The problem is that you don't draw it correctly. You are just drawing a texture, so if you want to set the alpha to 0, you would have to add this line before your actual drawing code:
But like this you would not need the sprite class at all. A Texture or TextureRegion class would suffice.
It you want to take advantage of the sprite class, then you would draw it like this:
Then the color of the sprite, but also the dimensions and positioning (maybe also rotation, not sure about that) would be taken into account. This means that you do not set the position and size in the draw method, but you set them as sprite properties:
sprite.setBounds(0, 0, 64, 64);
Hope this helps