Several factors generally contribute to variation among proteomic studies. Hence, the preparation of the samples (e.g., in-gel trypsin digestion versus liquid digestion and chromatography) may lead to the detection of different populations of tryptic peptides. Moreover, the sensitivity of the mass spectrometers and the abundance of the proteins in the samples also impact peptide detection. The relative abundance of a peptide is itself influenced by the complexity of the samples, where some proteins may evade identification. Finally, each protein differs in its properties (ionization, resolution in SDS-PAGE gels), which will be reflected in their detection. This includes SNARES, which are transmembrane proteins resistant to SDS extraction (Yang et al., 1999; Kubista et al., 2004) . It is thus likely that some of the proteins in Table 1 are present in more viral particles than reported and that additional proteins are indeed incorporated in herpesvirions. More specific aspects regarding herpesviruses includes the purification schemes employed to enrich the viral particles, which will directly influence the purity of the samples and hence the potential detection of contaminants. One important caveat is that some host proteins may simply stick to the large viral particles. Another one is common contaminants such as some hair/skin associated keratins or as mentioned above actin, which may simply fill the virions. However, even potential contaminants cannot simply be discarded since actin and even some keratins may indeed participate in viral life cycles. Moreover, the relative abundance of all the cellular proteins within the cell is unknown, so it is not possible to rule out potential contaminants on the sole basis of abundance. It is thus critical to orthogonally validate all proteomics hits.