Local immune responses to influenza antigen are synergistically enhanced by the adjuvant ISCOMATRIX

The peripheral (draining) lymph node, as the primary site of immune induction, determines the course of systemic responses to an injected antigen. Lymphatic duct cannulation procedures in sheep were used to investigate local immunoreactivity to human influenza virus antigen (Flu ag) admixed with the adjuvant ISCOMATRIX (IMX). Compared to Flu ag or IMX alone, the co-administration of Flu ag and IMX (Flu ag+IMX) synergistically enhanced a number of immunological responses (lymphocyte and blast migration from the node, antigen-specific antibody levels and IL6 output in efferent lymph, and antigen-induced proliferation in cultured efferent lymph cells). Together, these results demonstrate that IMX is an immune modulator, and that lymphatic duct cannulation procedures may be used to evaluate antigen/adjuvant combinations for vaccine development.

Intranasal immunisation with influenza-ISCOM induces strong mucosal as well as systemic antibody and cytotoxic T-lymphocyte responses

Intranasal administration of vaccines is preferred for induction of mucosal immune responses. In this study, mice were immunised intranasally and subcutaneously with influenza-immuno stimulating complexes (influenza-ISCOM). The intranasal dose was 15-times the subcutaneous dose. All mice dosed with influenza-ISCOMs survived challenge with live virus and comparable serum antibody and splenic cytotoxic T-lymphocyte responses were detected in both groups. Induction of mucosal IgA was significantly higher with intranasal immunisation and was comparable to responses induced with the heat labile enterotoxin of Escherichia coli as adjuvant. These findings demonstrate that intranasal administration of high dose influenza-ISCOM results in potent systemic and mucosal immune responses.

Induction of lymphocyte recruitment in the absence of a detectable immune response

Lymphocyte recruitment from blood into the lymph node is thought to be initiated by the presence of antigen. In this study, we have used lymphatic cannulation in sheep to demonstrate that the adjuvant ISCOMATRIX can induce dramatic lymph node activation in the absence of antigen. Consistent patterns of node shutdown (decreased output) and cell recruitment (increased output) with minimal blast cell responses were observed indicating that an antigen-specific immune response is not required. Production of IL-6, IL-8 and IFN-gamma, and the transient presence of red blood cells and neutrophils in the efferent lymph were associated with changes in efferent lymph cell trafficking. These early events may facilitate the screening of low frequency antigen-specific cells for binding to antigen and the subsequent amplification of the immune response.