he knows he's immune to pretty much any virus and the serum flushes out bacteria too. he also knows what its like to live with a weakened immune system and almost dying at every corner. and he knows what its like to be utterly alone and abandoned by the general population

and so he looks into the scientists looking for a cure. he vets the team he likes, makes utterly sure they were never in any way involved with shield or any attempts to recreate the serum. both sides sign a contract including a painful amount of NDAs and the scientists also get protection details juuust in case it leaks anyway

turns out the serum can fight HIV, wildly efficiently, and due to its regenerative abilities can reverse at least some of the effects of aids too. the scientists isolate the antibodies, and, damn, okay that works

Steve is utterly delighted. he makes sure the research and all future treatments are fully funded

Bucky cradles her to his chest like the precious bundle of joy that she is, one hand carefully supporting her butt while the other bestows generous ear-scritches upon her. He tucks her in his jackets and hoodies, lets her curl up in the crook of his arm when she jumps up on the bed to claim her morning kissies, and he often puts her in one of those baby slings so he can keep her close and have her fuzzy little head within kissing distance all the time, while she purrs the day away in a state of perfect bliss. Alpine adores him. He calls her "baby" and "his best girl", and she regales him with her softest mrrrp's and mrrow's in return - and when she gently rubs her head to his cheek, Bucky's world instantly feels a little brighter.

Steve, on the other hand.

Steve wears her like a scarf, her long fluffy body slung around his neck, hands holding both ends so she won't fall off. Steve carries her under his arm like she's a baguette, her butt to the world, her head tucked just below his armpit, and she never even complains (not after the first ten times anyway).

Steve play-wrestles with her, winds her up good and then lets her swat her paws at him, all soft fur and righteous fury, and he plays up the punching sound effects when she hits his palms, all the while going "Come on girl, get in here, show me whatchu got," and "Pow pow, thwap boom fshhhhhh, oh no, oh no she got me, I'm going down, Sergeant Stinkass Fishbreath is too strong for me, nooo!". Steve likes to spin her in circles on the floor, and Alpine loves it - in fact, if Steve is around and failing to give her the required attentions, she screams at him with that blood-curdling yowl of hers until he finally gets the hint, grabs her with one hand and turbo-twirls her at maximum speed, like a feather duster in a salad spinner.