LangChain supports chat models hosted by Deep Infra through the ChatDeepInfra wrapper. First, you’ll need to install the @langchain/community package:
See this section for general instructions on installing LangChain packages.
npm
npm install @langchain/community @langchain/core
You’ll need to obtain an API key and set it as an environment variable named DEEPINFRA_API_TOKEN (or pass it into the constructor), then call the model as shown below: 
import { ChatDeepInfra } from "@langchain/community/chat_models/deepinfra";
import { HumanMessage } from "@langchain/core/messages";

const apiKey = process.env.DEEPINFRA_API_TOKEN;

const model = "meta-llama/Meta-Llama-3-70B-Instruct";

const chat = new ChatDeepInfra({
  model,
  apiKey,
});

const messages = [new HumanMessage("Hello")];

const res = await chat.invoke(messages);

console.log(res);