There isn't a built in Unbounce/GetResponse integration but you there are three options for connecting the two services.
Zapier lets you to connect online services and can act as the glue between Unbounce and GetResponse. (We use it ourselves to connect Unbounce & GoToWebinar).
You can check out the Unbounce/GetResponse Zap at the link below:
We highly recommend the Zapier method, as it's the simplest.
Unbounce's Webhook lets you build custom integrations between Unbounce and other services/CRMs. Unlike Zapier, the Webhook requires some development on your end.
You can read about the webhook in the article below:
Embed a GetResponse form on your page
With this option, you could replace Unbounce's form with your GetResponse form instead. This causes your leads to skip Unbounce altogether though and head straight to GetResponse.
You can see how to create GetResponse web forms and embed them on your Unbounce pages in the article below: