Immune responses elicited by a fourth dose of the HPV-16/18 AS04-adjuvanted vaccine in previously vaccinated adult women.

BACKGROUND: Vaccines are now available for the prevention of HPV-16/18-related cervical infections and pre-cancers, primarily targeting adolescent girls. Since the risk of HPV exposure potentially persists throughout a woman's sexual life, vaccine-derived immunity should be long-term. The current study, HPV-024 (NCT00546078, http://clinicaltrials.gov), assessed the immune memory in North American women who received three doses of HPV-16/18 AS04-adjuvanted vaccine 7 years earlier in HPV-001 (NCT00689741). METHODS: Women vaccinated in HPV-001 received a 4th-dose of the HPV-16/18 vaccine (024-4DV group, N=65). Post 4th-dose immune responses were compared with post 1st-dose immune responses in cross-vaccination controls (024-3DV group, N=50). Reactogenicity was compared between the 4th-dose and the 1st-dose administration. RESULTS: Pre 4th-dose, 100% of subjects in the 024-4DV group remained seropositive for anti-HPV-16/18 antibodies (ELISA). Compared to pre 4th-dose, GMTs for anti-HPV-16 and anti-HPV-18 antibodies were respectively 9.3-fold and 8.7-fold higher at day 7, and 22.7-fold and 17.2-fold higher at month 1. Compared to post 1st-dose, GMTs for anti-HPV-16 and anti-HPV-18 were respectively 80.5-fold and 205.4-fold higher at day 7, and 11.8-fold and 20.5-fold higher at month 1. Furthermore, 68.2% and 77.3% of women had HPV-16/18 specific memory B-cells, respectively, pre 4th-dose, rising to 100% one month post 4th-dose vaccination. The 4th-dose was generally well tolerated. CONCLUSION: A 4th-dose of HPV-16/18 AS04-adjuvanted vaccine triggered a rapid and strong anamnestic response in previously vaccinated women, demonstrating vaccine-induced immune memory.

Potent induction of focused Th1-type cellular and humoral immune responses by RTS,S/SBAS2, a recombinant Plasmodium falciparum malaria vaccine.

The RTS,S/SBAS2 vaccine confers sterile protection against Plasmodium falciparum sporozoite challenge. The mechanisms underlying this are of great interest, yet little is known about the immune effector mechanisms induced by this vaccine. The immune responses induced by RTS,S/SBAS2 were characterized in 10 malaria-naive volunteers. Several epitopes in the circumsporozoite protein (CSP) were identified as targets of cultured interferon (IFN)-gamma-secreting CD4+ T cells. RTS,S-specific IFN-gamma-secreting effector T cells were induced in 8 subjects; this ex vivo response mapped to a single peptide in Th2R. CSP-specific CD8+ cytotoxic T lymphocytes were not detected. RTS, S-specific IFN-gamma production was universal, whereas interleukin-4 and -5 production was rare. RTS,S-specific lymphoproliferative responses and antibodies to CSP were strongly induced in all volunteers. Responses waned with time but were boostable. Thus, RTS, S/SBAS2 is a potent inducer of Th1-type cellular and humoral immunity. These results highlight possible immune mechanisms of protection and have important implications for vaccine design in general.

Comparison of three luminescent assays combined with a sandwich hybridization for the measurement of PCR-amplified human cytomegalovirus DNA.

Identification of human tissue contaminated by cytomegalovirus is currently carried out by PCR amplification followed by measurement of the amplicons. Three luminescent detection systems undertaken after sandwich hybridization of the amplicons were compared. The sandwich hybridization takes place between a covalent linked capture probe, bound onto a plastic 96-well plate, and a biotinylated or digoxigenin-labeled detection probe. The three non-isotopic luminescent detection systems need either streptavidin-conjugated peroxydase or streptavidin-conjugated pyruvate kinase or antibodies conjugated with alkaline phosphatase. Detection of the enzymes was carried out by measurement of light emission in the presence of, respectively, luminol for peroxidase or dioxethane for alkaline phosphatase. The kinase assay was carried out not only in the presence of its substrates, ADP and phospho-enol pyruvate, but also of luciferase, which converts the produced ATP into light. The method was found to be sensitive, with the luciferase bioluminescent assay with the production of a long lasting signal. Amplicons from eight clinical samples were detected by this combination of sandwich hybridization and the three luminescent assays. The results were comparable with nested PCR for the identification of positive samples. The same correlation was obtained with 45 clinical samples using only the pyruvate kinase detection system. The high performance of these assays is given by the specificity of the sandwich hybridization combined with the sensitivity of the luminescent detection systems.

DNA probe hybridisation in microwells using a new bioluminescent system for the detection of PCR-amplified HIV-1 proviral DNA.

A new bioluminescent detection system combined with a sandwich DNA hybridisation reaction in microwells has been developed for the detection of human immunodeficiency virus type 1 (HIV-1) provirus DNA amplified by the polymerase chain reaction (PCR). First, a fragment of the HIV-1 gag gene was amplified. The amplified DNA fragments were denatured and hybridised to a capture probe immobilised in microwells and to a biotinylated detection probe. A streptavidin-pyruvate kinase conjugate could then react on the biotinylated probe and the kinase activity detected by means of the luciferin-luciferase system, with production of a bioluminescent signal. This sandwich assay followed by a bioluminescent reaction detected as little as 7 amol of target DNA. The bioluminescent assay detected 5 HIV copies generated after one round of PCR, even if no band was seen on an agarose gel. The assay was applied to the detection of HIV-proviral DNA in peripheral blood mononuclear cells after one round of PCR and allowed to clearly identify a positive sample as compared to nested PCR.