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THE discovery of two chemicals that make it tough for HIV to worm its way
into human chromosomes may give scientists a new mode of attack against the
virus.

Existing anti-HIV drugs target one of two viral enzymes: reverse
transcriptase, which transforms HIV鈥檚 RNA into DNA once it enters a cell; or HIV
protease, which gives the new virus particles their protein coat.

Before it can replicate itself, however, HIV has to hijack the host cell鈥檚
biochemical machinery by integrating itself into human DNA. The enzyme
responsible for this is called HIV integrase. And now a team of researchers at
Merck Research Laboratories in West Point, Pennsylvania, have found two organic
chemicals, from a class known as diketo acids, that appear to interfere with
integrase.

The integration of HIV鈥檚 DNA into our DNA involves two principal steps. The
first is the assembly of special DNA sequences at the ends of the viral DNA
strand, needed to grab hold of the human DNA. The second is 鈥渟trand transfer鈥�,
in which the viral DNA bonds chemically to the host DNA. It鈥檚 this second stage
that the two diketo acid compounds seem to block.

The chemicals prevented various strains of HIV from spreading from cell to
cell in lab cultures. That鈥檚 encouraging news, as new classes of AIDS drugs will
be badly needed if, as some experts fear, side effects or drug resistance begin
to compromise the effectiveness of today鈥檚 treatments.