Placenta(1991), l&669-672
Conference Report: Workshop on the Role of the Placenta in HIV Infection and Therapy, Nantucket, Massachusetts, lo-13 September 1990 POLLY R. SAGER DevelopmentalTherapeuticsBranch, Basic Research and Development Program, Division ofAIDS, National InstituteofAllergy and InfectiousDisease,NIH Bethesda,MD 20892, USA
The number of women infected with human immunodeficiency virus (HIV) in the USA has been increasing during the past several years, bringing with it the risk of transmitting HIV to their offspring. Indeed, children born to HIV positive women are the fastest growing population of HIV-infected patients in the USA. At present, few therapies are available to treat pregnant women who are infected with HIV. While little is known about the timing and frequency of transmission of HIV from mother to infant, even less is known about therapies to interrupt perinatal transmission of HIV. Increasingly, evidence points to the placenta as playing a role in either protection or transmission of HIV and as a potential target for therapy to interrupt perinatal infection. To identify needed areas of research and to develop collaborations to provide necessary basic information to support eventual clinical trials, the Division of AIDS of the National Institute of Allergy and Infectious Diseases (NIAID), NIH convened a workshop, ‘The Role of the Placenta in HIV Infection and Therapy’. This workshop was sponsored by the Developmental Therapeutics Branch and the Epidemiology Branch, organized by Drs Polly Sager and Evelyn Rodruguez, Division of AIDS, and was held on Nantucket Island lo-13 September 1990. The purpose was to bring together clinicians, scientists working in areas related to perinatal transmission of HIV and those conducting basic research on the placenta. Forty scientists were invited to participate. The meeting began with a session on the epidemiology of maternal-fetal transmission of HIV. Dr Tedd Ellerbrock (CDC, Atlanta) presented data from CDC on the incidence of HIV infection in women and children. HIV infection is now among the 10 leading causes of death in children l-4 years of age. Dr W. P. Parks, (New York University School of Medicine), reviewed information on rates ofperinatal infection of children, which range from about 20 to 35 per cent; he also noted that there does not appear to be any consistent pattern of transmission even for sequential births to an infected mother. The prenatal and perinatal transmission of other viruses, such as CMV, HSV, hepatitis, rubella, and others, was reviewed by Dr A. J. Nahmias (Emory University School of Medicine). Dr Teresa Calvelli (Albert Einstein College of Medicine) presented data that suggest a correlation between lack 0343-4004/91/060669
+ 04 $05.00/O
@ 1991 Baillike
Tindall Ltd
670
Placenta(1991), Vol. 12
of HIV transmission of virus and the presence of maternal high-affinity antibodies against HIV gp-120; this observation is being examined further in larger, prospective studies. Dr Rodney Hoff, (Division of AIDS, NIAID), concluded this session with a discussion of placental transport and fetal production of antibodies. He also described attempts to identify early diagnostic markers of infection; currently there is no reliable method to determine neonatal infection. Much of the discussion at this session focused on the lack of information on timing of fetal/neonatal infection, on possible protective maternal factors (265 per cent children not infected), and on early markers of fetavinfant infection. The second session focused on the structure and physiology of the placenta. Dr Maurice Panigel (University of Paris & M. Curie), described the structure and correlated function of the human placenta, along with methods for sampling and identifying cells and viruses in the placenta. He highlighted those cells which are thought to be CD4 positive at different times during the development of the placenta, and thus may be targets for HIV infection. Dr E. K. Mains, (UC San Francisco, Children’s Hospital), discussed the immunology of the placenta, including production of a number of cytokines. He noted that the placenta produces large amounts of IL-2 and that progesterone may regulate IL- 1 levels. Dr R. K. Miller, (University of Rochester Medical Center), reviewed markers of placental toxicity, including both markers for exposure and for effects. He described the anchor, control, and transport functions of the placenta and various methods for studying the human placenta. HIV infection of the placenta was the topic of the third session. Dr Adolf0 Firpo, (Armed Forces Institute of Pathology), described various methods for detecting HIV in human placenta: viral culture, direct visualization, genomic recognition, and immunological characteristics. He also noted that a non-specific increase in Hofbauer cells may occur in placentas from HIV-infected women, although other groups have not reported this. Several studies investigating HIV infection of early and late placenta using p24 antibody stain or in situ hybridization were reviewed by Dr J, F. Modlin, (Johns Hopkins University School of Medicine). Localization of HIV has been reported in trophoblasts and/or villous macrophages. Dr Gordon Douglas, (UC Davis School of Medicine), described methods for isolating and culturing placental cytotrophoblasts as well as enriched macrophage populations; only the latter cells were infected by HIV in vitro. Dr D. M. Phillips, (The Population Council, New York), described studies on the cell-cell movement of HIV using cultured cells. By electron microscopy, there appeared to be polarized release of HIV that was taken up by endosomes, coated pits, and by direct fusion into epithelial cells; however, there was no evidence of HIV replication in the epithelial cells. Dr A. S. Goustin, (Wayne State University), described the use of reverse transcriptase polymerase chain reaction (RT-PCR) to detect HIV m-RNA in placenta; his hypothesis that splicing of HIV message was altered was discussed. Discussion from this session focused on the lack of very basic information on the sites of HIV infection in the placenta and on the mechanism and the route(s) of HIV transmission from mother to fetus. The fourth session dealt with interactions of drugs and therapies with the placenta. Dr M. R. Juchau, (University Washington School of Medicine), began with a description of the drug metabolizing enzymes of the placenta. While mixed function oxidase activity increases with gestational age, the glucuronyl transferases do not appear to be present in placenta; this was of interest because glucuronidation is the major inactivation pathway for AZT in humans. Dr L. E. Mathes, (Ohio State University), described the prenatal and perinatal transmission of feline leukemia virus (FeLV) from infected queens to kittens; this model may be useful for examining the movement of virus across the placenta and for testing the efficacy of therapies. The use ofchronically catheterized pregnant baboons was described
Sager: The Role of the Placenta in HIVInfction and Therap])
671
by Dr R. I. Stark, (Columbia University). Extensive monitoring of the fetus makes this a potential model for obtaining data on long-term exposure to AIDS therapies. Three talks discussed the placental transport and pharmacokinetics of AZT in pregnant women, in perfused human term placenta, and in monkeys. Dr M. J. O’Sullivan (University of Miami) described results from a pharmacokmetics study in pregnant women conducted through the NIAID AIDS Clinical Trial Groups (ACTG). Parameters for pregnant women were not different from non-pregnant women; however, clearance of AZT in the neonate was reduced (half life about 13 h). Dr J. Dancis, (New York University Medical Center), described the transfer rates for AZT across the perfused human term placenta. Transfer indices were approximately equal for movement in both directions and greater than for glucose. Phosphorylated forms of AZT were identified from the perfused placental tissues. Dr J. D. Unadkat, (University of Washington), has used pregnant macaques to study the pharmacokinetics of AZT. As for humans, there were no significant differences with pregnancy except in clearance rates in the newborn. Clinical trials of drugs in children and pregnant women were discussed by Drs E. M. Connor, (Children’s Hospital of New Jersey), and Rhoda Sperling (Mount Sinai School of Medicine). Dr Connor, Chairman of the Pediatric Core Committee of the ACTGs, outlined the types of therapies that are being investigated. In addition, he highlighted the information gaps that make design of clinical trials for very young children and for pregnant women difficult. Dr Sperling reviewed the retrospective data gathered on 33 women who had received AZT during pregnancy. She also presented the standard of care guidelines developed by the Obstetrics and Gynecology working group of the ACTG. The workshop concluded with the presentations of recommendations for research in the areas of: epidemiology and transmission studies; HIV infection of the placenta; and placentadrug interactions. Drs A. Firpo and A. Nahmias summarized the questions that should receive priority for epidemiology and transmission studies. Those include a need to identify those HIV’ positive women who are at greatest risk for transmitting HIV to their offspring. Factors that related to differing rates of transmission or co-factors, such as drug use, smoking, or sexual activity, that may alter transmission must be identified. The timing of transmission and the proportion of infections occurring in utero and intrapartum must be determined, as well as those occurring early and late in gestation, this effort could be aided by concerted efforts to obtain histopathological material from HIV-infected and non-infected individuals from the same populations. In addition, prevalence ofHIVinfection and maternal risk factors for women, including IV drug users (IVDU) and sexual partners of IVDUs, need to be documented. For all of these questions to be addressed successfully, methods to diagnose neonatal infection must be developed. At present, very little is known about the infection of the placenta by HIV. Drs S. M. Wolinsky, (Northwestern University Medical School), and J. F. Modlin suggested that research must answer basic questions related to mechanisms of infection. At present it is not known when infection occurs; studies of maternal-fetal transfusion or cell exchange in the normal placenta, or in vitro models might be useful in addressing this question. Studies are also needed to evaluate the role of cell-associated virus and free virus in transmission; in addition, the role ofviremia in risk of transmission must be determined. The question ofviral tropism and the identification of infected cells in the placenta have not been adequately addressed. For example, it is now known whether maternal and fetal strains of virus differ, or whether placental cells might be infected for transmission to occur. It was also recommended that research focus on why the placenta is a relatively effective barrier, concentrating on alterations in the integrity of the placenta and potential confounding factors. Other studies
672
Placenta (I 994
Vol. I2
are needed to investigate the placenta as a mechanical, physiologic, and immunologic barrier and to identify host factors that correlate with infection. Recommendations for research on the interaction of therapies and the placenta were summarized by Dr William Slikker, Jr (National Center for Toxicological Research) and J. Dancis. There is a real need to encourage pharmaceutical studies (pharmacokinetics, bioavailability, placental transfer) in controlled experimental models to provide a scientific basis for design and interpretation of human clinical studies. These studies can be done using animal models, human placenta, and other in vitro methods to assess the effects of stage of gestation, dose and dosing schedules, and combination of therapies. There is also a need to develop and validate assessment techniques for efficacy and toxicity of therapies during gestation and after delivery; non-human primate models are available to assess multiple endpoints including immunologic, neurologic and behavioral development. The recommendations for future research needs highlighted the extent of information that is lacking. The basic questions of timing, routes, and mechanism of infection of the fetus or neonate are unanswered, as well as those concerning the role of the placenta in these events. Neither is there an adequate scientific basis for the optimal design and choice of therapies to interrupt the ‘perinatal’ transmission of HIV from a mother to her offspring.
Conference Report: Workshop on the Role of the Placenta in HIV Infection and Therapy, Nantucket, Massachusetts, lo-13 September 1990 POLLY R. SAGER DevelopmentalTherapeuticsBranch, Basic Research and Development Program, Division ofAIDS, National InstituteofAllergy and InfectiousDisease,NIH Bethesda,MD 20892, USA
The number of women infected with human immunodeficiency virus (HIV) in the USA has been increasing during the past several years, bringing with it the risk of transmitting HIV to their offspring. Indeed, children born to HIV positive women are the fastest growing population of HIV-infected patients in the USA. At present, few therapies are available to treat pregnant women who are infected with HIV. While little is known about the timing and frequency of transmission of HIV from mother to infant, even less is known about therapies to interrupt perinatal transmission of HIV. Increasingly, evidence points to the placenta as playing a role in either protection or transmission of HIV and as a potential target for therapy to interrupt perinatal infection. To identify needed areas of research and to develop collaborations to provide necessary basic information to support eventual clinical trials, the Division of AIDS of the National Institute of Allergy and Infectious Diseases (NIAID), NIH convened a workshop, ‘The Role of the Placenta in HIV Infection and Therapy’. This workshop was sponsored by the Developmental Therapeutics Branch and the Epidemiology Branch, organized by Drs Polly Sager and Evelyn Rodruguez, Division of AIDS, and was held on Nantucket Island lo-13 September 1990. The purpose was to bring together clinicians, scientists working in areas related to perinatal transmission of HIV and those conducting basic research on the placenta. Forty scientists were invited to participate. The meeting began with a session on the epidemiology of maternal-fetal transmission of HIV. Dr Tedd Ellerbrock (CDC, Atlanta) presented data from CDC on the incidence of HIV infection in women and children. HIV infection is now among the 10 leading causes of death in children l-4 years of age. Dr W. P. Parks, (New York University School of Medicine), reviewed information on rates ofperinatal infection of children, which range from about 20 to 35 per cent; he also noted that there does not appear to be any consistent pattern of transmission even for sequential births to an infected mother. The prenatal and perinatal transmission of other viruses, such as CMV, HSV, hepatitis, rubella, and others, was reviewed by Dr A. J. Nahmias (Emory University School of Medicine). Dr Teresa Calvelli (Albert Einstein College of Medicine) presented data that suggest a correlation between lack 0343-4004/91/060669
+ 04 $05.00/O
@ 1991 Baillike
Tindall Ltd
670
Placenta(1991), Vol. 12
of HIV transmission of virus and the presence of maternal high-affinity antibodies against HIV gp-120; this observation is being examined further in larger, prospective studies. Dr Rodney Hoff, (Division of AIDS, NIAID), concluded this session with a discussion of placental transport and fetal production of antibodies. He also described attempts to identify early diagnostic markers of infection; currently there is no reliable method to determine neonatal infection. Much of the discussion at this session focused on the lack of information on timing of fetal/neonatal infection, on possible protective maternal factors (265 per cent children not infected), and on early markers of fetavinfant infection. The second session focused on the structure and physiology of the placenta. Dr Maurice Panigel (University of Paris & M. Curie), described the structure and correlated function of the human placenta, along with methods for sampling and identifying cells and viruses in the placenta. He highlighted those cells which are thought to be CD4 positive at different times during the development of the placenta, and thus may be targets for HIV infection. Dr E. K. Mains, (UC San Francisco, Children’s Hospital), discussed the immunology of the placenta, including production of a number of cytokines. He noted that the placenta produces large amounts of IL-2 and that progesterone may regulate IL- 1 levels. Dr R. K. Miller, (University of Rochester Medical Center), reviewed markers of placental toxicity, including both markers for exposure and for effects. He described the anchor, control, and transport functions of the placenta and various methods for studying the human placenta. HIV infection of the placenta was the topic of the third session. Dr Adolf0 Firpo, (Armed Forces Institute of Pathology), described various methods for detecting HIV in human placenta: viral culture, direct visualization, genomic recognition, and immunological characteristics. He also noted that a non-specific increase in Hofbauer cells may occur in placentas from HIV-infected women, although other groups have not reported this. Several studies investigating HIV infection of early and late placenta using p24 antibody stain or in situ hybridization were reviewed by Dr J, F. Modlin, (Johns Hopkins University School of Medicine). Localization of HIV has been reported in trophoblasts and/or villous macrophages. Dr Gordon Douglas, (UC Davis School of Medicine), described methods for isolating and culturing placental cytotrophoblasts as well as enriched macrophage populations; only the latter cells were infected by HIV in vitro. Dr D. M. Phillips, (The Population Council, New York), described studies on the cell-cell movement of HIV using cultured cells. By electron microscopy, there appeared to be polarized release of HIV that was taken up by endosomes, coated pits, and by direct fusion into epithelial cells; however, there was no evidence of HIV replication in the epithelial cells. Dr A. S. Goustin, (Wayne State University), described the use of reverse transcriptase polymerase chain reaction (RT-PCR) to detect HIV m-RNA in placenta; his hypothesis that splicing of HIV message was altered was discussed. Discussion from this session focused on the lack of very basic information on the sites of HIV infection in the placenta and on the mechanism and the route(s) of HIV transmission from mother to fetus. The fourth session dealt with interactions of drugs and therapies with the placenta. Dr M. R. Juchau, (University Washington School of Medicine), began with a description of the drug metabolizing enzymes of the placenta. While mixed function oxidase activity increases with gestational age, the glucuronyl transferases do not appear to be present in placenta; this was of interest because glucuronidation is the major inactivation pathway for AZT in humans. Dr L. E. Mathes, (Ohio State University), described the prenatal and perinatal transmission of feline leukemia virus (FeLV) from infected queens to kittens; this model may be useful for examining the movement of virus across the placenta and for testing the efficacy of therapies. The use ofchronically catheterized pregnant baboons was described
Sager: The Role of the Placenta in HIVInfction and Therap])
671
by Dr R. I. Stark, (Columbia University). Extensive monitoring of the fetus makes this a potential model for obtaining data on long-term exposure to AIDS therapies. Three talks discussed the placental transport and pharmacokinetics of AZT in pregnant women, in perfused human term placenta, and in monkeys. Dr M. J. O’Sullivan (University of Miami) described results from a pharmacokmetics study in pregnant women conducted through the NIAID AIDS Clinical Trial Groups (ACTG). Parameters for pregnant women were not different from non-pregnant women; however, clearance of AZT in the neonate was reduced (half life about 13 h). Dr J. Dancis, (New York University Medical Center), described the transfer rates for AZT across the perfused human term placenta. Transfer indices were approximately equal for movement in both directions and greater than for glucose. Phosphorylated forms of AZT were identified from the perfused placental tissues. Dr J. D. Unadkat, (University of Washington), has used pregnant macaques to study the pharmacokinetics of AZT. As for humans, there were no significant differences with pregnancy except in clearance rates in the newborn. Clinical trials of drugs in children and pregnant women were discussed by Drs E. M. Connor, (Children’s Hospital of New Jersey), and Rhoda Sperling (Mount Sinai School of Medicine). Dr Connor, Chairman of the Pediatric Core Committee of the ACTGs, outlined the types of therapies that are being investigated. In addition, he highlighted the information gaps that make design of clinical trials for very young children and for pregnant women difficult. Dr Sperling reviewed the retrospective data gathered on 33 women who had received AZT during pregnancy. She also presented the standard of care guidelines developed by the Obstetrics and Gynecology working group of the ACTG. The workshop concluded with the presentations of recommendations for research in the areas of: epidemiology and transmission studies; HIV infection of the placenta; and placentadrug interactions. Drs A. Firpo and A. Nahmias summarized the questions that should receive priority for epidemiology and transmission studies. Those include a need to identify those HIV’ positive women who are at greatest risk for transmitting HIV to their offspring. Factors that related to differing rates of transmission or co-factors, such as drug use, smoking, or sexual activity, that may alter transmission must be identified. The timing of transmission and the proportion of infections occurring in utero and intrapartum must be determined, as well as those occurring early and late in gestation, this effort could be aided by concerted efforts to obtain histopathological material from HIV-infected and non-infected individuals from the same populations. In addition, prevalence ofHIVinfection and maternal risk factors for women, including IV drug users (IVDU) and sexual partners of IVDUs, need to be documented. For all of these questions to be addressed successfully, methods to diagnose neonatal infection must be developed. At present, very little is known about the infection of the placenta by HIV. Drs S. M. Wolinsky, (Northwestern University Medical School), and J. F. Modlin suggested that research must answer basic questions related to mechanisms of infection. At present it is not known when infection occurs; studies of maternal-fetal transfusion or cell exchange in the normal placenta, or in vitro models might be useful in addressing this question. Studies are also needed to evaluate the role of cell-associated virus and free virus in transmission; in addition, the role ofviremia in risk of transmission must be determined. The question ofviral tropism and the identification of infected cells in the placenta have not been adequately addressed. For example, it is now known whether maternal and fetal strains of virus differ, or whether placental cells might be infected for transmission to occur. It was also recommended that research focus on why the placenta is a relatively effective barrier, concentrating on alterations in the integrity of the placenta and potential confounding factors. Other studies
672
Placenta (I 994
Vol. I2
are needed to investigate the placenta as a mechanical, physiologic, and immunologic barrier and to identify host factors that correlate with infection. Recommendations for research on the interaction of therapies and the placenta were summarized by Dr William Slikker, Jr (National Center for Toxicological Research) and J. Dancis. There is a real need to encourage pharmaceutical studies (pharmacokinetics, bioavailability, placental transfer) in controlled experimental models to provide a scientific basis for design and interpretation of human clinical studies. These studies can be done using animal models, human placenta, and other in vitro methods to assess the effects of stage of gestation, dose and dosing schedules, and combination of therapies. There is also a need to develop and validate assessment techniques for efficacy and toxicity of therapies during gestation and after delivery; non-human primate models are available to assess multiple endpoints including immunologic, neurologic and behavioral development. The recommendations for future research needs highlighted the extent of information that is lacking. The basic questions of timing, routes, and mechanism of infection of the fetus or neonate are unanswered, as well as those concerning the role of the placenta in these events. Neither is there an adequate scientific basis for the optimal design and choice of therapies to interrupt the ‘perinatal’ transmission of HIV from a mother to her offspring.
