Induction of Positive Cellular and Humoral Immune Responses by a Prime-Boost Vaccine Encoded with Simian Immunodeficiency Virusgag/pol

Biodistribution and immunity of adenovirus 5/35 and modified vaccinia Ankara vector vaccines against human immunodeficiency virus 1 clade C

Previously, we developed a chimeric adenovirus type 5 with type 35 fiber (Ad5/35), which has high tropism to dendritic cells and low hepatoxicity. For further clinical use, we constructed two recombinant vectors expressing human immunodeficiency virus 1 (HIV-1) clade C gag (Ad5/35-Cgag and MVA-Cgag). The biodistribution of the two viral vectors in a mouse model and immunity in monkeys were assessed. The mice received a single intramuscular injection with the vectors alone. The gag gene in the tissues were periodically detected using a real-time quantitative polymerase chain reaction. The distribution of Ad5/35 was also detected using an in vivo imaging system, followed by luciferase-expressing Ad5/35 administration. We found that Ad5/35-Cgag DNA and luciferase activity were detectable until 8 weeks post-administration, whereas MVA-Cgag was undetectable 72 h post-administration. Furthermore, viral administration did not increase serum aspartate aminotransferase and alanine aminotransferase levels in either mouse or monkey models. Moreover, intramuscular administration of Ad5/35-Cgag induced the gag-specific antibody level and IFNγ-secreting PBMCs, the boost with MVA-Cgag further increased the responses and lasted more than 20 weeks from the initial administration. These data demonstrate that Ad5/35 and MVA vectors are safe for in vivo use, and prime-boost with Ad5/35-MVA vaccines is suitable for clinical use against HIV-1 clade C.

Recombinant BCG-Prime and DNA-Boost Immunization Confers Mice with Enhanced Protection against Mycobacterium kansasii

The incidence of infections with nontuberculous mycobacteria (NTM) has been increasing worldwide. The emergence of multidrug-resistant NTM is a serious clinical concern, and a vaccine for NTM has not yet been developed. We previously developed a new recombinant Bacillus Calmette–Guérin (rBCG) vaccine encoding the antigen 85B (Ag85B) protein of Mycobacterium kansasii—termed rBCG-Mkan85B—which was used together with a booster immunization with plasmid DNA expressing the same M. kansasii Ag85B gene (DNA-Mkan85B). We reported that rBCG-Mkan85B/DNA-Mkan85B prime–boost immunization elicited various NTM strain-specific CD4⁺ and CD8⁺ T cells and induced Mycobacterium tuberculosis-specific immunity. In this study, to investigate the protective effect against M. kansasii infection, we challenged mice vaccinated with a rBCG-Mkan85B or rBCG-Mkan85B/DNA-Mkan85B prime–boost strategy with virulent M. kansasii. Although BCG and rBCG-Mkan85B immunization each suppressed the growth of M. kansasii in the mouse lungs, the rBCG-Mkan85B/DNA-Mkan85B prime–boost vaccination reduced the bacterial burden more significantly. Moreover, the rBCG-Mkan85B/DNA-Mkan85B prime–boost vaccination induced antigen-specific CD4⁺ and CD8⁺ T cells. Our data suggest that rBCG-Mkan85B/DNA-Mkan85B prime–boost vaccination effectively enhances antigen-specific T cells. Our novel rBCG could be a potential alternative to clinical BCG for preventing various NTM infections.

The evolution of poxvirus vaccines

After Edward Jenner established human vaccination over 200 years ago, attenuated poxviruses became key players to contain the deadliest virus of its own family: Variola virus (VARV), the causative agent of smallpox. Cowpox virus (CPXV) and horsepox virus (HSPV) were extensively used to this end, passaged in cattle and humans until the appearance of vaccinia virus (VACV), which was used in the final campaigns aimed to eradicate the disease, an endeavor that was accomplished by the World Health Organization (WHO) in 1980. Ever since, naturally evolved strains used for vaccination were introduced into research laboratories where VACV and other poxviruses with improved safety profiles were generated. Recombinant DNA technology along with the DNA genome features of this virus family allowed the generation of vaccines against heterologous diseases, and the specific insertion and deletion of poxvirus genes generated an even broader spectrum of modified viruses with new properties that increase their immunogenicity and safety profile as vaccine vectors. In this review, we highlight the evolution of poxvirus vaccines, from first generation to the current status, pointing out how different vaccines have emerged and approaches that are being followed up in the development of more rational vaccines against a wide range of diseases.

A critical analysis of the cynomolgus macaque, Macaca fascicularis, as a model to test HIV-1/SIV vaccine efficacy

The use of a number of non-rhesus macaque species, but especially cynomolgus macaques as a model for HIV-1 vaccine development has increased in recent years. Cynomolgus macaques have been used in the United Kingdom, Europe, Canada and Australia as a model for HIV vaccine development for many years. Unlike rhesus macaques, cynomolgus macaques infected with SIV show a pattern of disease pathogenesis that more closely resembles that of human HIV-1 infection, exhibiting lower peak and set-point viral loads and slower progression to disease with more typical AIDS defining illnesses. Several advances have been made recently in the use of the cynomolgus macaque SIV challenge model that allow the demonstration of vaccine efficacy using attenuated viruses and vectors that are both viral and non-viral in origin. This review aims to probe the details of various vaccination trials carried out in cynomolgus macaques in the context of our modern understanding of the highly diverse immunogenetics of this species with a view to understanding the species-specific immune correlates of protection and the efficacy of vectors that have been used to design vaccines.

Priming with a recombinant pantothenate auxotroph of Mycobacterium bovis BCG and boosting with MVA elicits HIV-1 Gag specific CD8+ T cells

A safe and effective HIV vaccine is required to significantly reduce the number of people becoming infected with HIV each year. In this study wild type Mycobacterium bovis BCG Pasteur and an attenuated pantothenate auxotroph strain (BCGΔpanCD) that is safe in SCID mice, have been compared as vaccine vectors for HIV-1 subtype C Gag. Genetically stable vaccines BCG[pHS400] (BCG-Gag) and BCGΔpanCD[pHS400] (BCGpan-Gag) were generated using the Pasteur strain of BCG, and a panothenate auxotroph of Pasteur respectively. Stability was achieved by the use of a codon optimised gag gene and deletion of the hsp60-lysA promoter-gene cassette from the episomal vector pCB119. In this vector expression of gag is driven by the mtrA promoter and the Gag protein is fused to the Mycobacterium tuberculosis 19 kDa signal sequence. Both BCG-Gag and BCGpan-Gag primed the immune system of BALB/c mice for a boost with a recombinant modified vaccinia virus Ankara expressing Gag (MVA-Gag). After the boost high frequencies of predominantly Gag-specific CD8(+) T cells were detected when BCGpan-Gag was the prime in contrast to induction of predominantly Gag-specific CD4(+) T cells when priming with BCG-Gag. The differing Gag-specific T-cell phenotype elicited by the prime-boost regimens may be related to the reduced inflammation observed with the pantothenate auxotroph strain compared to the parent strain. These features make BCGpan-Gag a more desirable HIV vaccine candidate than BCG-Gag. Although no Gag-specific cells could be detected after vaccination of BALB/c mice with either recombinant BCG vaccine alone, BCGpan-Gag protected mice against a surrogate vaccinia virus challenge.

Intradermal delivery of recombinant vaccinia virus vector DIs induces gut-mucosal immunity

Antigen-specific mucosal immunity is generally induced by the stimulation of inductive mucosal sites. In this study, we found that the replication-deficient vaccinia virus vector, DIs, generates antigen-specific mucosal immunity and systemic responses. Following intradermal injection of recombinant DIs expressing simian immunodeficiency virus gag (rDIsSIVgag), we observed increased levels of SIV p27-specific IgA and IgG antibodies in faecal extracts and plasma samples, and antibody-forming cells in the intestinal mucosa and spleen of C57BL/6 mice. Antibodies against p27 were not detected in nasal washes, saliva, and vaginal washes. The enhanced mucosal and systemic immunity persisted for 1 year of observation. Induction of Gag-specific IFN-gamma spot-forming CD8(+) T cells in the spleen, small intestinal intraepithelial lymphocytes, and submandibular lymph nodes was observed in the intradermally injected mice. Heat-inactivated rDIsSIVgag rarely induced antigen-specific humoral and T-helper immunity. Moreover, rDIsSIVgag was detected in MHC class II IA antigen-positive (IA(+)) cells at the injection site. Consequently, intradermal delivery of rDIs effectively induces antigen-specific humoral and cellular immunity in gut-mucosal tissues of mice. Our data suggest that intradermal injection of an rDIs vaccine may be useful against mucosally transmitted pathogens.

Immunogenicity of newly constructed attenuated vaccinia strain LC16m8Delta that expresses SIV Gag protein

We developed the method to efficiently construct recombinant vaccinia viruses based on LC16m8Delta strain that can replicate in mammalian cells but is still safe in human. Immunization in a prime-boost strategy using DNA and LC16m8Delta expressing SIV Gag elicited 7-30-fold more IFN-gamma-producing T cells in mice than that using DNA and non-replicating vaccinia DIs recombinant strain. As the previous study on the DNA-prime and recombinant DIs-boost anti-SIV vaccine showed protective efficacy in the macaque model [Someya K, Ami Y, Nakasone T, Izumi Y, Matsuo K, Horibata S, et al. Induction of positive cellular and humoral responses by a prime-boost vaccine encoded with simian immunodeficiency virus gag/pol. J Immunol 2006;176(3):1784-95], LC16m8Delta would have potential as a better recombinant viral vector for HIV vaccine.

Prime-boost vaccination with a combination of proteosome-degradable and wild-type forms of two influenza proteins leads to augmented CTL response

Targeting viral antigens for proteosomal degradation has previously been proposed as a means for immunogenicity augmentation. However, utilization of modified unstable antigens may be insufficient for potent T-cell cross-presentation by APCs, a mechanism that requires high levels of the antigenic protein. Therefore, we hypothesized that a recombinant vaccine utilizing a combination of proteosome-sensitive and proteosome-resistant versions of an antigen in a prime-boost regimen may provide the most efficient CTL response. To address this hypothesis, we utilized conserved proteosome-resistant influenza A virus proteins M1 and NS1. Unstable versions of these polypeptides were constructed by destroying their 3D structure via truncations or short insertions into predicted alpha-helical structures. These modified polypeptides were stabilized in the presence of the proteosome inhibitor MG132, strongly suggesting that they are degraded via a ubiquitin-proteosome pathway. Importantly, with both M1 and NS1antigens, homologous DNA vaccination with a mixture of unstable and proteosome-resistant wt forms of these proteins resulted in significantly higher CTL activity than vaccination with either wt or degradable forms. The most dramatic effect was seen with NS1, where homologous immunization with a mixture of these two forms was the only regimen that produced a notable elevation of CTL response, compared to vaccination with the wt NS1. Additionally, for M1 protein, heterologous vaccination utilizing the unstable form as prime and wild-type form as boost, demonstrated significant augmentation of the CTL response. These data indicate that combining proteosome-sensitive and proteosome-resistant forms of an antigen during vaccination is advantageous.

Live attenuated Listeria monocytogenes expressing HIV Gag: immunogenicity in rhesus monkeys

Induction of strong cellular immunity will be important for AIDS vaccine candidates. Natural infection with wild-type Listeria monocytogenes (Lm), an orally transmitted organism, is known to generate strong cellular immunity, thus raising the possibility that live attenuated Lm could serve as a vaccine vector. We sought to examine the potential of live attenuated Lm to induce cellular immune responses to HIV Gag. Rhesus macaques were immunized with Lmdd-gag that expresses HIV gag and lacks two genes in the D-alanine (D-ala) synthesis pathway. Without this key component of the bacterial cell wall, vaccine vector replication critically depends on exogenous D-ala. Lmdd-gag was given to animals either solely orally or by oral priming followed by intramuscular (i.m.) boosting; D-ala was co-administered with all vaccinations. Lmdd-gag and D-ala were well tolerated. Oral priming/oral boosting induced Gag-specific cellular immune responses, whereas oral priming/i.m. boosting induced systemic as well as mucosal anti-Gag antibodies. These results suggest that the route of vaccination may bias anti-Gag immune responses either towards T-helper type 1 (Th1) or Th2 responses; overall, our data show that live attenuated, recombinant Lmdd-gag is safe and immunogenic in primates.

Chimeric adenovirus type 5/35 vector encoding SIV gag and HIV env genes affords protective immunity against the simian/human immunodeficiency virus in monkeys

Replication-defective adenovirus type 5 (Ad5) vector-based vaccines are widely known to induce strong immunity against immunodeficiency viruses. To exploit this immunogenicity while overcoming the potential problem of preexisting immunity against human adenoviruses type 5, we developed a recombinant chimeric adenovirus type 5 with type 35 fiber vector (rAd5/35). We initially produced a simian immunodeficiency virus (SIV) gag DNA plasmid (rDNA-Gag), a human immunodeficiency virus type 1 (HIV-1) 89.6 env DNA plasmid (rDNA-Env) and a recombinant Ad5/35 vector encoding the SIV gag and HIV env gene (rAd5/35-Gag and rAd5/35-Env). Prime-boost vaccination with rDNA-Gag and -Env followed by high doses of rAd5/35-Gag and -Env elicited higher levels of cellular immune responses than did rDNAs or rAd5/35s alone. When challenged with a pathogenic simian human immunodeficiency virus (SHIV), animals receiving a prime-boost regimen or rAd5/35s alone maintained a higher number of CD4(+) T cells and remarkably suppressed plasma viral RNA loads. These findings suggest the clinical promise of an rAd5/35 vector-based vaccine.

Recombinant vaccinia DIs expressing simian immunodeficiency virus gag and pol in mammalian cells induces efficient cellular immunity as a safe immunodeficiency virus vaccine candidate

A highly attenuated vaccinia virus substrain of Dairen-I (DIs) shows promise as a candidate vector for eliciting positive immunity against immune deficiency virus. DIs was randomly obtained by serial 1-day egg passages of a chorioarantoic membrane-adapted Dairen strain (DIE), resulting in substantial genomic deletion, including various genes regulating the virus-host-range. To investigate the impact of that deletion and of the subsequent insertion of a foreign gene into that region of DIs on the ability of the DIs recombinant to induce antigen-specific immunity, we generated a recombinant vaccinia DIs expressing fulllength gag and pol genes of simian immunodeficiency virus (SIV) (rDIsSIV gag/pol) and studied the biological and immunological characteristics of the recombinant natural mutant. The rDIsSIV gag/pol developed a tiny plaque on the chick embryo fibroblast (CEF). Viral particles of rDIsSIV gag/pol as well as SIV Gag-like particles were electromicroscopically detected in the cytoplasm. Interestingly, the recombinant DIs strain grows well in CEF cells but not in mammalian cells. While rDIsSIV gag/pol produces SIV proteins in mammalian HeLa and CV-1 cells, recombinant modified vaccinia Ankara strain (MVA) expressing SIV gag and pol genes (MVA/SIV239 gag/pol) clearly replicates in HeLa and CV-1 cell lines under synchronized growth conditions and produces the SIV protein in all cell lines. Moreover, intradermal administration of rDIsSIV gag/pol or of MVA/SIV239 gag/pol elicited similar levels of IFN-gamma spot-forming cells specific for SIV Gag. If the non-productive infection characteristically induced by recombinant DIs is sufficient to trigger immune induction, as we believe it is, then a human immunodeficiency virus vaccine employing the DIs recombinant would have the twin advantages of being both effective and safe.

Comparison of different delivery systems of DNA vaccination for the induction of protection against tuberculosis in mice and guinea pigs

The great challenges for researchers working in the field of vaccinology are optimizing DNA vaccines for use in humans or large animals and creating effective single-dose vaccines using appropriated controlled delivery systems. Plasmid DNA encoding the heat-shock protein 65 (hsp65) (DNAhsp65) has been shown to induce protective and therapeutic immune responses in a murine model of tuberculosis (TB). Despite the success of naked DNAhsp65-based vaccine to protect mice against TB, it requires multiple doses of high amounts of DNA for effective immunization. In order to optimize this DNA vaccine and simplify the vaccination schedule, we coencapsulated DNAhsp65 and the adjuvant trehalose dimycolate (TDM) into biodegradable poly (DL-lactide-co-glycolide) (PLGA) microspheres for a single dose administration. Moreover, a single-shot prime-boost vaccine formulation based on a mixture of two different PLGA microspheres, presenting faster and slower release of, respectively, DNAhsp65 and the recombinant hsp65 protein was also developed. These formulations were tested in mice as well as in guinea pigs by comparison with the efficacy and toxicity induced by the naked DNA preparation or BCG. The single-shot prime-boost formulation clearly presented good efficacy and diminished lung pathology in both mice and guinea pigs.

DNA vaccines for HIV: challenges and opportunities

In December 2005, the UNAIDS and WHO reported that the global epidemic known as acquired immunodeficiency syndrome (AIDS) has claimed the lives of more than 25 million adults and children over the past 26 years. These figures included an estimated 3.1 million AIDS-related deaths in 2005. Despite enormous efforts to control the spread of human immunodeficiency virus (HIV) new infection rates are on the rise. An estimated 40.3 million people are now living with HIV, including 4.9 million new infections this past year. Nearly half of new HIV infections are in young people between the ages of 15 and 24. While drug therapies have helped sustain the lives of infected individuals in wealthy regions, they are relatively unavailable to the poorest global regions. This includes sub-Saharan Africa which has approximately 25.8 million infected individuals, more than triple the number of infections of any other region in the world. It is widely believed that the greatest hope for controlling this devastating pandemic is a vaccine. In this review, we will discuss the current state of DNA-based vaccines and how they compare to other vaccination methods currently under investigation. We will also discuss innovative ideas for enhancing DNA vaccine efficacy and the progress being made toward developing an effective vaccine.

Anti-V3 humanized antibody KD-247 effectively suppresses ex vivo generation of human immunodeficiency virus type 1 and affords sterile protection of monkeys against a heterologous simian/human immunodeficiency virus infection

In an accompanying report (Y. Eda, M. Takizawa, T. Murakami, H. Maeda, K. Kimachi, H. Yonemura, S. Koyanagi, K. Shiosaki, H. Higuchi, K. Makizumi, T. Nakashima, K. Osatomi, S. Tokiyoshi, S. Matsushita, N. Yamamoto, and M. Honda, J. Virol. 80:5552-5562, 2006), we discuss our production of a high-affinity humanized monoclonal antibody, KD-247, by sequential immunization with V3 peptides derived from human immunodeficiency virus type 1 (HIV-1) clade B primary isolates. Epitope mapping revealed that KD-247 recognized the Pro-Gly-Arg V3 tip sequence conserved in HIV-1 clade B isolates. In this study, we further demonstrate that in vitro, KD-247 efficiently neutralizes CXCR4- and CCR5-tropic primary HIV-1 clade B and clade B' with matching neutralization sequence motifs but does not neutralize sequence-mismatched clade B and clade E isolates. Monkeys were provided sterile protection against heterologous simian/human immunodeficiency virus challenge by the passive transfer of a single high dose (45 mg per kg of body weight) of KD-247 and afforded partial protection by lower antibody doses (30 and 15 mg per kg). Protective neutralization endpoint titers in plasma at the time of virus challenge were 1:160 in animals passively transferred with a high dose of the antibody. The antiviral efficacy of the antibody was further confirmed by its suppression of the ex vivo generation of primary HIV-1 quasispecies in peripheral blood mononuclear cell cultures from HIV-infected individuals. Therefore, KD-247 promises to be a valuable tool not only as a passive immunization antibody for the prevention of HIV infection but also as an immunotherapy for the suppression of HIV in phenotype-matched HIV-infected individuals.

Sequential immunization with V3 peptides from primary human immunodeficiency virus type 1 produces cross-neutralizing antibodies against primary isolates with a matching narrow-neutralization sequence motif

An antibody response capable of neutralizing not only homologous but also heterologous forms of the CXCR4-tropic human immunodeficiency virus type 1 (HIV-1) MNp and CCR5-tropic primary isolate HIV-1 JR-CSF was achieved through sequential immunization with a combination of synthetic peptides representing HIV-1 Env V3 sequences from field and laboratory HIV-1 clade B isolates. In contrast, repeated immunization with a single V3 peptide generated antibodies that neutralized only type-specific laboratory-adapted homologous viruses. To determine whether the cross-neutralization response could be attributed to a cross-reactive antibody in the immunized animals, we isolated a monoclonal antibody, C25, which neutralized the heterologous primary viruses of HIV-1 clade B. Furthermore, we generated a humanized monoclonal antibody, KD-247, by transferring the genes of the complementary determining region of C25 into genes of the human V region of the antibody. KD-247 bound with high affinity to the "PGR" motif within the HIV-1 Env V3 tip region, and, among the established reference antibodies, it most effectively neutralized primary HIV-1 field isolates possessing the matching neutralization sequence motif, suggesting its promise for clinical applications involving passive immunizations. These results demonstrate that sequential immunization with B-cell epitope peptides may contribute to a humoral immune-based HIV vaccine strategy. Indeed, they help lay the groundwork for the development of HIV-1 vaccine strategies that use sequential immunization with biologically relevant peptides to overcome difficulties associated with otherwise poorly immunogenic epitopes.