Browsing by Author "Tarragona, Tony"

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    Concordant Proficiency in Measurement of T-Cell Immunity in Human Immunodeficiency Virus Vaccine Clinical Trials by Peripheral Blood Mononuclear Cell and Enzyme-Linked Immunospot Assays in Laboratories from Three Continents
    (Clinical and vaccine immunology, 2009-02) Boaz, Mark J.; Hayes, Peter; Tarragona, Tony; Seamons, Laura; Cooper, Andrew; Birungi, Josephine; Kitandwe, Paul; Semaganda, Aloysius; Kaleebu, Pontiano; Stevens, Gwynneth; Anzala, Omu; Farah, Bashir; Ogola, Simon; Indangasi, Jackton; Mhlanga, Patrick; Eeden, Melanie Van; Thakar, Madhuri; Pujari, Ashwini; Mishra, Shadri; Goonetilleke, Nilu; Moore, Stephen; Mahmoud, Abdul; Sathyamoorthy, Pattabiraman; Mahalingam, Jayashri; Narayanan, Paranji R.; Ramanathan, Vadakkuppattu D.; Cox, Josephine H.; Dally, Len; Gill, Dilbinder K.; Gilmour, Jill
    The gamma interferon (IFN-_) enzyme-linked immunospot (ELISPOT) assay is used routinely to evaluate the potency of human immunodeficiency virus (HIV) vaccine candidates and other vaccine candidates. In order to compare candidates and pool data from multiple trial laboratories, validated standardized methods must be applied across laboratories. Proficiency panels are a key part of a comprehensive quality assurance program to monitor inter- and intralaboratory performance, as well as assay performance, over time. Seven International AIDS Vaccine Initiative-sponsored trial sites participated in the proficiency panels described in this study. At each laboratory, two operators independently processed identical sample sets consisting of frozen peripheral blood mononuclear cell (PBMC) samples from different donors by using four blind stimuli. PBMCM recovery and viability after overnight resting and the IFN-_ ELISPOT assay performance were assessed. All sites demonstrated good performance in PBMC thawing and resting, with a median recovery of 78% and median viability of 95%. The laboratories were able to detect similar antigen-specific T-cell responses, ranging from 50 to >3,000 spot-forming cells per million PBMC. An approximate range of a half log in results from operators within or across sites was seen in comparisons of antigen-specific responses. Consistently low background responses were seen in all laboratories. The results of these proficiency panels demonstrate the ability of seven laboratories, located across three continents, to process PBMC samples and to rank volunteers with differential magnitudes of IFN-_ ELISPOT responses. These findings also illustrate the ability to standardize the IFN-_ ELISPOT assay across multiple laboratories when common training methods, reagents such as fetal calf serum, and standard operating procedures are adopted. These results are encouraging for laboratories that are using cell-based immunology assays to test HIV vaccines and other vaccines.
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    A Phase 2 Study to Evaluate the Safety and Immunogenicity of a Recombinant HIV Type 1 Vaccine Basedon Adeno-Associated Virus.
    (Mary Ann Liebert, Inc., 2010-08-12) Vardas, Eftyhia; Kaleebu, Pontiano; Bekker, Linda-Gail; Hoosen, Anwar; Chomba, Elwyn; Johnson, Philip R.; Anklesaria, Pervin; Birungi, Josephine; Barin, Burc; Boaz, Mark; Cox, Josephine; Lehrman, Jennifer; Stevens, Gwynn; Gilmour, Jill; Tarragona, Tony; Hayes, Peter; Lowenbein, Sarah; Kizito, Eva; Fast, Patricia; Heald, Alison E.; Schmidt, Claudia
    The recombinant vaccine, tgAAC09, based on an adeno-associated virus serotype 2 (AAV2) vector encoding HIV-1 subtype C Gag, protease, and part of reverse transcriptase, induced robust T cell and antibody responses in nonhuman primates. In a previous phase I study in 80 healthy HIV-seronegative European and Indian adults, the vaccine was generally safe, well tolerated, and modestly immunogenic when administered once at doses up to 3x10 11 DRP. This phase II double-blind, randomized, placebo-controlled trial tested two administrations and a higher dosage of tgAAC009. Ninety-one healthy HIV-seronegative adults from three African countries were given one of three dosage levels of tgAAC09 (3x1010, 3x10 11, or 3x10 12 DRP) intramuscularly, either at a 6- or 12-month interval; follow-up was 18 months. Overall, 65% and 57% of vaccine recipients experienced local and systemic signs and symptoms, respectively, most being mild. Frequency and severity were not dose related and were similar to those in placebo recipients. No vaccine-related serious adverse events were reported. Overall, HIV-specific T cell responses were detected by IFN-g ELISPOT in 17/69 (25%) vaccine recipients with 38% (10/26) responders in the highest dosage group. The response rate improved significantly with boosting at 6, but not 12 months, in the 3x10 11 and 3x10 12 dosage groups only. Neutralizing antibody titers to the AAV2 did not alter the frequency of immune responses to HIV. Two doses of tgAAC09 were well tolerated at the dosage levels given. Fewer than half the recipients of the highest vaccine dosage, 3x10 12 DRP, had T cell responses to HIV.