Thank you for the question.  Unfortunately, Virginia creeper is one of the plants Japanese beetles prefer so we don't have a concrete answer for you.  Our publication "Japanese beetle management in Minnesota" describes the beetle's life cycle and possible control measures for the Japanese beetle grub and adult.  According to the information, you could apply Japanese beetle grub control now to control the number of beetles emerging next year.  You can try to control the adults but this will be difficult and some of the insecticides that kill the beetles, also harm our pollinators.  The publication states that the presence of Japanese beetles doesn't mean you have a Japanese beetle grub infestation because the adults are strong fliers and will come in from great distance to find attractive plant material.  

Please read the article to find out what you can do to try to reduce the numbers of beetles on your property, but realize that you can't control the ones that fly in from next door or miles away!

The long term solution for all of us is to cultivate plants less attractive to the beetle in our landscapes and reduce the amount of turfgrass the grubs need to grow and develop into adult beetles.

Repeated defoliation of your vines will probably weaken them over a period of years.  We do recommend using plants the beetles don't prefer although do recognize that this is difficult when you have such established plantings.  Plant options are listed in the publication as well: