRMA tumor. However, none of the three peptides immunized against the original polyoma-virus-negative RMA line.

Polyomavirus persists in CD4/8 double-knockout, but not in CD4 or CD8 single-knockout mice.

The effects of incomplete immunocompetence on possible persistence and reactivation of polyomavirus in adult mice were investigated by a polyomavirus-specific polymerase chain reaction (PCR). The presence of virus DNA was followed between 4 days and 2 months postinfection (p.i.) in polyomavirus-infected normal adult A/Sn mice and CD4-/- and CD8-/- single-knockout, as well as CD4-/-8-/- double-knockout BALB/c or C57BL/6 mice. The same study was performed in A/Sn mice immunosuppressed by thymectomy (THX), cytosine-beta-D-arabinofuranoside (Ara-C) treatment, and total body irradiation (TBI). Primary polyomavirus infection of CD4-/- or CD8-/- single-knockout mice was similar to that obtained in normal adult mice when followed by PCR. Viral DNA was detected in a limited number of organs during 4 weeks p.i., but was no longer observed after 1-2 months. In contrast, the virus could be detected in most organs of CD4-/-8-/- double-negative mice and in THX-, Ara-C-, and TBI-treated adult mice and was still present 1-2 months p.i. In polyomavirus-infected normal adult mice a later immunosuppression did not lead to reactivation of the virus. Furthermore, if a second challenge of polyomavirus was administered 4 weeks after primary infection in both normal or recently immunosuppressed mice no viral DNA could be detected by PCR.

In frame deletion of intron-7 in the p53 gene in a human tonsil tumor.

We here report a unique intron deletion in the p53 gene. Analysis of a human tonsil tumor that expressed elevated levels of p53 showed a deletion of the entire intron 7 in one of the p53 alleles, leaving the coding sequence intact. The significance of the intron 7 deletion for the development of the tonsil tumor is discussed.

Involvement of aberrant p53 expression and human papillomavirus in carcinoma of the head, neck and esophagus.

Biopsies from 34 patients with cancer of the head, neck or esophagus, 2 laryngeal papillomas, and 2 normal tonsils were analysed for human papillomavirus (HPV), Epstein Barr virus (EBV) genomes and mutated or elevated levels of p53. In 4 biopsies p53 was also analysed by DNA sequencing. HPV type 31 was found in one laryngeal cancer with normal p53 and HPV type 16 in two tonsil cancers with aberrant p53 expression. EBV was detected by PCR in 11 biopsies, but in situ hybridisation and immunohistochemistry, did not confirm this finding. Aberrant p53 expression was observed in approximately half of the tumours. These results support the involvement of both aberrant p53 expression and HPV in the aetiology of squamous cell carcinoma of the head and neck.

Persistence of polyomavirus in adult SCID C.B-17 mice.

C.B-17 mice with the Severe Combined Immune Deficiency (SCID) mutation were infected with the naturally occurring murine polyomavirus. Using the Polymerase Chain Reaction (PCR) technique, persistence of polyomavirus was followed in different tissues of the mice between 24 hours and 2 months post infection (p.i.). Viral DNA appeared by 3-5 days and was detected in all studied organs by 3 weeks p.i. From 4 weeks to 2 months p.i. viral DNA was present at high levels in all studied organs in all of the animals. As controls normal C.B-17 and A/Sn mice were used. Viral DNA appeared by 2-4 days. The infection reached a peak around 1 week p.i. This was followed by a clearing stage and viral DNA was no longer detectable by 4-5 weeks p.i. Most organs studied with PCR were also examined histologically, but no lesions were observed. Consequently persistence and organ distribution of polyomavirus in adult SCID mice differs greatly from that in normal adult mice.

Persistence of polyomavirus in mice infected as adults differs from that observed in mice infected as newborns.

By using the polymerase chain reaction (PCR) technique, a technique more sensitive than Southern analysis, which allows detection of polyomavirus DNA only in newborn and nude adult mice, it has now been possible to monitor the persistence pattern of polyomavirus DNA after infection of normal adult CBA mice for the first time. Viral signs appeared gradually, showing variations in time course and organ distribution between mice, and reached a peak activity after 2 to 3 weeks, when they could be found in bone, heart, gonads, lymph node, and skin, but disappeared by 2 to 5 months. No virus DNA was detected in the kidneys or lungs, which is in contrast to what is observed after infection of newborn mice. This finding suggests that the persistence pattern of polyomavirus is age dependent.