HERV-K inactive or potential pathogens from within?

Human endogenous retroviruses (HERVs) count for up to 8% of our genome, remnants of an ancestral infection and inherited through germlines [ [1] Steinhuber S. Brack M. Hunsmann G. Schwelberger H. Dierich M.P. Vogetseder W. Distribution of human endogenous retrovirus HERV-K genomes in humans and different primates. Hum. Genet. 1995; 96: 188-192 Crossref PubMed Scopus (74) Google Scholar ]. Multiple HERV families have been identified in the past decades [ [2] Nelson P.N. Carnegie P.R. Martin J. Davari Ejtehadi H. Hooley P. Roden D. et al. Demystified. Human endogenous retroviruses. Mol. Pathol. 2003; 56: 11-18 Crossref PubMed Scopus (132) Google Scholar ] and although many are inactive due to a subsequent accumulation of mutations within their sequences, a small subset have been acknowledged to be the most biologically active such as HERV type- K (HERV-K, subtype HML-2) and current research indicates that it's reactivation can be implicated in certain autoimmune disease and cancers [ [3] Boller K. König H. Sauter M. Mueller-Lantzsch N. Löwer R. Löwer J. et al. Evidence that HERV-K is the endogenous retrovirus sequence that codes for the human teratocarcinoma-derived retrovirus HTDV. Virology. 1993; 196: 349-353 Crossref PubMed Scopus (167) Google Scholar , [4] Nelson P.N. Lever A.M. Smith S. Pitman R. Murray P. Perera S.A. et al. Molecular investigations implicate human endogenous retroviruses as mediators of anti-retroviral antibodies in autoimmune rheumatic disease. Immunol. Investig. 1999; 28: 277-289 Crossref PubMed Scopus (40) Google Scholar ]. Studies showed that HERV-K (HML-2) viral-like particles can be induced in HIV-1 infected individuals but the pathogenic impact of HERV-K in HIV-1 infection remained an open question and deserves further study [ [5] Contreras-Galindo R. Kaplan M.H. Markovitz D.M. Lorenzo E. Yamamura Y. Detection of HERV-K(HML-2) viral RNA in plasma of HIV type 1-infected individuals. AIDS Res. Hum. Retrovir. 2006; 22: 979-984 Crossref PubMed Scopus (71) Google Scholar , [6] Contreras-Galindo R. Kaplan M.H. Contreras-Galindo A.C. Gonzalez-Hernandez M.J. Ferlenghi I. Giusti F. et al. Characterization of human endogenous retroviral elements in the blood of HIV-1-infected individuals. J. Virol. 2012; 86: 262-276 Crossref PubMed Scopus (73) Google Scholar ].