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: A prime-boost schedule consisting of a rabies virus (RV) vaccine strain and a recombinant vesicular stomatitis virus (VSV) both expressing HIV Envelope shows that it is feasible to elicit robust cellular and humoral anti-HIV responses using two different live attenuated Rhabdovirus vectors to sequentially prime and boost.
47 citations
Cites background from "Design and tests of an HIV vaccine...."
..., 2002, 2003) suggesting that activation of the humoral and cellular immune response is necessary for a potent HIV vaccine (McMichael and Hanke, 2003; McMichael et al., 2002)....
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TL;DR: Results showed that a single administration of PEI-pgp120 complexes, eliciting strong immune responses, is an effective vaccination approach to generate protection against systemic and mucosal viral infections.
42 citations
TL;DR: A dose as small as 0.01 mg of the codon-optimized rBCG per animal proved capable of eliciting immune responses, suggesting that even low doses of a cod on-target, recombinant BCG-based vaccine could effectively elicit HIV-1-specific immune responses.
Abstract: Although its potential for vaccine development is already known, the introduction of recombinant human immunodeficiency virus (HIV) genes to Mycobacterium bovis bacille Calmette-Guerin (BCG) has thus far elicited only limited responses. In order to improve the expression levels, we optimized the codon usage of the HIV type 1 (HIV-1) p24 antigen gene of gag (p24 gag) and established a codon-optimized recombinant BCG (rBCG)-p24 Gag which expressed a 40-fold-higher level of p24 Gag than did that of nonoptimized rBCG-p24 Gag. Inoculation of mice with the codon-optimized rBCG-p24 Gag elicited effective immunity, as evidenced by virus-specific lymphocyte proliferation, gamma interferon ELISPOT cell induction, and antibody production. In contrast, inoculation of animals with the nonoptimized rBCG-p24 Gag induced only low levels of immune responses. Furthermore, a dose as small as 0.01 mg of the codon-optimized rBCG per animal proved capable of eliciting immune responses, suggesting that even low doses of a codon-optimized rBCG-based vaccine could effectively elicit HIV-1-specific immune responses.
39 citations
Cites methods from "Design and tests of an HIV vaccine...."
...One of the prospective measures is to evoke host immunity by delivering recombinant vector-based vaccines expressing recombinant antigens, e.g., modified vaccinia virus Ankara (4, 21), adenovirus type 5 (29), fowlpox virus (16), canarypox virus (8), and NYVAC (5)....
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..., modified vaccinia virus Ankara (4, 21), adenovirus type 5 (29), fowlpox virus (16), canarypox virus (8), and NYVAC (5)....
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TL;DR: Testing different DNA vectors in mice and macaques revealed that a combination of DNAs producing different forms of the same antigen generated more balanced immune responses, a desirable feature for an optimal AIDS vaccine.
31 citations
TL;DR: The results suggest that different routes of infection induce virus-specific CD8 T cells with distinct homing phenotypes and effector functions as well as variable abilities to clear infection.
Abstract: CD8 T-cell response provides an important defense against rotavirus, which infects a variety of systemic locations in addition to the gut. Here we investigated the distribution, phenotype, and function of rotavirus-specific CD8 T cells in multiple organs after rotavirus infection initiated via the intranasal, oral, or intramuscular route. The highest level of virus-specific CD8 T cells was observed in the Peyer's patches of orally infected mice and in the lungs of intranasally infected animals. Very low levels of virus-specific CD8 T cells were detected in peripheral blood or spleen irrespective of the route of infection. Rotavirus-specific CD8 T cells from Peyer's patches of orally infected mice expressed high levels of CCR9, while CXCR6 and LFA-1 expression was associated with virus-specific CD8 T cells in lungs of intranasally infected mice. Oral infection induced the highest proportion of gamma interferon− CD107a/b+ CD8 T cells in Peyer's patches. When equal numbers of rotavirus-specific CD8 T cells were transferred into Rag-1 knockout mice chronically infected with rotavirus, the donor cells derived from Peyer's patches of orally infected mice were more efficient than those derived from lungs of intranasally infected animals in clearing intestinal infection. These results suggest that different routes of infection induce virus-specific CD8 T cells with distinct homing phenotypes and effector functions as well as variable abilities to clear infection.
27 citations
Cites result from "Design and tests of an HIV vaccine...."
...In agreement with the findings of others (31, 34), our data indicated that mucosal inoculation induced the strongest immune response at mucosal sites, rather than systemic sites....
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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