Design and tests of an HIV vaccine.
TL;DR: Experiments in macaques and man suggest that a prime boost regimen using DNA and recombinant pox virus is highly effective at stimulating cellular immunity, but the difficulty of inducing broad cellular responses able to protect against all clades of HIV, remains an important issue.
Abstract: It is likely that a successful vaccine against HIV will need to stimulate the innate immune system, generate high levels of neutralising antibody, strong cellular immune responses, and mucosal immunity. Early efforts to develop HIV vaccines attempted to use the virus glycoprotein, gp120, to induce neutralising antibody, but did not take into account the trimeric structure of the native glycoprotein or the complex nature of the CD4 and chemokine receptor binding sites. Recently, attention has been focused on cellular immune responses, particularly T-cell cytotoxicity, based on evidence from the SIV model and from exposed and uninfected humans. Recent experiments in macaques and man suggest that a prime boost regimen using DNA and recombinant pox virus is highly effective at stimulating cellular immunity. However, in addition to the problems of generating neutralising antibodies and mucosal immunity, the difficulty of inducing broad cellular responses able to protect against all clades of HIV, remains an important issue.
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TL;DR: This work describes the generation of immune response generation by naked DNA vaccines and discusses the routes and mode of DNA vaccine delivery-routes and mode.
Abstract: 1
Historical Background
2
Description of DNA Expression Vectors
3
Routes and Mode of DNA Vaccine Delivery
4
Generation of Immune Responses by Naked DNA Vaccines
5
Augmenting the Immunogenicity of DNA Vaccines
6
Safety Considerations for Vaccine Administration in Humans
7
Clinical Trials
8
Conclusions
9
Acknowledgments
Keywords:
naked DNA vaccines;
DNA expression vectors;
DNA vaccine delivery-routes and mode;
immune response generation by naked DNA vaccines;
DNA vaccines containing human cytomegalovirus (CMV) immediate/early (IE) promoter;
CpG motifs of plasmid DNA;
augmenting DNA vaccine immunogenicity;
codon optimization usage for eukaryotic cells-enhancing antigen expression
TL;DR: The HIV-v synthetic polypeptide vaccine described here sets a new standard in antigen design by selecting conserved regions of global HIV-1 and HIV-2 isolates and epitopes from most frequent HLA types of the human population.
Abstract: Evaluation of: Pleguezuelos O, Stoloff GA, Caparros-Wanderley W. Synthetic immunotherapy induces HIV virus specific Th1 cytotoxic response and death of an HIV-1 infected human cell line through classic complement activation. Virol. J. 10(1), 107 (2013). AIDS vaccine development represents an unprecedented challenge in both immunogen design and delivery to induce potent and long-lasting HIV-specific immune responses, including neutralizing antibodies and cytotoxic T lymphocytes (CTL). Pleguezuelos and coworkers recognized that immunogen design must address both HIV and HLA diversity to make a global vaccine. The HIV-v synthetic polypeptide vaccine described here sets a new standard in antigen design by selecting conserved regions of global HIV-1 and HIV-2 isolates and epitopes from most frequent HLA types of the human population. The new vaccine induced both antibody and CTL responses. Importantly, the authors demonstrated vaccine-specific HLA restricted CD8+ CTL responses for one HLA allele that was invol...
01 Dec 2004
TL;DR: Preliminary results are encouraging and suggest that live, attenuated Shigella vaccines can be engineering to deliver both prokaryotic and eukaryotic antigens to the mucosal system.
Abstract: : Several live attenuated Shigella vaccines of different serotypes have been shown to be safe, immunogenic, and in one case effective against challenge with virulent strains. The ability to invade epithelial cells remains critical for the success of these vaccine candidates. Live, orally administered Shigella vaccine derivatives are also being evaluated as multivalent mucosal vaccines able to deliver both bacterial antigens and eukaryotic genes to the gut associated lymphoid tissues of the common mucosal immune system. Fimbrial and enterotoxin antigen genes from enterotoxigenic E. coli (ETEC) were cloned into a plasmid encoding the gene for aspartate semialdehyde dehyrogenase (asd) and expressed within SC608, and asd mutant of Shigella flexneri 2a vaccine strain SC602. Guinea pigs immunized intranasally with SC608 expressing the ETEC antigens demonstrated serum and mucosal immune responses to antigens from both diarrheal pathogens. SC608, in the absence of an asd-based plasmid, lyses with epithelial cells after invasion. This phenotype has also been used to deliver plasmid DNA vaccines containing eukaryotic genes into the host cell cytoplasm for expression. Splenocytes from mice immunized intranasally with asd mutants of Shigella containing plasmid HIV DNA vaccines demonstrated HIV antigen-specific IFN-gamma ELISPOTS after in vitro expansion. These preliminary results are encouraging and suggest that live, attenuated Shigella vaccines can be engineering to deliver both prokaryotic and eukaryotic antigens to the mucosal system.
Cites background from "Design and tests of an HIV vaccine...."
...A recent review on the design of an ideal HIV vaccine suggest that it may be necessary to build several vaccine components which collectively stimulate production of neutralizing antibodies, CTLs, mucosal immunity and the innate immune system (24)....
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01 May 2010
TL;DR: It is demonstrated that pE7HBE6 DNA vaccine was immunogenic at a single low dose which was enhanced by boosting, and understanding the CTL response interplay between E6 and E7, within the context of pE 7HBE 6 is important for its application as a vaccine.
Abstract: Hepatitis B surface antigen (HBsAg) vaccines elicit strong cytotoxic T-lymphocyte (CTL) responses when delivered as DNA or virus-like particles. When foreign antigens are coexpressed with HBsAg as a fusion protein, powerful antigen-specific CTL responses are achieved. Therefore, HBsAg is an attractive vaccine vector for delivery of disease-related foreign epitopes. The capacity to elicit CTL responses compares favourably when rHBsAg vaccines are delivered by DNA- rather than virus like particle (VLP)-modalities. Human papillomavirus (HPV)-associated carcinoma is the second most frequent cancer causing death in women worldwide. A major feature of the HPV lifecycle is the immortalisation of the squamous epithelium and neoplastic growth, a result of HPV E6 and E7 oncogene expression. E6 and E7 oncoproteins are essential to maintain a transformed cell phenotype and are present in all stages of cervical intra-epithelial neoplasia (CIN), which make them ideal targets for immunotherapeutic therapy. In this study, we have generated an HBsAg-based vaccine platform. Using splice overlap extension (SOE)-PCR the HPV-16 E6 and E7 oncogenes were fused to HBsAg (E7HBE6). In the process, E6 and E7 were mutated to eliminate potential oncogenicity and were codon optimised for enhanced expression. The effector and memory CTL response, as well as tumour protection and therapy afforded by immunisation with E7HBE6 vaccine was evaluated in mice. The E7HBE6 construct was evaluated for the potential to form VLPs. Insect cells expressed E7HBE6 protein at low levels which appeared to form aggregates and did not demonstrate VLP formation. The formation of E7HBE6 VLPs and E7HBE6 protein were undetectable when expressed from two different mammalian cell lines. Observations within these experiments suggested that the E7HBE6 protein maybe unstable. Understanding the CTL response interplay between E6 and E7, within the context of pE7HBE6 is important for its application as a vaccine. Studies were conducted using DNA plasmid HBsAg-HPV vaccine (pE7HBE6). We demonstrated that pE7HBE6 DNA vaccine was immunogenic at a single low dose which was enhanced by boosting. Effector and memory CTL responses to E6 and E7 were maintained for 23 weeks post-immunisation. A maximal CTL response was achieved from a single dose at 30-100μg with a significant response also detected from a single dose of 10μg. When a dominant CTL epitope was eliminated from within pE7HBE6, a subdominant epitope response was detected. The presence of a subdominant epitope enhanced the response to the dominant epitope, at the cost of a decrease in its own effector CTL response. The immunodominance effect was decreased by combining epitope knockout vaccines, allowing processing of E6 and E7 CTL epitopes in separate cells. Furthermore, administration of antigens at separate anatomical sites also interfered with immunodominance. Original antigenic sin was examined by the immunisation of HBsAg-experienced mice with recombinant pE7HBE6 DNA vaccine. Prevention of the growth of HPV-16-associated subcutaneous TC-1 tumour was achieved in 100% of mice by immunisation with pE7HBE6, compared to mice immunised with HBsAg wildtype DNA vaccine, all of which presented with tumour. When pE7HBE6 was used as a therapeutic agent, a significant increase in survival and decreased tumour volume were demonstrated. In a TC-1 tumour metastasis model, where mice were inoculated with TC-1 intravenously, therapy was highly effective. Mice immunised with HBsAg-HPV DNA vaccines (either pE7HBE6, or combined epitope knockouts) remained 100% tumour free compared to mice immunised with HBsAg DNA, of which 80% displayed lung tumours. The results from this study demonstrate that a HBsAg-vectored DNA vaccine encoding both HPV-16 E6 and E7 oncoproteins can be used to provide protection and therapy against a tumour expressing HPV-16 oncogenes. This study supports previously published studies that demonstrates an enhanced HPV-specific CTL response when both E6 and E7 are administered together in the context of a vaccine. These results have generic implications for the design and administration of DNA vaccines encoding chimeric antigens. The results of this study have specific implications for the design of HBsAg-based DNA vaccines delivering HPV antigens for the protection and therapy of HPV-associated squamous carcinomas. An effective therapeutic vaccine designed to treat HPV-associated cancers has the potential to dramatically reduce the burden of cervical carcinoma and associated death rate.
References
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TL;DR: The results confirm the importance of cell-mediated immunity in controlling HIV-1 infection and support the exploration of vaccination approaches for preventing infection that will elicit these immune responses.
Abstract: Clinical evidence suggests that cellular immunity is involved in controlling human immunodeficiency virus-1 (HIV-1) replication. An animal model of acquired immune deficiency syndrome (AIDS), the simian immunodeficiency virus (SIV)-infected rhesus monkey, was used to show that virus replication is not controlled in monkeys depleted of CD8+ lymphocytes during primary SIV infection. Eliminating CD8+ lymphocytes from monkeys during chronic SIV infection resulted in a rapid and marked increase in viremia that was again suppressed coincident with the reappearance of SIV-specific CD8+ T cells. These results confirm the importance of cell-mediated immunity in controlling HIV-1 infection and support the exploration of vaccination approaches for preventing infection that will elicit these immune responses.
2,276 citations
TL;DR: With the use of the tetrameric complexes, a significant inverse correlation was observed between HIV-specific CTL frequency and plasma RNA viral load and suggest a considerable cytopathic effect of the virus in vivo.
Abstract: Although cytotoxic T lymphocytes (CTLs) are thought to be involved in the control of human immunodeficiency virus-type 1 (HIV-1) infection, it has not been possible to demonstrate a direct relation between CTL activity and plasma RNA viral load. Human leukocyte antigen-peptide tetrameric complexes offer a specific means to directly quantitate circulating CTLs ex vivo. With the use of the tetrameric complexes, a significant inverse correlation was observed between HIV-specific CTL frequency and plasma RNA viral load. In contrast, no significant association was detected between the clearance rate of productively infected cells and frequency of HIV-specific CTLs. These data are consistent with a significant role for HIV-specific CTLs in the control of HIV infection and suggest a considerable cytopathic effect of the virus in vivo.
1,480 citations
TL;DR: It is demonstrated that CD8 cells play a crucial role in suppressing SIV replication in vivo and are examined using an anti-CD8 monoclonal antibody, OKT8F.
Abstract: To determine the role of CD8(+) T cells in controlling simian immunodeficiency virus (SIV) replication in vivo, we examined the effect of depleting this cell population using an anti-CD8 monoclonal antibody, OKT8F. There was on average a 99.9% reduction of CD8 cells in peripheral blood in six infected Macaca mulatta treated with OKT8F. The apparent CD8 depletion started 1 h after antibody administration, and low CD8 levels were maintained until day 8. An increase in plasma viremia of one to three orders of magnitude was observed in five of the six macaques. The injection of a control antibody to an infected macaque did not induce a sustained viral load increase, nor did it significantly reduce the number of CD8(+) T cells. These results demonstrate that CD8 cells play a crucial role in suppressing SIV replication in vivo.
1,455 citations
TL;DR: The spatial organization of conserved neutralization epitopes on gp120 is described, using epitope maps in conjunction with the X-ray crystal structure of a ternary complex that includes a gp120 core, CD4 and a neutralizing antibody.
Abstract: The human immunodeficiency virus HIV-1 establishes persistent infections in humans which lead to acquired immunodeficiency syndrome (AIDS). The HIV-1 envelope glycoproteins, gp120 and gp41, are assembled into a trimeric complex that mediates virus entry into target cells. HIV-1 entry depends on the sequential interaction of the gp120 exterior envelope glycoprotein with the receptors on the cell, CD4 and members of the chemokine receptor family. The gp120 glycoprotein, which can be shed from the envelope complex, elicits both virus-neutralizing and non-neutralizing antibodies during natural infection. Antibodies that lack neutralizing activity are often directed against the gp120 regions that are occluded on the assembled trimer and which are exposed only upon shedding. Neutralizing antibodies, by contrast, must access the functional envelope glycoprotein complex and typically recognize conserved or variable epitopes near the receptor-binding regions. Here we describe the spatial organization of conserved neutralization epitopes on gp120, using epitope maps in conjunction with the X-ray crystal structure of a ternary complex that includes a gp120 core, CD4 and a neutralizing antibody. A large fraction of the predicted accessible surface of gp120 in the trimer is composed of variable, heavily glycosylated core and loop structures that surround the receptor-binding regions. Understanding the structural basis for the ability of HIV-1 to evade the humoral immune response should assist in the design of a vaccine.
1,290 citations
TL;DR: The replication-defective adenovirus is a promising vaccine vector for development of an HIV-1 vaccine and elicited by a replication-incompetent Ad5 vector, used either alone or as a booster inoculation after priming with a DNA vector.
Abstract: Recent studies of human immunodeficiency virus type 1 (HIV-1) infection in humans and of simian immunodeficiency virus (SIV) in rhesus monkeys have shown that resolution of the acute viral infection and control of the subsequent persistent infection are mediated by the antiviral cellular immune response. We comparatively assessed several vaccine vector delivery systems-three formulations of a plasmid DNA vector, the modified vaccinia Ankara (MVA) virus, and a replication incompetent adenovirus type 5 (Ad5) vector-expressing the SIV gag protein for their ability to elicit such immune responses in monkeys. The vaccines were tested either as a single modality or in combined modality regimens. Here we show that the most effective responses were elicited by a replication-incompetent Ad5 vector, used either alone or as a booster inoculation after priming with a DNA vector. After challenge with a pathogenic HIV-SIV hybrid virus (SHIV), the animals immunized with Ad5 vector exhibited the most pronounced attenuation of the virus infection. The replication-defective adenovirus is a promising vaccine vector for development of an HIV-1 vaccine.
1,240 citations