Presentation at the"Twentieth Century Plagues" Symposium
Embassy Suites Hotel, Los Angeles International Airport, March 1, 1996
Marriott Hotel,San Francisco Airport, March 2, 1996.
Overview: Stealth viruses are defined as cytopathic viruses able to establish a persistent infection because of deletion and/or mutation of specific genes which, if expressed, would evoke effective anti-viral cellular immunity (1-5). This presentation will mainly focus on stealth viruses derived from African green monkey simian cytomegalovirus (SCMV). Federal health authorities have been slow in addressing the potential transmission of stealth viruses in live polio viral vaccines.
Bief History of Poliomyelitis: Epidemic paralytic polio began to appear towards the end of the 19th century (6). The first report of a major outbreak was made by the Swedish pediatrician Dr. Carl Medin in 1889. Polio epidemics soon appeared throughout Europe. Attempts at animal transmission failed until 1908 when Dr. Carl Landsteiner (of blood group fame), inoculated two monkeys with a spinal cord extract obtained at autopsy from a 12 year-old boy. One monkey died acutely while a Rhesus monkey became paralyzed.
A major outbreak of paralytic polio occurred in the United States in 1916 affecting nine thousand individuals in New York City (7). Each summer there were reported clusters of polio in various parts of the United States. An unusual polio-like illness affected California in 1934. One hundred and ninety eight medical personnel at the Los Angeles County Hospital became sick (6). They were not paralyzed, but instead developed a chronic fatigue syndrome (CFS)-like illness. Attempts to isolate polio virus were unsuccessful. A class action suit was settled in 1938 for several million dollars, supposedly with the stipulation that there be no publicity to suggest that caring for polio patients could possibly be hazardous.
Basic studies showed that (i) polio virus initially infected the alimentary tract; (ii) Only a small percentage (<1%) of infected individuals actually developed paralysis; (iii) there were 3 serologically distinct Types (1, 2 and 3); (iii) most cases of paralytic polio were due to Type I, as exemplified by the highly virulent Mahoney strain; (iv) serum from a previously infected individual contained protective type-specific antibodies; (v) polio virus could be passed in monkey and mouse brains but "brain adapted" polio did not grow well in non-nervous tissues (6).
A major breakthrough occurred in 1948 when Dr. John Enders showed that by using antibiotics, it was possible to culture intestinal cells on which polio virus could be propagated and could produce a quantifiable cytopathic effect (CPE).
Development of Polio Vaccines: There were two competing approaches to vaccine development. The influenza vaccine model involved the use of inactivated (killed) virus. The yellow fever vaccine model involved the use of a weakened or attenuated strain as a live viral vaccine. Several unsuccessful efforts were made in the 1930's using these approaches with the polio virus grown in monkey or mouse brain.(6).
Following the work of Dr. Enders, Dr. Jonas Salk was commissioned in 1953 by Basil O'Connor, Director of the National Foundation for Infantile Paralysis (March of Dimes Foundation), to produce an inactivated polio vaccine (IPV). Dr. Salk grew virulent polio viruses on Rhesus monkey kidney cells and inactivated the harvested viruses using a 1:4,000 dilution of formaldehyde. Serious questions concerning (i) the necessity of using the Mahoney isolate for Type 1 polio, (ii) the dynamics and completeness of formaldehyde inactivation and (iii) statistical analyses of the early trial data using experimental vaccine lots were smothered by O'Connor's powerful Public Relations campaign and by the public's eagerness for a vaccine. The Federal Laboratory of Biological Safety (a component of the National Institutes of Health) licensed polio vaccine on April 12, 1954. This occurred in spite of Dr. Bernice Eddy notifying her supervisors that several monkeys developed paralysis from the vaccine made at Cutter Laboratories.
Soon after the launching of the commercial vaccine lots in April 1955, there were 10 deaths and 192 cases of vaccine induced paralytic polio. Most of the cases were traced to the Cutter vaccine. Vaccine lots from Park Davis and Eli Lilly were also found to contain live virus and the Industry knew that Dr. Salk's assumptions about formaldehyde were invalid. Efforts were made to single out Cutter as the only defective vaccine, while at the same time improve upon the inactivation protocol. The vaccine program was halted on April 27th and resumed on May 27th, hopefully still in time for the anticipated July onset of natural polio cases. By November, new manufacturing safeguards were introduced, such as an additional filtering step, without any recalls of existing lots. The Laboratory of Biological Safety was reorganized and placed under the Food and Drug Administration (FDA) as the Division of Biological Standards. For her good work, Dr. Eddy was removed from polio vaccine testing!
Although the efficacy of IPV was exaggerated by changing the clinical definition of paralytic polio and other maneuvers, it led to a significant reduction in polio cases. It still probably caused several cases from residual live virus. Public Health critics of the program were shunned and their protests nullified by legislating compulsory vaccination. Dr. Albert Sabin, Dr. Hilary Koprowski and others were more interested in developing an attenuated polio virus which could be administered as a live vaccine. Dr. Koprowski conducted extensive human and animal trials in Central Africa. A 1956 trial in Ireland was marred by the occurrence of polio in vaccine recipients. Dr. Sabin had more success, mainly because he made use of Dr. Renato Dulbecco's technique of plaque purifying attenuated viral isolates. By 1960, Dr. Sabin had convinced much of Europe that his vaccine was less expensive and created more rapid and longer lasting immunity than did IPV. Moreover, excretion of live vaccine virus indirectly vaccinated others within a community and helped out-compete virulent viral strains.
The subtle nucleotide changes, mainly within the 5' non-coding region, that distinguish attenuated from wild type virus have recently been identified. Much of the difference involves a single nucleotide substitution. The attenuated strains can revert to more pathogenic variants, and even approved vaccine lots contain some revertants. This problem occurs more frequently with the least altered, Type 3 polio vaccine strain.
SV40 Contamination: From 1957 Dr. Eddy was involved in pioneering work with Dr. Sarah Stewart on the ability of a mouse Polyoma virus to induce tumors in hamsters. Dr. Eddy was suspicious that monkey kidney cells might have a polyoma-like virus. In April 1960, she reported to her supervisor, Dr. Joseph Smadel, that extracts from Rhesus monkey kidneys induced tumors in hamsters similar to those induced with Polyoma virus. Her work was dismissed by Dr. Smadel. Moreover, she was severely chastised for subsequently mentioning her findings at a Polyoma virus conference held in New York in August, 1960. She was instructed that all future utterances had to be written and submitted for approval by Dr. Smadel.
Dr. Maurice Hillerman of Merck was also concerned that the Rhesus monkeys being used for polio vaccine were becoming increasingly infected with unknown viral agents. He asked the Director of the Washington D.C. Zoo to arrange a shipment of a different species of monkey, imported separately from the usual routing. He received African green monkeys from Africa via Madrid and Baltimore. Extracts from Rhesus monkeys produced a strong vacuolating cytopathic effect on the African green monkey kidney cells. The responsible virus was the 40th virus isolated from Rhesus monkeys and called SV40. It was subsequently shown to be the same virus as found by Dr. Eddy to cause cancer in hamsters.
SV40 is endemic in Rhesus monkeys, producing very little CPE. It does not occur naturally in African green monkeys and when present, it produces a strong CPE. With suppressed publicity, FDA undertook a major effort to switch the polio vaccine seed lots from Rhesus to African green monkeys using anti-SV40 antibodies to neutralize the contaminating virus. Brief and belated mention of the problem occurred in the press; even Dr. Eddy was subsequently allowed to publish her findings. She had, however, lost her laboratory and her research support.
The SV40 issue was initially seen as a problem for the live viral vaccine. Unfortunately, the virus was not inactivated by 1:4,000 formaldehyde and parental inoculation created more infections than oral administration. However, since there were no apparent ill effects, the concern over this virus subsequently waned. Yet, recently there have been reports of SV40 virus in both childhood choroid plexus brain tumors (8) and in mesotheliomas (9). The children were too young to have received SV40 directly from a vaccine and in all likelihood this virus is now circulating within the human population.
Live polio virus vaccine was licensed to Lederle (American Cyanimid) as Orimune(R) in 1961 and has since largely replaced inactivated vaccines. Occasionally (8-10 cases per year in the United States), the Type 3 vaccine polio reverts to virulence and induces disease.
Viral Contamination of Live Polio Virus Vaccines: During early vaccine developments almost 50% of the kidney cultures established for polio vaccine production were discarded because of obvious viral contaminants (mainly foamy retroviruses but also adenoviruses and non-identifiable agents). Few if any of these adventitious agents were thought to be pathogenic for man. An exception was the monkey B virus, a herpes simplex-like virus known to cause a fatal encephalitis. Another major scare arose in 1968 in Marburg, Germany when monkeys intended for vaccine production transmitted an acute hemorrhagic illness to their caretakers. Renewed efforts went into screening for unknown viruses. In 1968, Dr. Kendall Smith, an electron microscopist at FDA Division of Biological Standards, detected viral-like agents in some batches of polio vaccines. He unsuccessfully argued for the use of a fluorescence focus assay using sera from monkeys tested on their own kidney cell cultures. Consideration was given by Lederle to switching from monkeys to human cells for vaccine production. This approach was taken by Pfizer, an English pharmaceutical company. Their product was called Diplovax and was derived from human diploid cells.
In a joint Lederle/Bureau of Biologics study conducted in 1972 "All eleven monkeys studied demonstrated the presence of CMV-like agents. These monkeys all originated from Kenya over a short period of time. Seven of these monkeys would have passed our existing test standards." In a "Cytomegalovirus Contingency Plan", dated August 4th, 1972, Dr. Vallancourt from Lederle argued that "Unless and until Pfizer's Diplovax is in abundant supply, the BB [Bureau of Biologics] cannot risk Lederle being off the market." On March 16th, 1973, Dr. Vallancourt wrote to the President of American Cyanamid, "I do not believe our problems with the slow release of specific lots of Orimune(R) are a result of a Pfizar influence..... Furthermore, if the Bureau wanted to restrict us they could bring up the subject of CMV (Cytomegalovirus) in our substrate (i.e. African green monkey kidney tissue) which they have not done, even though they have told us the monkeys in the collaborative study performed in 1972 were all positive for this agent."
In 1977 assays for retroviral reverse transcriptase activity were applied to some polio vaccines. Certain vaccine lots tested positive and this activity could be transmitted to cell cultures which developed an atypical CPE. It is now known that many of the African green monkeys used were infected with simian immunodeficiency virus (SIV). Interestingly, African green monkeys brought to the Caribbean earlier this century were not infected with SIV, raising the possibility that SIV is a more recent infection than generally thought and possibly of experimental vaccine origin. Discussion at the time of possible Type C retroviruses in polio vaccines led to more detailed electron microscopy. Particles were seen in polio batch 3-444, but were considered more likely to be cell debri than actual viruses. I worked at the time as Director of the Viral Oncology Laboratory at the Bureau of Biologics. In 1978, Dr. G. Aulakh and I confirmed that a bulk monopool of polio vaccine contained a considerable amount of DNA, not all of which could be accounted for as simple cellular debri. I was not provided any information on the earlier concern about CMV, but was told that the monopools were submitted only to determine if they met the mutually approved and mandated tests for polio vaccines. In other words, they were not available to continue this line of experiments. I still remember the project terminating statement from the Bureau's Director: "Stop worrying about it, every time you eat an apple you ingest foreign DNA."
The issue of probable contamination of polio vaccines with adventitious viruses was difficult for anyone to contradict. Maintaining support for the established vaccine program was, however, variously argued: (i) The continued use of primary cultures from kidney cells would help avoid any suggestions that established cell lines may have progressed towards cancer and may contain "oncogenes". (ii) The polio vaccine had been administered to many millions of individuals without apparent adverse effects. It was, therefore, unnecessary and anyhow too late, to correct the situation; (iii) The viruses detected were not the dreaded Marburg agent or the much feared Type C cancer associated retroviruses and were, therefore, of little significance and were probably destroyed when passing through the stomach; (iv) The pharmaceutical industry had to be encouraged to manufacture vaccines and the public had to be encouraged to take vaccines for the government-sponsored immunization programs to be successful. (v) The programs were predicated on existing costs and profit margins and could be threatened if additional testing was imposed. (vi) Many companies had ceased vaccine manufacturing within the United States and any further reduction could make the country more vulnerable to threatened germ warfare, etc., etc.
Neuropsychiatric Illnesses: It is generally believed that the incidence of chronic brain dysfunctional disorders has steadily increased over the last several decades. Conditions such as chronic fatigue syndromes, fibromyalgia, migraine, attention deficit hyperactivity disorder, autism, mental depression, dementia, schizophrenia, etc., are being increasingly diagnosed. Our society has somewhat complacently accepted these conditions as inevitable consequence of "progress". Moreover, compared to efforts aimed at clinical management of these diseases, relatively little effort has gone into identifying their etiology. The involvement of basic researchers has been especially hampered by the imposition of confusing clinical case definitions. Medical specialists have somewhat arbitrarily segregated various facets of neuropsychiatric illnesses into a wide array of nosologically distinct, territorily protected, clinical entities. The ever increasing multiplicity of named dysfunctional brain syndromes may simply reflect the complexity of the brain, rather than imply the presence of innumerable etiologic processes.
Search for Viral Infections in Neuropsychiatric Diseases: I initiated a project in 1986 to see if patients diagnosed as having the chronic fatigue syndrome (CFS) were virally infected (1). Early findings using the polymerase chain reaction (PCR) with primer sets cross-reactive with all of the known human herpesviruses gave weak positive signals with one third of CFS patients, but not with any of several laboratory controls (10). I later found that many CFS patients would also give low, but detectable PCR responses using primers designed to amplify the tax gene of human T lymphocytotropic viruses.
The potential significance of the marginal responses seen in CFS patients became clearer in 1990 when strikingly positive PCR responses occurred with cerebrospinal fluid (CSF) samples from two patients and on a brain biopsy of a third patient. All three patients had unexplained severe encephalitis-like illnesses. The brain biopsy came from a school teacher who had gradually lost her capacity for written and oral communication, but was otherwise alert with no localizing neurological signs. She did, however, have an abnormal MRI with periventricular lesions. The brain biopsy showed mild gliosis with no inflammation. Complete and incomplete forms of herpesvirus-like particles were present in several of the glial cells. Some of the virus positive cells showed marked vacuolated changes and lipid accumulation (11). The PCR positive CSF samples were acellular, indicating an absence of inflammation. One had come from a newborn infant with delayed neural development. The other from an adolescent with residual severe brain dysfunction following what was called an atypical herpes simplex encephalitis.
From about 1987, I had devised several approaches to try to grow human herpes virus-6 (HHV-6) from CFS patients using cord blood lymphocytes. Routine human fibroblast cultures were also established. The latter cells frequently showed a delayed, transient CPE somewhat suggestive of human CMV. Buoyed by the PCR findings in the severe encephalopathy cases, efforts were again undertaken to culture a virus from a PCR positive CFS patient (D.W.). After 6 weeks of culture, enlarged, rounded, vacuolated cells suddenly began to appear in both human and monkey derived cell lines. Cell syncytia were easily recognized. The CPE could be passed to many other cell types and to cells of multiple species. By electron microscopy, numerous complete and incomplete herpesvirus-like viral particles were seen. The foamy, vaccuolated cells did not, however, stain with antisera specific for the immediate-early gene of human CMV. Nor did the cells stain with antisera specific for HSV, HHV-6/7, VZV or adenoviruses. PCR assay using the HTLV tax gene primer gave two well defined products. Sequencing of one of the PCR products (GenBank accession # U09212) identified a region of partial sequence homology to the UL34 gene of human CMV. The sequence of the other PCR product (GenBank accession # U09213) was suggestive of a possible herpesvirus origin but could not be aligned with any of the known herpesviruses (3). Viral DNA was isolated and cloned. A region of sequence homology to African green monkey simian cytomegalovirus (SCMV) was first found in early 1994. Unrelated to our work, Dr. Gary Hayward of Johns Hopkins University submitted additional sequence data on SCMV to GenBank in December 1994. From his sequence data, it was unequivocal that the CFS patient's virus had originated from SCMV (5).
In 1991 I coined the term "stealth" to describe the viruses I had been seeking. I used this term primarily because it carried the connotation that the viruses could occur in the absence of inflammation. The SCMV-derived virus was designated stealth virus-1. A closely related virus (stealth virus-2) was isolated in early 1991 from the CSF of a patient with an acute severe encephalopathy following a 4 year history of a manic depressive illness. The patient (B.H.) has remained in a vegetative state since 1991. DNA sequencing of a PCR amplified product from her infected cultures has identified the virus as being similar but not identical to the SCMV-derived stealth virus-1. Numerous other stealth viral isolates have been obtained and are awaiting resources to perform the necessary sequencing analyses.
Animal Studies: Stealth virus-1 induces an acute neurological illness when inoculated into cats (12). The early manifestations developed within a week and included gingivitis, bloody ocular and nasal discharge, lymphadenopathy, pupil dilatation with photophobia (squinting in response to light) and nuchal hair loss from rubbing against the cage. There was a reduction in body temperature beginning in the second week which averaged 0.6oF at 2 weeks and 0.8oF at weeks 3 and 4. Most striking was the marked behavioral changes in all of the virus-inoculated cats. They lost the playfulness that was present prior to injection and became reclusive and irritable. They resisted being handled and the animal caretakers resorted to wearing leather gloves. By palpation, the enlarged lymph nodes and various muscle groups were identified as being painful for the animals. The severity of the illness peaked at around 4 weeks with definite improvement noted in the cat necropsied at 6 weeks. A cat that was maintained to 15 weeks had resumed normal activities by week 10 and appeared to be symptom free. Histological examination of animals' brain tissue showed foci of cells with cytoplasmic vacuolization and an absence of any inflammatory reaction. Electron microscopy on several cats confirmed the presence of occasional herpes-like viral particles and, more commonly, the presence of variable patterns of accumulations of viral-like granular and other membranous structures suggestive of subgenomic viral expression.
Unstable, Fragmented Nature of the Stealth Virus-1 Genome: Restriction enzyme digests of stealth virus-1 have been cloned and partially sequenced. The genome appears to comprise multiple fragments of approximately 20 kilobase pairs. The virus displays an unusually high degree of sequence microheterogeneity suggesting infidelity of DNA replication or an alternative replication strategy (13). The concept of a fragmented, unstable viral genome is consistent with electron microscopic observations (14). It has important implications for the approaches to be taken in using molecular techniques to screen for these viruses. It also raises concerns about the possible oncogenicity of stealth viruses (16).
Stealth Viruses Isolated from Patients with Severe Encephalopathy: Since the beginning of these studies, a number of patients have been identified with strongly positive cultures and complex clinical case histories. While the initial focus was on CFS patients, the more recent emphasis has been on patients with severe encephalopathy. In many of these cases, a preceding CFS-like illness was present. The clinical observations support the concept of potentially infectious neuropsychiatric illnesses attributed to varying degrees of dysfunction of different regions of the brain (2). Brain biopsies have been obtained in five patients and have shown many of the characteristic changes noted in the infected cats. In some of the biopsies, there is an additional vasculitis component. Possibly, the most promising clinical aspect of these illnesses is the recovery process seen in several, but not all, severely ill patients. The mechanism of recovery is the most important goal of stealth virus research. In a step towards this goal, I am hoping to obtain sufficient sequence data on isolates from severely ill adult patients and from autistic children, to determine which, if any, have originated from African green monkeys. I realize that while monkey cells have been used for polio and adenovirus vaccines; dog and duck kidney cells have been used for rubella vaccines; chicken cells have been used for measles and mumps vaccines; and a very wide range of animals cells have been used for animal vaccines. Unfortunately, only limited sequence data are available on most animal viruses. Some stealth viruses may simply have originated by the down sizing of known human viruses, especially human herpesviruses. In these endeavors, I have so far unsuccessfully sought the help of both the FDA and the CDC.
Notification to CDC, FDA and Lederle: CDC was notified in early 1991 that a repeat positive culture was obtained on patient D.W. and a similarly positive culture was obtained on the comatose patient B.H. An invitation to visit my laboratory to see the cultures was declined. CDC was again notified in mid 1994 when the sequence data on stealth virus-1 showed a greater relatedness to SCMV than human CMV. FDA Center for Biologics Evaluation and Research (CBER) was contacted in March of 1995 and the President of Lederle sent a letter in July, 1995. Prompted by FDA personnel, unsolicited requests for collaborative and financial assistance were sent to CDC and to FDA in June 1995, followed by visits to both agencies. The unsolicited proposal format is designed to protect an agency from the accusation that it has given a competitive advantage to someone seeking government funds. The proposals included detailed clinical descriptions of 12 cases of severe, otherwise unexplained, encephalopathy. In the FDA proposal, I asked to do a surveillance study to determine the prevalence of simian CMV-derived stealth viruses in humans and in the monkeys used for polio vaccine production. I also wanted to test some vaccine monopools. In the CDC proposal, I asked for help in sequencing the viral isolates from the 12 patients.
Response from CDC Received 5 Months After Submission: "Reviewed by the National Immunization Program (NIP) and the National Center for Infectious Diseases (NCID) of CDC. It was determined that the proposal did not address NIP research needs at this time. There was also the comment from NCID that "The twelve patients reported have variable clinical histories with no obvious epidemiological links between them. The evidence that a virus can be isolated from these cases is unconvincing. No independent confirmation has been reported in the results described in this proposal and the evidence for the existence of an infectious agent which the offeror (sic) calls a 'stealth virus' remains unconvincing."
Unofficially, I was told that Ms. Joanne Patton, now working in Dr. John Stewart's laboratory at NCID, recalled hearing of a patient becoming infected with SCMV which had contaminated a rubella virus vaccine grown on African green monkey cells. From discussions with Ms. Patton and Dr. Stewart, there seems to be some regret that CDC had not made efforts to pursue this event. A request for a brief statement in the Mortality and Morbidity Weekly (MMWR) on atypical viral encephalopathy was also denied.
Response from FDA Received 7 Months after Submission: "Request for support to screen for the prevalence of simian cytomegalovirus derived stealth viruses in humans is best sought from an agency such as the NIH, rather than the FDA.Requests to screen the monkey colonies that are used in vaccine production for the presence of stealth viruses. These are studies that would need to be conducted with the manufacturers.
Request to screen polio samples (the bulk mono-pools) for stealth viruses. Screening of these samples, if done, should be carried out in CBER's own laboratories. We are evaluating the types of studies that might be best done using PCR-based techniques. However, even if such sequences are found in a PCR-based assay, the question whether transmissible, replication competent viruses are present would still need to be addressed.
We appreciate your informing us and others, not only in your submitted proposal but also at the FDA Workshop on cell substrates and at the IOM meeting on vaccine safety, about your concerns vis-a-vis simian cytomegalovirus and potential related viruses in the polio vaccine. We will be addressing this concern in our Laboratories".
Other Relevant Actions: The Advisory Committee on Immunization Practices (ACIP) had made a recommendation to move from a series of four injections of live polio vaccine to a split protocol of two injections of inactivated vaccine (IPOLTM, produced by Pasteur Merieux-Connaught Laboratories) followed by two injections of live vaccine. This was obstensibly to help reduce the occurrence of the approximately 8-10 cases a year of poliomyelitis from Type 3 vaccine revertants. Although not cited as a reason, such a move would expand the production of inactivated vaccines should a subsequent total switch to inactivated vaccine be recommended. A decision to delay the implementation of this plan was made at the February ACIP meeting. There will be opportunity for public input at the June meeting.
FDA has held open meetings to discuss possible hazards of interspecies bone marrow therapy in AIDS patients and interspecies liver and other organ transplants. FDA was unable to muster support to restrict the first baboon bone marrow trial.
Summary: The concepts that certain stealth viruses may have arisen as contaminants of live viral vaccines, and that vaccinations may have had untoward consequences, have not been embraced by either vaccine manufacturers or Public Health agencies. As the experimental data unfold, however, the existence and the clinical importance of stealth viral infections are less easily reputed. Indeed, stealth viral infections may explain a wide range of neurological and neuropsychiatric diseases, serving as a common thread linking these diseases, and possibly accounting for their ever increasing prevalence.
If a vaccine program were to be initiated today, one would surely not import wild monkeys from Africa, create short term primary kidney cultures, add a human virus and administer the crude gamish derived from the virally infected cells to virtually every child in the country. Nor would one want to withhold applying the many molecular biological techniques developed over the last 30 years to assess vaccine purity. Yet this is essentially the situation with live polio vaccine and comparable arguments can be made for other human and animal viral vaccines.
Various meetings, phone calls and document exchange have uncovered a sense of frustration within the Federal Public Health System, Industry, and the general public with what appears to be a resistance of those in authority to face the issue of prior, if not also present, vaccine contamination. If animal viruses have been inadvertently introduced into humans, the sooner we find out the better. I would very much appreciate continuing to hear about patients with seemingly complex infectious and/or neuropsychiatric illnesses. Volunteers are needed to help bring these patients to the attention of the Public Health System. Work on the in vitro efficacy of stealth virus inhibitors needs support so that clinical therapeutic trials may soon become a reality. Phone and FAX messages can be left at 818 799-4500 and 818 799-1700 in the Los Angeles area and at 510 222-9466 and 510 222-9466 in the San Francisco area. The e-mail address is firstname.lastname@example.org