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Most studies on E1-deleted adenovirus (Ad) vectors as vaccine carriers for antigens of HIV-1 have focused on induction of central immune responses, although stimulation of mucosal immunity at the genital tract (GT), the primary port of entry of HIV-1, would also be highly desirable. In this study, different immunization protocols using chimpanzee-derived adenoviral (AdC) vectors expressing Gag of HIV-1 clade B given in heterologous prime-boost regimens were tested for induction of systemic and genital immune responses. Although i.n. immunization stimulated CD8(+) T-cell responses that could be detected in the GT, this route induced only marginal cellular responses in systemic tissues and furthermore numbers of Gag-specific CD8(+) T cells contracted sharply within a few weeks. On the contrary, i.m. immunization induced higher and more sustained frequencies of vaccine-induced cells which could be detected in the GT as well as systemic compartments. Antigen-specific CD8(+) T cells could be detected 1 year after immunization in all compartments analyzed. Genital memory cells secreted IFN-γ, expressed high levels of CD103 and their phenotypes were consistent with a state of activation. Taken together, the results presented here show that i.m. vaccination with chimpanzee-derived (simian) adenovirus vectors is a suitable strategy to induce a long-lived genital CD8(+) T-cell response., (Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Simian adenoviral vectors (SAd) offer an attractive alternative to standard human adenovirus serotype 5 (AdH5) subunit vaccination, due to pre-existing immunity affecting vaccine performance. We have used a mouse model of liver-stage malaria to test the efficiency of three chimpanzee-origin adenoviral vectors, AdC6, AdC7 and AdC9 containing ME.TRAP as an insert. AdC7 and AdC9 elicited strong immunogenicity ( approximately 20% of CD8(+) T cells in spleen), equivalent to or outperforming AdH5 and inducing sterile protection in 92% (C9), 83% (H5 and C7) and 67% (C6) of the mice, providing the first evidence of single-dose protection to Plasmodium berghei. Protection was afforded by the SAd despite high levels of pre-existing immunity to AdH5. Phenotypic analysis showed that all adenoviral vectors (Ad) elicited CD8(+) T cell responses with an effector memory T cell (T(EM)) phenotype. By contrast, vaccination with poxviral vectors did not confer protection to P. berghei and induced a predominantly CD8(+) central memory T cell (T(CM)) response. Multifunctional CD8(+) T cell responses (co-expressing IFN-gamma, TNF-alpha and IL-2) were also induced by the Ad in higher percentages than the poxviral vectors. Our data suggest that T(EM) cells are important as a first line of defense against fast-replicating pathogens such as murine Plasmodium and demonstrate the potential of replication-defective SAd as future malaria vaccines for humans.

T cell clones and subsequently hybridomas were generated from rabies virus-immune C3H/He mice to an immunodominant epitope of the viral nucleoprotein, termed 31D, that had previously been identified by a 15-amino acid-long synthetic peptide. T cells to this epitope that by phenotypical and functional characteristics belonged to the T helper cell subset were shown to respond to most rabies and rabies-related viruses. In order to define the minimal sequence needed to elicit a response from 31D-specific T cell clones or hybridomas, a number of peptides of varied lengths, i.e. 3-32 amino acids long, were tested. The ability of the peptides to induce a response was inversely correlated in their lengths, i.e., short peptides (3-5 amino acids long) had to be used at 10(6) times higher concentrations as compared to long peptides (15 or 32 amino acids long). Conversely, the specificity of the T cell response was directly correlated to the length of the peptides, i.e., while the response to 15-amino acid-long peptides exhibited a high degree of specificity, the response to 3- to 5-amino acid-long peptides showed a high degree of flexibility. The long as well as the short peptides had to be presented in association with I-Ek. We speculate that in this system the T cell receptor interacts predominantly with a peptide-induced modification of the I-Ek molecule.

Mice injected with inactivated (UV light-irradiated) influenza virus produce specific antibody, become sensitized for a delayed-type hypersensitivity reaction, but do not generate specific cytotoxic T (Tc) cells. If injected 4-5 days later with infectious virus, the formation of Tc cells is suppressed by > 90%. If A strain viruses are used, the suppression observed is cross-reactive within A strain viruses but does not extend to B/LEE or to Sendai virus. Serum from mice injected with UV-irradiated virus contains antibodies which on adoptive transfer can inhibit Tc cell formation when infectious homologous virus is used to challenge the recipients. Spleen cells from the same mice, upon adoptive transfer, also inhibit (50-70%) Tc cell formation if transferred within 24 h of injection of infectious virus, and the specificity pattern observed is cross-reactive within A strains. The activity of the cells mediating suppression is destroyed by monospecific anti-Thy-1.2 antibody and complement. The immune cells require I region sharing between donor and recipient mice for their suppressor activity to be effective. (There is also a partial requirement for K, D region sharing, but the possible rejection of transferred cells is not excluded.) Dilution assays in which clonal expansion of Tc precursors is used to estimate their frequency and the presence of T helper (Th) cells indicate that suppressed mice possess Tc precursors and primed cells which, upon restimulation, act as Th cells. Furthermore, injection of irradiated Th cells with inactivated virus does not significantly reduce the ensuing suppression.

T helper cells for the promotion of Sendai virus-specific antibody production were generated in vitro. They could be stimulated by infectious, UV light-inactivated or fusion-negative Sendai virus, which had to be presented by adherent cells. Induction of T helper cells was virus-specific and required H-2 IA region compatibility between T cells and antigen-presenting cells. Delivery of help to B lymphocytes was neither virus-specific nor H-2-restricted.

Interferon (IFN) was detected upon co-culture of cloned Sendai virus (SV)-specific T lymphocyte with SV-presenting syngeneic stimulator cells. The antiviral activity was defined as IFN-alpha, beta. The T cell clones, upon contact with antigen-presenting stimulator cells, stimulated adherent cells present in the stimulator cell population to secrete IFN. Induction of IFN production was independent from interleukin 2 production by the T cell clones.