Michael Storcksdieck genannt Bonsmann

Targeting Antibody Responses to the Membrane Proximal External Region of the Envelope Glycoprotein of Human Immunodeficiency Virus

Although human immunodeficiency type 1 (HIV-1) infection induces strong antibody responses to the viral envelope glycoprotein (Env) only a few of these antibodies possess the capacity to neutralize a broad range of strains. The induction of such antibodies represents an important goal in the development of a preventive vaccine against the infection. Among the broadly neutralizing monoclonal antibodies discovered so far, three (2F5, Z13 and 4E10) target the short and hidden membrane proximal external region (MPER) of the gp41 transmembrane protein. Antibody responses to MPER are rarely observed in HIV-infected individuals or after immunization with Env immunogens. To initiate antibody responses to MPER in its membrane-embedded native conformation, we generated expression plasmids encoding the membrane-anchored ectodomain of gp41 with N-terminal deletions of various sizes. Following transfection of these plasmids, the MPER domains are displayed on the cell surface and incorporated into HIV virus like particles (VLP). Transfected cells displaying MPER mutants bound as efficiently to both 2F5 and 4E10 as cells transfected with a plasmid encoding full-length Env. Mice immunized with VLPs containing the MPER mutants produced MPER-specific antibodies, the levels of which could be increased by the trimerization of the displayed proteins as well as by a DNA prime-VLP boost immunization strategy. Although 2F5 competed for binding to MPER with antibodies in sera of some of the immunized mice, neutralizing activity could not be detected. Whether this is due to inefficient binding of the induced antibodies to MPER in the context of wild type Env or whether the overall MPER-specific antibody response induced by the MPER display mutants is too low to reveal neutralizing activity, remains to be determined.

GagPol-specific CD4 + T-cells increase the antibody response to Env by intrastructural help

BackgroundImmunization of rhesus macaques against Gag of SIV resulted in a more rapid appearance of Env antibodies after infection with SIV or SHIV challenge viruses although the vaccines lacked an Env component. We therefore explored whether T helper cells specific for internal HIV proteins could provide intrastructural help for Env-specific B cells and thus increase the Env antibody response.ResultsMice were immunized by adenoviral vector or DNA vaccines against GagPol and then boosted with virus-like particles (VLP) containing GagPol and Env. Env-specific antibody levels after the VLP booster immunizations were significantly higher in GagPol-immunized mice than in mock-vaccinated controls. Adoptive transfer of CD4+ T cells from GagPol-immunized mice also enhanced the Env antibody response to VLP immunization in the recipient mice. Depending on the presence of VLPs, co-cultivation of CD4+ T cells from GagPol-primed mice with BCR transgenic B cells specific for a protein presented on the surface of the VLPs also resulted in the activation of the B and T cells.ConclusionsOur study indicates that GagPol-specific T helper cells may provide intrastructural help for Env antibody responses. This cross-talk between immune responses directed against different components of the retroviral particle may be relevant for the immunopathogenesis of retroviral infections and allow to improve virus like particle vaccine approaches against HIV.

Enhancing the Quality of Antibodies to HIV-1 Envelope by GagPol-Specific Th Cells

The importance of Fc-dependent effector functions of Abs induced by vaccination is increasingly recognized. However, vaccination of mice against HIV envelope (Env) induced a skewed Th cell response leading to Env-specific Abs with reduced effector function. To overcome this bias, GagPol-specific Th cells were harnessed to provide intrastructural help for Env-specific B cells after immunization with virus-like particles containing GagPol and Env. This led to a balanced Env-specific humoral immune response with a more inflammatory Fc glycan profile. The increased quality in the Ab response against Env was confirmed by FcγR activation assays. Because the Env-specific Th cell response was also biased in human vaccinees, intrastructural help is an attractive novel approach to increase the efficacy of prophylactic HIV Env-based vaccines and may also be applicable to other particulate vaccines.

Protective Efficacy and Immunogenicity of a Combinatory DNA Vaccine against Influenza A Virus and the Respiratory Syncytial Virus

The Respiratory Syncytial Virus (RSV) and Influenza A Virus (IAV) are both two major causative agents of severe respiratory tract infections in humans leading to hospitalization and thousands of deaths each year. In this study, we evaluated the immunogenicity and efficacy of a combinatory DNA vaccine in comparison to the single component vaccines against both diseases in a mouse model. Intramuscular electroporation with plasmids expressing the hemagglutinin (HA) of IAV and the F protein of RSV induced strong humoral immune responses regardless if they were delivered in combination or alone. In consequence, high neutralizing antibody titers were detected, which conferred protection against a lethal challenge with IAV. Furthermore, the viral load in the lungs after a RSV infection could be dramatically reduced in vaccinated mice. Concurrently, substantial amounts of antigen-specific, polyfunctional CD8+ T-cells were measured after vaccination. Interestingly, the cellular response to the hemagglutinin was significantly reduced in the presence of the RSV-F encoding plasmid, but not vice versa. Although these results indicate a suppressive effect of the RSV-F protein, the protective efficacy of the combinatory vaccine was comparable to the efficacy of both single-component vaccines. In conclusion, the novel combinatory vaccine against RSV and IAV may have great potential to reduce the rate of severe respiratory tract infections in humans without increasing the number of necessary vaccinations.

Targeting the antigen encoded by adenoviral vectors to the DEC205 receptor modulates the cellular and humoral immune response

Replication-defective adenoviral vectors have emerged as promising vaccine candidates for diseases relying on strong CD8(+) T-cell responses for protection. In this study, we modified a non-replicative adenoviral vector to selectively deliver, in situ, an encoded ovalbumin (OVA) model antigen to dendritic cells (DCs). Efficient uptake and presentation of OVA was achieved through fusion of the antigen to a single-chain antibody directed against DEC205, an endocytic receptor expressed on DCs. The immunogenicity of the vaccine was thereby enhanced as demonstrated by elevated antibody levels and increased T-cell responses after low-dose vaccination with 10(7) viral particles compared with a non-targeted control. Nevertheless, after immunization with higher doses of the targeted vaccine, the capacity of vaccine-induced CD8(+) T cells to produce the cytokine IL-2 was diminished and the CD8(+) T-cell response was dominated by an effector memory phenotype (CD62L(-)/CD127(+)) in contrast to the effector phenotype (CD62L(-)/CD127(-)) observed after non-targeted antigen delivery. Interestingly, the protective capacity of the non-targeted vaccine was superior to that of the targeted vaccine in an antigen-specific vaccinia virus infection as well as in a tumor challenge model. In the latter, the low dose of the DC-targeted vaccine also conferred partial protection from tumor growth, demonstrating dose-dependent effects of the DC-targeting on the quality of the vaccine-induced immune response. Significant differences could be observed in regard to the antibody pattern, the functional and phenotypic T-cell repertoire, and to the protective capacity.

Codelivery of the Chemokine CCL3 by an Adenovirus-Based Vaccine Improves Protection from Retrovirus Infection

ABSTRACT Processing and presentation of vaccine antigens by professional antigen-presenting cells (APCs) is of great importance for the efficient induction of protective immunity. We analyzed whether the efficacy of an adenovirus-based retroviral vaccine can be enhanced by coadministration of adenovirus-encoded chemokines that attract and stimulate APCs. In the Friend retrovirus (FV) mouse model we coexpressed CCL3, CCL20, CCL21, or CXCL14 from adenoviral vectors, together with FV Gag and Env antigens, and then analyzed immune responses and protection from pathogenic FV infection. Although most tested chemokines did not improve protection against FV challenge, mice that received adenoviral vectors encoding CCL3 together with FV antigens showed significantly better control over viral loads and FV-induced disease than mice immunized with the viral antigens only. Improved protection correlated with enhanced virus-specific CD4+ T cell responses and higher neutralizing antibody titers. To apply these results to an HIV vaccine, mice were immunized with adenoviral vectors encoding the HIV antigens Env and Gag-Pol and coadministered vectors encoding CCL3. Again, this combination vaccine induced higher virus-specific antibody titers and CD4+ T cell responses than did the HIV antigens alone. These results indicate that coexpression of the chemokine CCL3 by adenovirus-based vectors may be a promising tool to improve antiretroviral vaccination strategies.

Comparison of polystyrene nanoparticles and UV-inactivated antigen-displaying adenovirus for vaccine delivery in mice

BackgroundInert nanoparticles are attracting attention as carriers for protein-based vaccines. Here we evaluate the immunogenicity of the model antigen ovalbumin delivered on polystyrene particles and directly compare particulate delivery with adenovirus-based immunization.FindingsMice were vaccinated with soluble ovalbumin, ovalbumin-coated polystyrene particles of different sizes, or an adenovirus-based expression-display vector that encodes and displays a pIX-ovalbumin fusion protein. Antibody responses were clearly higher when ovalbumin was administered on polystyrene particles compared to soluble protein administration, regardless of the particle size. Compared to adenovirus-based immunization, antibody levels were lower if an equivalent amount of protein was delivered, and no cellular immune response was detectable.ConclusionsWe demonstrate in a side-by-side comparison that inert nanoparticles allow for the reduction of the administered antigen amount compared to immunization with soluble protein and induce strongly enhanced antibody responses, but responses are lower compared to adenovirus-based immunization.

DNA vaccines encoding DEC205-targeted antigens: immunity or tolerance?

Targeting of antigens to the endocytic uptake receptor DEC205 resulted in enhanced antigen presentation by dendritic cells (DCs). In combination with adjuvants for DC maturation, proteins coupled to an antibody against DEC205 induced strong pathogen‐specific immune responses, whereas without additional adjuvant tolerance could be induced. As less is known about DNA vaccines encoding DEC205‐targeted antigens, we explored the immunogenicity and efficacy of a dendritic cell‐targeted DNA vaccine against influenza A virus (IAV) delivered by electroporation. Although coupling of haemagglutinin to a single‐chain antibody against DEC205 enhanced antigen presentation on MHC class II and activation of T‐cell receptor‐transgenic CD4 T cells, the T‐cell responses induced by the targeted DNA vaccine in wild‐type BALB/c mice were significantly reduced compared with DNA encoding non‐targeted antigens. Consistently, these mice were less protected against an IAV infection. Adoptive transfer experiments were performed to assess the fate of the antigen‐specific T cells in animals vaccinated with DNA encoding DEC205‐targeted antigens. By this, we could exclude the general deletion of antigen‐specific T cells as cause for the reduced efficacy, but observed a local expansion of antigen‐specific regulatory T cells, which could suppress the activation of effector cells. In conclusion, DNA vaccines encoding DEC205‐targeted antigens induce peripheral tolerance rather than immunity in our study. Finally, we evaluated our DNA vaccines as prophylactic or therapeutic treatment in an allergen‐induced asthma mouse model.

The improved antibody response against HIV-1 after a vaccination based on intrastructural help is complemented by functional CD8+ T cell responses.

Despite more than three decades of intense research, a prophylactic HIV-1 vaccine remains elusive. Four vaccine modalities have been evaluated in clinical efficacy studies, but only one demonstrated at least modest efficacy, which correlated with polyfunctional antibody responses to the HIV surface protein Env. To be most effective, a HIV-1 vaccine probably has to induce both, functional antibody and CD8(+) T cell responses. We therefore analyzed DNA/DNA and DNA/virus-like particle (VLP) regimens for their ability to induce humoral and cellular immune responses. Here, DNA vaccination of mice induced strong CD8(+) responses against Env and Gag. However, the humoral response to Env was dominated by IgG1, a subclass known for its low functionality. In contrast, priming only with the Gag-encoding plasmid followed by a boost with VLPs consisting of Gag and Env improved the quality of the anti-Env antibody response via intrastructural help (ISH) provided by Gag-specific T cells to Env-specific B cells. Furthermore, the Gag-specific CD8(+) T cells induced by the DNA prime immunization could still protect from a lethal infection with recombinant vaccinia virus encoding HIV Gag. Therefore, this immunization regimen represents a promising approach to combine functional antibody responses toward HIV Env with strong CD8(+) responses controlling early viral replication.

Correction: GagPol-specific CD4+ T-cells increase the antibody response to Env by intrastructural help

Background: Immunization of rhesus macaques against Gag of SIV resulted in a more rapid appearance of Env antibodies after infection with SIV or SHIV challenge viruses although the vaccines lacked an Env component. We therefore explored whether T helper cells specific for internal HIV proteins could provide intrastructural help for Env-specific B cells and thus increase the Env antibody response. Results: Mice were immunized by adenoviral vector or DNA vaccines against GagPol and then boosted with virus-like particles (VLP) containing GagPol and Env. Env-specific antibody levels after the VLP booster immunizations were significantly higher in GagPol-immunized mice than in mock-vaccinated controls. Adoptive transfer of CD4+ T cells from GagPol-immunized mice also enhanced the Env antibody response to VLP immunization in the recipient mice. Depending on the presence of VLPs, co-cultivation of CD4+ T cells from GagPol-primed mice with BCR transgenic B cells specific for a protein presented on the surface of the VLPs also resulted in the activation of the B and T cells.