TreatmentUpdate 62 - Volume 7, No. 8 - August 1995 --------------------------------------------------- Published by Community AIDS Treatment Information Exchange (CATIE), 420-517 rue College St., Toronto, ONT Canada M6G 4A2 --------------------------------------------------- --------------------------------------------------- I HIV/AIDS THEORY A. HIV/AIDS: an overall picture What usually happens when people first become infected with HIV is that the virus infects many cells which, in turn, produce a huge number of viruses (detectable in blood samples). The immune system responds by producing T cells which attack HIV-infected cells. Later, B cells make antibodies to attack the virus. During this response people may experience symptoms of a flu-like syndrome. Levels of HIV in the blood quickly fall and symptoms clear. For many years the immune system appears to "trap" the virus in the lymph nodes and tissues. Although infected people may live for many years without symptoms, the virus continues to infect CD4+ cells and other cells, such as macrophages. Infected CD4+ cells may not immediately begin to turn into 'virus factories.' Research suggests that HIV stays silent in those cells until the cells are activated. Activation may occur because the immune system is stimulated by other infections, but given that HIV-infection is a chronic infection, some researchers think the virus itself could cause the activation signal. Once the cell becomes activated, the virus can take over and cause the cell to produce new viruses. Over many years (10 to 15) this hidden infection may destroy many CD4+ cells. In the final years of HIV infection, it appears that lymph nodes become damaged and contain fewer cells. When they collapse, the nodes release HIV which enters the blood, and it is believed that this may increase the amount of HIV in the blood. Although researchers have an overall picture of what happens to an HIV-infected immune system, many questions remain unanswered. * MONKEYS WITH AIDS State of the art research on HIV-infected humans and monkeys infected with the related SIV suggest that events in the lymph nodes and tissues are important. Research teams are studying lymph nodes to try and understand how HIV infection damages them. In this issue of TreatmentUpdate we present reports on: - a study looking at what happens to T cells in the lymph nodes of HIV-infected subjects - studies of AZT's effects on the amount of HIV in T cells in the blood (viral load) - results from trials of newer anti-HIV agents called proteinase or protease (they mean the same thing) inhibitors. REFERENCES: 1. Koup RA, Safrit JT, Cao Y. et al. Temporal association of cellular immune responses with initial control of viraemia in primary Human Immunodeficiency Virus type 1 syndrome. Journal of Virology 1994;64(7):4650-4655. 2. Panteleo G. Menzo S. Vaccarezza M, et al. Studies in subjects with long-term non-progressive Human Immunodeficiency Virus infection. New England Journal of Medicine 1995;323(4):209-216. 3. Embretson J. Zupanic M, Ribas IL. Massive covert infection of helper T lymphocytes and macrophages by HIV during the incubation of AIDS. Nature 1993;362:359-362. 4. Fields BN. AIDS: time to turn to basic science. Nature 1994;369:95-96. 5. Rosenberg YJ, Lewis MG, Leon EC, et al. Viral DNA burden and decline in percentage of CD4-positive cells in the lymphoid compartments of SIV-infected macaques. AIDS Research and Human Retroviruses 1994;10(10):1269-1276. B. Benefit(s) from anti-HIV drugs * BACKGROUND Although a number of anti-HIV drugs are licensed for the treatment of HIV/AIDS, ultimately none of these drugs improve survival compared to subjects who do not use these drugs. Even though AZT can cause statistically significant increases in CD4+ cell counts, the benefit is temporary. Drug manufacturers are trying to find other ways to show that their products provide benefit to users. What's more, doctors and their patients with HIV/AIDS may not be sure when to start or stop using those drugs. As one American doctor noted: "I remember when [AZT] increased everyone's CD4+ cell counts; when it increased CD4+ cell counts when they were greater than [200 cells]; when it increased CD4+ cell counts for long periods; when it raised them for only a few weeks; when high [CD4/CD8] ratios were good; and when [CD4/CD8] ratios were no longer important (long term survivors had high CD8+ cell levels)." Moreover, since 98% of CD4+ cells are located in the lymph nodes/tissues, it is not clear that measuring 2% of lymphocytes in the blood will provide accurate information as to how well anti-HIV agents work. Research teams are trying to bridge the gap between the two locations of cells by devising various tests and studying lymph node samples from subjects with HIV/AIDS and also from monkeys with SIV/AIDS. * LYMPH NODES/TISSUES SIV is related to HIV and can cause AIDS in certain monkeys. Researchers studying monkeys with "early-stage SIV-infection" found that: - lymph nodes with normal proportions of CD4+ and CD8+ cells usually occur in monkeys with low levels of SIV-infection of cells in the blood. - In monkeys with AIDS, less than normal proportions of CD4+ and CD8+ cells were found in lymph nodes, while increased numbers of SIV-infected blood cells were detected. The decline in CD4+ and CD8+ cells in the lymph nodes may occur before the number of SIV infected cells in the blood increases. The results of further studies of lymph nodes of HIV- infected subjects using anti-HIV drugs may prove interesting. Among humans with breast cancer (without HIV infection), the proportion of CD4+ and CD8+ cells in lymph nodes can be different from that found in healthy humans without breast cancer. * VIRAL LOAD One lab test that is receiving increased attention is the viral load test. This usually refers to the amount of cells infected with HIV in the blood. The theory underpinning this test is that AIDS is a condition caused by a virus. Treatment with anti-HIV agents should reduce the amount of virus being made by HIV-infected cells. Therefore people using these drugs should benefit from a decline in viral production. As well, among patients using anti-HIV drugs, an increased viral load may suggest that HIV has become resistant to these drugs. There are tests that can measure the amount of virus in the blood (outside of blood cells), however, detecting changes in viral load may not always be useful nor linked to the development of symptoms or survival. There is also the issue of measuring viral load in lymph nodes and its relation to viral load in the blood. Given recent findings from human lymph node analyses (see next article) that report no relation between viral load and the number of T-cells being destroyed, there is reason to wonder about the role of such testing. Hopefully this issue will become clear over the next year. The following example illustrates this difficulty: "Spencer Cox, a member of the AIDS-treatment watchdog group TAG, cites the infamous example of arrhythmia, in which the heart beats irregularly. Applying common sense, researchers assumed that arrhythmia was a surrogate marker for cardiac failure. Two drugs were developed that suppressed arrhythmia quite effectively, but bath drugs also caused fatal heart attacks. If you take out the word arrhythmia and put in the wards viral burden, says Con, we're having the same conversation." According to Dr. Deborah Cotton (Mass. General Hospital, and Harvard Medical School, Boston), "the only sure way to tell whether a drug works...is to conduct large clinical trials that measure actual survival and [the development of symptoms of AIDS]." A problem with this approach is that people with HIV/ AIDS do not have the time to wait for those results. REFERENCES: 1. Harris PJ. CD4+ cell counts as surrogate markers for progression to AIDS. Annals of Internal Medicine 1994;120(1):88. 2. Rosenberg YJ, Lewis MG, Leon EC, et al. Viral DNA burden and decline in percentage of CD4-positive cells in the lymphoid compartments of SIV-infected macaques. AIDS Research and Human Retroviruses 1994;10(10):1269-1276 3. Whitford Pj Alam SM, George WD and Campbell AM. Flow cytometric analysis of tumour-draining lymph nodes in breast cancer patients. European Journal of Cancer 1992;28(2/3):350-356. 4. Margolis LB, Glushakova S. Baibakov B and Zimmerberg J. Syncytium formation in cultured human lymphoid tissue: fusion of implanted HIV glycoprotein 14/120-expressing cells with native CD4+ cells. AIDS Research and Human Retroviruses 1995;11(6):697 704. 5. Schoofs M. A new AIDS trial tries to stop HIV by attacking it early. Village Voice 15 August, 1995, pages 23-25. C. Looking inside lymph nodes * BACKGROUND The slow loss of CD4+ cells over time eventually weakens the immune system's ability to keep infections under control. Most CD4+ cells (98%) are found in lymph nodes and tissues and in organs such as the spleen. Only 2% of these cells are in the blood. Therefore, researchers are studying what happens to these cells in the lymph nodes of HIV-infected humans and SIV-infected monkeys. Although HIV can infect and destroy CD4+ cells, these cells may also be destroyed in other ways. CD4+ cells have the ability to destroy themselves through a method called programmed cell death (PCD) or apoptosis. Cells of the immune system that are exhausted and unable to fight infections can also undergo apoptosis. Researchers describe these cells as anergic. One research team in the USA has recently released their results from a study of lymph nodes taken from 67 HIV-infected subjects in various stages of HIV/AIDS and from 15 healthy, non-HIV-infected subjects for comparison. They also looked at the amount of cells which were undergoing apoptosis. * RESULT-INSIDE THE NODES In the lymph nodes taken from HIV-infected subjects the researchers found that the level of apoptosis was not related to the CD4+ cell count nor the number of T cells that were infected with HIV. All lymph nodes taken from HIV-infected subjects showed some level of apoptosis, while the researchers detected apoptosis in only 50% of lymph node samples from the non-HIV-infected subjects. The difference in the number of cells undergoing apoptosis between the two groups was statistically significant, that is, not likely due to chance alone. The researchers also found that in addition to CD4+ cells, CD8+ and B cells were also undergoing apoptosis. * WHAT CAUSES APOPTOSIS? Cells of the immune system can capture invading microbes (or pieces of them) and take them to the lymph nodes where many more cells can be alerted and activated to prepare them for fighting the infection. The research team thinks that the activation of cells by the immune system of people with HIV/AIDS either prepares cells to engage in or directly cause apoptosis. Activation may also result from the continuous attacks on the immune system by HIV, thereby causing apoptosis of T and B cells on a regular basis. Levels of apoptosis in the blood of HIV-infected subjects in this study were very low compared to levels in the lymph nodes. Finally, the level of apoptosis in the lymph nodes of HIV-infected subjects was not related to viral load. * WHAT NEXT? Further research needs to be done to investigate these events. If the cells that are undergoing apoptosis are exhausted immunologically (anergic), that is they cannot perform their functions such as controlling infections, apoptosis may not necessarily be a bad event as such cells are not useful. It is critical that researchers discover just how HIV weakens the immune system and how CD4+ and other cells become anergic. In related research, another team has found that exposing healthy, non-HIV-infected CD4+ cells to the HIV protein gp120 can trigger those cells to commit suicide. REFERENCES: 1. Muro-Cacho CA, Pantaleo G and Fauci AS. Analysis of apoptosis in lymph nodes of HIV-infected persons: intensity of apoptosis correlates with the general state of activation of the lymphoid tissue and not with disease or viral burden. Journal of Immunology 1995; 154:5555-5566. 2. Laurent-Crawford AG, Coccia E, Krust B and Hovanessian AG. Membrane expressed HIV envelope glycoprotein heterodimer is a powerful inducer of cell death in uninfected CD4+ target cells. Research in Virology 1995;146:5-17. 3. Cohen JJ. Exponential growth in apoptosis. Immunology Today 1995;16(7):346-348. D. AZT and ddI--samples from lymph nodes * STUDY DETAILS To discover changes in the production of HIV in 16 subjects using anti-HIV drugs, one research team in the USA has been comparing blood and lymph node samples of HIV-infected subjects. The researchers reported data on 16 subjects (1 female, 15 males) whose average CD4+ cell count was about 400 cells. All subjects had used AZT between 300 and 600 mg/day for at least 6 months before entering this study. The researchers randomly assigned 10 subjects to receive continued AZT and 6 others to continue taking AZT and ddI 200 mg twice daily. Researchers took blood and lymph node samples at the beginning of the study and again 8 weeks later. * RESULTS--CONTINUED AZT Production of virus from HIV-infected cells in the lymph nodes remained relatively high during the 8 weeks of the study while it remained "relatively unchanged" in cells taken from the blood. * RESULTS-AZT AND DDI Cells taken from lymph of 4 subjects receiving both drugs had a "sharp decrease" in production of HIV by the 8th week of the study. This change, when compared with the results from subjects who used AZT alone was not statistically significant. In the remaining 2 subjects, production of HIV increased in one and remained stable in the other. Again, production of HIV in cells in the blood remained low. Statistically significant changes in the amount of viruses in the blood occurred in 4 of 6 subjects. * LYMPH NODES VERSUS BLOOD The researchers confirmed that the amount of HIV produced by infected cells was greater in the lymph nodes (ranging from 3 to 200 times more) than in cells taken from blood. Decreases in the amount of HIV in the blood happened simultaneously with decreases in the lymph nodes. Unfortunately the researchers did not explain why they decided to test lymph node samples after only 8 weeks, nor did they release data on survival or the incidence of life-threatening infections. They concluded by stating that measuring the amount of virus in the blood (but not inside blood cells) likely reflects the changes in production of HIV in the lymph nodes. REFERENCES: 1. Cohen OJ, Pantaleo G. Holodniy M, et al. Decreased Human Immunodeficiency Virus type I plasma viraemia during antiretroviral therapy reflects down regulation of viral replication in lymphoid tissue. Proceedings of the National Academy of Sciences USA 1995;92:6017-6021. 2. Simmonds P. Zhang LQ, McOmish F. et al. Discontinuous sequence change of Human Immunodeficiency Virus (HIV) type 1 env sequences in plasma viral and lymphocyte associated proviral populations in viva: implications for pathogenesis. Journal of Virology 1991;65(11):6266-6276. 3. Lin HJ, Siwak EB, Lauder LT and Holinger FB. Single-strand conformational polymorphism study of HIV type I RNA and DNA in plasma, peripheral blood mononuclear cells, and their virologic cultures. Journal of Infectious Diseases 1995;171:1619-1622. E. Understanding HIV infection and redirecting research * BACKGROUND In early 1995, 2 research teams working independently published results from their experiments using anti-HIV drugs in HIV-infected humans. Data from these studies suggest that huge numbers of CD4+ cells and HIV are produced and destroyed every day. The drugs used in these experiments included ABT-538 (Ritonavir) and L-735,524, and nevirapine. Detailed reports on protease drugs appear in the section on anti-HIV agents. The two research teams had mathematicians and both produced equations to try and explain the changes in CD4+ cell counts and HIV. Although the results of their experiments may be useful when making decisions about the effects of anti-HIV agents, the researchers clearly did not understand the complex interplay between the immune system and HIV. Unfortunately, this lack of understanding extends beyond the 2 research teams and it may also explain why no effective therapy for AIDS has been developed 15 years into the AIDS epidemic. * A LOT OF VIRUSES The results from the 2 teams suggest that millions of viruses are created and destroyed every day in the bodies of people with HIV/AIDS. Treating HIV-infected subjects with ABT-538 and other drugs reduced the amount of virus in the blood and temporarily raised CD4+ cell counts. As well, the researchers' reports suggest that HIV continuously infects new uninfected cells and therefore treatment with drugs that can block HIV infection of uninfected cells may stop the damage to the immune system caused by HIV-infection. The two teams may have been impressed by the huge number of HIVs found (as many as 1 million viruses in a drop of blood) and the increased CD4+ cell counts in the blood samples of their subjects. Other researchers have also found large numbers of HIVs in the blood of subjects with or without AIDS. In some cases these viruses were not able to infect cells. Had the 2 teams looked beyond HIV/AIDS, they would have found that in another chronic viral infection-Hepatitis B-a drop of blood from symptom-free subjects can have as many as "one billion [viruses]." Thus, the amount of virus in the blood may not be related to the development of symptoms. * WHERE HIV IS MADE Most CD4+ cells are found in lymph nodes and tissues and organs such as the spleen. Most HIV-infected cells are also found in lymph nodes and tissues. These HIV-infected cells produce the viruses that eventually appear in the blood. There are also cells that can survive infection by HIV, and as these cells travel throughout the body, they release the virus. In a person infected with HIV there may be "100 billion or 25% of all CD4+ cells" infected with HIV. In most of these cells, HIV is "silent" and these cells are not producing viruses. However, between 1 and 2 billion of those cells are "actively producing HIV." Although standard anti- HIV agents can reduce the amount of virus in the blood, "the number of virus-infected cells is not substantially affected." Researcher Jay Levi (University of California, San Francisco) thinks that treatment should focus on cells chronically infected with HIV. * THE VIRUS FACTORY HIV-infected cells: - produce more viruses - produce chemicals that weaken the immune system - trigger T cell suicide (apoptosis) As well, viral proteins such as gp120 that come into contact with T cells may also set those cells for destruction either by apoptosis or attacks by the immune system. Stopping the "continuous production of HIV or its proteins" may be a more useful objective than blocking infection of new cells. * VACCINE'S To date, most attempts at making anti-HIV vaccines have focused on the production of antibodies that attack the virus. HIV can be spread by an infected cell coming into contact with an uninfected cell (called cell-to-cell transmission). Antibodies cannot block cell-to-cell transmission. Moreover, anti-HIV antibodies can help the virus infect cells. Researchers have to find ways to boost the ability of T cells to find and destroy HIV- infected cells. * CD8+ CELLS It appears that people who can produce a strong T cell-based immune response may be able to contain HIV infection. As well, research on "Long term symptom-free survival of [people] with HIV infection" suggests that a "strong" antiviral response by CD8+ cells targets HIV-infected cells and this type of response may be important. * BETTER THERAPIES Attempts to boost the ability of T cells to destroy HIV- infected cells and contain the infection are underway. In some cases these involve: - infusions of CD4+ or CD8+ cells - injections of drugs such as IL-12 - vaccines that help T cells fight infected cells By destroying virus-infected cells, production of HIV will decrease. Until a cure is developed, therapies that can reduce the production of HIV from infected cells may be a reasonable goal. REFERENCES: 1. Wei X, Ghosh SK, Taylor ME, et al. Viral dynamics in Human Immunodeficiency Virus type 1 infection. Nature 1995;373: 117- 122. 2. Ho DD, Neumann AU, Perelson AS, et al. Rapid turnover of plasma virions and CD4 lymphocytes in HIV-1 infection. Nature 1995;373:123-126. 3. Levy JA. HIV research: a need to focus on the right target. Lancet 1995;345:1619-1621. 4. Garbuglia AR, Salvi R. Di Caro A, et al. Peripheral lymphocytes of clinically non-progressor patients harbour inactive and uninducible HIV proviruses. Journal of Medical Virology 1995;46:116-121. 5. Kozlowski PA, Black KP, Shen L and Jackson S. High prevalence of serum IgA HIV-1 infection-enhancing antibodies in HIV- infected persons: masking by IgG. Journal of Immunology 1995;154:6163-6173. 6. Brander C, Pichler WJ and Corradin G. Identification of HIV protein-derived cytotoxic T lymphocytes (CTL) epitopes for their possible use in a synthetic vaccine. Clinical and Experimental Immunology 1995;100:107-113. 7. Bridges SH and Sarver. Gene therapy and immune restoration for HIV disease. Lancet 1995;345:427432. II ANTI-HIV AGENTS A. Interesting results from a short AZT study * STUDY DETAILS Researchers in England recruited 11 subjects with AIDS who had never used AZT. Their average CD4+ cell count was 118 cells at the start of the study. They received 1,000 mg/day of AZT, but subjects who could not tolerate this dose could reduce their dose to 800 or 500 mg/day. Nurses took blood samples from subjects before they began using AZT and then every 4 days "during the first month of [the study]", and "[then once per month]." Subjects remained in the study for an average of 80 days. * RESULTS Levels of HIV in the blood fell to 10% of their pre-AZT level. On average, the decrease in virus levels reached its lowest point 7 days after subjects began using AZT. Despite continued use of AZT in seven subjects, the amount of virus in their blood began to increase to their pre-study levels. In three of the seven the increase was "rapid, occurring over a few weeks." * LOOKING FOR RESISTANCE Generally, the increase in virus levels despite continued use of AZT might suggest that HIV-infected cells had become resistant to the drug's anti-HIV effects. However, technicians could find "no association between the early [increase in viral levels] and [drug- resistant virus]" in the blood samples of the 7 subjects whose levels of virus in the blood "returned towards" their pre-AZT values. While technicians detected viruses with some level of AZT resistance, there were not enough of these viruses to account for the increased levels of HIV in the blood. * CAUTION ABOUT VIRAL LOAD The detailed analysis of blood samples in this study suggest that large quantities of HIV are produced by HIV-infected cells. Although HIV levels in the blood increased despite continued use of AZT, the researchers could not find enough drug-resistant virus to account for the increase. Measuring the amount of virus in the blood or virus in white blood cells (viral load) is one laboratory test that is becoming more common in clinical trials of anti-HIV agents. The study researchers warn that "since we do not know [how] HIV-1 causes damage to the immune system, "the principle that virus suppression will produce a major clinical benefit must remain an article of faith." REFERENCES: 1. Loveday C, Kaye S. Tenant-Flowers M, et al. HIV-1 RNA serum-load and resistant viral genotypes during early Zidovudine therapy. locket 1995;345:1619-1621. B. Protease inhibitors * BACKGROUND Drugs such as AZT, ddC, ddI, and 3TC are supposed to work by preventing HIV infection of new, uninfected cells. These drugs affect the viral enzyme RT (reverse transcriptase). Treatment with these drugs can result in temporarily increased CD4+ cell counts and decreased production of virus by HIV-infected cells. As well, short term use of AZT can temporarily boost cell-mediated immunity, an arm of the immune system that is severely damaged in AIDS. Nevertheless, some of the beneficial effects begin to fade "within 3 [to] six months" of use. It is important to remember that "AZT prevents the infection of new cells, but not the production of virus from cells already infected [by HIV]." The loss of AZT's beneficial effects may be due to the development of virus that can resist its effects, the increasing toxicity over time of AZT, or other unknown reasons. Doctors and their patients are experimenting with various combinations of AZT and related compounds "with the hope that [production of HIV can be reduced for longer periods of time] and delay or prevent the development of [HIV that can resist] these [drugs]." * ANOTHER APPROACH Another approach is to use drugs that can affect different parts of an HIV-infected cell and reduce its production of virus. A number of drugs that can affect the viral enzyme called "HIV proteinase" are being developed. Drugs that affect the activity of that enzyme are called proteinase or protease inhibitors. In TreatmentUpdate 51 we reported results from an American study using a combination of a protease inhibitor (saquinavir) with drugs such as AZT and ddC. In this issue we publish reports on: - a study of saquinavir - HIV that is resistant to protease drugs - results from short term trials of protease inhibitors REFERENCES: 1. Loveday C, Kaye S. Tenant-Flowers M, et al. HIV RNA serum-load and resistant viral genotypes during early Zidovudine therapy. Lancet 1995;345:820. 2. Levy JA. HIV research: a need to focus on the right target. Lancet 1995;345:1619-1621. 3. Jurriaans S. Weverling GJ, Goudsmit J. et al. Distinct changes in HIV type I RNA versus p24 antigen levels in serum during short term Zidovudine therapy in asymptomatic individuals with and without progression to AIDS. AIDS Research and Human Retroviruses 1995;11(4):473479. 4. Nowak MA, Bonhoeffer S. Loveday C, et al. HIV results in the frame: results confirmed. Nature 1995;375:193 5. Holodniy M, Mole L, Margolis D, et al. Determination of Human Immunodeficiency Virus RNA in plasma and cellular viral DNA genotypic Zidovudine resistance and viral load during Zidovudine-didanosine combination therapy. Journal of Virology 1995;69(6):3510-3516. 6. Lipsky JJ. The glimmer of HIV proteinase inhibitors. Lancet 1995;345:936-937. 7. Richmann DD. Protease uninhibited. Nature 1995;374:494. C. Saquinavir for HIV * STUDY DETAILS Researchers in England reported results from testing saquinavir on 44 male subjects "with few or no symptoms of HIV infection." Subjects had less than 501 CD4+ cells and had not used any anti-HIV agents before entering this study. The researchers approved the use of drugs to prevent various infections while in the study. Drugs included acyclovir (no more than 1 gram), amphotericin B lozenges, fluconazole and "standard [PCP prevention]." The trial lasted for 4 months and researchers randomly assigned subjects to receive different doses of saquinavir, "25, 75, 200 or 600 mg all three times daily." Neither subjects nor researchers knew which subjects received which dose. Due to the small number of subjects in this study, no results of statistical significance could be calculated from these tests. * RESULTS - CD4+ cells Among subjects who were in the 600 mg group, there was a trend of increased CD4+ cell counts. Half of the subjects in this group had an increase of 104 CD4+ cells by the 6th week of the study. - Infections/cancer One subject in the 25 mg group developed a bacterial infection in his lungs for which he received amoxicillin. One subject in the 600 mg group developed Kaposi's sarcoma. Both of these events happened during the 4th week of the study. - HIV In analyzing blood samples from subjects, technicians detected virus producing cells in 91% of samples at the start of the study. In some subjects in the 200 and 600 mg groups, production of HIV fell to one tenth of their pre-study levels. The researchers did state that, "in most [subjects] there was no significant change in [production of HIV from infected cells]." - Toxicity The researchers noted that "Saquinavir was well tolerated" and side effects were "mild". One subject in the 200 mg group developed a headache which cleared without treatment or interruption of his use of the drug. While some subjects had increased levels of liver enzymes and ions (calcium, phosphates, potassium) and lower levels of neutrophils and white blood cells, these did not appear to be affected by the dose of saquinavir used. Moreover, none of these changes made subjects ill. * WHAT NEXT? Results from this study suggest that higher doses of saquinavir may cause an increase of CD4+ cells in subjects with no or few symptoms of HIV infection and who have never used drugs such as AZT. The researchers do not know if these increased CD4+ cell counts will result in a reduced risk of developing a life- threatening infection or cancer or in improved survival compared to other subjects who do not use saquinavir. Saquinavir is supposed to work by affecting the viral enzyme "HIV proteinase". This enzyme is used in the final stages of the viral "assembly line" in infected cells. Without the help of this enzyme, the viruses produced are not supposed to be able to infect cells. Despite use of saquinavir, technicians were still able to detect intact and infectious samples of HIV in subjects at each dose level. The manufacturer is providing the drug on a compassionate basis to some people with HIV/AIDS. Doctors interested in obtaining this drug for their patients may call: 1-800-257-3741. REFERENCES: 1. Kitchen VS, Lkinner C, Ariyoshi K. et al. Safety and activity of saquinavir in HIV infection. Lancet 1995;345:952-955. 2. Lipsky JJ. Glimmer of HIV proteinase inhibitors. Faucet 1995;345:936-937. D. Experiments with pretense drugs produce surprising results * BACKGROUND In early 1995,2 research teams working independently testing a number of anti-HIV drugs found some surprising results. In their studies subjects received one of the following: the protease inhibitors ABT-538 or MK-639 (formerly L-735,524) or nevirapine which affects another viral enzyme RT (reverse transcriptase). The reports from these studies focused on changes in CD4+ cells and HIV in the blood and mathematical relationships between those 2 variables. Unfortunately we cannot provide the usual details on subjects because the researchers have yet to release them. * PROTEASE INHIBITORS In one of the studies, 18 HIV-infected subjects with CD4+ cell counts ranging between 36 and 490 cells received either 600 mg or 1200 mg of ABT-538 daily for 20 days. The researchers found that "every [subject] had a rapid and dramatic decline in [the amount of HIV in their blood] over the first 2 weeks of the study]." On average, the amount of virus in their blood fell to one-sixty-sixth of its pre-study level. The decline in the quantity of virus was not related to the CD4+ cell counts of subjects at the start of the study. In all subjects, CD4+ cell counts increased during the first 2 weeks. (When questioned about the value of increased CD4+ cell counts in subjects receiving anti-HIV drugs, the head of one of the research teams said that "we have reason to believe that the cells that are coming back are not entirely functional. Clearly patients are improved...But it's not the same functional level that you would see in another patient whose CD4+ cells are on the way down.") After the 2nd week of the study, HIV began to develop resistance and viral production increased. In addition, CD4+ cell counts began to decline in some subjects. Researchers found a similar trend when subjects used MK-639 at doses between 1600 and 2400 mg/day. The researcher noted that "there were no significant differences in viral clearance rates in subjects treated with ABT-538, [MK-639] or [nevirapine]." Perhaps the most useful idea to take from these 2 studies was a comment by researcher DD Richman, an expert on HIV drug resistance: "if a drug doesn't have an effect by day 14 [it is not worth developing]." That HIV could develop resistance to a drug in as little as 2 weeks may not be unique to protease inhibitors. In an analysis of blood samples from subjects in a Dutch trial of AZT, researchers found that production of HIV in some subjects began to increase just after 4 weeks of therapy. By the 8th week, production of HIV had increased to a level almost 10 times greater than in the 4th week. * HIV RESISTANCE TO SEVERAL PROTEASE INHIBITORS Meanwhile, researchers working for the pharmaceutical firm Merck have found that when HIV does become resistant to one protease inhibitor, it also becomes resistant to several other related protease inhibitors. The researchers were testing Merck's protease inhibitor MK-639 in HIV-infected humans and found that after 6 months of use, HIV had developed resistance not only to Merck's drug but also to: + XM 323 + A-80987 + Saquinavir + VX-478 + SC-52151 The concentration of these drugs needed to suppress production of HIV by 95% had doubled 6 months after using MK-639. These findings suggest that combination therapy with these protease inhibitors may not prevent the development of HIV that is resistant to all of them. Moreover, if a person using one of these drugs develops virus that is resistant to it, the virus is also likely to be resistant to the other, related, drugs. - AG 1343 At Agouron Pharmaceuticals (San Diego) research teams using computer simulations have developed a group of proteinase inhibitors that may be different from the ones listed above. Agouron has been testing one of their protease inhibitors, AG 1343, in HIV-infected humans in England. They plan to conduct further testing in San Francisco using 30 subjects who will receive a variety of doses of AG 1343 in the form of tablets. REFERENCES: 1. Wei X, Ghosh SK, Taylor ME, et al. Viral dynamics in Human Immunodeficiency Virus type I infection. Nature 1995;373:117- 122. 2. Ho DD, Neumann AU, Perelson AS, et al. Rapid turnover of plasma virions and CD4 lymphocytes in HIV-1 infection. Nature 1995;373: 123-126. 3. Vacca JP, Dorsey BD, Schlief WA, et al. L-735,525: an orally bioavailable Human Immunodeficiency Virus type 1 protease inhibitor. Proceedings of the National Academy of Sciences USA 1994;91:4096-4100. 4. Cohen J. High turnover of HIV in blood revealed by new studies. Science 1995;267:179. 5. Kempf DJ, March KC, Denissen JF, et al. ABT-538 is a potent inhibitor of Human Immunodeficiency Virus protease and has high oral bioavailablilty. Proceedings of the National Academy of Sciences USA 1995;92:2484-2488. 6. Condra JH, Schlief WA, Blahy OM, et al. In viva emergence of HIV-1 variants resistant to multiple protease inhibitors. Nature 1995;374:569-571. 7. Jurriaans S. Weverling GJ, Goudsmit J. et al. Distinct changes in HIV type I RNA versus p24 antigen levels in serum during short-term Zidovudine therapy in asymptomatic individuals with and without progression to AIDS. AIDS Research and Human Retroviruses 1995;11(4):473479. 8. Reich SH, Melnick M, Davies JF, et al. Protein structure-based design of potent orally bioavailability, nonpeptide inhibitors of Human Immunodeficiency Virus protease. Proceedings of the National Academy of Sciences USA 1995;92:3298-3302. 9. Nichols D. Agouron pharmaceuticals extends clinical testing of HIV drug into US. Press release. July 6, 1995. 10. Eberle J. Bechowsky B. Rose D, et al. Resistance of HIV type I to proteinase inhibitor Ro 31-8959. AIDS Research and Human Retroviruses 1995;11(6):671-676. 11. Schoofs M. A new AIDS trial tries to stop HIV by attacking it early. Village Voice 15 August, 1995, pages 23-25. E. AZT-virus production and worsening symptoms * STUDY DETAILS Researchers in Amsterdam analysed blood samples from 28 subjects with HIV infection, looking for changes in production of HIV by infected cells (a double blind placebo-controlled study). All subjects were men with no symptoms of HIV infection who had received AZT 1,000 mg/day taken as 500 mg twice daily for 2 years. Their average CD4+ cell count was 287 cells. Monitoring of these subjects extended to 4 years after entering the study. * RESULTS The researchers found that 4 years after entering the study 16 subjects remained symptom-free ("non-progressors") and the other 12 developed AIDS ("progressors"). The researchers looked for differences between the 2 groups. They found that after 4 weeks of AZT, both groups had statistically significant decreases in the level of HIV in the blood, "but a much stronger decline was observed in the group of non-progressors." Among the non-progressors, the amount of virus in their blood fell to one-tenth of their pre-AZT level. By the 8th week of AZT use, the amount of virus in the blood increased and reached a level close to that of the progressor group. The researchers did not provide data beyond the first 8 weeks of the study. * OTHER STUDIES Other studies have also found that use of AZT decreases the amount of virus in the blood of subjects in the first 2 to 6 weeks of use. However, "the favourable effect of [AZT] on [levels of HIV in the blood] was lost within 3 to 6 months." * SI AND NSI When cells are in physical contact with one another, HIV can move from an infected cell to the next cell and infect it. When this happens to several adjacent cells, giant clumps of cells called syncytia can form. Viruses that can cause syncytia are called SI (syncytia-inducing) and viruses that cannot are called NSI (nonsyncytia inducing). The amount of HIV found in the blood of subjects with or without SI or NSI strains of HIV was not different. * FOUR WEEKS? That a change in the amount of HIV in the blood after only 4 weeks of AZT treatment could be linked to the development of symptoms of HIV infection years later is interesting and raises many questions. First, should HIV-infected people who are free of symptoms take AZT 1,000 mg/day for 4 weeks and have the amount of HIV in their blood checked and compared with the pre-AZT level? Second, is 4 weeks of AZT therapy enough "treatment"? Clearly, making important decisions based on laboratory tests for HIV alone may not be the best course of action. Further data, on the type of infections and survival of subjects may be helpful in forming a useful analysis of this study. It is not clear why there was a difference between the 2 groups' response to the drug in the first place. REFERENCES: 1. Jurriaans S. Weverling GJ, Goudsmit J. et al. Distinct changes in HIV type I RNA versus p24 antigen levels in serum during short-term Zidovudine therapy in asymptomatic individuals with and without progression to AIDS. AIDS Research and Human Retroviruses 1995;1 1(4):473-479. Copyright (c) 1995. Non-commercial reproduction encouraged. Distributed by AEGIS, your online gateway to a world of people, knowledge, and resources.