Herpesviruses do not undermine immune protection in old age
A study conducted by HZI scientists alleviates concerns about CMV infections
Herpesviruses, such as the cytomegalovirus (CMV), have been associated with changes in the immune system of older people for a long time. However it remained unclear, if this means that immune protection and function are impaired by a herpesvirus infection. A new study by scientists from the Helmholtz Centre for Infection Research (HZI) in Braunschweig suggests that herpesviruses do not undermine immune protection against emerging infections. The results were published in the “Journal of Virology”. The findings alleviate concerns about herpesvirus infections in aging individuals.
CMV is one of the most studied viruses in the herpes family as most of people are carrying it. Once someone gets infected, the virus stays in the body for life with no harm in a “silent mode” unless when the host’s immune system is compromised which may lead to reactivation of the virus. The adverse effect of CMV infection may be seen in people with a weak immune system, like organ transplant recipients, AIDS patients, or unborn babies infected during pregnancy. Another thing that has worried experts about CMV is its effect in older people. “CMV demands permanent attention from the T cells, the major defense cells of the immune system. The basis for the idea to conduct this study was from the hypothesis that the longer the mice were infected with CMV, the more of these cells were engaged with this virus and were missing for the fight against other pathogens”, says Prof Luka Cicin-Sain, head of the junior research group “Immune Aging and Chronic Infections” at the HZI. Moreover, it was not clear if the previously published results regarding CMV could be generalized to any virus from the herpes family.
Previous studies conducted by scientists in the lab of Luka Cicin-Sain at HZI and elsewhere had shown that CMV infections increase the amount of activated CD8 T cells. This was linked to a persisting immune response against the virus and it was thought that it may impair the immunity against other infections. “Previous studies had never compared herpesviruses from all the three subfamilies and groups carrying the combination of the herpesviruses with the controls side by side”, says Dr. Thomas Marandu, first author of the study. “Most of the MCMV-oriented studies have reported changes in the homeostasis of CD8 T cells and their response against new infections by comparing the relative but not the absolute number, something that our study did.” The HZI researchers challenged old mice carrying latent herpesviruses with several other emerging viruses. “Our results show that there was hardly a difference in immune protection between mice carrying herpesviruses and the controls”, says Marandu. “Moreover, latent infections did not affect the T cell response against other pathogens”.
Therefore, herpesviruses do not appear to undermine the immune protection against emerging infections in old people. This opens the door to utilize CMV as vaccine vectors, immunological Trojan horses to deliver pieces of other pathogens into the body and provide lasting immunity against difficult targets, such as hepatitis or AIDS. “In light of the extremely strong natural immunity to CMV, our findings bring good news to vaccine developers who would like to harness the immunological potential of CMV-based vectors”, says Cicin-Sain.
This publication was selected by editors of the Journal of Virology as one of the spotlights publication (an article of significant interest) in the current issue.
Citation: Marandu TF, Oduro JD, Borkner L, Dekhtiarenko I, Uhrlaub J, Drabig A, Kröger A, Nikolich-Zugich J, Cicin-Sain L. 2015. Immune protection against virus challenge in aging mice is not affected by latent herpesviral infections. J Virol 89:11715–11717. doi:10.1128/JVI.01989-15.