ng-init fetches value only once, even if the model value changes - angularjs

Question

I have a status filed deep nested to 3 levels in my model, I want to apply different classes to a div based on the value of the status. In order the save the typing and keep the html tidy, I wanted to apply short name to this status so I used ng-init to copy the values and use ng-class on ng-init variable. But ng-init gets its value only once, when I change the status again in controller it doesnt change but holds the old value. Is there a way to give short names to response.obj1.obj2.status at least inside a div?
<div ng-app="app">
<div ng-controller="statusCtrl">
<button ng-click="toggle()">toggle</button>
<div id="section1" ng-init="s1Status=response.section1.status">
<div id="statusIndicator" ng-class="{'success':s1Status==0,'error':s1Status==1}">Status</div>
</div>
<span>{{response.section1.status}}</span>
</div>
var app = angular.module('app', [])
app.controller('statusCtrl', function ($scope) {
$scope.response = {
section1: {
status: 1
}
};
$scope.toggle = function () {
if ($scope.response.section1.status === 0) $scope.response.section1.status = 1;
else $scope.response.section1.status = 0;
}
});
Demo: http://plnkr.co/edit/ES7rgf97BPFAWzkfIEhw?p=preview
EDIT:
Knockout JS has nice way to do this, where you can bind a model at any level to a div and any models referred inside that div will work with the parnet model as context. Thats what I'm looking for.
<div id="section1" data-bind="response.section1">
<div id="statusIndicator" data-bind=" css:{success:status==0, error:status=1 }">Status</div>
</div>