HIV-1 in trophoblastic and villous Hofbauer cells, and haematological precursors in eight-week fetuses

Human alpha-fetoprotein binds to primary macrophages

We have previously reported that alpha-fetoprotein (AFP) inhibits infection of human monocyte-derived macrophages (MDM) by R5-HIV-1 strains and that a peptide mimicking the clade B HIV-1 gp120 consensus V3 domain (V3Cs) binds to CCR5. We demonstrate here that AFP binds high- and low-affinity binding sites of MDM, characterized, respectively, by 5.15 and 100nM K(d) values. Heat denaturation or neuraminidase treatment of AFP inhibits this binding, suggesting the involvement of protein-protein and lectin-carbohydrate interactions. Moreover, AFP displaces V3Cs binding to MDM. In addition, MIP-1beta, the most specific CCR5 ligand, displaces AFP binding to MDM (IC(50)=4.3nM). Finally, we demonstrate that AFP binds to a ligand of HIV-gp120 V3Cs domain, CCR5, expressed by MDM and by HeLa cells expressing CCR5. Such binding is not observed in the presence of HeLa cells lacking CCR5. The present results provide strong evidence that AFP directly binds to CCR5 expressed by human primary macrophages and by transfected CCR5+ HeLa cells.

Vertical transmission of human immunodeficiency virus

Sensitive detection methods, such as DNA PCR and RNA PCR suggest that vertical transmission of human immunodeficiency virus (HIV) occurs at three major time periods; in utero, around the time of birth, and postpartum as a result of breastfeeding (Fig. 1). Detection of proviral DNA in infant's blood at birth suggests that transmission occurred prior to delivery. A working definition for time of infection is that HIV detection by DNA PCR in the first 48 h of life indicates in utero transmission, while peripartum transmission is considered if DNA PCR is negative the first 48 h, but then it is positive 7 or more days later [1]. Generally, in the breastfeeding population, breast milk transmission is thought to occur if virus is not detected by PCR at 3-5 months of life but is detected thereafter within the breastfeeding period [2]. Using these definitions and guidelines, studies has suggested that in developed countries the majority, or two thirds of vertical transmission occur peripartum, and one-third in utero [3-6]. The low rate of breastfeeding transmission is due to the practice of advising known HIV-positive mothers not to feed breast milk. However, since the implementation of antiretroviral treatment in prophylaxis of HIV-positive mothers, some studies have suggested that in utero infection accounts for a larger percentage of vertical transmissions [7]. In developing countries, although the majority of infections occurs also peripartum, a significant percentage, 10-17%, is thought to be due to breastfeeding [2, 8, 9].

Mother-to-child transmission of HIV-1: the role of HIV-1 variability and the placental barrier

The acquired immunodeficiency syndrome (AIDS), which is caused by the human immunodeficiency virus (HIV), was first described in the United States of America in 1981 [1]. The worldwide spread of HIV has soon been recognized and AIDS has become one of the most alarming infectious diseases of our days. Its impact has been tremendous, high morbidity and mortality has caused a reversal of socioeconomic gains previously recorded in several developing countries, especially those in Sub-Saharan Africa [2]. Epidemiological data about the HIV and AIDS pandemic are updated by the Joint United Nation Programme on HIV/AIDS, UNAIDS (http://www.unaids.org). Their latest report from December 2000 states that in year 2000 approximately 5.3 million people have become newly infected with HIV, of which 2.2 were women and 600,000 children younger than 15 years of age. The estimated number of people living with HIV/AIDS globally is 36.1 million, of which 16.4 million are women and 1.4 million are children younger than 15 years of age. Approximately 25.3 million (70%) of these HIV infected people live in Sub-Saharan Africa, 5.8 million in South- and South-East Asia (15%), and 1.4 million in Latin-America (5%). During year 2000, 3 million people died of AIDS (1.3 million women and 500,000 children younger than 15 years of age). This means that an estimated total of 21.8 million persons have died of AIDS since the beginning of the epidemic, including 4.3 million children younger than 15 years of age.

Human herpesvirus 6 variant a infects human term syncytiotrophoblasts in vitro and induces replication of human immunodeficiency virus type 1 in dually infected cells

Human herpesvirus 6 (HHV-6) and human immunodeficiency virus type 1 (HIV-1) may interact during transplacental transmission of HIV-1. The placental syncytiotrophoblast layer serves as the first line of defense of the fetus against viruses. Patterns of replication of HHV-6 variant A (HHV-6A) and HIV-1 were analyzed in singly and dually infected human term syncytiotrophoblast cells cultured in vitro. For this purpose, the GS strain of HHV-6A and the Ba-L and IIIB strains of HIV-1 were used. HHV-6A replication was restricted at the level of early gene products in singly infected syncytiotrophoblasts, whereas no viral protein expression was found in cells infected with HIV-1 alone. Coinfection of syncytiotrophoblast cells with HHV-6A and HIV-1 resulted in production of infectious HIV-1. In contrast, no enhancement of HHV-6A expression was observed in cell cultures infected with both viruses. Uninfected syncytiotrophoblast cells were found to express CXCR4 and CCR3 but not CD4 or CCR5 receptors. Infection of syncytiotrophoblasts with HHV-6A did not induce CD4 expression and had no influence on chemokine receptor expression. Activation of HIV-1 from latency in coinfected cells was mediated by the immediate-early (IE)-A and IE-B gene products of HHV-6A. Open reading frames U86 and U89 of the IE-A region were able to activate HIV-1 replication in a synergistic manner. The data suggest that in vivo double infection of syncytiotrophoblast cells with HHV-6A and HIV-1 could contribute to the transplacental transmission of HIV-1 but not HHV-6A.

The significance of the placenta in assessment of the newborn

The placenta may harbor many diagnostic tools available for the care of ill neonates. Such tools enable fine-tuning of diagnoses or even the establishment of diagnoses not considered during the investigation and care of the newborn. For this reason, obstetricians, pediatricians, and pathologists should all be familiar with common placental diagnoses so that sharing of the available data among these specialists may, in many cases, provide supportive and diagnostic information critical to the management of the newborn.

Placental expression of DC-SIGN may mediate intrauterine vertical transmission of HIV

Mechanisms of transplacental transmission of human immunodeficiency virus (HIV) are poorly understood. DC-SIGN is a C-type lectin able to bind HIV gp120 with high affinity, mediating HIV adsorption to the surface of dendritic cells for up to several days. Via this mechanism, DC-SIGN significantly enhances the infection of CD4(+) co-receptor (CCR5 or CXCR4)(+) T lymphocytes in trans. In this study, DC-SIGN-specific serum was developed to investigate the cell type responsible for the high level of DC-SIGN RNA expression previously observed in the placenta. DC-SIGN expression was shown on CD68(+) HLA-II(+) CD14(low) S100(+/-) CD83(-) CD86(-) cmrf-44(-) villous cells consistent with Hofbauer cells and also on CD68(+) HLA-II(+) CD14(high) S100(-) CD83(-) CD86(-) cmrf-44(-) decidual macrophages. The DC-SIGN(+) Hofbauer cells co-express CD4 and the chemokine receptors, CCR5 and CXCR4, observations which may account for the ability of these cells to become infected with HIV. These fetal DC-SIGN(+) cells are separated by only a layer of trophoblast from both DC-SIGN(+) maternal cells and maternal blood, potential sources of HIV in infected mothers. Previous studies have suggested that this trophoblast layer is frequently breached during pregnancy. It is therefore proposed that DC-SIGN may facilitate the transplacental transmission of HIV.

Induction of HIV-1 replication in latently infected syncytiotrophoblast cells by contact with placental macrophages: role of interleukin-6 and tumor necrosis factor-alpha

The syncytiotrophoblast (ST) layer of the human placenta has an important role in limiting transplacental viral spread from mother to fetus. Although certain strains of human immunodeficiency virus type 1 (HIV-1) may enter ST cells, the trophoblast does not exhibit permissiveness for HIV-1. The present study tested the possibility that placental macrophages might induce replication of HIV-1 carried in ST cells and, further, that infected ST cells would be capable of transmitting virus into neighboring macrophages. For this purpose, we investigated HIV-1 replication in ST cells grown alone or cocultured with uninfected placental macrophages. The macrophage-tropic Ba-L strain of HIV-1, capable of entering ST cells, was used throughout our studies. We demonstrated that interactions between ST cells and macrophages activated HIV-1 from latency and induced its replication in ST cells. After having become permissive for viral replication, ST cells delivered HIV-1 to the cocultured macrophages, as evidenced by detection of virus-specific antigens in these cells. The stimulatory effect of coculture on HIV-1 gene expression in ST cells was mediated by marked tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) release from macrophages, an effect caused by contact between the different placental cells. Results of this study suggest an interactive role for the ST layer and placental macrophages in the dissemination of HIV-1 among placental tissue. Data reported here may also explain why macrophage-tropic HIV-1 strains are transmitted preferentially during pregnancy.

Placental cytokine and chemokine production in HIV-1-infected women: trophoblast cells show a different pattern compared to cells from HIV-negative women

In utero transmission of HIV-1 has been demonstrated and may account for around 10-20% of all materno-fetal HIV-1 transmission. The possible routes for such transmission are transannexial or transplacental. In both cases, the microenvironment (cytokines and chemokines) at the placental interface could be an important regulatory factor in viral transmission. We therefore performed explant cultures of placental villi, and isolated purified trophoblasts, from term placentae obtained from HIV-1-seropositive and HIV-1-seronegative women in order to assess and compare the cytokine and chemokine secretion profiles using ELISA and semiquantitative RT-PCR. No major differences could be seen in the secretions of cytokines and chemokines at the level of whole placental tissue in HIV-1-positive and HIV-1-negative women. However, variations were observed in the expression of inflammatory cytokines and chemokines from trophoblastic cells, depending on the status of HIV-1 infection of the mothers but not the babies, all of which remained uninfected. The significance of these data is discussed.

Pseudotypes of vesicular stomatitis virus-bearing envelope antigens of certain HIV-1 strains permissively infect human syncytiotrophoblasts cultured in vitro: implications for in vivo infection of syncytiotrophoblasts by cell-free HIV-1

Intrauterine infection of the fetus is clearly an important mode of vertical transmission of human immunodeficiency virus type 1 (HIV-1). The syncytiotrophoblast layer of the human placenta must be traversed by HIV-1 in order to reach underlying cells and fetal capillaries. Although HIV-1 has been detected in the syncytiotrophoblast layer in situ, there is conflicting evidence regarding infection of syncytiotrophoblast cells with cell-free virus. The phenotypic mixing between HIV-1 and vesicular stomatitis virus (VSV) has been exploited to assay the susceptibility of human term syncytiotrophoblast cells to penetration by various strains of HIV-1. VSV(HIV-1(IIIB)) and VSV(HIV-1(Ba-L)) pseudotypes were found to enter syncytiotrophoblast cells. In contrast, VSV pseudotyped with envelope glycoproteins of RF, MN, or Ada-M strains of HIV-1 did not infect syncytiotrophoblasts. Plating efficiency of VSV(HIV-1(IIIB)) and VSV(HIV-1(Ba-L)) was 10-fold lower on syncytiotrophoblasts than on T-cells and macrophages, respectively. Incubation of VSV(HIV-1(IIIB)) and VSV(HIV-1(Ba-L)) viruses with appropriate HIV-1 neutralizing sera before infection strongly inhibited entry of pseudotyped VSV into syncytiotrophoblast cells. These findings demonstrated that infection of syncytiotrophoblasts with VSV(HIV-1) pseudotypes was mediated by Env from IIIB and Ba-L strains of HIV-1. Monoclonal antibodies (MAb) to CD4, CXCR4, CCR5, and CCR3 were tested for their ability to block VSV(HIV-1) infection of syncytiotrophoblast cells. Neither the anti-CD4 nor the anti-CXCR4, anti-CCR5, and anti-CCR3 MAb had any inhibitory effect on infection of syncytiotrophoblast cells with VSV(HIV-1) pseudotypes. Results from this study suggest that cell-free HIV-1 can enter syncytiotrophoblasts and the susceptibility of these cells to penetration by the virus is strain dependent. Pseudotype infection merely demonstrates that the first steps in HIV-1 replication are possible in syncytiotrophoblast cells.

Cell-to-cell contact results in a selective translocation of maternal human immunodeficiency virus type 1 quasispecies across a trophoblastic barrier by both transcytosis and infection

Mother-to-child transmission can occur in utero, mainly intrapartum and postpartum in case of breastfeeding. In utero transmission is highly restricted and results in selection of viral variant from the mother to the child. We have developed an in vitro system that mimics the interaction between viruses, infected cells present in maternal blood, and the trophoblast, the first barrier protecting the fetus. Trophoblastic BeWo cells were grown as a tight polarized monolayer in a two-chamber system. Cell-free virions applied to the apical pole neither crossed the barrier nor productively infected BeWo cells. In contrast, apical contact with human immunodeficiency virus (HIV)-infected peripheral blood mononuclear cells (PBMCs) resulted in transcytosis of infectious virus across the trophoblastic monolayer and in productive infection correlating with the fusion of HIV-infected PBMCs with trophoblasts. We showed that viral variants are selected during these two steps and that in one case of in utero transmission, the predominant maternal viral variant characterized after transcytosis was phylogenetically indistinguishable from the predominant child's virus. Hence, the first steps of transmission of HIV-1 in utero appear to involve the interaction between HIV type 1-infected cells and the trophoblastic layer, resulting in the passage of infectious HIV by transcytosis and by fusion/infection, both leading to a selection of virus quasispecies.

Automated quantitation of cell-mediated HIV type 1 infection of human syncytiotrophoblast cells by fluorescence in situ hybridization and laser scanning cytometry

Infection of human placental syncytiotrophoblast cells with HIV requires direct contact with infected leukocytes. In vitro investigations into mechanisms regulating placental HIV transmission and into the development of therapeutic interventions have been hampered by difficulties inherent in quantitating HIV levels in cocultures of infected lymphocytes and adherent multinucleated syncytiotrophoblast cells. Here, we have used fluorescence in situ hybridization (FISH) for the direct detection of HIV-1 RNA within syncytiotrophoblast cells combined with laser scanning cytometry (LSC) to quantitate HIV levels exclusively in the syncytiotrophoblast cells. HIV-1-infected lymphocytic MOLT-4 cells were cocultured with primary human syncytiotrophoblast cells. Lymphocytic cells were identified with an anti-vimentin antibody and Cy5. HIV RNA was localized by in situ hybridization, using a digoxigenin-labeled riboprobe detected by Oregon Green, and nuclei were stained with 7-aminoactinomycin D. The three-color cocultures were analyzed by LSC to remove unwanted cell populations and quantitate HIV expression levels. The total HIV RNA level (green fluorescence integral) in each colony was normalized for cell size by dividing by the total DNA content (red fluorescence integral). The nuclear-normalized fluorescence integral was 2.3 times higher in infected cocultures than in uninfected cultures. When cocultures were incubated with 10 microM AZT, the green/red fluorescence integral value was significantly lower than that of cocultures incubated in the absence of AZT, corresponding to a 78% reduction in fluorescence. Laser scanning cytometry can be used to quantitate cell-mediated HIV infection in syncytiotrophoblast cells and should allow drug assessment studies and studies aimed at understanding the mechanism of virus entry into trophoblast cells to be carried out.

Chemokine receptor expression by human syncytiotrophoblast

Despite their potential importance in placental HIV infection and placental immune function, nothing is known about the expression of chemokine receptors by human syncytiotrophoblast cells. Immunocytochemical analysis revealed that primary cultures of term syncytiotrophoblast cells express CCR1, CCR3, CXCR4, and CCR6. Immunohistochemical examination of cryosections of term placental villous tissue confirmed the expression of CCR3, CXCR4, and CCR6 by trophoblast cells. The primary syncytiotrophoblast cultures showed no reactivity with antibodies against CCR5. In the villous tissue sections, CCR5 was detected in stromal cells and blood vessel walls but was not found in trophoblast cells. RT-PCR analysis of RNA extracted from cultured syncytiotrophoblast cells confirmed that the cells express message for CCR1, CCR3, CXCR4, CCR6 and CCR10. No transcripts corresponding to CCR2b, CCR5, or CCR8 were detected. Other experiments showed that exposure of syncytiotrophoblast cells to soluble SDF-1alpha elicited a calcium mobilization response, consistent with the expression of functional CXCR4. Thus, human syncytiotrophoblast cells express CXCR4, a known co-receptor for TCL-tropic HIV-1 isolates but do not express CCR5, the major co-receptor for M-tropic isolates. In addition to implications for the maternal-fetal transmission of HIV, the expression of chemokine receptors by syncytiotrophoblast cells could be important in other aspects of placental immune function.

Vertical human immunodeficiency virus type 1--HIV-1--transmission--a review

Several factors appear to affect vertical HIV-1 transmission, dependent mainly on characteristics of the mother (extent of immunodeficiency, co-infections, risk behaviour, nutritional status, immune response, genetical make-up), but also of the virus (phenotype, tropism) and, possibly, of the child (genetical make-up). This complex situation is compounded by the fact that the virus may have the whole gestation period, apart from variable periods between membrane rupture and birth and the breast-feeding period, to pass from the mother to the infant. It seems probable that an extensive interplay of all factors occurs, and that some factors may be more important during specific periods and other factors in other periods. Factors predominant in protection against in utero transmission may be less important for peri-natal transmission, and probably quite different from those that predominantly affect transmission by mothers milk. For instance, cytotoxic T lymphocytes will probably be unable to exert any effect during breast-feeding, while neutralizing antibodies will be unable to protect transmission by HIV transmitted through infected cells. Furthermore, some responses may be capable of controlling transmission of determined virus types, while being inadequate for controlling others. As occurrence of mixed infections and recombination of HIV-1 types is a known fact, it does not appear possible to prevent vertical HIV-1 transmission by reinforcing just one of the factors, and probably a general strategy including all known factors must be used. Recent reports have brought information on vertical HIV-1 transmission in a variety of research fields, which will have to be considered in conjunction as background for specific studies.

Up-regulation of CCR5 expression in the placenta is associated with human immunodeficiency virus-1 vertical transmission

The role of placenta in vertical transmission is not yet fully understood. A protective role of the placenta during gestation is suggested by the finding that caesarian sections reduce the risk of transmission of human immunodeficiency virus (HIV)-1 from mother to child three- to fourfold. Here we investigated whether the immunological milieu of the placenta might be important in HIV-1 transmission. In situ imaging of immunohistochemically stained placenta sections and reverse transcriptase-polymerase chain reaction demonstrated a fourfold increase in CCR5:CXCR4 expression ratio in placentae from transmitting women compared to placentae from nontransmitting women. This chemokine receptor repertoire was consistent with an up-regulation of interleukin-4 and interleukin-10 expression in placentae from nontransmitting placentae compared to transmitting placentae. In situ imaging demonstrated that CCR5 and CXCR4 were expressed on placental macrophages and lymphocytes but not in trophoblasts. Simultaneous immunofluorescence/ultrasensitive in situ hybridization for HIV-1 gag-pol mRNA revealed that HIV-1 infects primarily CXCR4-expressing cells in placentae from nontransmitting women whereas predominantly CCR5-expressing cells were infected in placentae from transmitting women. These data are consistent with transmission of a homogeneous population of nonsyncytium-inducing HIV-1 isolates that use CCR5 as co-receptor.

Cytokines and placental macrophages in regulation of birth activity

The article reviews present notions on functional activity of cytokines of the fetoplacental complex. Particular emphasis is placed on the role of these molecules in the regulation of gestation processes and in pregnancy incompetence. The mechanism of the involvement of placental macrophages and their products in gestation and delivery is discussed.

Women and HIV--revisited ten years on

This article compares how women and their relationship to HIV has changed since the original publication of this article in 1990. The number of women infected with HIV has continued to rise, but, in contrast, there have been few changes in their management. We review transmission risks and manifestations of the infection, and also discuss the issues faced by women with HIV.

HIV-1 co-receptor expression on trophoblastic cells from early placentas and permissivity to infection by several HIV-1 primary isolates

We examined CD4 and major HIV-1 co-receptor expression by trophoblast cells (TC) from early placentas, and the permissiveness of TC for infection by several natural HIV-1 isolates in vitro. Ten early placentas (4-6 weeks of gestation) from HIV- women were obtained after elective abortion. CD4 and HIV-1 co-receptor expression by TC was examined in terms of both mRNA and protein. The same TC were then challenged with three clinical HIV isolates of known phenotype, two originating from mothers who transmitted the virus to their child and one from a vertically infected newborn. TC infection was detected by polymerase chain reaction. CD4 expression was detected in five of the 10 placentas, while membrane protein expression of CCR3, CXCR4 and CCR5 was detected in every case, despite quantitative differences among individuals. Bonzo, GPR1 and ChemR23 mRNAs were detected in all TC preparations. TC from seven out of eight placentas were permissive to HIV entry, but no productive viral replication was detected (reverse transcriptase activity in culture supernatants). Interestingly, the addition of chemokine(s) or a CD4-blocking antibody to the cultures failed to inhibit TC virus entry. These data point to marked interindividual variability in HIV co-receptor expression by trophoblast cells and show that TC from early placentas can be infected in vitro by clinical HIV-1 isolates. They also suggest that viral entry in vitro might occur through a mechanism independent of both CD4 and chemokine receptors.

Genetic analysis reveals ongoing HIV type 1 evolution in infected human placental trophoblast

To provide a better understanding of the role of placenta in vertical human immunodeficiency virus (HIV) transmission, we have studied the infection of placental trophoblast in a group of 15 mother-neonate pairs. By nested PCR amplification of the C2V3 env gene region, HIV-1 has been found to infect the placenta in five cases (33%). Phylogenetic analysis of the cloned sequences showed that all recovered maternal variants were of the B subtype. Further investigation into the ancestral relationships at the nucleotide level revealed that the trophoblast sequences evolved into a quasispecies population clearly distant from that observed in the mother. As expected, the populations transmitted to the trophoblast were also found to be more homogeneous than those in the mothers when characterized on the basis of pairwise nucleotide sequence distances. With regard to the predicted biological properties, the primary amino acid structure of the V3 loop domain was consistent, with a macrophage-tropic, non-syncytium-inducing phenotype in all patients. We also attempted to determine if any of a number of selected maternal or viral factors was associated with trophoblast infection. However, none of the followed parameters, including maternal age, disease stage, antiretroviral therapy, CCR5delta32 deletion status of the infant, and viral genotype, could be associated with viral transmission. Moreover, in one pair with proven trophoblast infection, HIV was also detected in the cord blood. Taken together, our data suggest that the productive trophoblast infection by HIV-1 in vivo is a relatively frequent event that may bear direct implications for a further transplacental propagation of the virus.

The trophoblastic epithelial barrier is not infected in full-term placentae of human immunodeficiency virus-seropositive mothers undergoing antiretroviral therapy

To study the mechanism of the placental barrier function, we examined 10 matched samples of term placentae, cord blood, and maternal blood obtained at delivery from human immunodeficiency virus (HIV)-infected mothers with children diagnosed as HIV negative in Sweden. All placentae were histologically normal, and immunochemistry for HIV type 1 p24 and gp120 antigens was negative. Highly purified trophoblasts (93 to 99% purity) were negative for HIV DNA and RNA, indicating that the trophoblasts were uninfected. Although HIV DNA was detected in placenta-derived T lymphocytes and monocytes, microsatellite analysis showed that these cells were a mixture of maternal and fetal cells. Our study indicates that the placental barrier, i.e., the trophoblastic layer, is not HIV infected and, consequently, HIV infection of the fetus is likely to occur through other routes, such as breaks in the placental barrier.

Vertical transmission of HIV: parameters which might affect infection of placental trophoblasts by HIV-1: a review. Biomed Group on the Study of in Utero Transmission of HIV 1

PROBLEM

To understand the mechanisms preventing and/or facilitating maternofetal transmission of human immunodeficiency virus (HIV)-1 across the placenta during pregnancy.

METHODS OF STUDY

Current experimental data were reviewed.

RESULTS AND CONCLUSIONS

The data about the production of cytokines by placental cells and explants, taken together with information indicating selective passage of certain HIV-1 variants across the placental trophoblast, suggest an intricate regulatory network operating at the fetomaternal interface. The data show a differential differentiation of early and late trophoblasts, as far as HIV entry routes are concerned. We believe this explains the relative predominance of the early infection window, as far as in utero infection is concerned. Whether such a differentiation state can be transiently induced on term placental trophoblasts by several differentiation agents, including cytokines, is being investigated. Whatever the results may be, it is obvious that infection of placental cells is an excellent model of passage infection by HIV of/through a mucosal barrier.

A Novel Factor Produced by Placental Cells with Activity Against HIV-1

The factors controlling the dynamics of HIV-1 transmission from mother to infant are not clearly known. Previous studies have suggested the existence of maternal and placental protective mechanisms that inhibit viral replication in utero. Preliminary studies from our laboratory revealed that supernatant from placental stromal cells protected HIV-1-infected PBMC from virus-induced apoptosis and suppressed virus production. We have attempted to characterize the antiviral activity of this placental factor (PF) and delineate the stages of HIV-1 replication affected. This activity was not due to the presence of any known cytokine reported to have anti-HIV effect. Direct exposure to PF had no suppressive effect on the infectivity of cell-free HIV-1, and envelope-mediated membrane fusion appeared to be unaffected. Western blot analysis of HIV-1 from infected PBMC treated with PF revealed that expression of all viral proteins was reduced proportionately, both intracellularly and in released virions. However, exposure of HIV-1-infected cells to PF resulted in production of virions with 10–100-fold-reduced infectivity. PF-treated virions contained two- to threefold reduced ratios of cyclophilin A:Gag protein as compared with untreated virus. Reduced cyclophilin A content resulting in decreased binding of cyclophilin A to Gag could account, in part, for the observed reduction in infectivity. Our results suggest that placental cells produce an antiviral factor that protects the fetus during gestation and may have therapeutic potential.

Human immunodeficiency virus infection in pregnancy

The incidence and prevalence of human immunodeficiency virus (HIV) infection in women of child-bearing age continue to increase both internationally and in Canada. The care of HIV-infected pregnant women is complex, and multiple issues must be addressed, including the current and future health of the woman, minimization of the risk of maternal-infant HIV transmission, and maintenance of the well-being of the fetus and neonate. Vertical transmission of HIV can occur in utero, intrapartum and postpartum, but current evidence suggests that the majority of transmission occurs toward end of term, or during labour and delivery. Several maternal and obstetrical factors influence transmission rates, which can be reduced by optimal medical and obstetrical care. Zidovudine therapy has been demonstrated to reduce maternal-infant transmission significantly, but several issues, including the short and long term safety of antiretrovirals and the optimal use of combination antiretroviral therapy in pregnancy, remain to be defined. It is essential that health care workers providing care to these women fully understand the natural history of HIV disease in pregnancy, the factors that affect vertical transmission and the management issues during pregnancy. Close collaboration among a multidisciplinary team of knowledgeable health professionals and, most importantly, the woman herself can improve both maternal and infant outcomes.

Chorioamnionitis and pregnancy outcome in HIV-infected African women. Pregnancy and HIV Study Group

OBJECTIVE

To assess the role of chorioamnionitis (CAM) on pregnancy outcome in HIV-1-infected (HIV-positive) pregnant women, treated for sexually transmitted diseases (STDs), during the last trimester of pregnancy in Kigali, Rwanda.

METHODS

At inclusion in a prospective cohort, from July 1992 to August 1993, 561 pregnant women between 24 and 28 weeks were systematically screened for HIV infection, STDs, anemia, malaria, and hepatitis B infection; a CD4 lymphocyte count was performed. Until delivery, each woman enrolled had a monthly clinical follow-up with STD treatment when needed. The pregnancy outcome was recorded. Diagnosis of CAM was based on histologic examination of the placenta.

RESULTS

Among the 275 placentas of HIV-negative women and 286 placentas of HIV-positive women examined, CAM was diagnosed (CAM-positive) in 27 HIV-positive women (9.8%) and in 28 HIV-negative women (9.8%). No statistical association was found between CAM and the following variables, independent of the HIV serostatus: age, parity, hepatitis B, anemia, STDs, and immune deficiency. Among HIV-negative women, CAM was significantly associated with prematurity (relative risk [RR] = 3.0; 95% confidence interval [CI] = 1.5-6.3), stillbirth (RR = 4.2; 95% CI = 1.6-11.0) and premature rupture of membranes (RR = 2.9; 95% CI = 1.4-6.1). Among HIV-positive women, early neonatal mortality was the only adverse outcome associated with CAM (RR = 2.0; 95% CI = 1.6-11.0).

CONCLUSIONS

In our study, the prevalence of CAM was low and no risk factor of CAM was identified, a probable consequence of the control factor of STDs. CAM was strongly associated with adverse pregnancy outcomes in HIV-infected women, reflecting a possible deleterious effect of HIV.

Detection of Chlamydia trachomatis intrauterine infection using polymerase chain reaction on chorionic villi

OBJECTIVE

To detect Chlamydia trachomatis intrauterine infection in the early pregnancy by using chorionic villi.

METHOD

The C. trachomatis infection in pregnant women was investigated by cervical specimens and Clearview kits. DNA of chorionic villi was extracted and the gene of a major outer membrane protein of C. trachomatis was amplified by polymerase chain reaction (PCR).

RESULTS

120 cervical specimens of the pregnant women were analyzed and 10 cervical specimens were positive for C. trachomatis infection. In this study, the prevalence of C. trachomatis infection was approx. 8.3%. Fifty-nine specimens of chorionic villi and three positive specimens of C. trachomatis infection were analyzed by PCR. The incidence of C. trachomatis intrauterine infection in the early pregnancy was 5.1%.

CONCLUSION

The vertical transmission of C. trachomatis infection in the early pregnancy may be a pathway of intrauterine infection. Chorionic villus sampling in early pregnancy and the PCR method could be developed as a technique for prenatal diagnosis of C. trachomatis intrauterine infection.

The maternal and child health sites' practices regarding HIV education, counseling, and testing of women of reproductive age in Chicago: barriers to universal implementation

OBJECTIVES

Women of reproductive age are increasingly at risk for human immunodeficiency virus (HIV) infection. Recent advances in reducing perinatal transmission have resulted in official guidelines on universal HIV education, counseling, and voluntary testing of women of reproductive age, especially pregnant women. This study assesses to what extent the maternal child health (MCH) sites are implementing these guidelines with their female patient population (including pregnant women) and examines the barriers that prevent them from implementing these guidelines.

METHOD

The study uses survey data from 92 hospitals and community health centers offering MCH services in Chicago regarding their providers' practices on HIV education, counseling, and testing, implementation of zidovudine (ZDV) therapy to reduce perinatal transmission, and the barriers to implementing these services. In addition, 20 taped in-depth interviews were conducted with experts to examine the barriers to universal implementation.

RESULTS

Almost half (45% of perinatal care and 50% of family planning providers) of the institutions are not consistently offering HIV testing. One-third of those institutions that offer testing are not offering pretest counseling. Thirty-nine percent of the perinatal care providers in these institutions are not providing posttest counseling to HIV-negative women. Over one-third (35%) of these institutions reported that they are not set up to implement ZDV therapy during labor and delivery. Almost half (49%) had no protocols for ZDV therapy in place. Barriers to implementation included lack of provider training, limited staff time, physician resistance, unavailability or avoidance to seek perinatal care by high-risk women, cost, absence of a statewide and hospital-specific plan, lack of reproductive choice focus in posttest counseling, lack of provider knowledge about the administration of ZDV or its availability during labor, and lack of consumer education on perinatal risk reduction.

CONCLUSIONS

MCH sites and their providers need assistance to overcome many barriers they face to implement universal HIV education, counseling, and testing of women of reproductive age.

The Structure of the Human Placenta: Implications for Initiating and Defending Against Virus Infections

The architecture of the human placenta permits an extensive and intimate association between the maternal and fetal circulations. The fetal component consists of the elaborately branched villous tree, and this is bathed directly by maternal blood circulating within the intervillous space. Whilst this arrangement may favour metabolic exchange, it poses considerable risks for the vertical transmission of pathogens. Some features of placental structure can be considered potential impediments to transmission, such as the syncytial nature of the outer villous covering, the syncytiotrophoblast, and the ability of this tissue to secrete both nitric oxide and interferons. Other features may facilitate vertical transmission, including the lack of expression of MHC Class 1 antigens by the syncytiotrophoblast, and its vesicular and immunoglobulin transport pathways. More importantly, it is known that physical defects occur in the trophoblast layers at all stages in gestation. Whilst repair processes have been identified it must be assumed that pathogens or infected maternal white cells have access to the trophoblastic basement membrane, albeit transiently. The universal nature of these defects suggests that the trophoblast cannot be of paramount importance in the prevention of transmission. Rather, the defence mechanisms must lie either at the level of the basement membrane or within the villous core. There they may be represented by the resident macrophage population or the capillary endothelial cells and their junctional complexes. Consequently, the placenta should be viewed as an active rather than a passive barrier. Copyright 1997 by John Wiley & Sons, Ltd.

Interaction of pregnancy steroid hormones and zidovudine in inhibition of HIV type 1 replication in monocytoid and placental Hofbauer cells: implications for the prevention of maternal-fetal transmission of HIV

Zidovudine (AZT) has been shown to reduce maternal-fetal transmission of HIV-1 by more than two-thirds in a variety of clinical settings. However, the mechanism of action of AZT in this setting is unclear. Suppression of vertical transmission has occurred in the absence of an impact on maternal plasma viremia and no lower threshold of viral load for such transmission has been identified. We hypothesized that augmentation of the anti-HIV effect of AZT may occur locally, at the maternal-fetal interface. We report that the pregnancy hormone progesterone at broad concentrations has little effect on acute HIV-1 infection of a monocytic cell line or primary peripheral blood cells. However, the combination of physiologic concentrations of progesterone (10[-7] to 10[-6] M) and low-dose AZT (10[-8] to 10[-9] M) produced markedly synergistic inhibition of HIV-1 replication within acutely infected monocytic cell lines (U937), and additive inhibition of HIV-1 growth within chronically infected monocytic cells (U1) and primary placental macrophages (Hofbauer cells). Anti-HIV effects were not seen with another pregnancy steroid hormone, estrogen. In terms of possible mechanisms of action for progesterone, we demonstrated that it incompletely suppressed tat activation of long terminal repeat (LTR)-driven gene expression in monocytic cells. However, the progesterone-mediated suppession of tat activation was not affected by mutation of the three consensus progesterone/androgen/glucocorticoid response elements within the HIV-1 LTR, previously shown by our group to be involved in glucocorticoid-mediated suppression of LTR-driven transcription. It is likely that progesterone suppresses LTR-driven gene expression through a nontranscriptional mechanism, and augments the efficacy of AZT through enhancement of its phosphorylation.

Elevated CD8+DR+ lymphocytes in HIV-exposed infants with early positive HIV cultures: a possible early marker of intrauterine transmission. Women and Infants Transmission Study Group

The associations among timing of maternal-fetal human immunodeficiency virus (HIV) transmission, infant age at first positive HIV culture, and CD8+ lymphocyte activation were examined for 74 perinatally infected infants. Nineteen of the infected infants had positive HIV cultures at < or =7 days of life, and 55 had negative HIV cultures at < or =7 days but were positive later. Of the infants with early positive HIV-1 cultures, 15 of the 17 tested with DNA polymerase chain reaction methods had concordant results. The percentage of CD8+ and HLA-DR+ lymphocytes (CD8+DR+%) during the first week of life was significantly higher in infants with early compared with late positive cultures (median CD8+DR+% of 5.0% versus 2.0%, p = 0.0006). The CD8+DR+% was similar between uninfected infants and infants with late positive cultures during the first week of life (median 2%) but increased in infants with late positive cultures to 6% by 1 month. The CD4+% during the first 6 months of life was not different between infants with early or with late positive cultures, but infants with the highest CD8+DR+% at < or =7 days of life had significantly lower CD4+% at < or =7 days and at 1, 2, and 4 months of age. These data show that early CD8+ lymphocyte activation is associated with early positive HIV cultures and lower CD4+ percentages during early infancy and are consistent with the hypothesis that early positive cultures positivity may indicate in utero HIV infection.

Failure of Neutralizing gp120 Monoclonal Antibodies to Prevent HIV Infection of Choriocarcinoma-Derived Trophoblasts

Although placental trophoblasts, the only fetal cells in direct contact with infectious maternal blood, can be infected with HIV, the precise cause for the low transmission rate of virus across the placental barrier is unknown. One of the most common conjectures is that maternal anti-HIV antibodies (Abs) contribute to the protection of the fetus. This hypothesis has been tested in vitro by infecting the CD4-negative placental trophoblast line, BeWo, with HIV-1(IIIB) in the presence of serial dilutions of neutralizing monoclonal Abs against the V3 loop (No. 694) or CD4-binding conformational domain (No. 588). The results, based on measurement of p24 production from virus-exposed cells, reveal that the titers of Abs, adequate in preventing the infection of control MT-4 T lymphocytes, were less effective in protecting trophoblasts. Furthermore, PCR analysis of HIV DNA formed after a single round of infection has shown no significant decrease in the number of viral copies in Ab-protected BeWo cells. An anti-HIV serum from a pregnant woman did also have no effect. Although our in vitro observations do not necessarily apply to the in vivo situation, the results suggest that the humoral immune response sustained by neutralizing Abs may be able to protect T lymphocytes, but not placental trophoblasts. The findings are consistent with recent clinical studies demonstrating a lack of correlation between the presence of neutralizing anti-HIV Abs in pregnant women and HIV transmission in utero. Copyright 1997 S. Karger AG, Basel

Inflammatory cytokine expression is correlated with the level of human immunodeficiency virus (HIV) transcripts in HIV-infected placental trophoblastic cells

The inflammatory cytokines interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor alpha (TNF-alpha) have been associated with increased human immunodeficiency virus (HIV) expression and enhanced lymphocyte adhesion to trophoblastic cells in experimental systems. To determine if there is a correlation between the expression of these cytokines and the levels of HIV transcripts in trophoblasts of term placentas from HIV-infected women, we studied the placentae of 30 HIV-positive and 13 control gravidae. Twenty-three of the HIV-positive women received zidovudine (ZDV) as prophylaxis against HIV vertical transmission; only one of the seven women who did not receive ZDV was a transmitter, for an overall vertical transmission rate of 3.8%. Cytokine production was measured by enzyme-linked immunosorbent assay in the supernatants of trophoblastic cell cultures. Additionally, cytokine transcripts and HIV gag sequences were determined by a quantitative reverse transcription-PCR assay. In general, trophoblastic cells of HIV-positive placentas expressed significantly higher levels of IL-1beta, IL-6, and TNF-alpha than those of control placentas. All placentas from HIV-positive women expressed HIV gag transcripts at either a low (<156 copies per microg of total RNA) or a high (>156 copies per microg of total RNA) level. There was a statistically significant positive association between the basal level of TNF-alpha production and the level of HIV gag transcripts of HIV-positive placental trophoblastic cells. Nevertheless, these data, coupled with a low transmission rate, would indicate that some other factors, perhaps working in concert with cytokines, are necessary for vertical transmission of HIV from mother to infant.

Worldwide prevention of vertical human immunodeficiency virus (HIV) transmission

Most human immunodeficiency virus (HIV) infected children acquire the infection by perinatal transmission. Strategies for the prevention of perinatal HIV transmission mainly focus on conditions that prevail in industrialized countries, although most of these children are born in areas with less privileged circumstances. This review takes these circumstances into consideration when addressing six potential strategies to reduce perinatal HIV transmission.

Natural and experimental bovine immunodeficiency virus infection in cattle

Since 1989, the LSU dairy herd, with its high seroprevalence of BIV, was recognized to have a high incidence of common diseases that reduced the economic viability of the dairy. The herd had a high percentage of cows with encephalitis associated with depression and stupor, alteration of the immune system associated with secondary bacterial infections, and chronic inflammatory lesions of the feet and legs. The occurrence of disease problems was associated with the stresses of parturition and early lactation and/or with unusual environmental stress cofactors.

Induction of inflammatory cytokines in placental monocytes of gravidae infected with the human immunodeficiency virus type 1

Placental mononuclear cells (PMC) are susceptible to infection with the human immunodeficiency virus (HIV). PMC secreted tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta), and IL-6 among other factors, which, in turn, regulate HIV replication in latently infected cells. We assessed the induction of these cytokines in PMC from HIV-infected (HIV+) and uninfected (control) gravidae following exposure to lipopolysaccharide (LPS), HIV lysate (iHIV), recombinant HIV env (GP160) and HIV gag (gag55), and synthetic HIV p17 (HGP30) antigens. In comparison to control PMC, HIV+ PMC constitutively secreted higher levels of IL-1beta and IL-6 and were refractory to stimulation by iHIV, GP160, gag55, and HGP30. Control PMC IL-1 beta levels were boosted by LPS; gag55 and HGP30 augmented IL-6 but not IL-1 beta. Both groups exhibited low basal TNF-alpha production that was augmented by LPS. HIV+ PMC exhibited higher constitutive levels of IL-1 beta, IL-6, and TNF-alpha gene transcription than control PMC. These levels could be further augmented by LPS, yet the incremental levels were lower than those obtained from PMC of uninfected women. The high basal constitutive secretion of cytokines by HIV+ PMC and their refractoriness to activation may reflect a virus-mediated dysregulation of cytokine expression culminating in compromised host defenses against secondary opportunistic infections associated with AIDS.

Significance of placental damage in vertical transmission of human immunodeficiency virus

The significance of physical breaches of the trophoblastic layer of the placenta in transmission of HIV from mother to infant was evaluated in 17 HIV-infected pregnant women. Samples of peripheral blood were obtained from the women during pregnancy and at delivery, at which time a small piece of placental tissue was obtained from a random site and immediately placed into fixative. Blood samples were obtained from infants at or shortly after birth and thereafter at approximately 3-month intervals, until the age of 18 months, in order to determine their HIV infection status. HIV RNA and p24 antigen were quantified in maternal plasma and CD4 cells enumerated. Paediatric diagnosis was conducted using polymerase chain reaction, virus isolation, detection of p24 antigen, and measurement of class-specific antibodies. Placental damage was quantified and evaluated using transmission electron microscopy. Maternal viral load was low, with a mean RNA copy number of 8,237 per millilitre of plasma (range 230-37,233 copies/ml). Only two women were p24-antigenaemic, and CD4 numbers ranged from 0.09 to 2.8 x 10(9)/l. There was evidence of breaks in the trophoblastic surface to the depth of the basement membrane in all 17 placentas, and perivillous fibrinoid deposits were also observed to a varying degree in all samples. However, none of the 13 infants available for follow-up had evidence of infection with HIV. Superficial damage to the trophoblastic surface of the placenta, with exposure of the basement membrane and potential exposure of CD4-expressing cells, does not appear to be a significant factor in the transmission of HIV from mother to infant during pregnancy.

Paediatric HIV infection

By the year 2000 there will be six million pregnant women and five to ten million children infected with HIV-1. Intervention strategies have been planned and in some instances already started. A timely and cost-effective strategy needs to take into account that most HIV-1 infected individuals reside in developing countries. Further studies are needed on immunological and virological factors affecting HIV-1 transmission from mother to child, on differential disease progression in affected children, and on transient infection.