Epigenetic control of virus genes during the latent phase

The influenza flu virus has always been an enigma. The virus is able to stay dormant for decades only to re-emerge later. It was suggested that the re-activation of a long dormant infection was a possibility except that the latent phase of the virus has not been found (CDC). It has also been suggested that the influenza virus could lie dormant in humans as opposed to birds and swine (Reid and Taubenberger, 2003, Hillman, 2002). The fact is that influenza virus is a lytic virus and it has no capacity to establish latency.

I would like to suggest a possibility that the influenza A virus could lie dormant if epigenetics factors come into the picture. Chromatin dynamics may come into play as the chromatin structure may regulate the expression of the virus genes. The association of the ORF 62 and 63 (Open Reading Frame) of the Varicella zoster virus with histones (Gary et al, 2006) and the epigenetic regulation of Epstein Barr virus genome by CpG methylation at promoter sites (Takacs et al, 2001) suggests a possibility that an intrinsically lytic virus can be in the dormant state pending on epigenetic factors and chromatin dynamics (heterochromatin VS euchromatin). At this stage, epigenetic and chromatin dynamics control of viral gene expression is merely a suggested possibility on my part.

Citations

1) Center for Disease Control http://www.cdc.gov/ncidod/EID/vol12no01/05-1254.htm

2) Reid AH, Taubenberger JK. The origin of the 1918 pandemic influenza virus: a continuing enigma. J Gen Virol. 2003 Sep;84(Pt 9):2285-92.

3) Hilleman MR. Realities and enigmas of human viral influenza: pathogenesis, epidemiology and control. Vaccine. 2002 Aug 19;20(25-26):3068-87.

4) Gary L, Gilden DH, Cohrs RJ. Epigenetic regulation of varicella-zoster virus open reading frames 62 and 63 in latently infected human trigeminal ganglia. J Virol. 2006 May;80(10):4921-6.

5) Takacs M, Salamon D, Myohanen S, Li H, Segesdi J, Ujvari D, Uhlig J, Niller HH, Wolf H, Berencsi G, Minarovits J. Epigenetics of latent Epstein-Barr virus genomes: high resolution methylation analysis of the bidirectional promoter region of latent membrane protein 1 and 2B genes. Biol Chem. 2001 Apr;382(4):699-705.