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Rabies remains a major neglected global zoonosis. New vaccine strategies are needed for human rabies prophylaxis. A single intramuscular immunization with a moderate dose of an experimental chimpanzee adenovirus (Ad) vector serotype SAd-V24, also termed AdC68, expressing the rabies virus glycoprotein, resulted in sustained titers of rabies virus neutralizing antibodies and protection against a lethal rabies virus challenge infection in a non-human primate model. Taken together, these data demonstrate the safety, immunogenicity, and efficacy of the recombinant Ad-rabies vector for further consideration in human clinical trials., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Vaccines based on adenovirus (Ad) vectors are currently in development against several pathogens. However, neutralizing antibodies (NAb) to human adenovirus type 5 (AdHu5), the best-studied vector, are highly prevalent in humans worldwide. Less-prevalent adenoviruses, including human and simian serotypes, provide alternative vaccine platforms. In this study, sera from 200 Brazilian human subjects and New-World monkeys were tested for NAb titers to human serotypes AdHu5 and AdHu26 and chimpanzee-origin Ad viruses of serotype 6 (AdC6) and serotype 68 (AdC68). Seroprevalence rates of NAb in humans were 69.5% for AdHu5, 44% for AdHu26, 21% for AdC6 and 23.5% for AdC68. In addition, NAb titers to human Ad were consistently higher than those found to simian serotypes. Surprisingly, sera from some New-World monkey species were able to neutralize AdC6 and/or AdC68. A possible explanation for these findings and the implications for the development of Ad-vector vaccines are discussed in detail., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Recombinant adenovirus vectors and MVA vectors were used in prime boost vaccine regimens to address the impact of repeated immunizations on transgene product-specific CD8(+) T cell frequencies, phenotypes, function, and localization. We show that a regimen with three immunizations incorporating MVA, human adenovirus serotype 5 and chimpanzee-derived adenoviruses serotype 68 or 7 yields high transgene product-specific CD8(+) T cell frequencies in spleen, blood, lymph nodes, and peritoneal lavage. Furthermore, upon triple immunization increased frequencies of transgene-specific T cells were measured at mucosal sites such as mesenteric lymph nodes, intestinal epithelium, and Peyer's patches. Multiple dose vaccine regimens that markedly increase functionally active transgene-specific T cells and target them to the appropriate ports of entry may be important in protection against pathogens such as HIV-1.

Most DNA vaccines rely on strong viral promoters to optimize levels of transgene expression. Some studies have demonstrated that the potency of viral promoters does not necessarily correlate with DNA vaccine efficacy in vivo. This has partly been attributed to downregulation of these promoters by cytokines such as interferon gamma induced by the CpG motives of these vaccines. In an attempt to avoid downregulation of viral promoters by IFN-gamma, we tested vaccine vectors driven by the MHC class II promoter. To enhance the activity of this promoter, another plasmid expressing the human MHC class II transactivator driven by a viral promoter, the native IFN-gamma inducible CIITA type IV promoter (PIV) or a synthetic promoter containing IFN-gamma inducible elements was co-inoculated. Our data show that a non-viral promoter such as the MHC class II promoter tested in this study can indeed be used in DNA vaccines.

Mice lacking CD4(+) T cells due to a knock-out mutation respond to vaccination with a replication-defective adenoviral recombinant expressing the glycoprotein of rabies virus with a long-lasting virus-neutralizing antibody response. The vaccine-induced B cells secrete antibodies that are mainly of IgG isotypes. The response can be enhanced upon booster immunization, indicating the induction of B cell memory in the absence of CD4(+) T cells. The antibody response is independent of CD8(+) T cells but requires the presence of CD3(+) cells carrying the NK1.1 markers.

Most cancerous lesions of the uterine cervix are linked to persistent infections with human papillomaviruses (HPV), most notably HPV-16 or -18. Vaccine-induced immune responses to the HPV early antigens E6 and E7, which contribute to cell transformation and are thus expressed in these cervical cancers, could potentially eradicate malignant cells. We generated recombinant vaccines based on E1-deleted adenovirus human strain 5 or on vaccinia virus strain Copenhagen expressing either the E6 or E7 oncoproteins of HPV-16. The different vaccines were compared in two experimental mouse tumor models employing Balb/c or C57Bl/6 mice. Data presented here demonstrate that depending on the model either CD4(+) or CD8(+) T cells provide protection to tumor cell challenge, resulting in striking differences in the efficacy of the four vaccines under investigation., (Copyright 2000 Academic Press.)

The effect of genetic immunization of neonatal mice was tested with a plasmid vector expressing the rabies virus glycoprotein. Mice inoculated within 24 hr after birth with the plasmid DNA developed antibodies as well as T helper cells to the rabies virus glycoprotein. The response could not be distinguished from that seen upon vaccination of adult mice. Taken together, these data clearly show that the immune system, known to be prone to induction of immunological tolerance to some antigens applied during the early neonatal period, can readily respond to rabies virus glycoprotein induced by a plasmid vector.

In this manuscript, an E1 and E3 deleted adenoviral recombinant expressing the rabies virus glycoprotein (G protein) under the control of the cytomegalovirus early promoter was tested for induction of a rabies virus-specific immune response in mice. The construct was found to induce neutralizing antibodies and cytolytic T cells to rabies virus. Mice vaccinated with the adenoviral construct either by the systemic route or by application into the airways were protected against a subsequent infection with a virulent strain of rabies virus. The efficacy of the replication-defective construct was far superior to that of a well-characterized vaccinia rabies glycoprotein recombinant.

Genetically engineered mice with targeted mutations in genes encoding immunologically relevant molecules were used to elucidate the role of different immune effector mechanisms in protection against a rabies virus (RV) infection. In vaccinated animals challenged with a highly virulent strain of RV, antibodies were crucial in protection. In naive mice challenged with an attenuated strain of the virus that does not cause disease in adult fully immunocompetent mice but kills RAG mice that lack functionally active T and B cells, different immune effector mechanisms were shown to suffice for protection.

A plasmid vector expressing the full-length rabies virus glycoprotein (G protein) under the control of the simian virus 40 (SV40) promoter has previously been shown to induce upon intramuscular (i.m.) inoculation into mice a specific B- and T-cell-mediated immune response and protection against challenge with a virulent strain of the virus. Here we tested two parameters that might affect the efficacy of this DNA vaccine. First, we replaced the SV40 promoter of the original vector with the early promoter derived from cytomegalovirus leaving all other parameters of the plasmid intact. Although upon transfection in vitro the two vectors showed a striking difference in their ability to cause stable expression of the rabies virus G protein, upon i.m. inoculation into mice both constructs induced comparable immune responses. Second, we constructed a vector that induces expression of a secreted form of rabies G protein by inserting a stop codon just upstream of the transmembrane domain of the rabies G protein gene. The immune responses to the DNA vaccines expressing the two different forms of the G protein, secreted and membrane bound, were compared and found to be similar in magnitude. The long-term effect of DNA vaccination was also investigated especially with regard to adverse immunological reactions such as the induction of unresponsiveness against rabies virus and the development of antibodies to DNA. DNA vaccination was found to induce long-lasting immunity to rabies virus without apparent negative side effects such as development of T cell tolerance or generation of anti-DNA antibodies.

A plasmid vector, termed pSG5rab.gp, that expresses the rabies virus glycoprotein under the control of an SV40 early promoter, was tested in C3H/He mice for induction of rabies virus-specific immune responses. Mice immunized intramuscularly with the pSG5rab.gp vector developed rabies virus glycoprotein-specific cytolytic T cells, lymphokine-secreting T helper cells of the TH1 subset, and rabies virus-neutralizing antibodies. Mice vaccinated with the pSG5rab.gp vector were fully protected against a subsequent challenge with rabies virus.