The results of the real-time PCR quantification were analyzed by two-dimensional cluster analysis. The first clustering was performed to group genes according to similar behavior in expression changes (upregulation or downregulation) following a stimulus ( Figure 6A ). This first cluster was then used for clustering in a second dimension to group experimental stimuli according to similar effects they had on changes in gene expression ( Figure 6A , right cluster). Analysis revealed genes that were upregulated at the 1 h and then downregulated at the 6 h time point (GADD45, DUSP2, IL-10), genes that were first downregulated and then upregulated (IDO, ISG 45K), a large group of genes induced at both time points, and finally genes that were downregulated at both time points (TLR3, GNA13). The second clustering ordered the experimental groups according to similar responses in gene expression ( Figure 6B ) and revealed the following three major clusters: 1) 1 h exposure to Ebola virions, LPS, and VLP VP40-GP , 2) 6 h exposure to Ebola virions, LPS, and VLP VP40-GP , and 3) 1 h and 6 h exposure to VLP VP40 and latex particles. This result suggests that Ebola virions, LPS, and VLP VP40-GP caused strikingly similar responses in comparison to the responses to VLP VP40 and latex particles. This further supports the notion that binding/entry of virions mediated by GP 1,2 plays a significant role in the host response to infection. Thirteen of the 21 genes tested responded to Ebola virions, VLP VP40-GP , and LPS at both time points. TNF-a, IL-1b, IL-6 and IL-8 were also found in a separate study on the effects of VLPs on macrophages [19] and CXCL1 represents a gene known to be affected by ZEBOV infection. However, COX-2, GCH1, GM-CSF, MIP-3a, t-Pa, GADD45A, and IDO (6 h) are genes identified to play a role in Ebola hemorrhagic fever for the first time.