An Alphavirus-Based Adjuvant Enhances Serum and Mucosal Antibodies, T Cells, and Protective Immunity to Influenza Virus in Neonatal Mice

Abstract

Neonatal immune responses to infection and vaccination are biased toward T H 2 at the cost of proinflammatory T H 1 responses needed to combat intracellular pathogens. However, upon appropriate stimulation, the neonatal immune system can induce adult-like T H 1 responses. Here we report that a new class of vaccine adjuvant is especially well suited to enhance early life immunity. The GVI3000 adjuvant is a safe, nonpropagating, truncated derivative of Venezuelan equine encephalitis virus that targets dendritic cells (DCs) in the draining lymph node (DLN) and produces intracellular viral RNA without propagating to other cells. RNA synthesis strongly activates the innate immune response so that in adult animals, codelivery of soluble protein antigens induces robust humoral, cellular, and mucosal responses. The adjuvant properties of GVI3000 were tested in a neonatal BALB/c mouse model using inactivated influenza virus (iFlu). After a single immunization, mice immunized with iFlu with the GVI3000 adjuvant (GVI3000-adjuvanted iFlu) had significantly higher and sustained influenza virus-specific IgG antibodies, mainly IgG2a (T H 1), compared to the mice immunized with antigen only. GVI3000 significantly increased antigen-specific CD4؉ and CD8 ؉ T cells, primed mucosal immune responses, and enhanced protection from lethal challenge. As seen in adult mice, the GVI3000 adjuvant increased the DC population in the DLNs, caused activation and maturation of DCs, and induced proinflammatory cytokines and chemokines in the DLNs soon after immunization, including gamma interferon (IFN-␥), tumor necrosis factor alpha (TNF-␣), granulocyte colony-stimulating factor (G-CSF), and interleukin 6 (IL-6). In summary, the GVI3000 adjuvant induced an adult-like adjuvant effect with an influenza vaccine and has the potential to improve the immunogenicity and protective efficacy of new and existing neonatal vaccines. IMPORTANCEThe suboptimal immune responses in early life constitute a significant challenge for vaccine design. Here we report that a new class of adjuvant is safe and effective for early life immunization and demonstrate its ability to significantly improve the protective efficacy of an inactivated influenza virus vaccine in a neonatal mouse model. The GVI3000 adjuvant delivers a truncated, self-replicating viral RNA into dendritic cells in the draining lymph node. Intracellular RNA replication activates a strong innate immune response that significantly enhances adaptive antibody and cellular immune responses to codelivered antigens. A significant increase in protection results from a single immunization. Importantly, this adjuvant also primed a mucosal IgA response, which is likely to be critical for protection during many early life infections.

Advax delta inulin adjuvant overcomes immune immaturity in neonatal mice thereby allowing single–dose influenza vaccine protection

“…The effectiveness of Advax adjuvant in protection of neonates stands in contrast to other adjuvants that have been shown to be ineffective in inducing neonatal influenza protection. For example, an alum-adjuvanted influenza vaccine provided no protection in neonatal mice [29] , despite use of a very similar influenza model to the one in the current study. This can be explained by the fact that alum adjuvant has reduced ability to induce IgG production, B-cell affinity maturation and germinal center formation in neonates [30] .…”

Inflammatory responses to influenza vaccination at the extremes of age

“…Our data support the idea that the neonatal response is different not deficient, with higher IL‐1 α , CRP, GM‐CSF, G‐CSF and MCP‐1 than other ages of mice. We and others have previously investigated adjuvants specifically for use in early life and have shown that MF59 is protective even after a single dose…”

Use of the Microparticle Nanoscale Silicon Dioxide as an Adjuvant To Boost Vaccine Immune Responses against Influenza Virus in Neonatal Mice

“…In the current study, we demonstrated that NanoSiO2 was effective in early life, leading to a significant reduction in disease following infection compared to the results seen with antigen alone. A recent study using a polysaccharide microparticle adjuvant (Advax) also demonstrated protection against influenza virus challenge (31); likewise, an alphavirus-based adjuvant improved protection compared to antigen alone (32). It is of note that all these formulations are microparticle based, though it is not clear how the particles are being recognized by the immune system as studies have suggested that IL-1␤ responses in early life are deficient (33); however, this may be dependent upon the agonist used (34).…”