Enhanced Influenza Virus-Like Particle Vaccination with a Structurally Optimized RIG-I Agonist as Adjuvant

Host and Viral Modulation of RIG-I-Mediated Antiviral Immunity

Innate immunity is the first line of defense against invading pathogens. Rapid and efficient detection of pathogen-associated molecular patterns via pattern-recognition receptors is essential for the host to mount defensive and protective responses. Retinoic acid-inducible gene-I (RIG-I) is critical in triggering antiviral and inflammatory responses for the control of viral replication in response to cytoplasmic virus-specific RNA structures. Upon viral RNA recognition, RIG-I recruits the mitochondrial adaptor protein mitochondrial antiviral signaling protein, which leads to a signaling cascade that coordinates the induction of type I interferons (IFNs), as well as a large variety of antiviral interferon-stimulated genes. The RIG-I activation is tightly regulated via various posttranslational modifications for the prevention of aberrant innate immune signaling. By contrast, viruses have evolved mechanisms of evasion, such as sequestrating viral structures from RIG-I detections and targeting receptor or signaling molecules for degradation. These virus–host interactions have broadened our understanding of viral pathogenesis and provided insights into the function of the RIG-I pathway. In this review, we summarize the recent advances regarding RIG-I pathogen recognition and signaling transduction, cell-intrinsic control of RIG-I activation, and the viral antagonism of RIG-I signaling.

Comparison of the patterns of antibody recall responses to HIV-1 gp120 and hepatitis B surface antigen in immunized mice

To date, we still lack an ideal strategy for designing envelope glycoprotein (Env) vaccines to elicit potent protective antibodies against HIV-1 infection. Since the human hepatitis B virus surface antigen (HBsAg) is representative of effective vaccines that can induce ideal humoral immune responses, knowledge of how it elicits antibody responses and T helper cells would be an useful reference for HIV vaccine development. We compared the characteristics of the HIV-1 Env gp120 trimer and HBsAg in antibody elicitation and induction of T follicular helper (Tfh) and memory B cells in immunized Balb/c mice. Using the strategy of protein prime-protein boost, we found that HIV-1 gp120 induced slower recall antibody responses but redundant non-specific IgG responses at early time after boosting compared to HBsAg. The higher frequency of PD-1^hiCD4⁺ T cells and Tfh cells that appeared at the early time point after gp120 boosting is likely to limit the development of memory B cells, memory T cells, and specific antibody recall responses. These findings regarding the different features of HIV envelope and HBsAg in T helper cell responses may provide a direction to improve HIV envelope immunogenicity.

Epidemiology and Management of the 2013-16 West African Ebola Outbreak

The 2013-16 West African Ebola outbreak is the largest, most geographically dispersed, and deadliest on record, with 28,616 suspected cases and 11,310 deaths recorded to date in Guinea, Liberia, and Sierra Leone. We provide a review of the epidemiology and management of the 2013-16 Ebola outbreak in West Africa aimed at stimulating reflection on lessons learned that may improve the response to the next international health crisis caused by a pathogen that emerges in a region of the world with a severely limited health care infrastructure. Surveillance efforts employing rapid and effective point-of-care diagnostics designed for environments that lack advanced laboratory infrastructure will greatly aid in early detection and containment efforts during future outbreaks. Introduction of effective therapeutics and vaccines against Ebola into the public health system and the biodefense armamentarium is of the highest priority if future outbreaks are to be adequately managed and contained in a timely manner.

Multi-subtype influenza virus-like particles incorporated with flagellin and granulocyte-macrophage colony-stimulating factor for vaccine design

Virus-like particle (VLP) technology is an attractive platform for seasonal and pandemic influenza vaccine development. We previously showed that influenza VLPs can be modified using M2 fusion with molecular adjuvants such as Salmonella typhimurium flagellin (FliC) to enhance VLP immunogenicity. For this study, three types of chimeric VLPs were incorporated with FliC, granulocyte-macrophage colony-stimulating factor (GM-CSF), or both GM-CSF and FliC (GM-CSF/FliC) to enhance anti-influenza immunogenicity. Our results indicate that immunizations with the chimeric FliC VLPs and GM-CSF/FliC H5N1 VLPs elicited more potent and broadly neutralizing antibodies and neuraminidase-inhibiting antibodies in sera, and induced higher numbers of hemagglutinin-specific antibody-secreting cells and germinal center B cell subsets in splenoctyes. Immunization with the chimeric GM-CSF H5N1 VLPs induced stronger Th1 and Th2 cellular responses. The chimeric GM-CSF/FliC H5N1 VLP constructs were further obtained to include H7 or H1H7 bi- or tri-subtype. It is our hope that these findings provide useful information for developing multi-subtype influenza vaccines.

Triggering Intracellular Receptors for Vaccine Adjuvantation

Immune adjuvants are components that stimulate, potentiate, or modulate the immune response to an antigen. They are key elements of vaccines in both the prophylactic and therapeutic domains. In the past decade substantial progress in our understanding of innate immunity has paved the way for the design of next-generation adjuvants that stimulate a wide range of receptors. Within the framework of vaccine adjuvant design, this review outlines the interest of targeting endosomal and intracellular receptors to enhance and guide the immune response. We present and compare the molecules as well as potential combinations which are currently in the spotlight. We emphasize how targeting the appropriate receptor can direct immunity towards the appropriate response, such as a cytotoxic or mucosal response.

Dengue Virus Immunopathogenesis: Lessons Applicable to the Emergence of Zika Virus

Dengue is the leading mosquito-transmitted viral infection in the world. There are more than 390 million new infections annually; while the majority of infected individuals are asymptomatic or develop a self-limited dengue fever, up to 1 million clinical cases develop severe manifestations, including dengue hemorrhagic fever and shock syndrome, resulting in ~25,000 deaths annually, mainly in children. Gaps in our understanding of the mechanisms that contribute to dengue infection and immunopathogenesis have hampered the development of vaccines and antiviral agents. Some of these limitations are highlighted by the explosive re-emergence of another arthropod-borne flavivirus-Zika virus-spread by the same vector, the Aedes aegypti mosquito, that also carries dengue, yellow fever and chikungunya viruses. This review will discuss the early virus-host interactions in dengue infection, with emphasis on the interrelationship between oxidative stress and innate immune pathways, and will provide insight as to how lessons learned from dengue research may expedite therapeutic strategies for Zika virus.