Thanks for asking.
Most humans who drink alcohol are unaware of about 30 ingredients that can be added without being listed
on any label. Manufacturers can manipulate the flavor of a very cheap wine, to taste very similar to a $40 bottle.
Manufacturers can legally use egg whites, milk, gelatin, sugar, isinglass (fish bladders) among other ingredients. I
personally believe they should list all ingredients on wine bottles so customers know what they are drinking
and paying for. Many customers do not care, but many also do care. I also wonder if wine growers may use some
animal-derived ingredients on their grapes. ( unrelated, but for instance, non-organic bananas can be sprayed with
shellfish residues).
I do not drink alcohol anymore, but there must be a vegan website with details of which are vegan. You can
also call some wine makers and ask specific questions.