Visna virus
... that the Visna virus, a retrovirus that causes encephalitis and chronic pneumonitis in sheep, is used as a model system for HIV infection?
... that the <b id="mwD8Y"><a class="mw-redirect" href="./Visna_virus" id="mwD8c" rel="mw:WikiLink" title="Visna virus">Visna virus</a></b>, a <a href="./Retrovirus" id="mwD8g" rel="mw:WikiLink" title="Retrovirus">retrovirus</a> that causes <a href="./Encephalitis" id="mwD8k" rel="mw:WikiLink" title="Encephalitis">encephalitis</a> and chronic <a href="./Pneumonitis" id="mwD8o" rel="mw:WikiLink" title="Pneumonitis">pneumonitis</a> in <a href="./Sheep" id="mwD8s" rel="mw:WikiLink" title="Sheep">sheep</a>, is used as a <a class="mw-redirect" href="./Model_system" id="mwD8w" rel="mw:WikiLink" title="Model system">model system</a> for <a href="./HIV" id="mwD80" rel="mw:WikiLink" title="HIV">HIV</a> infection?