How do friendly and enemy Ana grenade effects interact?

Ana has a biotic grenade as one of her abilities, which gives allies a boost of health and a boost to healing for a period of time, and prevents enemies from healing at all. If I get hit by a friendly biotic grenade, immediately followed by an enemy biotic grenade, what will happen? Will the healing boost effect be negated? What about if I am hit by an enemy biotic grenade first, then a friendly biotic grenade?

The healing boost will have no effect because you have the debuff, which allows to no healing at all. However, if you're hit by the friendly grenade first, you will receive the 100 Healing. If you get hit by the enemy grenade first, the effect from the friendly one will be negated for it's duration (both the 100 initial healing and the boost).