News
12/13/1988

<TITLE>AIDS Test licensed</TITLE>
<PRE>
AIDS Test licensed

P88-39                                      Food and Drug Administration
FOR IMMEDIATE RELEASE                       Brad Stone - (301) 443-3285 

    The Food and Drug Administration today licensed a five-minute screening 
test for detecting antibodies to the AIDS virus.  This test is the first
AIDS-related diagnostic test which uses a protein engineered by 
recombinant-DNA technology rather than the AIDS virus itself. 
    Useful when a quick screening result is required, the new test also is
designed to be used by trained health professionals in settings in which
other types of AIDS antibody detection tests cannot be performed because of 
the lack of refrigeration and sophisticated equipment.
    FDA Commissioner Frank E. Young, M.D., Ph.D., said that the test is the 
first for AIDS virus infection to be developed by gene-splicing techniques. 
"This technical advance," Dr. Young said, "should help make testing 
available to all who want to be tested.  It will also be particularly useful
in remote areas of the world that lack the facilities for earlier approved
tests and may also be very useful as a preliminary screening measure in 
emergency situations in this country. 
                                   

                                            Page 2

    "It is not, however, intended to replace the current tests used by blood
banks for screening donated blood.  Furthermore, any positive reactions 
using this screening test must be confirmed because false-positive reactions
can occur." 
    Called a latex agglutination test kit, the new test is a suspension of
microscopic latex beads coated with a genetically engineered protein which
contains portions of the outer surface, or envelope, of the AIDS virus. 
The engineered protein is produced by a process in which a part of the AIDS 
virus genetic material is inserted into E. coli bacteria.  As the bacteria
grow, a large amount of the modified AIDS virus envelope protein is 
produced.  The engineered virus protein is purified further before it is
coated onto the latex beads.
    This production process is much safer than previous methods relying on
growing live AIDS viruses in a cell culture.
    When a sample of whole blood, plasma or serum is mixed with the 
protein-coated latex beads, AIDS antibodies, if present in the sample, will 
bind to the beads causing them to clump, or agglutinate.  A trained 
professional can visually detect this clumping reaction with a bright 
light.
    The agglutination test supplements the series of other approved AIDS
antibody test kits that have been used to screen the blood supply.  The 
screening test which is recommended for routine use in blood banks and
clinical laboratories, the enzyme-linked immunosorbent assay, or ELISA, was 
first licensed by FDA in March 1985.
                                   


                                            Page 3
Another, more specific test known as the Western blot was approved in April 
1987.  The universal use of these two types of blood screening kits by blood
establishments within the United States -- along with voluntary 
self-exclusion by high risk groups -- has effectively safeguarded the 
nation's blood supply from contamination with the AIDS virus. 
    When properly performed by trained medical professionals, the latex 
agglutination test can provide a highly sensitive assay for AIDS virus
antibodies within five minutes, compared to the several hours it takes to 
develop results using the other test kits.  The new test kit is not well
adapted, however, for screening very large numbers of samples.  Also, 
false-positive reactions can occur because of interpretation errors, some 
medical conditions and problems of sample quality that do not ordinarily
affect the ELISA test.  As with other screening tests, positive test results
should be further investigated by repeat testing, including a test with a 
fresh sample, and by validation with additional, more specific tests based
on independent methods such as the Western blot.
    The approved test kit will be manufactured by Cambridge Bioscience Corp.
of Worcester, Mass., and distributed by Baxter Health Care Corp. under the
trade name Recombigen HIV-1 Latex Agglutination Test. 
</PRE>