Exposure to Human Herpes Virus Type 6 Protects Against Allergic Asthma in Mice

We have previously shown that infection with Human Herpes Virus (HHV)-6 during the fi rst 18 months in life protects against IgE sensitization and Th2 driven immunity.The aim of this study was to investigate if exposure to HHV-6 affects the allergic response and the adaptive immunity in vivo.For this purpose, a well known mouse model of ovalbumin (OVA)-induced allergic asthma was used.BALB/c mice were OVA sensitized, and exposed to HHV-6 intraperitoneal on two occasions, followed by intranasal challenge with OVA on fi ve consecutive days one week after the second sensitization.24 hours after the fi nal OVA exposure, serum, bronchoalveolar lavage (BAL) and lung-tissue were collected.We show that mice exposed to HHV-6 have signifi cantly lower frequency of OVA-specifi c IgE compared to control mice.This was associated with signifi cantly reduced numbers of infl ammatory cells and eosinophils in the BAL fl uid of HHV-6 exposed mice.HHV-6 exposure also signifi cantly inhibited the production of IL-4, IL-5 and IL-13 in the BAL fl uid and in the lung tissue of the virus exposed mice.In conclusion, we suggest that exposure to HHV-6 protect against allergic asthma in mice, by limiting the Th2-driven infl ammation.