multisite multilanguage and theme localization

Hi guys, i'm stucked with a problem i really don't know how to solve, i have a multisite installation, with two website that has different language settings (english and italian), and when i pass from the italian one to the english, the theme just seem to not load the localization file (now my theme is based in italian).

- I’m using all the translatable strings like _e() and __()
- Created the en_EN .po and .mo files (located in the /lang folder inside the theme)
- created a text domain name as the “slug” of the theme:

/*
Theme Name: translate test
Theme URI:
Description:
Author: Fab
Author URI:
Version: 1
Text Domain: translate-test
Domain Path: /lang
*/

- Loaded the text domain in the functions.php:

<?php
add_action('after_setup_theme', 'my_theme_setup');
function my_theme_setup(){
load_theme_textdomain('translate-test', get_template_directory().'/lang');
}
?>

this is a index.php test i’m using

<!DOCTYPE html>
<html <?php language_attributes(); ?>>
<head>
<meta charset=utf-8 />
<title>translate test</title>
<link target="_blank" href="http:////netdna.bootstrapcdn.com/bootstrap/3.1.0/css/bootstrap.min.css" rel="stylesheet" type="text/css" />
<link href="<?php bloginfo('stylesheet_url');?>" type="text/css" rel="stylesheet" media="all">
</head>
<body>
<h1><?php _e('questo è un test','translate-test')?></h1>
<?php var_dump($locale)?>
</body>
</html>

i really can’t find what’s wrong with it