(1/7909) Suppression of Moloney sarcoma virus immunity following sensitization with attenuated virus.

Murine sarcoma virus (Moloney strain) (MSV-M)-induced tumors are unusual in that they regularly appear less than 2 weeks after virus inoculation, progress for 1 to 2 weeks, and are rejected by normal adult BALB/c mice. Rejectio leaves the animals immune to tumor induction. In the present study, presensitization of normal adult BALB/c mice with attenuated MSV-M resulted in an altered pattern of tumor immunity. Injection of active MSV-M into the presensitized animals resulted in tumor induction and rejection similar to that observed in normal animals, but rejection failed to produce protection against the secondary inoculation with MSV-M. After the second inoculation with active MSV-M, tumors appeared and progressed but ultimately were rejected. Over 80% of the mice died, 25% after the primary challenge and the remainder after the secondary challenge. At death, all mice had histological evidence of leukemia which was the probable cause of death. The animals that died following the secondary challenge also had evidence of disseminated MSV-M. Solid tumor nodules were found in skeletal muscle distant from the original site of inoculation, and active MSV-M was isolated from spleen and lungs. The possibility that the results were produced by specific suppression of MSV-Moloney leukemia virus immunity is discussed.  (+info)

(2/7909) Transcutaneous immunization with bacterial ADP-ribosylating exotoxins as antigens and adjuvants.

Transcutaneous immunization (TCI) is a new technique that uses the application of vaccine antigens in a solution on the skin to induce potent antibody responses without systemic or local toxicity. We have previously shown that cholera toxin (CT), a potent adjuvant for oral and nasal immunization, can induce both serum and mucosal immunoglobulin G (IgG) and IgA and protect against toxin-mediated mucosal disease when administered by the transcutaneous route. Additionally, CT acts as an adjuvant for coadministered antigens such as tetanus and diphtheria toxoids when applied to the skin. CT, a member of the bacterial ADP-ribosylating exotoxin (bARE) family, is most potent as an adjuvant when the A-B subunits are present and functional. We now show that TCI induces secondary antibody responses to coadministered antigens as well as to CT in response to boosting immunizations. IgG antibodies to coadministered antigens were also found in the stools and lung washes of immunized mice, suggesting that TCI may target mucosal pathogens. Mice immunized by the transcutaneous route with tetanus fragment C and CT developed anti-tetanus toxoid antibodies and were protected against systemic tetanus toxin challenge. We also show that bAREs, similarly organized as A-B subunits, as well as the B subunit of CT alone, induced antibody responses to themselves when given via TCI. Thus, TCI appears to induce potent, protective immune responses to both systemic and mucosal challenge and offers significant potential practical advantages for vaccine delivery.  (+info)

(3/7909) Zonula occludens toxin is a powerful mucosal adjuvant for intranasally delivered antigens.

Zonula occludens toxin (Zot) is produced by toxigenic strains of Vibrio cholerae and has the ability to reversibly alter intestinal epithelial tight junctions, allowing the passage of macromolecules through the mucosal barrier. In the present study, we investigated whether Zot could be exploited to deliver soluble antigens through the nasal mucosa for the induction of antigen-specific systemic and mucosal immune responses. Intranasal immunization of mice with ovalbumin (Ova) and recombinant Zot, either fused to the maltose-binding protein (MBP-Zot) or with a hexahistidine tag (His-Zot), induced anti-Ova serum immunoglobulin G (IgG) titers that were approximately 40-fold higher than those induced by immunization with antigen alone. Interestingly, Zot also stimulated high anti-Ova IgA titers in serum, as well as in vaginal and intestinal secretions. A comparison with Escherichia coli heat-labile enterotoxin (LT) revealed that the adjuvant activity of Zot was only sevenfold lower than that of LT. Moreover, Zot and LT induced similar patterns of Ova-specific IgG subclasses. The subtypes IgG1, IgG2a, and IgG2b were all stimulated, with a predominance of IgG1 and IgG2b. In conclusion, our results highlight Zot as a novel potent mucosal adjuvant of microbial origin.  (+info)

(4/7909) Noncompetitive expansion of cytotoxic T lymphocytes specific for different antigens during bacterial infection.

Listeria monocytogenes is an intracellular bacterium that elicits complex cytotoxic T-lymphocyte (CTL) responses in infected mice. The responses of CTL populations that differ in antigen specificity range in magnitude from large, dominant responses to small, subdominant responses. To test the hypothesis that dominant T-cell responses inhibit subdominant responses, we eliminated the two dominant epitopes of L. monocytogenes by anchor residue mutagenesis and measured the T-cell responses to the remaining subdominant epitopes. Surprisingly, the loss of dominant T-cell responses did not enhance subdominant responses. While mice immunized with bacteria lacking dominant epitopes developed L. monocytogenes-specific immunity, their ability to respond to dominant epitopes upon rechallenge with wild-type bacteria was markedly diminished. Recall responses in mice immunized with wild-type or epitope-deficient L. monocytogenes showed that antigen presentation during recall infection is sufficient for activating memory cells yet insufficient for optimal priming of naive T lymphocytes. Our findings suggest that T-cell priming to different epitopes during L. monocytogenes infection is not competitive. Rather, T-cell populations specific for different antigens but the same pathogen expand independently.  (+info)

(5/7909) Ovine MHC class II DRB1 alleles associated with resistance or susceptibility to development of bovine leukemia virus-induced ovine lymphoma.

For the further characterization of bovine leukemia virus (BLV)-induced leukemogenesis, we investigated the association between polymorphism of ovine leukocyte antigen (OLA)-DRB1 gene and tumor development after infection of sheep with BLV. We infected 28 sheep with BLV and cloned exon 2 of the OLA-DRB1 gene from asymptomatic animals and from animals with lymphoma Sequence analysis revealed that, among 12 healthy sheep without any evidence of tumor, ten (83.3%) carried DRB1 alleles encoding Arg-Lys (RK) at positions beta70/71 as compared with only 6 (37.5%) of the 16 sheep with lymphoma, which suggested that alleles encoding the RK motif might protect against development of tumors after infection by BLV. By contrast, alleles encoding Ser-Arg (SR) at positions beta70/71 were present at a significantly elevated frequency in sheep with lymphoma as compared with the healthy carriers, which indicated that OLA-DRB1 alleles encoding the SR motif might be positively related to susceptibility to tumor development. The two amino acids in these motifs line a pocket that accommodates the side chain of a bound peptide according to a model of the crystal structure of human leukocyte antigen (HLA)-DR1. To analyze immunoreactions of sheep with alleles that encoded RK or SR at beta70/71, we selected sheep with either the RK/SR genotypes or the SR/SR genotypes and immunized them with a mixture of multiple synthetic antigenic peptides that corresponded to T-helper, T-cytotoxic, and B-cell epitopes of the BLV envelope glycoprotein gp51. Two weeks after the last immunization, all of the sheep were challenged with BLV. Sheep with the RK/SR genotype produced neutralizing antibodies against BLV; they eliminated BLV completely within 28 weeks of the BLV challenge, and they gave strong lymphocyte-proliferative responses to the peptides used for immunization. Moreover, such animals did not develop lymphoma. By contrast, sheep with the SR/SR genotype continued to produce BLV throughout the experimental period and developed terminal disease. Our results indicate that the differences in immunoresponse were due to differences in major histocompatibility complex class II alleles and reflected the risk of BLV-induced leukemogenesis. In addition, it appears that susceptibility to tumor development may be determined to some extent by polymorphic residues binding to antigenic peptides directly within the binding cleft of the OLA-DR molecule.  (+info)

(6/7909) Immunosurveillance and the evaluation of national immunization programmes: a population-based approach.

Mass vaccination can change the epidemiological dynamics of infectious diseases. It may result in a limited persistence of natural and vaccine-induced immunity and a higher mean age of infection, which may lead to a greater risk of complications. The epidemiological situation should be monitored and immunosurveillance based on the assessment of specific antibodies against vaccine-preventable diseases in human serum is one of the tools. In order to estimate the immunity of the Dutch population reliably, a large-scale, population-based, collection of serum samples was established (8359 sera in a nation-wide sampling and 1589 sera from municipalities with low vaccine coverage). In contrast to collecting residual sera from laboratories, this approach gains extensive information by means of a questionnaire regarding the determinants of the immune status and the risk factors for the transmission of infectious diseases in general. The population-based approach gives a better guarantee that the data are representative than collecting sera from laboratories does.  (+info)

(7/7909) Rubella immunisation and contraception--a case for re-examining the policy of the Department of Health and Social Security.

Now that immunisation against rubella is available, it would at first sight seem reasonable to identify all potential mothers susceptible to this disease and immunise them. Preliminary screening, however, carried out in order to restrict vaccination to seronegative subjects, not only serves no useful purpose, but is counter-productive.  (+info)

(8/7909) Chlamydia infections and heart disease linked through antigenic mimicry.

Chlamydia infections are epidemiologically linked to human heart disease. A peptide from the murine heart muscle-specific alpha myosin heavy chain that has sequence homology to the 60-kilodalton cysteine-rich outer membrane proteins of Chlamydia pneumoniae, C. psittaci, and C. trachomatis was shown to induce autoimmune inflammatory heart disease in mice. Injection of the homologous Chlamydia peptides into mice also induced perivascular inflammation, fibrotic changes, and blood vessel occlusion in the heart, as well as triggering T and B cell reactivity to the homologous endogenous heart muscle-specific peptide. Chlamydia DNA functioned as an adjuvant in the triggering of peptide-induced inflammatory heart disease. Infection with C. trachomatis led to the production of autoantibodies to heart muscle-specific epitopes. Thus, Chlamydia-mediated heart disease is induced by antigenic mimicry of a heart muscle-specific protein.  (+info)