Vaccine with bacterium-like particles displaying HIV-1 gp120 trimer elicits specific mucosal responses and neutralizing antibodies in rhesus macaques

Grand Challenges on HIV/AIDS in China - The 5th Symposium, Yunnan 2024

HIV-1 infection has led to 1.329 million people living with the virus and 0.474 millions of deaths by the middle of 2024 in China. Achieving the goal of ending HIV/AIDS in China by 2030 has faced several grand challenges including currently having a diagnostic rate of less than 85%, an estimated annual cost burden of 6.3 billion RMB for antiretroviral therapy (ART) alone, and the lack of therapeutic cure and preventive vaccine and so on. To address these challenges, Chinese scientists initiated the programme of Grand Challenges on HIV/AIDS in China (GCC) in 2017. The inauguration symposium was held from 30 November to 1 December 2017 in Hong Kong - Asia's World City - to commemorate the 10th anniversary of AIDS Institute at The University of Hong Kong and Comprehensive AIDS Research Center at Tsinghua University. The mission of the GCC is to advance HIV/AIDS prevention, prioritize research on therapeutic cure and vaccine, disseminate new scientific findings, and foster broader collaborations. Following the inaugural event, subsequent symposia were held at Fudan University in 2018, Sun Yat-Sen University in 2019, Tsinghua University in 2023, and Dali University in 2024. This review reports the scientific presentations and progresses made by the GCC scientists, highlighting efforts to combat HIV/AIDS in China.

An experimental chimeric hepatitis E virus vaccine elicits both local and systemic immune responses

Introduction

The development of a hepatitis E virus (HEV) vaccine is critical, with ORF2 capsid protein as the main target. We previously demonstrated that oral coadministration of recombinant ORF2 with immunomodulatory bacterium-like-particles (IBLP) induces a specific immune response in mice, particularly using IBLP derived from Lacticaseibacillus rhamnosus IBL027 (IBLP027), which was effective in eliciting a local humoral response. IBLP are non-live bacteria with adjuvant and carrier properties, serving as a platform for exposing proteins or antigens fused to LysM (lysine motif) domains, protein modules that bind to cell wall polysaccharides like peptidoglycan.

Materials

We cloned the most immunogenic domain of ORF2 (O2P2) fused to five LysM domains (LysM5O2P2) and displayed this chimeric protein on the surface of IBLP027 to create a prototype vaccine (IBLP027-LysM5O2P2). We evaluated its capacity to induce an immune response in vivo by immunizing mice with three doses of either the experimental vaccine or the chimeric protein alone, using an oral or a combined schedule with subcutaneous priming followed by oral boosting. Control groups received IBLP027. Sera and small intestine fluid were analyzed for humoral response, while Peyer's patches and spleen immune cells were used for ex vivo stimulation with capsid protein to assess cellular response.

Results

The oral scheme failed to elicit an IgG response, but this was overcome by a subcutaneous priming dose followed by oral boosters, which led to increasing IgG titers in the combined scheme. The highest IgG titers were seen in the vaccine prototype group. Most groups produced significantly higher IgA levels in intestinal fluid, especially in those that received the oral scheme. Cellular response studies showed increased tumor necrosis factor (TNF)-α, interferon (IFN)-γ interleukin (IL)-4, and IL-17 levels in groups receiving the chimeric protein via oral or combined schedules.

Conclusion

Further and continuous research is needed to better understand both the needs and expectations of students and supervisors in different academic realities, including in Veterinary Medicine schools, from which the information available on the subject is scarce.

Immunogenicity and protective efficacy of a novel bacterium-like particle-based vaccine displaying canine distemper virus antigens in mice and dogs

Canine distemper virus (CDV) poses a severe threat to both domesticated and wild animals, including multiple carnivores. With the continued expansion of its host range, there is an urgent need for the development of a safer and more effective vaccine. In this study, we developed subunit vaccines based on a bacterium-like particle (BLP) delivery platform containing BLPs-F and BLPs-H, which display the CDV F and H glycoprotein antigens, respectively, using the antigen-protein anchor fusions produced by a recombinant baculovirus insect cell expression system. The combination of BLPs-F and BLPs-H (CDV-BLPs), formulated with colloidal manganese salt [Mn jelly (MnJ)] adjuvant, triggered robust CDV-specific antibody responses and a substantial increase in the number of interferon gamma (IFN-γ)-secreting CD4+ and CD8+ T cells in mice. Dogs immunized intramuscularly with this vaccine not only produced CDV-specific IgG but also displayed elevated concentrations of IFN-γ and interleukin 6 in their serum, along with an increase of the CD3+CD4+ and CD3+CD8+ T cell subsets. Consequently, this heightened immune response provided effective protection against disease development and reduced viral shedding levels following challenge with a virulent strain. These findings suggest that this BLP-based subunit vaccine has the potential to become a novel canine distemper vaccine.

IMPORTANCE

Many sensitive species require a safe and effective distemper vaccine. Non-replicating vaccines are preferred. We constructed subunit particles displaying canine distemper virus (CDV) antigens based on a bacterium-like particle (BLP) delivery platform. The CDV-BLPs formulated with theMn jelly adjuvant induced robust humoral and cell-mediated immune responses to CDV in mice and dogs, thereby providing effective protection against a virulent virus challenge. This work is an important step in developing a CDV subunit vaccine.

Bacterium-like particles derived from probiotics: progress, challenges and prospects

Bacterium-like particles (BLPs) are hollow peptidoglycan particles obtained from food-grade Lactococcus lactis inactivated by hot acid. With the advantage of easy preparation, high safety, great stability, high loading capacity, and high mucosal delivery efficiency, BLPs can load and display proteins on the surface with the help of protein anchor (PA), making BLPs a proper delivery system. Owning to these features, BLPs are widely used in the development of adjuvants, vaccine carriers, virus/antigens purification, and enzyme immobilization. This review has attempted to gather a full understanding of the technical composition, characteristics, applications. The mechanism by which BLPs induces superior adaptive immune responses is also discussed. Besides, this review tracked the latest developments in the field of BLPs, including Lactobacillus-derived BLPs and novel anchors. Finally, the main limitations and proposed breakthrough points to further enhance the immunogenicity of BLPs vaccines were discussed, providing directions for future research. We hope that further developments in the field of antigen delivery of subunit vaccines or others will benefit from BLPs.

Comparison of Effects of Multiple Adjuvants and Immunization Routes on the Immunogenicity and Protection of HSV-2 gD Subunit Vaccine

Genital herpes caused by herpes simplex virus type 2 (HSV-2) poses a global health issue. HSV-2 infection increases the risk of acquiring HIV infection. Studies have demonstrated that HSV-2 subunit vaccines have potential benefits, but require adjuvants to induce a balanced Th1/Th2 response. To develop a novel, effective vaccine, in this study, a truncated glycoprotein D (aa 1-285) of HSV-2 was formulated with an Al(OH)₃ adjuvant, three squalene adjuvants, MF59, AS03, and AS02, or a mucosal adjuvant, bacterium-like particles (BLPs). The immunogenicity of these subunit vaccines was evaluated in mice. After three immunizations, vaccines formulated with Al(OH)_3, MF59, AS03, and AS02 (intramuscularly) induced higher titers of neutralizing antibody than that formulated without adjuvant, and in particular, mice immunized with the vaccine plus AS02 had the highest neutralizing antibody titers and tended to produce a more balanced immune reaction than others. Intranasal gD2-PA-BLPs also induced excellent IgA levels and a more balanced Th1 and Th2 responses than intranasal gD2. After challenge with a lethal dose of HSV-2, all five adjuvants exhibited a positive effect in improving the survival rate. AS02 and gD2-PA-BLPs enhanced survival by 50% and 25%, respectively, when compared with the vaccine without adjuvant. AS02 was the only adjuvant that resulted in complete vaginal virus clearance and genital lesion healing within eight days. These results demonstrate the potential of using AS02 as a subunit vaccine adjuvant, and BLPs as a mucosal vaccine adjuvant.