News of the Week Attention has focused instead on whether USDA's Animal & Plant Health Inspection Service (APHIS), the agency that oversees licensure of veterinary vaccines, followed USDA procedures for regulation of a recombinant product. Rifkin's petitions charged that APHIS should have presented the license application formally to USDA's Recombinant DNA Research Committee (RDRC), a panel established to guide decisions on biotechnology products, and should have conducted a formal environmental assessment. APHIS, which says it informally notified RDRC, says a formal assessment was unnecessary because the product was deemed very similar to existing products. The agency claims it acted properly, but suspended the license while it compiles a formal assessment from existing data. On April 14, APHIS ignored a Rifkin deadline on demands that the license be suspended until an RDRC review and an entirely new assessment is completed. "We are not changing anything regarding our position/' says David A. Espeseth, a senior staff veterinarian in APHIS. ' O n the 23rd, we will
lift the license suspension and the product will return to the market/' Meanwhile, Rep. Volkmer says USDA documents show APHIS approved field tests of Omnivac in April 1985 without knowing it qualified as a recombinant organism and licensed it on Jan. 16, 1986, despite the fact that field-test data were not in until Feb. 7. Volkmer, who investigated the Advanced Genetic Sciences controversy last month (C&EN, March 10, page 4), says, 'This series of events raises serious questions about USDA's ability and willingness to respond to the concerns of the public, Congress, and the scientific community regarding the release of genetically engineered organisms." On April 3, the General Accounting Office released a report criticizing USDA's biotechnology regulatory structure. The Industrial Biotechnology Association, trying to slow the rush of bad news about biotechnology commercialization, last week backed APHIS's regulatory actions, noted that USDA's comprehensive policy for biotechnology regulation is due soon, and criticized recent newspaper accounts of the vaccine issue. D
Cetus technique detects AIDS virus A method for detecting the virus that causes acquired immune deficiency syndrome (AIDS) in cells from infected individuals has been developed by researchers at Cetus Corp. Based on what is known as DNA probe technology, the technique could lead to a routine and inexpensive assay for the AIDS virus, the company says. The method involves amplification of viral nucleic acid sequences by a technique called a polymerase chain reaction (PCR) and rapid detection of the sequences by a technique called oligomer restriction (OR) analysis. Both technologies were developed by Cetus, based in Emeryville, Calif., which has applied for a number of patents on them. Cetus researchers first applied the PCR-OR method to the detection of the human gene that causes sickle cell anemia [Science, 230,1350 (1985)]. Cetus senior scientist and director 8
April 2 1 , 1986 C&EN
of R&D John J. Sninsky described application of the technique to detecting the AIDS virus at a symposium on "Monoclonal Antibodies and DNA Probes in Diagnostic and Preventative Medicine" held earlier this month in Florence, Italy. Tests currently being used for identifying individuals who have been infected with AIDS detect antibodies to the virus rather than the virus itself. The meaning of a positive result from such a test, however, is ambiguous because individuals with antibodies may no longer have the virus and individuals with the virus may not exhibit antibodies. Detecting the virus itself is more useful both in terms of AIDS diagnosis and evaluation of various drugs designed to eliminate the virus. Unfortunately, such tests are inherently difficult. In the case of AIDS, they are particularly so be-
cause the AIDS virus is often present at extremely low levels. The AIDS virus is a retrovirus; its genetic material is RNA. When the virus infects a cell, it triggers production of an enzyme called reverse transcriptase that causes the viral RNA to be copied into DNA. It is this DNA, some of which is incorporated into the infected cell's genome and some of which remains unincorporated, that is detected by the Cetus technique. According to Sninsky, the researchers identified a number of viral nucleic acid sequences that are invariant across the numerous strains of the AIDS virus whose genomes have been sequenced. Two such invariant regions containing convenient restriction enzyme sites were chosen for study. The PCR technique is used to amplify the number of copies of one of these sequences present in a clinical sample by a factor of about 1 million. Other DNA sequences present in the sample are not multiplied. A radioactively labeled DNA probe is then introduced to the sample of amplified, denatured DNA. The probe is an oligonucleotide complementary to the sequence containing the restriction site. If the sequence is present—that is, if the sample is from an individual infected with AIDS—the probe will hybridize with it. Subsequent digestion with the appropriate restriction enzyme generates a short, single strand of labeled DNA that is easily detected by gel electrophoresis and autoradiographic imaging of the gel. Sninsky points out that the PCR procedure requires 20, six-minute cycles of denaturation, reannealing, and chain elongation. That process has now been automated. So far, studies have been done by culturing cells in the presence of AIDS patients' blood and semen. AIDS virus that is present in the samples infects the cells and this infection is detected by the test. Cetus researchers are working to enhance the sensitivity of the test so that the virus can be detected directly in blood samples from patients. If these efforts prove successful, a DNA probe test could be developed for introduction and evaluation in 1987, the company says. D
