Maintenance of CD8(+) T-cell memory following infection with recombinant sindbis and vaccinia viruses

Vaccination with Human Induced Pluripotent Stem Cells Creates an Antigen-Specific Immune Response Against HIV-1 gp160

Induced pluripotent stem cells (iPSCs) are artificially derived from somatic cells that have been transduced with defined reprogramming factors. A previous report has indicated the possibility of using iPSCs as an immune stimulator to generate antigen-specific immunity. In our current study, we have investigated whether human iPSCs (hiPSCs) have the ability to enhance specific immune response against a human immunodeficiency virus type 1 (HIV-1) antigen in a xenogenic mouse model. Our results show that BALB/c mice immunized with hiPSCs transduced with an adenoviral vector encoding HIV-1 gp160 exhibited prominent antigen-specific cellular immune responses. We further found that pre-treatment of hiPSCs with ionizing radiation promotes the secretion of pro-inflammatory cytokines such as interleukin-1 alpha (IL-1α), IL-12, and IL-18. These cytokines might promote the activation of antigen-presenting cells and the effective induction of cellular immunity. Our present findings thus demonstrate that a hiPSCs-based vaccine has the potential to generate cellular immunity against viral antigens such as HIV-1 gp160 in a xenogenic condition.

Adenovirus type 5 with modified hexons induces robust transgene-specific immune responses in mice with pre-existing immunity against adenovirus type 5

BACKGROUND

Adenovirus type 5 (Ad5) is widely used as a vehicle for vaccine delivery in the treatment of infectious disease and cancer. However, the efficacy of Ad5 vectors has been limited in humans because exposure to Ad5 infections results in most adults having neutralizing antibodies against Ad5. To overcome this limitation, the hexon epitope present in the fifth hypervariable region of Ad5 was modified.

METHODS

To evaluate the ability of Ad5 vectors encoding the HIV env protein to induce Ag-specific immune responses in the face of pre-existing anti-Ad5 immunity, mice were administrated intramuscularly with the Ad-Luc vector, and then vaccinated with parental or hexon-modified Ad5 vectors (Ad-HisHIV, Ad-END/AAAHIV or Ad-HIV) at week 8. HIV-specific cell-mediated immune responses were detected through a combination of tetramer assays and intracellular cytokine staining from weeks 8-23.

RESULTS

The hexon-modified Ad vector was able to escape from anti-Ad5 neutralizing antibody, and mice with the modified vector generated significantly lower individual neutralizing antibody than those immunized with the parental vector. Furthermore, mice with pre-existing anti-Ad immunity immunized with the modified vector generated significantly stronger cell-mediated anti-env responses than those immunized with the parental vector.

CONCLUSIONS

These data demonstrate that Ad5 vector with hexon modification reduce their sensitivity to pre-existing anti-Ad immunity and improve their clinical utility.

Virus-specific and bystander CD8 T cells recruited during virus-induced encephalomyelitis

Neurotropic coronavirus-induced encephalitis was used to evaluate recruitment, functional activation, and retention of peripheral bystander memory CD8+ T cells. Mice were first infected with recombinant vaccinia virus expressing a non-cross-reactive human immunodeficiency virus (HIV) epitope, designated p18. Following establishment of an endogenous p18-specific memory CD8+ T-cell population, mice were challenged with coronavirus to directly compare recruitment, longevity, and activation characteristics of both primary coronavirus-specific and bystander memory populations trafficking into the central nervous system (CNS). HIV-specific memory CD8+ T cells were recruited early into the CNS as components of the innate immune response, preceding CD8+ T cells specific for the dominant coronavirus epitope, designated pN. Although pN-specific T-cell numbers gradually exceeded bystander p18-specific CD8+ T-cell numbers, both populations peaked concurrently within the CNS. Nevertheless, coronavirus-specific CD8+ T cells were preferentially retained. By contrast, bystander CD8+ T-cell numbers declined to background numbers following control of CNS virus replication. Furthermore, in contrast to highly activated pN-specific CD8+ T cells, bystander p18-specific CD8+ T cells recruited to the site of inflammation maintained a nonactivated memory phenotype and did not express ex vivo cytolytic activity. Therefore, analysis of host CD8+ T-cell responses to unrelated infections demonstrates that bystander memory CD8+ T cells can comprise a significant proportion of CNS inflammatory cells during virus-induced encephalitis. However, transient CNS retention and the absence of activation suggest that memory bystander CD8+ T cells may not overtly contribute to pathology in the absence of antigen recognition.

IL-15-independent antiviral function of primary and memory CD8+ T cells

Memory CD8⁺ T cells are comprised of CD122^hi IL-15-dependent and CD122^lo IL-15-independent subsets. Induction and retention of IL-15-independent memory CD8⁺ T cells was assessed in IL-15^−/− and wild-type (wt) mice immunized with recombinant vaccinia virus (rVV) or Sindbis virus (rSIN) vectors expressing the identical foreign epitope. Both vectors induced epitope-specific CD8⁺ T cell expansion and function, independent of IL-15. Similar kinetics of rVV clearance confirmed effective CD8⁺ T cell function in IL-15^−/− mice. CD44^hi CD122^hi CD8⁺ T cells, mainly of the CD62L^−/lo phenotype, increased more dramatically and declined more rapidly in IL-15^−/− mice, independent of the vector. Rapid IL-15-independent memory CD8⁺ T cell expansion following challenge of immune mice compensated for the limited memory CD8⁺ populations in IL-15^−/− mice. However, despite expansion and expression of potent effector function, viral clearance was delayed in the absence of IL-15, coinciding with a rapid loss in cytolytic function.

Kunjin virus replicon vectors for human immunodeficiency virus vaccine development

We have previously demonstrated the ability of the vaccine vectors based on replicon RNA of the Australian flavivirus Kunjin (KUN) to induce protective antiviral and anticancer CD8+ T-cell responses using murine polyepitope as a model immunogen (I. Anraku, T. J. Harvey, R. Linedale, J. Gardner, D. Harrich, A. Suhrbier, and A. A. Khromykh, J. Virol. 76:3791-3799, 2002). Here we showed that immunization of BALB/c mice with KUN replicons encoding HIV-1 Gag antigen resulted in induction of both Gag-specific antibody and protective Gag-specific CD8+ T-cell responses. Two immunizations with KUNgag replicons in the form of virus-like particles (VLPs) induced anti-Gag antibodies with titers of > or =1:10,000. Immunization with KUNgag replicons delivered as plasmid DNA, naked RNA, or VLPs induced potent Gag-specific CD8+ T-cell responses, with one immunization of KUNgag VLPs inducing 4.5-fold-more CD8+ T cells than the number induced after immunization with recombinant vaccinia virus carrying the gag gene (rVVgag). Two immunizations with KUNgag VLPs also provided significant protection against challenge with rVVgag. Importantly, KUN replicon VLP vaccinations induced long-lasting immune responses with CD8+ T cells able to secrete gamma interferon and to mediate protection 6 to 10 months after immunization. These results illustrate the potential value of the KUN replicon vectors for human immunodeficiency virus vaccine design.

Contribution of the rev gene to the immunogenicity of DNA vaccines targeting the envelope glycoprotein of HIV

BACKGROUND

The Rev protein of HIV plays a critical role in the export of viral mRNA from the nucleus to the cytoplasm of infected cells. This work examines the effect of introducing rev into a DNA vaccine encoding the Env protein of HIV, and compares the activity of env genes regulated by CMV versus CAG promoters.

METHODS

The HIV Env gp160 encoding gene with or without the rev gene was subcloned into a CMV promoter or a CAG promoter-driven expression plasmid. The Env protein expression of the plasmids was examined in vitro and the HIV-specific immunity was explored in BALB/c mice by an intramuscular route. The immune mice were intraperitoneally challenged with an HIV Env-expression vaccinia virus.

RESULTS

Results indicate that the CAG promoter induces significantly higher levels of Env expression, and better immune responses, than the CMV promoter. Incorporating the rev gene into these plasmids further boosts antigen expression and immunogenicity. Indeed, vaccination with the pCAGrev/env or pCMVrev/env plasmid resulted in 1000-fold lower viral load than that with pCMVenv when the mice were challenged with an Env-expressing vaccinia virus.

CONCLUSIONS

Incorporating rev into a DNA vaccine significantly increases the level of expression and immunogenicity of a co-expressed env gene, and that protective efficacy is further improved by utilizing a pCAG promoter.

Use of transgenic HLA A*0201/Kb and HHD II mice to evaluate frequency of cytomegalovirus IE1-derived peptide usage in eliciting human CD8 cytokine response

Unlike the pp65 protein of human cytomegalovirus (CMV), which has an immunodominant peptide, pp65(495-503), recognized by human CD8(+) cells in the context of HLA A*0201, the fine peptide specificity for CMV IE1 has shown no such immunodominance. With the use of transgenic HLA A*0201/Kb and HHD II mice, a selected pool of IE1 peptides, including IE1(p256-264), IE1(p297-304), and IE1(p316-324), were shown to stimulate cytolytic T-lymphocyte lysis in the context of HLA A*0201. Based on an intracellular gamma interferon response, IE1(p297-304), a previously unrecognized CD8 epitope, triggered a prominent response to CMV IE1 in HLA A*0201 subjects.

A review of vaccines for HIV prevention

HIV/AIDS has become the most devastating pandemic in recorded history. It has killed 40 million people in the last 20 years and the World Health Organisation estimated that at least 14,000 new infections occurred daily in 2001. There will be up to 100 million new infections in the next 10 years (for current updates, visit http://www.unaids.org/epidemic_update/). Most HIV infections occur in the developing world, and the adverse social and economic impact of the HIV/AIDS pandemic, particularly in the developing world, is unprecedented. Highly active antiretroviral therapy (HAART) has had significant effects on HIV/AIDS in the developed world. The drugs have acted to prolong survival, reduce the viral load, and to alleviate suffering. However, the incidence of side effects and resistance is high and the drugs are unaffordable and unavailable in the developing world. HAART regimens are difficult to comply with. Public health efforts to modify the behaviour, attitude and culture that accelerate the spread of HIV/AIDS have had only modest success. There is urgent need for a prophylactic and/or therapeutic HIV vaccine. This is a review of the obstacles and current trends in HIV vaccine development.

Oral administration of recombinant adeno-associated virus elicits human immunodeficiency virus-specific immune responses

Oral vaccines can induce both systemic and mucosal immunity. Mucosal immunity, especially regional cell-mediated immunity, plays an important role in protecting individuals from infectious diseases such as acquired immunodeficiency syndrome. In this study, a recombinant adeno-associated virus vector expressing human immunodeficiency virus type 1 env gene (AAV-HIV) was orally administered to BALB/c mice. Systemic and regional immunity was induced in the mice. Furthermore, the immunization significantly reduced viral load after an intrarectal challenge with a recombinant vaccinia virus expressing HIV env gene. Moreover, we also show that dendritic cells might contribute to the AAV-HIV vector-induced immune responses.

Adjuvant effect of multi-CpG motifs on an HIV-1 DNA vaccine

Synthetic oligodeoxynucleotides (ODN) containing unmethylated CpG motifs trigger an immune response characterized by the activation of B cells, NK cells and monocytes/macrophages. Based on evidence that the immunogenicity of DNA vaccines can be augmented by the addition of CpG motifs, 5-20 additional CpG motifs were cloned into a pUC-derived plasmid. Treating bone-marrow derived dendritic cells (BM-DCs) with CpG-enriched plasmids in vitro boosted their expressions of MHC class II molecules, the CD40 and CD86 activation markers. Co-administering the CpG-enriched plasmids with a DNA vaccine encoding the envelope glycoprotein of HIV to BALB/c mice significantly increased HIV-specific cell mediated and humoral immunity. A significant boost was observed when the CpG plasmid was administered either 2 or 4 days after DNA vaccination. Plasmids containing 20 CpG copies were the most effective immune enhancers both in vitro and in vivo. These results suggest that plasmids containing multiple CpG motifs may improve the immunogenicity of DNA vaccines.

Kinase-deficient CMVpp65 triggers a CMVpp65 specific T-cell immune response in HLA-A*0201.Kb transgenic mice after DNA immunization

CMVpp65, a candidate component of human cytomegalovirus (CMV) vaccines, has phosphokinase (PK) activity that could affect vaccine safety. A mutated form of CMVpp65 substituting asparagine for lysine at the adenosine triphosphate (ATP)-binding site (CMVpp65mII) is kinase-deficient. Using DNA immunizations in a transgenic human leucocyte antigen (HLA)A*0201.Kb mouse model, the mutated CMVpp65 induced cytotoxic T lymphocytes (CTL) immunity similarly to native CMVpp65. Murine CTL lines generated from these immunizations killed human cells either after sensitization with CMVpp65-specific peptides or after infection with either CMV-Towne strain or rvac-pp65. It is proposed that CMVpp65mII be evaluated in candidate vaccines for CMV.

Natural killer T cell ligand alpha-galactosylceramide enhances protective immunity induced by malaria vaccines

The important role played by CD8(+) T lymphocytes in the control of parasitic and viral infections, as well as tumor development, has raised the need for the development of adjuvants capable of enhancing cell-mediated immunity. It is well established that protective immunity against liver stages of malaria parasites is primarily mediated by CD8(+) T cells in mice. Activation of natural killer T (NKT) cells by the glycolipid ligand, alpha-galactosylceramide (alpha-GalCer), causes bystander activation of NK, B, CD4(+), and CD8(+) T cells. Our study shows that coadministration of alpha-GalCer with suboptimal doses of irradiated sporozoites or recombinant viruses expressing a malaria antigen greatly enhances the level of protective anti-malaria immunity in mice. We also show that coadministration of alpha-GalCer with various different immunogens strongly enhances antigen-specific CD8(+) T cell responses, and to a lesser degree, Th1-type responses. The adjuvant effects of alpha-GalCer require CD1d molecules, Valpha14 NKT cells, and interferon gamma. As alpha-GalCer stimulates both human and murine NKT cells, these findings should contribute to the design of more effective vaccines against malaria and other intracellular pathogens, as well as tumors.