Abstract
Recent reports highlight the potential for integrase-defective lentiviral vectors (IDLV) to be developed as vaccines due to their ability to elicit cell-mediated and humoral immune responses after intramuscular administration. Differently from their integrase-competent counterpart, whose utility for vaccine development is limited by the potential for insertional mutagenesis, IDLV possess a mutation in their integrase gene that prevents genomic integration. Instead, they are maintained as episomal DNA circles that retain the ability to stably express functional proteins. Despite their favorable profile, it is unknown whether IDLV elicit immune responses after intranasal administration, a route that could be advantageous in the case of infection with a respiratory agent. Using influenza as a model, we constructed IDLV expressing the influenza virus nucleoprotein (IDLV-NP), and tested their ability to generate NP-specific immune responses and protect from challenge in vivo. We found that administration of IDLV-NP elicited NP-specific T cell and antibody responses in BALB/c mice. Importantly, IDLV-NP was protective against homologous and heterosubtypic influenza virus challenge only when given by the intranasal route. This is the first report demonstrating that IDLV can induce protective immunity after intranasal administration, and suggests that IDLV may represent a promising vaccine platform against infectious agents.
Highlights
Viral vectors represent an attractive platform for vaccine development due to their ability to effectively deliver genes of interest into cells, and generate humoral and cell-mediated immune responses [1]
We assessed the ability of Integrase-defective Lentiviral vectors (LV) (IDLV) to transduce cells and express proteins in vitro, in comparison to their integrating counterparts. 293T cells were transduced with IDLV and integrase-competent LV (ICLV) expressing either green fluorescent protein (GFP) or influenza NP, and protein expression was evaluated visually by fluorescence microscopy for GFP, and quantitatively by flow cytometry for NP (Figure 2A)
In both cases, cells were efficiently transduced (65.0% or 86.6% of cells positive for NP expression 2 days after transduction with IDLV expressing NP (IDLV-NP) or ICLV expressing NP (ICLV-NP), respectively) and proteins were expressed by IDLV, albeit, as expected, at lower levels than those expressed from ICLV (MFI of 16.7 versus 39.2 for IDLV-NP or ICLV-NP, respectively) (Figure 2A)
Summary
Viral vectors represent an attractive platform for vaccine development due to their ability to effectively deliver genes of interest into cells, and generate humoral and cell-mediated immune responses [1]. Preexisting immunity to LV is absent in humans, making them unlikely to be cleared by the host [8], a major hurdle for other vector-based strategies. Despite their appealing features, integrase-competent LV (ICLV) are limited as vaccine delivery tools by their potential to integrate into host cell chromosomes [9], which poses the health risk of insertional mutagenesis. From the perspective of vaccine development, both muscle (terminally differentiated cells) and airway epithelial cells (turnover .12 months)[14] represent ideal targets for IDLV administration because they would allow persistent antigen expression. IDLV vaccination has been shown to provide sterilizing immunity against malaria [18]
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