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Tomás Hanke

Publications and source records attributed to Tomás Hanke.

At least 19 recordsLinked to original sources
PubMed2007

Combined single-clade candidate HIV-1 vaccines induce T cell responses limited by multiple forms of in vivo immune interference.

We assessed in mice whether broad CD8+ T cell responses capable of efficient recognition of multiple HIV-1 clades could be induced using current single-clade vaccine constructs that were or will be used in clinical trials in Europe and Africa. We found that single-clade A, B and C vaccines applied alone induced only limited cross-clade reactivity and that the epitope hierarchy varied according to the immunizing clade. However, combining single-clade HIV-1 vaccines into multi-clade formulations resulted in multiple forms of in vivo immune interference such as original antigenic sin and antagonism, which dampened or even abrogated induction of responses to epitope variants and reduced the breadth of induced T cell responses. Simultaneous administration of individual clade-specific vaccines into anatomically separated sites on the body alleviated antagonism and increased the number of detectable epitope responses. Although cross-reactivity of murine CD8+ T cells does not directly translate to humans, the molecular interactions involved in triggering T cell responses are the same in mouse and man. Thus, these results have important ramifications for the design of both prophylactic and therapeutic vaccines against HIV-1 and other highly variable pathogens.

AIDS Vaccines↗
PubMed2006

On DNA vaccines and prolonged expression of immunogens.

Persistent hepatitis B virus (HBV) infection represents a major public health concern because of its association with chronic liver disease and the propensity of the disease to progress to cirrhosis and hepatocellular carcinoma. Despite the availability of a prophylactic vaccine effective in a majority of the population, alternative vaccination strategies are being sought to induce protective responses in healthy non-responders and to boost and broaden T cell responses in chronically infected patients, which may lead to a better control of the virus and/or its eventual complete clearance. In this issue of the European Journal of Immunology immunization of BALB/c mice intramuscularly with a DNA vaccine encoding the hepatitis virus B surface antigen (HBsAg) was shown to result in prolonged secretion of HBsAg into the serum and the elicitation of HBsAg-specific antibodies. In fact, the vaccine was so efficient that the antibodies and HBsAg formed circulating immune complexes and induced kidney and liver lesions similar to those observed in chronically infected patients. This commentary discusses these results in terms of the safety of plasmid DNA-vectored genetic vaccines in general, the use of DNA vaccines expressing HBsAg for the treatment of chronic hepatitis and the consequences of prolonged immunogen expression for the development of protective immune responses.

Animals↗
PubMed2006

Induction of long-lasting multi-specific CD8+ T cells by a four-component DNA-MVA/HIVA-RENTA candidate HIV-1 vaccine in rhesus macaques.

As a part of a long-term effort to develop vaccine against HIV-1 clade A inducing protective T cell responses in humans, we run mutually complementing studies in humans and non-human primates (NHP) with the aim to maximize vaccine immunogenicity. The candidate vaccine under development has four components, pTHr.HIVA and pTH.RENTA DNA, and modified vaccinia virus Ankara (MVA).HIVA and MVA.RENTA, delivered in a heterologous DNA prime-MVA boost regimen. While the HIVA (Gag/epitopes) components have been tested in NHP and over 300 human subjects, we plan to test in humans the RENTA (reverse transcriptase, gp41, Nef, Tat) vaccines designed to broaden HIVA-induced responses in year 2007. Here, we investigated the four-component vaccine long-term immunogenicity in Mamu-A*01-positive rhesus macaques and demonstrated that the vaccine-induced T cells were multi-specific, multi-functional, readily proliferated to recall peptides and were circulating in the peripheral blood of vaccine recipients over 1 year after vaccine administration. The consensus clade A-elicited T cells recognized 50% of tested epitope variants from other HIV-1 clades. Thus, the DNA-MVA/HIVA-RENTA vaccine induced memory T cells of desirable characteristics and similarities to those induced in humans by HIVA vaccines alone; however, single-clade vaccines may not elicit sufficiently cross-reactive responses.

AIDS Vaccines↗
PubMed2006

Immunisation with recombinant modified vaccinia virus Ankara expressing HIV-1 gag in HIV-1-infected subjects stimulates broad functional CD4+ T cell responses.

Virus-specific CD4+ T cells with IL-2-secreting and/or proliferative capacity are detected readily in HIV-1-infected long-term nonprogressors and rarely in persons with untreated progressive infection. The contribution of these cells to viraemia control is uncertain, but this question might be addressed in clinical therapeutic vaccination studies. However, the quality of T helper responses induced by currently available HIV-1 vaccine candidates has not been explored in depth. We determined the effect of vaccination with modified vaccinia virus Ankara (MVA) expressing HIV-1 gag p24/p17 (MVA.HIVA) on HIV-1-specific CD4+ T cell responses in 16 chronically infected, highly active antiretroviral therapy (HAART)-treated subjects using CD8-depleted IFN-gamma ELISPOT assays, intracellular cytokine staining assays for IL-2 and IFN-gamma, and a CFSE-based proliferation assay. Gag-specific CD4+ T cell responses were significantly increased in magnitude and breadth after vaccination and targeted both known and new epitopes, several of which were also recognised by healthy HIV-uninfected volunteers immunised with the same vaccines. The frequencies of CD4+ T cells expressing IL-2 or IFN-gamma, alone or simultaneously, were also augmented. These findings indicate that functional virus-specific T helper cells can be boosted by vaccination in chronic HIV-1 infection. Further evaluation of their role in viraemia control is warranted.

AIDS Vaccines↗
PubMed2006

Expansion and diversification of virus-specific T cells following immunization of human immunodeficiency virus type 1 (HIV-1)-infected individuals with a recombinant modified vaccinia virus Ankara/HIV-1 Gag vaccine.

Affordable therapeutic strategies that induce sustained control of human immunodeficiency virus type 1 (HIV-1) replication and are tailored to the developing world are urgently needed. Since CD8(+) and CD4(+) T cells are crucial to HIV-1 control, stimulation of potent cellular responses by therapeutic vaccination might be exploited to reduce antiretroviral drug exposure. However, therapeutic vaccines tested to date have shown modest immunogenicity. In this study, we performed a comprehensive analysis of the changes in virus-specific CD8(+) and CD4(+) T-cell responses occurring after vaccination of 16 HIV-1-infected individuals with a recombinant modified vaccinia virus Ankara-vectored vaccine expressing the consensus HIV-1 clade A Gag p24/p17 sequences and multiple CD8(+) T-cell epitopes during highly active antiretroviral therapy. We observed significant amplification and broadening of CD8(+) and CD4(+) gamma interferon responses to vaccine-derived epitopes in the vaccinees, without rebound viremia, but not in two unvaccinated controls followed simultaneously. Vaccine-driven CD8(+) T-cell expansions were also detected by tetramer reactivity, predominantly in the CD45RA(-) CCR7(+) or CD45RA(-) CCR7(-) compartments, and persisted for at least 1 year. Expansion was associated with a marked but transient up-regulation of CD38 and perforin within days of vaccination. Gag-specific CD8(+) and CD4(+) T-cell proliferation also increased postvaccination. These data suggest that immunization with MVA.HIVA is a feasible strategy to enhance potentially protective T-cell responses in individuals with chronic HIV-1 infection.

AIDS Vaccines↗
PubMed2005

Phase I clinical trial safety of DNA- and modified virus Ankara-vectored human immunodeficiency virus type 1 (HIV-1) vaccines administered alone and in a prime-boost regime to healthy HIV-1-uninfected volunteers.

DNA- and modified virus Ankara (MVA)-vectored candidate vaccines expressing human immunodeficiency virus type 1 (HIV-1) clade A-derived p24/p17 gag fused to a string of HLA class I epitopes, called HIVA, were tested in phase I trials in healthy, HIV-1/2-uninfected adults in Oxford, United Kingdom. Eighteen volunteers were vaccinated with pTHr.HIVA DNA (IAVI-001) alone, 8 volunteers received MVA.HIVA (IAVI-003) alone and 9 volunteers from study IAVI-001 were boosted with MVA.HIVA 9-14 months after DNA priming (IAVI-005). Immunogenicity results observed in these trials was published previously [Mwau M, Cebere I, Sutton J, Chikoti P, Winstone N, Wee EG-T, et al. An HIV-1 clade A vaccine in clinical trials: stimulation of HIV-specific T cell responses by DNA and recombinant modified vaccinia virus Ankara (MVA) vaccines in humans. J Gen Virol 2004;85:911-9]. Here, we report on the safety of the two vaccines and the vaccine regimes. Overall, both candidate vaccines were safe and well tolerated. There were no reported vaccine-related adverse events over the 6-month period of the study and up to 2 years after the last vaccination. There were no moderate or severe local symptoms recorded after the pTHr.HIVA DNA intramuscular administration. Almost all participants experienced local reactogenicity events such as redness and induration after MVA.HIVA intradermal injection. Thus, the results from these initial small phase I trials administering the pTHr.HIVA DNA and MVA.HIVA vaccines either alone or in a prime-boost regime to healthy HIV-1/2-negative adults indicated that the vaccines were safe and warranted further testing of this approach in larger phase I/II studies.

AIDS Vaccines↗
PubMed2005

Therapeutic immunization of highly active antiretroviral therapy-treated HIV-1-infected patients: safety and immunogenicity of an HIV-1 gag/poly-epitope DNA vaccine.

In view of the global emergency posed by lack of access to highly active antiretroviral therapy (HAART) and the limitations of current drug regimens, alternative therapeutic strategies are urgently needed. Cellular immune responses elicited by HIV-1 exert some control over virus replication, therefore the enhancement of HIV-1-specific responses by therapeutic vaccination might lead to viral containment without HAART. We evaluated the safety and immunogenicity, in HIV-1-infected individuals under HAART suppression, of a DNA vaccine, pTHr.HIVA.

AIDS Vaccines↗
PubMed2005

Biodistribution and persistence of an MVA-vectored candidate HIV vaccine in SIV-infected rhesus macaques and SCID mice.

Recombinant modified vaccinia virus Ankara (MVA) is together with a few other attenuated viral vectors on the forefront of human immunodeficiency virus type 1 (HIV-1) vaccine development. As such, MVA-vectored vaccines are likely to be administered into immunocompromized individuals. Here, we demonstrated in a good laboratory practice study safety and biological clearance of candidate HIV-1 vaccine MVA.HIVA in simian immunodeficiency virus (SIV)-infected rhesus macaques and mice with a severe combined immunodeficiency (SCID) following an intradermal vaccine administration. In SIV-infected macaques, MVA.HIVA DNA was undetectable by nested PCR 6 weeks after dosing. In SCID mice, the MVA.HIVA vaccine was well tolerated and a positive PCR signal was only observed at the site of injection 49 days after dosing in four out of six mice, but even these sites were negative by day 81 post-injection. Therefore, the MVA.HIVA vaccine is considered safe for application in phase I clinical trials in HIV-1-infected human subjects. These results also contribute to the confidence of using MVA as a smallpox vaccine.

AIDS Vaccines↗
PubMed2005

Altered primary CD8+ T cell response to a modified virus Ankara(MVA)-vectored vaccine in the absence of CD4+ T cell help.

T cell receptor-transgenic F5 mice were used to assess primary CD8+ T cell responses to a modified virus Ankara (MVA)-vectored vaccine in the absence of CD4+ T cell help. Naive, CD8-enriched, CFSE-labelled F5 cells were transferred into normal or CD4+ cell-depleted mice and the mice were vaccinated with MVA.HIVA-NP. At different time points during the primary response, F5 cells were re-isolated and analysed on divisional basis for a number of parameters. We demonstrated that the primary CD8+ T cell response in the absence of CD4+ T cell help differed from that in normal CD4+ cell-undepleted mice. While in the absence of CD4+ T cell help, the initial migratory progress from the local response to a systemic one was not grossly affected, the proportion of dying F5 cells during the expansion phase was markedly increased and resulted in an overall smaller expansion and significantly decreased frequency of CD8+ T cell memory after contraction. T cells primed without help displayed accelerated proliferation and activation, while expression of interferon-gamma remained similar. These phenomena were observed in the lymph nodes draining the MVA.HIVA-NP immunization site and were similar, but delayed by 2-3 days in spleen and non-draining lymph nodes.

Animals↗
PubMed2005

Vaccine route, dose and type of delivery vector determine patterns of primary CD8+ T cell responses.

The dynamics of primary CD8+ T cell responses following administration of modified virus Ankara (MVA)- and DNA-vectored vaccines was investigated in a mouse model. To overcome the low frequency of naive antigen-specific precursors and follow the early expansion events, naive CFSE-labelled T cell receptor-transgenic F5 lymphocytes were transferred into syngeneic non-transgenic recipients prior to vaccination. Using the i.d., i.v. and i.m. routes and increasing recombinant MVA (rMVA) vaccine doses, the primary response was analysed on a divisional basis at local and distant lymphoid organs at various times after vaccination. The results indicated that F5 cell divisions were initiated in the local draining lymph nodes and cells only after five to six divisions appeared at more distant sites. The rMVA dose affected frequencies of cells entering division and at the peak response. When priming induced by rMVA and plasmid DNA was compared, dramatic differences in the cycling patterns were observed with plasmid DNA inducing a response slower and more sustained over the first 2 wk than rMVA. Both rMVA and DNA induced comparable IFN-gamma production, which increased with cell divisions. Taken together, the vaccine type, dose and route have a strong influence on the spatial and temporal patterns of initial T cell responses.

AIDS Vaccines↗
PubMed2005

Induction of human immunodeficiency virus type 1-specific T cells by a bluetongue virus tubule-vectored vaccine prime-recombinant modified virus Ankara boost regimen.

In the absence of strategies for reliable induction of antibodies broadly neutralizing human immunodeficiency virus type 1 (HIV-1), vaccine efforts have shifted toward the induction of cell-mediated immunity. Here we describe the construction and immunogenicity of novel T-cell vaccine NS1.HIVA, which delivers the HIV-1 clade A consensus-derived immunogen HIVA on the surface of tubular structures spontaneously formed by protein NS1 of bluetongue virus. We demonstrated that NS1 tubules can accommodate a protein as large as 527 amino acids without losing their self-assembly capability. When injected into BALB/c mice by several routes, chimeric NS1.HIVA tubules induced HIV-1-specific major histocompatibility complex class I-restricted T cells. These could be boosted by modified virus Ankara expressing the same immunogen and generate a memory capable of gamma interferon (IFN-gamma) production, proliferation, and lysis of sensitized target cells. Induced memory T cells readily produced IFN-gamma 230 days postimmunization, and upon a surrogate virus challenge, NS1.HIVA vaccine alone decreased the vaccinia virus vv.HIVA load in ovaries by 2 orders of magnitude 280 days after immunization. Thus, because of its T-cell immunogenicity and antigenic simplicity, the NS1 delivery system could serve as a priming agent for heterologous prime-boost vaccination regimens. Its usefulness in primates, including humans, remains to be determined.

Animals↗
PubMed2004

DNA vaccines against human immunodeficiency virus type 1.

Development of a vaccine against human immunodeficiency virus type 1 (HIV-1) is the main hope for controlling the acquired immunodeficiency syndrome pandemic. An ideal HIV vaccine should induce neutralizing antibodies, CD4+ helper T cells, and CD8+ cytotoxic T cells. While the induction of broadly neutralizing antibodies remains a highly challenging goal, there are a number of technologies capable of inducing potent cell-mediated responses in animal models, which are now starting to be tested in humans. Naked DNA immunization is one of them. This review focuses on the stimulation of HIV-specific T cells and discusses in the context of the current 'state-of-art' of DNA vaccines, the areas where this technology might assist either alone or as a part of more complex vaccine formulations in the HIV vaccine development.

AIDS Vaccines↗
PubMed2004

MVA as a vector for vaccines against HIV-1.

A vaccine against HIV Type 1 (HIV-1) is urgently needed. Modified vaccinia virus Ankara is an attenuated smallpox vaccine which can be adapted to express HIV-1 antigens. In this review, we discuss the features which make modified vaccinia virus Ankara an attractive vector for genetic vaccines and have put it, together with several other recombinant viral vectors, at the forefront of HIV-1 vaccine development. Many candidate vaccines including those vectored by modified vaccinia virus Ankara are now entering human trials, the results of which will become available in the coming years.

AIDS Vaccines↗
PubMed2003

Construction and characterisation of a candidate HIV-1 subtype C DNA vaccine for South Africa.

A candidate DNA vaccine pTHgagC expressing the immunodeficiency virus-1 (HIV-1) gag gene from South African isolate Du422 was constructed and characterised. The isolate was selected on the basis of being the closest to the South African subtype C consensus sequence. Sequence analysis of cytotoxic T lymphocyte (CTL) epitopes showed that HIV subtype C-infected individuals have CTL responses to a number of epitopes present in the vaccine, but also revealed a more limited presence of subtype A- and any B-derived epitopes. A high level of expression of the immunogen was demonstrated in human cells and a potent, long-lived CTL response to a single inoculation of the DNA vaccine was elicited in BALB/c mice, which could be significantly increased by a boost vaccination at 4 weeks. This is the first candidate HIV-1 DNA vaccine employing the South African subtype C sequences, and constitutes a part of a vaccine scheduled to enter a clinical evaluation in South Africa in 2004.

AIDS Vaccines↗
PubMed2003

Mucosal immunization with PLGA-microencapsulated DNA primes a SIV-specific CTL response revealed by boosting with cognate recombinant modified vaccinia virus Ankara.

Systemically administered DNA encoding a recombinant human immunodeficiency virus (HIV) derived immunogen effectively primes a cytotoxic T lymphocyte (CTL) response in macaques. In this further pilot study we have evaluated mucosal delivery of DNA as an alternative priming strategy. Plasmid DNA, pTH.HW, encoding a multi-CTL epitope gene, was incorporated into poly(D,L-lactic-co-glycolic acid) microparticles of less than 10 microm in diameter. Five intrarectal immunizations failed to stimulate a circulating vaccine-specific CTL response in 2 Mamu-A*01(+) rhesus macaques. However, 1 week after intradermal immunization with a cognate modified vaccinia virus Ankara vaccine MVA.HW, CTL responses were detected in both animals that persisted until analysis postmortem, 12 weeks after the final boost. In contrast, a weaker and less durable response was seen in an animal vaccinated with the MVA construct alone. Analysis of lymphoid tissues revealed a disseminated CTL response in peripheral and regional lymph nodes but not the spleen of both mucosally primed animals.

AIDS Vaccines↗
PubMed2003

Development of prophylactic AIDS vaccines: the current state of affairs.

Despite an urgent need for a prophylactic vaccine against human immunodeficiency virus (HIV) type 1, progress in this area has been slow. The initial euphoria after identifying and sequencing the causative agent of the acquited immunodeficiency syndrome (AIDS) was followed by a realization that for HIV, traditional vaccine approaches would not be applicable. Frustrations with the induction of neutralizing antibodies led to the development of new vaccine focusing on the induction of cytotoxic T-lymphocytes (CTLs). While CTLs cannot confer sterilizing immunity, there are encouraging data from animal models suggesting that these vaccines may increase the threshold of infection and delay the onset of AIDS in humans. The CTL hypothesis and the possibility that some non-neutralizing antibodies may assist CTLs in the prophylaxis against HIV have yet to be tested in phase III efficacy trials.

AIDS Vaccines↗
PubMed2002

Design and validation of an enzyme-linked immunospot assay for use in clinical trials of candidate HIV vaccines.

The enzyme-linked immunosorbent (ELISPOT) assay, which enumerates peripheral blood mononuclear cells (PBMCs) releasing interferon gamma (IFN-gamma) on specific antigen stimulation, is becoming the assay of choice for evaluation of vaccine-induced cell-mediated immune responses in many clinical trials. A properly conducted trial requires the assays to be validated, especially should the trial lead to vaccine licensure. Here, the design and validation of an ELISPOT assay are described for use in clinical trials of candidate human immunodeficiency virus (HIV) vaccines, using a particular immunogen termed HIVA. This assay employs eight pools of 20 to 23 peptides each: seven pools are derived from the immunogen and one pool is derived from cytotoxic T cell epitopes of common human viruses serving as an internal positive control. The validation determined that first, the overall variation of a positive response of approximately 500 spot-forming units (SFU)/10(6) cells was 21%, while second, the average of 5 SFU/10(6) cells was detected for the seven HIVA-derived pools in HIV-uninfected individuals; third, a positive response to a peptide added to the assay pools was not occluded by the other pool peptides; fourth, the frequencies detected in fresh PBMCs were 2- to 3-fold higher compared with the same samples that had been cryopreserved; and finally, all seven HIV-derived pools induced IFN-gamma responses in PBMCs isolated from HIV-infected individuals. The limits of the validation of assays involving biological responses of living cells are discussed.

AIDS Vaccines↗