Cellular immunity induced by the recombinant Plasmodium falciparum malaria vaccine, RTS,S/AS02, in semi-immune adults in The Gambia.

Vaccination of malaria-naive humans with recombinant RTS,S/AS02, which includes the C-terminus of the circumsporozoite protein (CS), has been shown to induce strong T cell responses to both the whole protein antigen and to peptides from CS. Here we show that strong T cell responses were also observed in a semi-immune population in The Gambia, West Africa. In a Phase I study, 20 adult male volunteers, lifelong residents in a malaria-endemic region, were given three doses of RTS,S/AS02 at 0, 1 and 6 months. Responses to RTS,S, hepatitis B surface antigen and peptides from CS were tested using lymphocyte proliferation, interferon (IFN)-gamma production in microcultures, and IFN-gamma ex vivo and cultured ELISPOT, before and after vaccination. Cytotoxic responses were tested only after vaccination and none were detected. Before vaccination, the majority of the volunteers (15/20) had detectable responses in at least one of the tests. After vaccination, responses increased in all assays except cytotoxicity. The increase was most marked for proliferation; all donors responded to RTS,S after the third dose and all except one donor responded to at least one peptide after the second or third dose. There was a lack of close association of peptide responses detected by the different assays, although in microcultures IFN-gamma responses were found only when proliferative responses were high, and responses by cultured ELISPOT and proliferation were found together more frequently after vaccination. We have therefore identified several peptide-specific T cell responses induced by RTS,S/AS02 which provides a mechanism to investigate potentially protective immune responses in the field.

Prospective randomised phase II study of gemcitabine at standard or fixed dose rate schedule in unresectable hepatocellular carcinoma.

The present randomised phase II study was an effort to evaluate single-agent gemcitabine as a first-line systemic treatment of Asian patients with unresectable hepatocellular carcinoma (HCC). Gemcitabine was given via intravenous infusion at 1250 mg m(-2) on days 1 and 8 of 3-week cycles. Patients were randomised to receive gemcitabine as a 30-min intravenous infusion (standard schedule) or at a fixed dose rate (FDR) of 10 mg m(-2) min(-1). A total of 50 patients were enrolled in the study, of whom 48 received study therapy. One patient on standard schedule had a partial response, for an overall response rate of 2.1% (95% CI: 0.05-11.1%). The median time to progression and survival time were 46 and 97 days, respectively. The overall rates of Grade 3 or 4 haematological and nonhaematological toxicities were 39.6 and 64.6%, respectively, with no significant difference between the two treatment arms. There were no drug-related deaths and severe clinical toxicities were rare. Both schedules of gemcitabine were safe and toxicity was well manageable in this patient population. However, gemcitabine seems no more active than other cytotoxic agents when used alone for systemic treatment of advanced HCC.

Naturally exposed populations differ in their T1 and T2 responses to the circumsporozoite protein of Plasmodium falciparum.

T-cell responses directed against the circumsporozoite protein (CS) of Plasmodium falciparum can mediate protection against malaria. We determined the frequency of T cells reactive to different regions of the CS in the blood of donors naturally exposed to P. falciparum by examining T1 (gamma interferon [IFN-gamma] ELISPOT assay), T2 (interleukin 4 [IL-4] ELISPOT assay), and proliferative T-cell responses. The proliferative responses were weak, which confirmed previous observations. The responses to the CS in the IL-4 and IFN-gamma ELISPOT assays were also weak (<40 responding cells per 10(6) cells), much weaker than the response to the purified protein derivative of Mycobacterium tuberculosis in the same donors. Moreover, a response in one assay could not be used to predict a response in either of the other assays, suggesting that although these assays may measure different responding cells, all of the responses are weakly induced by natural exposure. Interestingly, the two different study populations used had significantly different T1 and T2 biases in their responses in the C terminus of the protein, suggesting that the extent of P. falciparum exposure can affect regulation of the immune system.