We evaluated the breadth of the NAb response against non-recombinant homologous and heterologous clade A and clade B viral variants, as well as recombinants, and assessed the results, testing for evidence of an association between the potency of the NAb response and the duration of infection, CD4+ T lymphocyte numbers, health status and survival times of the infected cats. The gene discussed is CD4; the disease is infection.