Induction of strong HIV-1-specific CD4+ T-cell responses using an HIV-1 gp120/NefTat vaccine adjuvanted with AS02A in antiretroviral-treated HIV-1-infected individuals

Nanotechnology-empowered vaccine delivery for enhancing CD8+ T cells-mediated cellular immunity

After centuries of development, using vaccination to stimulate immunity has become an effective method for prevention and treatment of a variety of diseases including infective diseases and cancers. However, the tailor-made efficient delivery system for specific antigens is still urgently needed due to the low immunogenicity and stability of antigens, especially for vaccines to induce CD8⁺ T cells-mediated cellular immunity. Unlike B cells-mediated humoral immunity, CD8⁺ T cells-mediated cellular immunity mainly aims at the intracellular antigens from microorganism in virus-infected cells or genetic mutations in tumor cells. Therefore, the vaccines for stimulating CD8⁺ T cells-mediated cellular immunity should deliver the antigens efficiently into the cytoplasm of antigen presenting cells (APCs) to form major histocompatibility complex I (MHCI)-antigen complex through cross-presentation, followed by activating CD8⁺ T cells for immune protection and clearance. Importantly, nanotechnology has been emerged as a powerful tool to facilitate these multiple processes specifically, allowing not only enhanced antigen immunogenicity and stability but also APCs-targeted delivery and elevated cross-presentation. This review summarizes the process of CD8⁺ T cells-mediated cellular immunity induced by vaccines and the technical advantages of nanotechnology implementation in general, then provides an overview of the whole spectrum of nanocarriers studied so far and the recent development of delivery nanotechnology in vaccines against infectious diseases and cancer. Finally, we look forward to the future development of nanotechnology for the next generation of vaccines to induce CD8⁺ T cells-mediated cellular immunity.

Balance between Retroviral Latency and Transcription: Based on HIV Model

The representative of the Lentivirus genus is the human immunodeficiency virus type 1 (HIV-1), the causative agent of acquired immunodeficiency syndrome (AIDS). To date, there is no cure for AIDS because of the existence of the HIV-1 reservoir. HIV-1 infection can persist for decades despite effective antiretroviral therapy (ART), due to the persistence of infectious latent viruses in long-lived resting memory CD4+ T cells, macrophages, monocytes, microglial cells, and other cell types. However, the biology of HIV-1 latency remains incompletely understood. Retroviral long terminal repeat region (LTR) plays an indispensable role in controlling viral gene expression. Regulation of the transcription initiation plays a crucial role in establishing and maintaining a retrovirus latency. Whether and how retroviruses establish latency and reactivate remains unclear. In this article, we describe what is known about the regulation of LTR-driven transcription in HIV-1, that is, the cis-elements present in the LTR, the role of LTR transcription factor binding sites in LTR-driven transcription, the role of HIV-1-encoded transactivator protein, hormonal effects on virus transcription, impact of LTR variability on transcription, and epigenetic control of retrovirus LTR. Finally, we focus on a novel clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR/dCas9)-based strategy for HIV-1 reservoir purging.

Stimulation Effects and Mechanisms of Different Adjuvants on a Norovirus P Particle-Based Active Amyloid-β Vaccine

BACKGROUND

Adjuvants are important components of vaccines and effectively enhance the immune response of specific antigens. However, the role of adjuvants or combinations of adjuvants in stimulating immunogenicity of the amyloid-β (Aβ) vaccine, as well as molecular mechanisms underlying such stimulation still remain unclear. A previous study of ours developed a norovirus P particle-based active Aβ epitope vaccine, PP-3copy-Aβ1-6-loop123, which stimulates a high titer of Aβ-specific antibodies in mouse Alzheimer's disease (AD) models.

OBJECTIVE

The most effective and safe adjuvant that maximizes the immunogenicity of our protein vaccine was determined.

METHODS

We investigated four adjuvants (CpG, AS02, AS03, and MF59), and combinations of those, for capacity to enhance immunogenicity, and performed transcriptome analysis to explore mechanisms underlying the role of these in AD immunotherapy.

RESULTS

Addition of the adjuvant, AS02, remarkably improved the immunogenicity of the PP-3copy-Aβ1-6-loop123 vaccine without triggering an Aβ-specific T-cell response. Combinations of adjuvants, particularly CpG +  AS02 and CpG + AS03, elicited a significantly elevated and prolonged Aβ-specific antibody response. Gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that a combination of two adjuvants was more effective in activating immune-related pathways, thereby enhancing the immunogenicity of PP-3copy-Aβ1-6-loop123.

CONCLUSION

These findings demonstrated that adjuvants can be used as enhancers in AD protein vaccination, and that a combination of CpG and AS-related adjuvants may be a very effective adjuvant candidate suitable for further clinical trials of the PP-3copy-Aβ1-6-loop123 vaccine. Our studies also revealed potential mechanisms underlying the stimulation of immune response of protein vaccines by adjuvants.

Characterization of T-cell immune responses in clinical trials of the candidate RTS,S malaria vaccine

The candidate malaria vaccine RTS,S has demonstrated 45.7% efficacy over 18 months against all clinical disease in a phase-III field study of African children. RTS,S targets the circumsporozoite protein (CSP), which is expressed on the Plasmodium sporozoite during the pre-erythrocyte stage of its life-cycle; the stage between mosquito bite and liver infection.

Early in the development of RTS,S, it was recognized that CSP-specific cell-mediated immunity (CMI) was required to complement CSP-specific antibody-mediated immunity. In reviewing RTS,S clinical studies, associations between protection and various types of CMI (CSP-specific CD4⁺ T cells and INF-γ ELISPOTs) have been identified, but not consistently. It is plausible that certain CD4⁺ T cells support antibody responses or co-operate with other immune-cell types to potentially elicit protection. However, the identities of vaccine correlates of protection, implicating either CSP-specific antibodies or T cells remain elusive, suggesting that RTS,S clinical trials may benefit from additional immunogenicity analyses that can be informed by the results of controlled human malaria infection studies.

Immunological strategies to target HIV persistence

PURPOSE OF REVIEW

The purpose of this article is to review recent advances in immunotherapeutic approaches aiming at reducing the latent HIV reservoir.

RECENT FINDINGS

HIV-1 establishes early during infection a pool of latently infected cells that persist long term and are largely undetectable to the immune system. Highly active antiretroviral therapy has dramatically improved the life expectancy and life quality of HIV-1-infected individuals, but is incapable of eliminating the pool of latently HIV-1-infected cells. Recent studies have started to test immunotherapeutic interventions in combination with latency reversing agents to reduce the latent HIV-1 reservoir, including approaches aimed at enhancing antiviral T-cell immunity, innate immunity, and virus-specific antibodies.

SUMMARY

The better understanding of virus-specific immunity and the pathways used by HIV-1 to evade host immune responses have enabled the development of new strategies focusing on targeting latently HIV-1-infected cells, with the goal to reduce the HIV-1 reservoir. Here, we will review recent advances in harnessing effector cells of the immune system, including CD8 T cells and natural killer cells, antiviral antibodies and new immunomodulatory molecules, to target HIV-1 persistence.

HIV-1 Tat and Viral Latency: What We Can Learn from Naturally Occurring Sequence Variations

Despite the effective use of antiretroviral therapy, the remainder of a latently HIV-1-infected reservoir mainly in the resting memory CD4⁺ T lymphocyte subset has provided a great setback toward viral eradication. While host transcriptional silencing machinery is thought to play a dominant role in HIV-1 latency, HIV-1 protein such as Tat, may affect both the establishment and the reversal of latency. Indeed, mutational studies have demonstrated that insufficient Tat transactivation activity can result in impaired transcription of viral genes and the establishment of latency in cell culture experiments. Because Tat protein is one of highly variable proteins within HIV-1 proteome, it is conceivable that naturally occurring Tat mutations may differentially modulate Tat functions, thereby influencing the establishment and/or the reversal of viral latency in vivo. In this mini review, we summarize the recent findings of Tat naturally occurring polymorphisms associating with host immune responses and we highlight the implication of Tat sequence variations in relation to HIV latency.

Second European Round Table on the Future Management of HIV: 10-11 October 2014, Barcelona, Spain

The Second European Round Table on the Future Management of HIV took place in Barcelona, 10-11 October 2014 and focused on the HIV-1 reservoir, strategies for HIV cure and primary HIV infection (PHI). Important issues in the HIV-1 reservoir research field are the validity of reservoir measurement techniques and the potential of new drugs to target latently infected cells. Current HIV-1 cure concepts are based on theoretical assumptions of biologically plausible mechanisms, supported by several clinical observations. Three main potential strategies are under investigation in order to achieve a sterilising cure or maintain HIV-1 remission: latency reversal resulting in antigen expression and viral cytolysis or immune targeted cell-death; immunological control of the reservoir; or replacement of the complete autologous haematopoietic and lymphoid stem-cell repertoire by transplantation. An interesting opportunity for restricting the size of the reservoir entails the early initiation of antiretroviral treatment (ART) during PHI. In terms of the reservoir, early treatment limits its size, alters its composition, and restricts the genetic variability of integrated proviral HIV-1 DNA. The challenges ahead involve the identification of patients undergoing seroconversion to HIV-1 and the prompt initiation of treatment. How the seemingly beneficial impact of early treatment will make cure more feasible, and whether the positive effects of the cure efforts outweigh the potentially negative impact of life-long ART, are important aspects of future collaborative research prospects.

Vaccine-elicited CD4 T cells induce immunopathology after chronic LCMV infection

CD4 T cells promote innate and adaptive immune responses, but how vaccine-elicited CD4 T cells contribute to immune protection remains unclear. We evaluated whether induction of virus-specific CD4 T cells by vaccination would protect mice against infection with chronic lymphocytic choriomeningitis virus (LCMV). Immunization with vaccines that selectively induced CD4 T cell responses resulted in catastrophic inflammation and mortality after challenge with a persistent strain of LCMV. Immunopathology required antigen-specific CD4 T cells and was associated with a cytokine storm, generalized inflammation, and multi-organ system failure. Virus-specific CD8 T cells or antibodies abrogated the pathology. These data demonstrate that vaccine-elicited CD4 T cells in the absence of effective antiviral immune responses can trigger lethal immunopathology.

Safety and immunogenicity of the M72/AS01 candidate tuberculosis vaccine in HIV-infected adults on combination antiretroviral therapy: a phase I/II, randomized trial

OBJECTIVE

Tuberculosis (TB) is highly prevalent among HIV-infected people, including those receiving combination antiretroviral therapy (cART), necessitating a well tolerated and efficacious TB vaccine for these populations. We evaluated the safety and immunogenicity of the candidate TB vaccine M72/AS01 in adults with well controlled HIV infection on cART.

DESIGN

A randomized, observer-blind, controlled trial (NCT00707967).

METHODS

HIV-infected adults on cART in Switzerland were randomized 3 : 1 : 1 to receive two doses, 1 month apart, of M72/AS01, AS01 or 0.9% physiological saline (N = 22, N = 8 and N = 7, respectively) and were followed up to 6 months postdose 2 (D210). Individuals with CD4⁺ cell counts below 200 cells/μl were excluded. Adverse events (AEs) including HIV-specific and laboratory safety parameters were recorded. Cell-mediated (ICS) and humoral (ELISA) responses were evaluated before vaccination, 1 month after each dose (D30, D60) and D210.

RESULTS

Thirty-seven individuals [interquartile range (IQR) CD4⁺ cell counts at screening: 438-872 cells/μl; undetectable HIV-1 viremia] were enrolled; 73% of individuals reported previous BCG vaccination, 97.3% tested negative for the QuantiFERON-TB assay. For M72/AS01 recipients, no vaccine-related serious AEs or cART-regimen adjustments were recorded, and there were no clinically relevant effects on laboratory safety parameters, HIV-1 viral loads or CD4⁺ cell counts. M72/AS01 was immunogenic, inducing persistent and polyfunctional M72-specific CD4⁺ T-cell responses [medians 0.70% (IQR 0.37-1.07) at D60] and 0.42% (0.24-0.61) at D210, predominantly CD40L⁺IL-2⁺TNF-α⁺, CD40L⁺IL-2⁺ and CD40L⁺IL-2⁺TNF-α⁺IFN-γ⁺]. All M72/AS01 vaccines were seropositive for anti-M72 IgG after second vaccination until study end.

CONCLUSION

M72/AS01 was clinically well tolerated and immunogenic in this population, supporting further clinical evaluation in HIV-infected individuals in TB-endemic settings.

CD4+ T-cell help enhances NK cell function following therapeutic HIV-1 vaccination

Increasing data suggest that NK cells can mediate antiviral activity in HIV-1-infected humans, and as such, novel approaches harnessing the anti-HIV-1 function of both T cells and NK cells represent attractive options to improve future HIV-1 immunotherapies. Chronic progressive HIV-1 infection has been associated with a loss of CD4(+) T helper cell function and with the accumulation of anergic NK cells. As several studies have suggested that cytokines produced by CD4(+) T cells are required to enhance NK cell function in various infection models, we hypothesized that reconstitution of HIV-1-specific CD4(+) T-cell responses by therapeutic immunization would restore NK cell activity in infected individuals. Using flow cytometry, we examined the function of CD4(+) T cells and NK cells in response to HIV-1 in subjects with treated chronic HIV-1 infection before and after immunization with an adjuvanted HIV-1 Gp120/NefTat subunit protein vaccine candidate provided by GlaxoSmithKline. Vaccination induced an increased expression of interleukin-2 (IL-2) by Gp120-specific CD4(+) T cells in response to HIV-1 peptides ex vivo, which was associated with enhanced production of gamma interferon (IFN-γ) by NK cells. Our data show that reconstitution of HIV-1-specific CD4(+) T-cell function by therapeutic immunization can enhance NK cell activity in HIV-1-infected individuals.

IMPORTANCE

NK cells are effector cells of the innate immune system and are important in the control of viral infection. Recent studies have demonstrated the crucial role played by NK cells in controlling and/or limiting acquisition of HIV-1 infection. However, NK cell function is impaired during progressive HIV-1 infection. We recently showed that therapeutic immunization of treated HIV-1-infected individuals reconstituted strong T-cell responses, measured notably by their production of IL-2, a cytokine that can activate NK cells. The current study suggests that reconstitution of T-cell function by therapeutic vaccination can enhance NK cell activity in individuals with chronic HIV-1 infection. Our findings provide new insights into the interplay between adaptive and innate immune mechanisms involved in HIV-1 immunity and unveil opportunities to harness NK cell function in future therapeutic vaccine strategies to target HIV-1.

Immunogenicity and safety of a booster dose of an investigational adjuvanted polyprotein HIV-1 vaccine in healthy adults and effect of administration of chloroquine

This phase II study evaluated the effect of chloroquine on the specific CD8(+) T-cell responses to and the safety of a booster dose of investigational human immunodeficiency virus type 1 (HIV-1) F4/AS01(B) vaccine containing 10 μg of recombinant fusion protein (F4) adjuvanted with the AS01(B) adjuvant system. Healthy adults aged 21 to 41 years, primed 3 years before with two F4/AS01(B) doses containing 10 or 30 μg of F4 (ClinicalTrials.gov registration number NCT00434512), were randomized (1:1) to receive the F4/AS01(B) booster administered alone or 2 days after chloroquine (300 mg). F4-specific CD8(+)/CD4(+) T-cell responses were characterized by intracellular cytokine staining and lymphoproliferation assays and anti-F4 antibodies by enzyme-linked immunosorbent assays (ELISAs). No effect of chloroquine on CD4(+)/CD8(+) T-cell and antibody responses and no vaccine effect on CD8(+) T-cell responses (cytokine secretion or proliferation) were detected following F4/AS01(B) booster administration. In vitro, chloroquine had a direct inhibitory effect on AS01(B) adjuvant properties; AS01-induced cytokine production decreased upon coincubation of cells with chloroquine. In the pooled group of participants primed with F4/AS01(B) containing 10 μg of F4, CD4(+) T-cell and antibody responses induced by primary vaccination persisted for at least 3 years. The F4/AS01(B) booster induced strong F4-specific CD4(+) T-cell responses, which persisted for at least 6 months with similar frequencies and polyfunctional phenotypes as following primary vaccination, and high anti-F4 antibody concentrations, reaching higher levels than those following primary vaccination. The F4/AS01(B) booster had a clinically acceptable safety and reactogenicity profile. An F4/AS01(B) booster dose, administered alone or after chloroquine, induced robust antibody and F4-specific CD4(+) T-cell responses but no significant CD8(+) T-cell responses (cytokine secretion or proliferation) in healthy adults. (This study has been registered at ClinicalTrials.gov under registration number NCT00972725).

Safety and immunogenicity of an adjuvanted protein therapeutic HIV-1 vaccine in subjects with HIV-1 infection: a randomised placebo-controlled study

The human immunodeficiency virus type-1 (HIV-1) vaccine candidate F4/AS01 has previously been shown to induce potent and persistent polyfunctional CD4(+) T-cell responses in HIV-1-seronegative volunteers. This placebo-controlled study evaluated two doses of F4/AS01 1-month apart in antiretroviral treatment (ART)-experienced and ART-naïve HIV-1-infected subjects (1:1 randomisation in each cohort). Safety, HIV-1-specific CD4(+) and CD8(+) T-cell responses, absolute CD4(+) T-cell counts and HIV-1 viral load were monitored for 12 months post-vaccination. Reactogenicity was clinically acceptable and no vaccine-related serious adverse events were reported. The frequency of HIV-1-specific CD4(+) T-cells 2 weeks post-dose 2 was significantly higher in the vaccine group than in the placebo group in both cohorts (p<0.05). Vaccine-induced HIV-1-specific CD4(+) T-cells exhibited a polyfunctional phenotype, expressing at least CD40L and IL-2. No increase in HIV-1-specific CD8(+) T-cells or change in CD8(+) T-cell activation marker expression profile was detected. Absolute CD4(+) T-cell counts were variable over time in both cohorts. Viral load remained suppressed in ART-experienced subjects. In ART-naïve subjects, a transient reduction in viral load from baseline was observed 2 weeks after the second F4/AS01 dose, which was concurrent with a higher frequency of HIV-1-specific CD4(+) T-cells expressing at least IL-2 in this cohort. In conclusion, F4/AS01 showed a clinically acceptable reactogenicity and safety profile, and induced polyfunctional HIV-1-specific CD4(+) T-cell responses in ART-experienced and ART-naïve subjects. These findings support further clinical investigation of F4/AS01 as a potential HIV-1 vaccine for therapeutic use in individuals with HIV-1 infection.

Barriers to a cure for HIV: new ways to target and eradicate HIV-1 reservoirs

Antiretroviral therapy for HIV infection needs lifelong access and strict adherence to regimens that are both expensive and associated with toxic effects. A curative intervention will be needed to fully stop the epidemic. The failure to eradicate HIV infection during long-term antiretroviral therapy shows the intrinsic stability of the viral genome in latently infected CD4T cells and other cells, and possibly a sustained low-level viral replication. Heterogeneity in latently infected cell populations and homoeostatic proliferation of infected cells might affect the dynamics of virus production and persistence. Despite potent antiretroviral therapy, chronic immune activation, inflammation, and immune dysfunction persist, and are likely to have important effects on the size and distribution of the viral reservoir. The inability of the immune system to recognise cells harbouring latent virus and to eliminate cells actively producing virus is the biggest challenge to finding a cure. We look at new approaches to unravelling the complex virus-host interactions that lead to persistent infection and latency, and discuss the rationale for combination of novel treatment strategies with available antiretroviral treatment options to cure HIV.