Long-term CD4+ and CD8+ memory T cells developed in severe combined immunodeficiency mice during homoeostasis exhibit differences in sensitivity to antigen

Differences in HIV-specific T cell responses between HIV-exposed and -unexposed HIV-seronegative individuals

HIV-1-specific T lymphocyte responses in individuals exposed to HIV-1 but who remain persistently seronegative (HESNs) have been reported in some but not all previous studies. This study was designed to resolve unequivocally the question of whether HESNs make HIV-1-specific T cell responses. We performed a blind investigation to measure HIV-1-specific T cell responses in both HIV-1-serodiscordant couples and HIV-1-unexposed seronegative controls (HUSNs). We found low-frequency HIV-1-specific T cells in both HESNs and HUSNs but show that the response rates were higher over time in the former (P = 0.01). Furthermore, the magnitudes of the HIV-1-specific T cell responses were significantly higher among responding HESNs than among HUSNs over time (P = 0.002). In both groups, responses were mediated by CD4 T cells. The responses were mapped to single peptides, which often corresponded to epitopes restricted by multiple HLA-DR types that have previously been detected in HIV-1-infected patients. HIV-1-specific T cell responses in HUSNs and some HESNs likely represent cross-reactivity to self or foreign non-HIV-1 antigens. The significantly greater T cell responses in HESNs, including in two who were homozygous for CCR5Δ32, demonstrates that HIV-1-specific T cell responses can be induced or augmented by exposure to HIV-1 without infection.

The Rb1 fraction of ginseng elicits a balanced Th1 and Th2 immune response

Porcine parvovirus (PPV) vaccines containing different adjuvants were evaluated for inducing Th1 or Th2 type of immunity in mice. Isotypes of antigen specific antibodies and levels of cytokines in serum and in lymphocyte culture supernatants measured by ELISA and the Gyrolab Bioaffy were used to determine the polarisation of the immune response. Enumeration of cytokine secreting cells was carried out by ELISPOT assays. Vaccines containing the ginseng-fraction Rb1 induced serum-detectable amounts of IL-4 and IL-10 as early as 24h after primary injection that was confirmed in sera collected at 24 and 72 h post re-vaccination. Five weeks after booster, immune lymphocytes were still producing large amounts of cytokines including IFN-gamma, IL-2, IL-4, IL-10 and TNF-alpha and the antibody titres were still similar to those titres recorded 1 week post booster. The Rb1 adjuvanted vaccines stimulated similar titres of antigen specific IgG1, IgG(2a) and IgG(2b). Thus, the cytokine and the serological data indicated that the Rb1 fraction of ginseng elicits a balanced Th1 and Th2 immune response.