Aspergillus fumigatus extract augments antigen specific T cell responses in vivo.

Tao J, Segal B, Dennis C, Shrikant P

Author address: 

Roswell Park Cancer Institute, Buffalo, USA


Purpose of study: A. fumigatus (AF) is a major cause of morbidity and mortality in the severely immunocompromised. Studies have suggested that AF may evade host defense by suppressing innate and antigen-specific T cell immunity. However, the impact of AF on antigen specific T cell responses is not clearly understood. The aim of our studies was to characterize the impact of AF extract on the induction and progression of an antigen specific T cell response in vivo. By using adoptive transfer of naive OVA peptide specific T cell receptor (TCR) transgenic CD4+ (OT-II) and CD8+ (OT-I), we have monitored and evaluated the impact of AF extract on antigen specific adaptive responses as they are initiated in vivo. Methods: Age and sex matched Thy 1.2+ C57BL/6 mice adoptively transferred with Thy1.1+ naive TCR transgenic T cells (i.v. 3 x 106 of OT-1 and/or OT-II cells on day 1), were sensitized (s.c.) with either; 1) OVA (10 ug + PBS/mouse) (negative control); 2) OVA plus AF extract (10 ug + 14 ug/mouse); or 3) OVA plus LPS (10 ug + 1 ug/mouse; positive control). At various times after sensitization, mice were sacrificed and the number of adoptively transferred OT- and OT-II T cells enumerated from the lymph nodes and spleen by flow cytometry. The CD4+ and CD8+/ Thy1.1+ population was gated and evaluate for proliferation (CFSE dye dilution) and differentiation (intra cytoplasmic staining-ICS for interferon-g). The potential of AF extract to promote CTL activity in vivo was characterized by performing in vivo CTL assay using OVA peptide loaded target cells. The % specific lysis was calculated as {[1-(ratio unprimed/ratio primed)] X100} after deducting the non-antigen specific killing. Results: Sensitization with AF extract plus OVA in comparison to OVA alone or OVA + LPS, produced significant clonal expansion of the adoptively transferred OT-I and OT-II T-cells in the lymph nodes and spleen optimally by day 4. However, by day 10 and 20, the induced T cell response had waned in both AF and LPS treated mice. The early expansion produced by AF extract was due to increased proliferation of both OT-I and OT-II T cells (lower CFSE staining) and the cell division was accompanied by robust interferon-γ production (ICS) and CTL maturation as demonstrated by marked increases in vivo killing of antigen specific target cells. Conclusion: AF extract induced naí¯ve antigen specific CD4+ and CD8+ T cell activation, proliferation and differentiation in vivo. The T cell augmentation achieved by AF extract was substantially better than LPS after a single injection. The transient nature of the observed adjuvant effect clearly warrants further testing AF extract for use in vaccination strategies. Our on-going studies are focused on characterizing the sensitization modalities for AF extract (systemic vs. inhaled, single vs. multiple) that optimally support the generation of adaptive immunity.

abstract No: 


Full conference title: 

15th Annual Focus on Fungal Infections
    • FFI 15th (2005)