The requirement of environmental acidification for Ibaraki virus infection to host cells

TSURUTA, Yuya; SHIBUTANI, Shusaku T.; WATANABE, Rie; IWATA, Hiroyuki

To confirm the effect of low pH on virus infectivity, purified IBAV was incubated in PBS (−) with several pH (pH=4, 7 or 9) for five min and infected to HmLu-1 at MOI=0.01. We employed lower MOI to protect cells from severe CPE at early time point and achieve multi cycle infection. DMEM without FBS was used for control incubation, and the significance in the difference between control and each test group was analyzed by Dunnet's test. As shown in Fig. 2a , the pro- Mouse antisera raised against VP2 (anti-VP2) or purified IBAV particle (anti-IBAV) were used as first antibodies. duction of progeny virus was significantly suppressed when IBAV was treated with PBS (pH4) compared to control treatment (P<0.001). Other conditions did not give any impact on IBAV infectivity (pH7 and pH9, P value was 0.993 and 0.906, respectively). The pH of PBS-IBAV mix solution was confirmed with pH test paper after 5 min incubation (data not shown). Many enveloped viruses lose its infectivity by low pH treatment, if they utilize endosomal acidification to trigger the activation of their protein that is responsible for infection [15, 17, 18] . The result obtained in this study was consistent with these observations suggesting that low pH treatment caused irreversible change on IBAV particle that leads to the loss of infectivity.