Expression of CD56 by human papillomavirus E7-specific CD8+ cytotoxic T lymphocytes correlates with increased intracellular perforin expression and enhanced cytotoxicity against HLA-A2-matched cervical tumor cells.

Human papillomavirus (HPV) infection represents the most important risk factor for developing cervical cancer. In this study, we examine the potential of full-length E7-pulsed autologous dendritic cells (DCs) to induce antigen-specific CTL responses from the peripheral blood of healthy individuals against HLA-A2-matched HPV-16 and HPV-18-positive tumor target cells in vitro. We show that DCs pulsed with E7 oncoprotein can consistently stimulate antigen-specific CTL responses that recognize and lyse HPV-16 or HPV-18-positive naturally infected cervical cancer cell lines. HPV-negative, EBV-transformed lymphoblastoid cell lines (LCLs) sharing the HLA haplotype of the target tumor cells, as well as autologous donor LCLs, were not significantly killed by E7-specific CTLs. Cytotoxicity against HLA-A2-matched HPV-16 and HPV-18 tumor target cells could be significantly inhibited by anti-HLA class I and by anti-HLA-A2 monoclonal antibodies. CD8+ CTLs expressed variable levels of CD56 and showed a strongly polarized Type 1 cytokine profile. Sorting of the CD8+ T cells on the basis of CD56 expression demonstrated that the most highly cytotoxic CTLs were CD56+ and expressed higher levels of perforin and IFN-gamma, compared with the CD8+/CD56- population. Taken together, these data demonstrate that full-length, E7-pulsed DCs can consistently induce E7-specific CD8+ CTL responses in healthy individuals that are able to kill naturally HPV-16 and HPV-18-infected cancer cells, and that CD56 expression defines a subset of CD8+ CTLs with high cytolytic activity against tumor cells.

Lanthanum and zinc sensitivity of GABAA-activated currents in adult medial septum/diagonal band neurons from ethanol dependent rats.

The impact of chronic ethanol treatment, sufficient to induce tolerance and physical dependence, on GABAA receptor function was studied in acutely isolated neurons from the medial septum/nucleus diagonal band (MS/nDB) of adult rats using whole cell, patch-clamp recordings. In ethanol-naive Controls, GABA (0.3-300 microM) induced concentration-dependent increases in Cl- current with a threshold of 0.3-1 microM, a mean maximal current of 7645 +/- 2148 pA at 100-300 microM, an EC50 of 11.3 +/- 1.3 microM and a slope of 1.53 +/- 0.07. GABA-activated currents in neurons from animals receiving two weeks of ethanol liquid diet treatment did not differ significantly on any of these measures. The rate of GABAA receptor desensitization (t1/2 = 6.49 +/- 1.19 s) estimated as the time required for loss of 50% of peak current during sustained application of 10 microM GABA, as well as the residual steady state current remaining following complete desensitization for controls was unchanged by chronic ethanol. The impact of chronic ethanol treatment on the GABAA receptor modulation by lanthanum and zinc which act as positive and negative allosteric modulators, respectively, was also evaluated. Test pulses of 3 microM GABA in control neurons showed maximal potentiation by 141 +/- 30% at approximately 1000 microM lanthanum with an EC50 of 107 +/- 34 microM and a slope of approximately 1. Lanthanum potentiation remained the same following chronic ethanol treatment. Initial estimates based on fitted concentration response curves suggested that maximal inhibition of 3 microM GABA responses by zinc at the level of 70.2 +/- 8.5% in control cells was significantly increased by chronic ethanol treatment to 95.3 +/- 2.5%, although the IC50 of 60.2 +/- 25 microM was not changed. However, this difference was not supported by direct tests of maximal 3-10 mM zinc concentrations. These results suggest that chronic ethanol treatment, sufficient to induce tolerance and physical dependence, probably does not lead to readily detectible changes in GABAA receptor function in MS/nDB neurons.