The "prisoner" of God is the characteristic of a man who, having realized the Wisdom of God's Will, His Commandments, having been convinced of their truth and grace by their fulfillment, has thus become a servant of His Will, totally subject to God, bound by His "bonds" of Love, which God manifests to man by revealing His Will to him.

A "prisoner" of Jesus Christ is a disciple of Jesus Christ, submissive to the spiritual greatness, the righteousness of his Master, captivated by His way of thinking and living, totally committed to doing the Will of God as expressed in the Teaching of Jesus Christ. 

Negative Meaning. 
"Prisoner" is a person captive to their own vices, the "fetters" of their sins holding them in bondage to sin, to the constant service of the sinful demands of the flesh. 
"Prisoners" are people fanatically serving false religious and violent political leaders and their pernicious ideologies and beliefs, unable to free themselves from a sinful worldview and way of life.