ERVW-1 and infection: When the anti-SU ELISA was first reported, a significant difference in mean antibody responses was noted between cats with progressive and regressive infections; however, a wide range of results and substantial overlap between infection categories limited its discriminatory ability.48 In the present study, with univariable analysis, cats administered Leucogen FeLV produced higher FeLV-A antibody levels, but lower FeLV-B antibody levels, than the other two vaccines at T2.