Induction and detection of T-cell responses

Reciprocal effects of Th1 and Treg cell inducing pathogen-associated immunomodulatory molecules on anti-tumor immunity

We have addressed the hypothesis that pathogen-associated immunomodulatory molecules may influence anti-tumor immunity through their pro- and anti-inflammatory activities and abilities to induce effector and regulatory T (Treg) cells. We found that CpG oligonucleotides (CpG) and cholera toxin (CT), which promote Th1 or Th2/Treg cell biased responses, respectively, had differential effects on tumor growth. Therapeutic peritumoral administration of CpG significantly reduced subcutaneous tumor growth and prolonged survival, whereas CT enhanced tumor growth and reduced survival. Peritumoral administration of CpG enhanced the frequency of IFN-gamma-secreting and reduced IL-10-secreting CD4(+) and CD8(+) T cells, in the tumor and in the draining lymph nodes, whereas, CT significantly enhanced the frequency of CD4(+)CD25(+)Foxp3(+) Treg cells, but reduced IFN-gamma-secreting T cells infiltrating the tumor. In contrast to the beneficial effect of CpG in mice with subcutaneous tumors, CpG or CT had no protective effect against tumor growth in the lungs when given therapeutically by the nasal route. However, prophylactic intranasal administration of CpG significantly reduced the number of lung metastases and this was associated with an enhanced frequency of IFN-gamma-secreting CD8(+) T cells in the draining lymph node and enhanced tumor-specific CTL responses. Our findings demonstrate that pathogen-associated molecules can either inhibit or enhance anti-tumor immunity by selectively promoting the induction of effector or regulatory T cells, and that the environment of the growing tumor influences the protective effect.

Cell mediated immune response elicited in mice after immunization with the P64k meningococcal protein: epitope mapping

The P64k protein of Neisseria meningitidis has been reported as an immunological carrier for weak immunogens. This investigation was aimed at characterizing the T-cell response produced in primed mice and at identifying T helper cell epitopes within this molecule. BALB/c mice subcutaneously immunized with the recombinant antigen provided inguinal lymph node cells (LNC) that proliferated in the presence of P64k in a dose-dependent manner. Proliferating cells secreted IL-4 while the concentration of IL-12 remained unaltered in the culture supernatant. By testing a panel of 59 overlapping synthetic peptides spanning the entire sequence of the antigen a T-cell determinant was localized. Prime-boost and lymphoproliferation experiments, conducted with highly purified synthetic peptides, confirmed that the segment including amino acids 470-485 comprises a T-cell epitope within the P64k molecule.

Fasciola hepatica infection downregulates Th1 responses in mice

Immune responses induced with helminth parasites have been extensively studied, but there is limited information on those to Fasciola hepatica, especially on the subtype of T cell induced with this parasite. We investigated the local and systemic T cell responses of different strains of mice following oral infection with doses of metacercariae from F. hepatica. Spleen cells from BALB/c and 129Sv/Ev mice given a low-dose (5 metacercariae) infection exhibited a Th2 response, producing high levels of the cytokines IL-4 and IL-5, and low levels of IFN-gamma and IL-2. In contrast, C57BL/6 mice showed a mixed Th1/Th2 response. A more marked polarization to a Th2 response was observed in BALB/c, 129Sv/Ev exposed to a high-dose (15 metacercariae) infection and the C57BL/6 mice also exhibited a clear Th2 response. IL-4 defective (IL-4-/-) C57BL/6 mice infected with 5 metacercariae produced less IFN-gamma and more IL-5 compared to their wild-type C57BL/6 counterparts, suggesting that IL-4 is important in establishing the Th2 type response in murine fasciolosis. However, the secretion of IFN-gamma and IL-2 was completely suppressed in the high-dose infection and this was also observed in IL-4-/- mice. Thus, liver flukes may secrete molecules that downregulate Th1 responses. T cell responses in the mesenteric (MLN) and hepatic lymph nodes (HLN) were also examined since newly excysted juveniles infect through the intestinal wall of their host before migrating to the hepatic tissue. Cells from both MLN and HLN secreted higher levels of IL-4 and IL-5 compared to spleen cells. We also observed a difference in cytokine profiles secreted by the MLN and HLN, which may reflect responses to antigens liberated by newly excysted juveniles and hepatic stage parasites, respectively.

Induction of inflammatory cytokines in the brain following respiratory infection with Bordetella pertussis

Parenteral injection of endotoxin has been used as a model to examine the role of pro-inflammatory cytokines in the centrally controlled responses to Gram-negative bacterial infection. However, the events that occur following mucosal exposure to live bacteria have received little attention. In this study, we have used a murine model to demonstrate that respiratory infection with Bordetella pertussis, which is associated with a number of systemic complications including fever, seizure and encephalopathy in children, resulted in persistent expression of mRNA transcripts for IL-1beta and TNFalpha and transient expression of IL-6 in the hippocampus and hypothalamus. These changes correlated with elevated levels of cytokine protein in the same brain areas. The results demonstrate that infection at a mucosal surface can result in the induction of pro-inflammatory cytokine production in the brain and suggest that these locally synthesized mediators may contribute to the centrally controlled clinical manifestations of B. pertussis infection.