Virus-like vaccines against HIV/SIV synergize with a subdominant antigen T cell vaccine

Additional file 1. Gating strategy for flow cytometry analysis of intracellular cytokine staining. First, the cells were gated for single cells (a) in a side scatter (SSC)-A/SSC-W plot, which were further gated for the lymphocyte population (b) in a plot of forward scatter (FCS)-A and SSC-A. The lymphocyte population was gated for CD8+ B220- cells (c) and CD4+ B220- cells (d). Next, these cells were gated for IFNγ+ CD44+ cells (e, upper rectangle), here shown representatively for the CD8+ population. From these populations the absolute number of IFNγ+ CD44+ B220- CD8+ and CD4+ T-cells was calculated by multiplying the percentage of IFNγ+ CD44+ B220- CD8+/CD4+ cells of the lymphocytes with the number of counted lymphocytes per spleen. To obtain the percentage of double positive (IFNγ+ TNFα+) cells of IFNγ+ CD8+ and CD4+ T-cells, CD8+/CD4+ B220- cells were also gated for CD44+ cells (e, both rectangles) in homologous prime-boost regimen and subsequently for IFNγ- TNFα+ (f, left rectangle) and IFNγ+ TNFα+ (f, right rectangle) cells

Targeting endogenous retroviruses using a novel adenoviral vaccine technology

Human Endogenous Retroviruses (HERVs) are promising cancer vaccine targets as they are reactivated in cancers while being silent in healthy tissues. Around 8-9% of our genome is made up of HERVs and reactivation of HERVs, especially HERV-K, have been implicated in tumorigenesis via oncogenic signaling and immune evasion. As one of the means for cancer immune evasion, HERVs utilize an Immune Suppressive Domain (ISD) located in their envelope protein (Env). Here, our cancer vaccine strategy was to evaluate if adenoviral vaccines encoding a virus-like particle immunogen design including Gag for particle formation and an ISD mutated Env protein (ISDmut) as a surface target, could induce potent and efficacious immune responses. For this purpose, we used the adenoviral vectors hAd19a and hAd5. Please click Download on the upper right corner to see the full abstract

Evaluation of antigen-displaying adeno-associated virus-like particles (AAVLPs) as future candidates for personalized cancer vaccination

Despite extensive research and significant advances in the past decades, cancer is still the second leading cause of deaths worldwide. Within cancer research, a promising and growing field is the immuno-oncology, which takes advantage of a patient’s immune system to elicit a protective response against malignant cells. Personalized vaccination against neoantigens is an encouraging approach to target different types of cancer. Neoantigens result from point mutations in the cancer cell genome and transform originally non-immunogenic sequences into immunogenic epitopes that overcome central immune tolerance. Despite different vaccine designs, which are primarily based on dendritic cells, DNA, RNA or synthetic peptides, additional strategies are required to reach sufficient immune responses. In this study, a novel approach was tested by displaying (neo-)antigens on adeno-associated virus-like particles (AAVLPs) to effectively prime CD8+ T cell responses. AAV was chosen as an antigen-presentation-scaffold owing to its excellent safety profile in humans and tolerance towards genetic engineering of the capsid, allowing presentation of 60 antigen copies per particle. The general vaccination strategy was tested in mice with AAVLPs displaying the ovalbumin-derived model antigen SIINFEKL. Initial experiments showed induction of long-lasting CD8+ T cell responses, sufficient to protect mice completely from B16F10-OVA tumor growth. Based on the SIINFEKL vaccine, the strategy was optimized by defining the most suitable injection routes, adjuvants and capsid insertion sites. Highest CD8+ T cell responses were achieved when the vaccine was I) injected s.c. into the hock, II) adjuvanted with Montanide ISA 51, III) injected at a high local concentration and IV) was composed of vector DNA-containing particles that V) display the antigen in the VR-IV loop of the capsid proteins. While tested prime-boost strategies and coupling of anti-CD40 to the capsid had no benefit for the vaccination, co-display of the immune stimulatory peptide J-ICBL improved T cell responses significantly. Interestingly, the presence of B cells was disadvantageous for the induction of antigen-specific CD8+ T cells and tumor protection, while the presence of CD4+ T cells was essential. Accordingly, T helper epitopes were identified within the AAVLP capsid sequence. In addition to SIINFEKL-presenting AAVLPs, particles were designed to present a set of different B16F10-derived neoantigens. While a head-to-head comparison showed no effect of a peptide vaccine against B16F10 tumor growth, injection of neoantigen-displaying AAVLPs significantly reduced the tumor growth rate. Although the general strategy requires further refinement and mechanistic analyses, neoantigen-AAVLPs represent an alternative for current therapy approaches and could be a promising candidate for future clinical applications

An Endogenous Retrovirus Vaccine Encoding an Envelope with a Mutated Immunosuppressive Domain in Combination with Anti-PD1 Treatment Eradicates Established Tumours in Mice

Endogenous retroviruses (ERVs) account for 8% of our genome, and, although they are usually silent in healthy tissues, they become reactivated and expressed in pathological conditions such as cancer. Several studies support a functional role of ERVs in tumour development and progression, specifically through their envelope (Env) protein, which contains a region described as an immunosuppressive domain (ISD). We have previously shown that targeting of the murine ERV (MelARV) Env using virus-like vaccine (VLV) technology, consisting of an adenoviral vector encoding virus-like particles (VLPs), induces protection against small tumours in mice. Here, we investigate the potency and efficacy of a novel MelARV VLV with a mutated ISD (ISDmut) that can modify the properties of the adenoviral vaccine-encoded Env protein. We show that the modification of the vaccine’s ISD significantly enhanced T-cell immunogenicity in both prime and prime-boost vaccination regimens. The modified VLV in combination with an α-PD1 checkpoint inhibitor (CPI) exhibited excellent curative efficacy against large established colorectal CT26 tumours in mice. Furthermore, only ISDmut-vaccinated mice that survived CT26 challenge were additionally protected against rechallenge with a triple-negative breast cancer cell line (4T1), showing that our modified VLV provides cross-protection against different tumour types expressing ERV-derived antigens. We envision that translating these findings and technology into human ERVs (HERVs) could provide new treatment opportunities for cancer patients with unmet medical needs