General Antonyms:
* Connection
* Interaction
* Engagement
* Community
* Togetherness
* Unity
* Association
* Integration
* Inclusion
* Socialization
Antonyms Relating to Physical Location:
* Proximity
* Accessibility
* Openness
* Exposure
* Accessibility
Antonyms Relating to Social Connections:
* Companionship
* Friendship
* Love
* Support
* Belonging
* Acceptance
Antonyms Relating to Mental State:
* Connection
* Openness
* Vulnerability
* Trust
* Confidence
* Hope
The best antonym will depend on the context in which you are using the word "isolation."