This is an abstract from 2004 that I hadn't seen before. It suggests the possibility that when present simultaneously, endogenous retrovirus and herpesvirus have a synergistic effect, and not in a good way. It is interesting as the multiple viral trigger possibility has been studied a bit.
Simultaneous presence of endogenous retrovirus and herpes virus antigens has profound effect on cell-mediated immune responses: implications for multiple sclerosis.
AIDS Res Hum Retroviruses. 2004 Apr;20(4):415-23.
Brudek T, Christensen T, Hansen HJ, Bobecka J, Moller-Larsen A.
Department of Medical Microbiology and Immunology, University of Aarhus, DK-8000 Aarhus C, Denmark. firstname.lastname@example.org
Retroviruses have been suggested as possible pathogenic factors in multiple sclerosis (MS), supported by the observation that endogenous retroviruses are activated in MS patients. Different members of the herpes family of which several are neurotropic have also been suggested as factors in MS pathogenesis. Further, interactions between retroviruses and herpes viruses have been implied in the development of MS.
The objective of the study was investigation of cell-mediated immune responses of MS patients to retrovirus and herpes virus antigens, particularly antigen combinations, with analyses of the influence of retrovirus antigens on cellular immunological reactivity toward other viral antigens. Cellular immunity as measured by blast transformation assays was analyzed using freshly isolated peripheral blood mononuclear cells from 47 MS patients and 36 healthy volunteers.
Combinations of the endogenous retrovirus HERV-H and herpes virus antigens resulted in highly increased cellular immune responses among both the MS patients and healthy subjects. The increase was synergistic in character in most samples. Very pronounced effects were obtained using HHV-6A and HSV-1 antigens. Blast transformation assays combining antigens from two different herpes viruses or combinations of measles and herpes antigens showed no synergy.
The obtained data indicate a pronounced synergistic effect on the cellular immune response when retrovirus and herpes antigens are present together. The cause of the synergy is unknown so far. The effect on the immune response may influence the disease progression.