Biomedical subjects

Thorsten U Vogel

Publications and source records attributed to Thorsten U Vogel.

8 recordsLinked to original sources

PubMed2003

Multispecific vaccine-induced mucosal cytotoxic T lymphocytes reduce acute-phase viral replication but fail in long-term control of simian immunodeficiency virus SIVmac239.

Given the current difficulties generating vaccine-induced neutralizing antibodies to human immunodeficiency virus (HIV), the focus of the vaccine community has shifted toward creating cytotoxic-T-lymphocyte (CTL)-based vaccines. Recent reports of CTL-based vaccine trials in macaques challenged with simian/human immunodeficiency virus SHIV-89.6P have supported the notion that such vaccines can ameliorate the course of disease. However, almost all of these studies included Env as an immunogen and since SHIV-89.6P is sensitive to neutralizing antibodies it is difficult to determine the mechanism(s) of protection. Consequently, SHIV-89.6P challenge of macaques may be a poor model for determining vaccine efficacy in humans. To ascertain the effect of vaccine-induced multispecific mucosal CTL, in the absence of Env-specific antibody, on the control of an immunodeficiency virus challenge, we vaccinated Mamu-A*01(+) macaques with constructs encoding a combination of CTL epitopes and full-length proteins (Tat, Rev, and Nef) by using a DNA prime/recombinant modified vaccinia virus Ankara (rMVA) boost regimen. The vaccination induced virus-specific CTL and CD4(+) helper T lymphocytes with CTL frequencies as high as 20,000/million peripheral blood mononuclear cells. The final rMVA vaccination, delivered intravenously, engendered long-lived mucosal CTL. At 16 weeks after the final rMVA vaccination, the vaccinees and naive, Mamu-A*01(+) controls were challenged intrarectally with SIVmac239. Massive early anamnestic cellular immune responses controlled acute-phase viral replication; however, the three vaccinees were unable to control virus replication in the chronic phase. The present study suggests that multispecific mucosal CTL, in the absence of neutralizing antibodies, can achieve a modicum of control over early viral replication but are unable to control chronic-phase viral replication after a high-dose mucosal challenge with a pathogenic simian immunodeficiency virus.

Acute Disease↗

PubMed2002

Differences between T cell epitopes recognized after immunization and after infection.

Evidence suggests that cellular immune responses play a crucial role in the control of HIV and SIV replication in infected individuals. Several vaccine strategies have therefore targeted these CD8(+) and CD4(+) responses. Whether vaccination induces the same repertoire of responses seen after infection is, however, a key unanswered question in HIV vaccine development. We therefore compared the epitope specificity induced by vaccination to that present postchallenge in the peripheral blood. Intracellular cytokine staining of PBMC stimulated with overlapping 15/20-mer peptides spanning the proteins of SIV were measured after DNA/modified vaccinia Ankara vaccination of eight rhesus macaques. Lymphocytes from 8 animals recognized a total of 39 CD8 epitopes and 41 CD4 epitopes encoded by the vaccine. T cell responses were again monitored after challenge with SIVmac239 to investigate the evolution of these responses. Only 57% of all CD8(+) T cell responses and 19% of all CD4(+) T cell responses present after vaccination were recalled after infection as measured in the peripheral blood. Interestingly, 29 new CD8 epitopes and 5 new CD4 epitopes were recognized by PBMC in the acute phase. These new epitopes were not detected after vaccination, and only some of them were maintained in the chronic phase (33% of CD8 and no CD4 responses). Additionally, 24 new CD8 epitopes and 7 new CD4 epitopes were recognized by PBMC in the chronic phase of infection. The repertoire of the immune response detected in the peripheral blood after immunization substantially differed from the immune response detected in the peripheral blood after infection.

Administration, Rectal↗

PubMed2002

Comparison of vaccine strategies using recombinant env-gag-pol MVA with or without an oligomeric Env protein boost in the SHIV rhesus macaque model.

Rhesus macaques were immunized with a replication-deficient vaccinia virus (MVA) expressing human immunodeficiency virus type 1 89.6 envelope (env) and SIV gagpol (MVA/SHIV89.6) with or without a protein boost consisting of soluble 89.6 env (gp140). Immunization with MVA/SHIV89.6 alone elicited binding antibodies in all animals and neutralizing antibodies in 5 of 15 animals. Both types of antibodies were enhanced by protein boosting. In addition, CD8 cells exhibiting CM9 tetramer binding were detected in the subset of animals that were Mamu-A*01 positive. Animals were challenged intravenously with either SHIV-89.6 (Study 1) or the more pathogenic derivative SHIV-89.6P (Study 2). In Study 1, all control and vaccinated animals except one became infected. However, the levels of viremia were as follows: controls > rMVA alone > rMVA + protein. The differences were statistically significant between immunized and control groups but not between the two immunized groups. In Study 2, all animals became infected; however, the vaccinated group exhibited a 5-fold reduction in peak viremia and a 10-fold reduction in the postacute phase viremia in comparison to the controls. All of the controls required euthanasia by 10 months after challenge. A relationship between vaccine-induced antibody titers and reduction in virus burden was observed in both studies. Thus, immunization with MVA/SHIV89.6 alone or with a protein boost stimulated both arms of the immune system and resulted in significant control of viremia and delayed progression to disease after challenge with SHIV-89.6P.

AIDS Vaccines↗

PubMed2002

Acute phase cytotoxic T lymphocyte escape is a hallmark of simian immunodeficiency virus infection.

Cytotoxic T-lymphocyte (CTL) responses peak coincident with the decline in acute HIV viremia. Despite two reports of CTL-resistant HIV variants emerging during acute infection, the contribution of acute CTL escape to HIV pathogenesis remains unclear. Difficulties inherent in studying acute HIV infection can be overcome by modeling virus-host interactions in SIV-infected rhesus macaques. We sequenced 21 complete simian immunodeficiency virus (SIV)mac239 genomes at four weeks post-infection to determine the extent of acute CTL escape. Here we show that viruses from 19 of 21 macaques escaped from CTLs during acute infection and that these escape-selecting CTLs were responsive to lower concentrations of peptide than other SIV-specific CTLs. Interestingly, CTLs that require low peptide concentrations for stimulation (high 'functional avidity') are particularly effective at controlling other viral infections. Our results suggest that acute viral escape from CTLs is a hallmark of SIV infection and that CTLs with high functional avidity can rapidly select for escape variants.

Acute Disease↗

PubMed2002

Induction of anti-simian immunodeficiency virus cellular and humoral immune responses in rhesus macaques by peptide immunogens: correlation of CTL activity and reduction of cell-associated but not plasma virus load following challenge.

Lipopeptides which carry the N-terminal moiety tripalmitoyl-S-glyceryl-cysteinyl-seryl-seryl (P(3)CSS) have been shown to have effective adjuvant and transmembrane carrier properties. To test the ability of these constructs to immunize against simian immunodeficiency virus [(SIV)(mac)] infection, rhesus macaques, prescreened for expression of the Mamu-A*01 MHC class I molecule, were immunized at regular intervals with lipopeptides corresponding to known SIV(mac) CTL epitopes alone or in combination with multiple antigenic peptides corresponding to neutralizing epitopes. Both humoral and CTL responses were elicited and the monkeys, along with non-immunized control animals, were challenged intravenously with 20 MID(50) of the homologous, uncloned SIV(mac251-32H) grown in rhesus monkey PBMC. Although none of the monkeys were protected from infection, most demonstrated an anamnestic CTL response with epitope-specific CTL precursor frequencies reaching as high as 1 in 20 total PBMC as measured by limiting dilution CTL assay or 25% of all CD8(+) T-cells using tetrameric MHC-I/peptide complexes. A significant inverse correlation between the levels of CTLp and the number of infected cells in circulation was observed. However, no such correlation with the plasma viral load (RNA copies/ml) was evident.

Amino Acid Sequence↗

PubMed2002

Immunization of rhesus macaques with a DNA prime/modified vaccinia virus Ankara boost regimen induces broad simian immunodeficiency virus (SIV)-specific T-cell responses and reduces initial viral replication but does not prevent disease progression following challenge with pathogenic SIVmac239.

Producing a prophylactic vaccine for human immunodeficiency virus (HIV) has proven to be a challenge. Most biological isolates of HIV are difficult to neutralize, so that conventional subunit-based antibody-inducing vaccines are unlikely to be very effective. In the rhesus macaque model, some protection was afforded by DNA/recombinant viral vector vaccines. However, these studies used as the challenge virus SHIV-89.6P, which is neutralizable, making it difficult to determine whether the observed protection was due to cellular immunity, humoral immunity, or a combination of both. In this study, we used a DNA prime/modified vaccinia virus Ankara boost regimen to immunize rhesus macaques against nearly all simian immunodeficiency virus (SIV) proteins. These animals were challenged intrarectally with pathogenic molecularly cloned SIVmac239, which is resistant to neutralization. The immunization regimen resulted in the induction of virus-specific CD8(+) and CD4(+) responses in all vaccinees. Although anamnestic neutralizing antibody responses against laboratory-adapted SIVmac251 developed after the challenge, no neutralizing antibodies against SIVmac239 were detectable. Vaccinated animals had significantly reduced peak viremia compared with controls (P < 0.01). However, despite the induction of virus-specific cellular immune responses and reduced peak viral loads, most animals still suffered from gradual CD4 depletion and progressed to disease.

AIDS Vaccines↗

PubMed2002

Dominance of CD8 responses specific for epitopes bound by a single major histocompatibility complex class I molecule during the acute phase of viral infection.

Cytotoxic T-lymphocyte (CTL) responses are thought to control human immunodeficiency virus replication during the acute phase of infection. Understanding the CD8(+) T-cell immune responses early after infection may, therefore, be important to vaccine design. Analyzing these responses in humans is difficult since few patients are diagnosed during early infection. Additionally, patients are infected by a variety of viral subtypes, making it hard to design reagents to measure their acute-phase immune responses. Given the complexities in evaluating acute-phase CD8(+) responses in humans, we analyzed these important immune responses in rhesus macaques expressing a common rhesus macaque major histocompatibility complex class I molecule (Mamu-A*01) for which we had developed a variety of immunological assays. We infected eight Mamu-A*01-positive macaques and five Mamu-A*01-negative macaques with the molecularly cloned virus SIV(mac)239 and determined all of the simian immunodeficiency virus-specific CD8(+) T-cell responses against overlapping peptides spanning the entire virus. We also monitored the evolution of particular CD8(+) T-cell responses by tetramer staining of peripheral lymphocytes as well as lymph node cells in situ. In this first analysis of the entire CD8(+) immune response to autologous virus we show that between 2 and 12 responses are detected during the acute phase in each animal. CTL against the early proteins (Tat, Rev, and Nef) and against regulatory proteins Vif and Vpr dominated the acute phase. Interestingly, CD8(+) responses against Mamu-A*01-restricted epitopes Tat(28-35)SL8 and Gag(181-189)CM9 were immunodominant in the acute phase. After the acute phase, however, this pattern of reactivity changed, and the Mamu-A*01-restricted response against the Gag(181-189)CM9 epitope became dominant. In most of the Mamu-A*01-positive macaques tested, CTL responses against epitopes bound by Mamu-A*01 dominated the CD8(+) cellular immune response.

Acute Disease↗

PubMed2002

Escape in one of two cytotoxic T-lymphocyte epitopes bound by a high-frequency major histocompatibility complex class I molecule, Mamu-A*02: a paradigm for virus evolution and persistence?

It is now accepted that an effective vaccine against AIDS must include effective cytotoxic-T-lymphocyte (CTL) responses. The simian immunodeficiency virus (SIV)-infected rhesus macaque is the best available animal model for AIDS, but analysis of macaque CTL responses has hitherto focused mainly on epitopes bound by a single major histocompatibility complex (MHC) class I molecule, Mamu-A*01. The availability of Mamu-A*01-positive macaques for vaccine studies is therefore severely limited. Furthermore, it is becoming clear that different CTL responses are able to control immunodeficiency virus replication with varying success, making it a priority to identify and analyze CTL responses restricted by common MHC class I molecules other than Mamu-A*01. Here we describe two novel epitopes derived from SIV, one from Gag (Gag(71-79) GY9), and one from the Nef protein (Nef(159-167) YY9). Both epitopes are bound by the common macaque MHC class I molecule, Mamu-A*02. The sequences of these two eptiopes are consistent with the molecule's peptide-binding motif, which we have defined by elution of natural ligands from Mamu-A*02. Strikingly, we found evidence for the selection of escape variant viruses by CTL specific for Nef(159-167) YY9 in 6 of 6 Mamu-A*02-positive animals. In contrast, viral sequences encoding the Gag(71-79) GY9 epitope remained intact in each animal. This situation is reminiscent of Mamu-A*01-restricted CTL that recognize Tat(28-35) SL8, which reproducibly selects for escape variants during acute infection, and Gag(181-189) CM9, which does not. Differential selection by CTL may therefore be a paradigm of immunodeficiency virus infection.

Amino Acid Sequence↗