Adjuvant activity of Interferon epsilon and toll-like receptor-9 to enhance HIV-specific mucosal immunity

Abstract

Effective mucosal vaccines that elicit strong sustained CD8 T cell immunity at mucosal surfaces are thought to be critical against mucosal transmitted infection like HIV. A novel type I Interferon epsilon (IFN-e) and toll-like receptor member 9 (TLR9) were co-expressed together with HIV antigens and were used in a homologous prime-boost setting to assess mucosal immunity against HIV-1. The immuno-biology studies of IFN-e indicated that intranasal (IN) infection of VV co-expressing IFN-e (VV-HIV-IFN-e) can induce rapid VV clearance in lung that correlated with (i) elevated lung VV-specific CD8+CD107a+IFNg+ population expressing activation markers CD69/CD103, (ii) enhanced lymphocyte recruitment to lung alveoli with reduced inflammation, and (iii) heightened cytotoxic CD8+CD4+ T cell subset (CD3high/CCR7high/CD62Llow) in lung lymph nodes. These responses were different to that observed with VV-HA-IFN-alpha or VV-HA-IFN-beta infection. When IFN-e was used in an IN/intramuscular(IM) HIV prime-boost immunization, elevated HIV-specific effector (but not memory) CD8 T cell response was observed in spleen, genito-rectal nodes, and peyer's patches. Homing markers (alpha4beta7 & CCR9) analysis indicated that unlike other type I IFNs, IFN-e could promote migration of antigen-specific CD8 T cells to the gut mucosae. The induction of gut-specific immunity was independent of the route of delivery. This suggested that IFN-e at the vaccination site may have the ability to activate unique APC subsets that promoted CD8 T cell homing to gut mucosae. These results for the first time have established that IFN-e plays an important and unique role in the mucosae. Following vaccination the short-lived CD8 T cell responses observed, indicate that rather than a vaccine adjuvant IFN-e could be used as a therapeutic to control local lung and/or gut infections. Specifically, IFN-e may have great potential to be used as microbicide to prevent mucosal disease (e.g TB, Chlamydia or HIV-1). When the immuno-biological properties of TLR9 were evaluated using the VV co-expression system, the IN VV-HIV-TLR9 infection showed a rapid viral clearance in lung compared to the control VV-HIV infection. These results also correlated with enhanced lung DC and lung alveolar macrophage subset that was specific to TLR9 infection. Next, in an IN/IM immunization modality, the TLR9 adjuvanted vaccination showed promising HIV-specific memory CD8 T cell responses at both systemic and mucosal compartments following 8-week post booster immunization. Compared to control vaccination, TLR9 adjuvanted vaccine generated higher HIV-tetramer reactive memory CD8 T cells and IFNg+TNFa+CD8+ T cells in spleen and lung, but unlike at the effector stage of immunity no difference in the IL-2+CD8+ T cells were detected. Interestingly, elevated IL-4 producing T cells were detected following TLR9 adjuvanted vaccination (expression of IL-4/IL-13 by CD8+ T cells is associated with low avidity T cells). The latter correlated with TLR9 vaccination strategy not inducing elevated numbers of high avidity CD8+ T cells and suboptimal protective immunity. In summary, data in this thesis demonstrated that IFN-e is uniquely involved in mucosal immunity among other type I IFNs. Both IFN-e and TLR9 have good potential to be used as mucosal therapeutics to enhance or modulate tissue-specific mucosal immunity at the first line of defense.