It seems to be about the most promising therapy at this time. Stay on top of kitty's oral health. Ask your vet to show you how to brush and take care of kitty's teeth. Oral problems can be deadly in an FeLV cat. But be VERY careful not to overdo the supplements or choose ones that are gharmful for your cat.
Studies show that aloe vera holds tremendous promise in treating all immunodeficiencies.
You can read about acemannan and ambrotose in the Research section of the website. I used pure aloe vera juice from whole leaves, which you can buy in a health food store, mixed with a buffered Vitamin C ascorbate with bioflavonoids and added vitamins and minerals, and with a DHEA precursor called Wild Yam Extract. Be very careful about the Vitamin C, because the acid can do more harm than good, and clinical trials at the pioneering Linus Pauling Institute and others show that the therapeutic range for Vitamin C may be quite narrow before toxic effects are observed. DHEA is commonly used to combat HIV and other immunological deficiencies such as lupus, but precious little has been done in terms of clinical testing. At the first sign of any illness, consult your vet .