Proliferate and Infect are two very strong mechanics, especially in combination with one another. So lets see how they do in pauper.
You might notice that this deck is both a low curve creature heavy deck, and also three colors, something that's pretty unusual for pauper due to the poor mana fixing. For this we have Pentad Prism, which is arguably the most powerful card in the deck. It will almost always be played for 2 charge counters, and because it doesn't tap to remove a charge counter and add mana, you'll likely be able to cast multiple additional spells per turn due to proliferating back the charge counters. The prism will also let you hold up mana for counters while maintaining aggressive play. Crumbling Vestige is great fixing for the deck as well, giving you a needed color of your choice as a one time bonus for playing it. This seems irrelevant but is great as we aren't held back from playing a one drop even if we dont have the land for it. The drawback of only tapping for colorless isn't a big deal as most spells in the deck only have a single colored pip and the ones that don't are higher costed. To round out the mana base, Thriving Isle can fix our mana, and the depletion lands are pretty cool since they'll rarely be sacrificed since you can proliferate their counters.
The deck's goal is pretty simple. Get as many poison counters on your opponent as you can early game and hold up blockers and proliferate them late game. There are some ways to get through despite your creatures being fairly weak stat wise, those being Incisor Glider to buff your board and Tyrranax Atrocity as a late game beater. The deck wants to win fast, but has access to multiple counterspells, and a lot of card draw to take on more of a midrange approach, just proliferating your opponents poison counters.
Sideboard is built around grindier games where an unboltable vigilance infect creature will gain much more value, also including more copies of value spells, and Aether Spellbomb for bounce or card draw. Tel-Jilad Fallen is pretty mana inefficient for aggro but is fantastic against aggro builds of affinity which swarms with big creatures that are hard for this deck to get around. Free space is included for typical pauper staples which can be added to taste
