Adenoviruses have transitioned from tools for gene replacement therapy to bona fide vaccine delivery vehicles. They are attractive vaccine vectors as they induce both innate and adaptive immune responses in mammalian hosts. Currently, adenovirus vectors are being tested as subunit vaccine systems for numerous infectious agents ranging from malaria to HIV-1. Additionally, they are being explored as vaccines against a multitude of tumor-associated antigens. In this review we describe the molecular biology of adenoviruses as well as ways the adenovirus vectors can be manipulated to enhance their efficacy as vaccine carriers. We describe methods of evaluating immune responses to transgene products expressed by adenoviral vectors and discuss data on adenoviral vaccines to a selected number of pathogens. Last, we comment on the limitations of using human adenoviral vectors and provide alternatives to circumvent these problems. This field is growing at an exciting and rapid pace, thus we have limited our scope to the use of adenoviral vectors as vaccines against viral pathogens.
IntroductionPreventative viral vaccines provide protection through induction of immunologic memory, most notably circulating neutralizing antibodies. 1 For some viruses, such as HIV-1, vaccines have failed to induce protective levels of antibodies and the focus of many of the ongoing HIV-1 vaccine efforts has shifted to T-cell responses. 2 Correlates of T-cell-mediated protection to viral infections remain ill-defined because of the not yet fully understood complexity of memory T-cell responses.Replication-defective adenovirus (Ad) vectors are at the forefront of HIV-1 vaccine research and have entered phase 2 clinical trials. [3][4][5] One of the most remarkable features of Ad-based vaccines is their ability to induce exceptionally high and sustained frequencies of transgene product-specific CD8 ϩ T cells that, unlike those induced by other subunit vaccine carriers such as DNA vaccines or poxvirus vectors, do not contract after the initial activation. 6,7 Here we show that replication-defective E1-deleted Ad vector genomes similar to those of Ads acquired by natural infections 8,9 persist. Persistent vector was found in muscle at the site of inoculation, in liver, and in lymphatic tissues of experimental animals. Within lymphatic tissues the vector genomes are enriched in T-cells directed to the antigen encoded by the viral vector. The vector's genome remains transcriptionally active, and the continued presence of transgene products appears to maintain high frequencies of activated antigen-specific CD8 ϩ T cells in addition to a pool of resting memory T cells. Although the concept of persisting vaccines may provide challenges for their eventual use for mass vaccination, concomitantly maintaining high frequencies of effector-like T cells and resting memory T cells may provide a solution to the dilemma of vaccines that rely on T-cell-mediated protection. Materials and methods MiceC57Bl/6 and BALB/c mice were purchased at 6 to 8 weeks of age from Charles River Laboratories (Boston, MA). OT1 and P14 mice were bred at the Animal Facility of the Wistar Institute (Philadelphia, PA) and typed by polymerase chain reaction (PCR) for homozygosity. Animals were treated according to guidelines of the Wistar Institute. Cell linesHEK 293 and HeLa cells were grown in Dulbecco Modified Eagle medium, supplemented with 10% fetal bovine serum. Viruses and viral vectorsAd vectors expressing Gag of HIV-1, the rabies virus glycoprotein or SIINFEKL as a fusion protein with influenza virus nucleoprotein and green fluorescent protein, the glycoprotein of lymphocytic choriomeningitis virus (LCMV), or green fluorescent protein were propagated on HEK 293 cells, purified, and quality-controlled as described previously. 10 Vaccinia virus vectors expressing Gag were grown on HeLa cells and titrated as described. 11 LCMV strain Armstrong was produced as described. 12 Immunization or infection of miceMice were immunized intramuscularly at 6 to 10 weeks of age with vectors diluted in 100 L PBS. Mice were infected with vaccinia virus vectors or L...
In this study we compared a prime-boost regimen with two serologically distinct replication-defective adenovirus (Ad) vectors derived from chimpanzee serotypes C68 and C1 expressing Gag, Pol, gp140, and Nef of human immunodeficiency virus type 1 with a regimen in which replication-defective Ad vectors of the human serotype 5 (AdHu5) were given twice. Experiments were conducted in rhesus macaques that had or had not been preexposed to antigens of AdHu5. There was no significant difference in T-cell responses tested from peripheral blood of the different groups, although responses were overall highest in nonpreexposed animals
TC10 possesses distinct features, but exhibits a phenotype most closely related to that of Cdc42. It interacts with a similar subset of effectors to Cdc42 but not with MLK3, WASP or ACK-1. It is regulated differentially by p50RhoGAP.
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