This is a bit more info on FeLV and age of cat, I wouldnt put such a young kitten in that situation.
WHAT HAPPENS WHEN A CAT IS EXPOSED TO INFECTION?
This depends on the age of the cat. Resistance to infection increases with age.
Most new-born kittens will receive maternal antibodies to FeLV, which protect them if they are exposed to the virus. However, if they have not, (because their mother has not encountered it) and they are exposed to it, they will be permanently infected. In kittens between six weeks and four months (whose maternal immunity has waned), 85% exposed to the virus will be permanently infected .
Of kittens over four months or adult cats, only 15% become permanently infected. The other 85% will produce antibodies to the virus and recover from the infection. These cats will have a life-long immunity to FeLV, which can be assessed by the Virus Neutralising Antibody (or VN) test. (This test is only carried out at the Feline Virus Unit at the University of Glasgow, and the vet will send a blood sample to them.). However, many vets do not appear to have heard of this test, so you may need to ask for it specifically.
It will be obvious from this, that the most susceptible age-group to infection with FeLV is the six weeks to four month-old kitten. Of those which become permanently infected, 80-85% will die within 2-5 years. Kittens infected before birth will also die within this time-scale. The long-term outlook is not good for kittens infected at this age.
The rest of the article is very interesting actuallyhttp://www.catchat.org/leukaemia.html