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

Frequent perinatal transmission of feline immunodeficiency virus by chronically infected cats

Vertical transmission of feline immunodeficiency virus (FIV) was studied in cats infected with either of two FIV clinical isolates (FIV-B-2542 or FIV-AB-2771) prior to breeding and conception. Queens infected 4 to 30 months (mean = 14 months) prior to conception transmitted FIV to 59 of 83 (71%) kittens; 50.6% were virus positive on the day of birth. To examine potential routes of FIV transmission from mother to offspring, kittens were delivered via either vaginal or cesarean birth and nursed by either their virus-infected natural mothers or uninfected surrogate mothers. Comparison of FIV infection rates at birth with those at 6 months of age in kittens delivered by cesarean and surrogate raised demonstrated that late in utero transmission occurred in approximately 20% of kittens. Comparison of kittens nursed by FIV mothers with those by uninfected surrogate mothers demonstrated a 13.5% increase in infection rate of kittens exposed to milk-borne virus. Isolation of virus from 40% of maternal vaginal wash samples and the slightly greater infection rate in vaginally versus cesarean-delivered surrogate-nursed kittens suggested that intrapartum transmission may occur. In addition, we found that low maternal CD4 count (<200 cells per microl), longer duration of maternal infection (>15 months), and maternal symptoms of clinical immunodeficiency correlated with increased rates of mother-to-kitten FIV transmission, paralleling observations in human immunodeficiency virus-infected women. We conclude that FIV infection provides a model in which to explore aspects of human immunodeficiency virus vertical transmission and intervention difficult to address in human patients.

Productive HIV-1 infection of human vascular endothelial cells requires cell proliferation and is stimulated by combined treatment with interleukin-1 beta plus tumor necrosis factor-alpha

Vascular endothelial cells (EC) play a key role in viral tropism in vivo. Since conflicting reports have been published on the capability of HIV to infect EC in vitro, we analyzed some factors potentially capable of influencing the susceptibility of human umbilical vein endothelial cells (HUVEC) to HIV-1. Both primary cultures and differentiated immortalized HUVEC lines were used. HUVEC were negative for the expression of CD4, but weakly CD26- and galactosylceramide-positive. Although binding of HIV to EC was substantial, the virus was apparently incapable of replicating in nonproliferating cultures. In resting cultures, the content of cell-associated HIV disappeared 4-6 days after infection without production of p24 and infectious progency. In contrast, infection of proliferating EC cultures led to the transient release of p24 and infectious virus (10(2.5)-10(3.5) SFU/ml) peaking 2-6 days postinfection. Antibody neutralization of cytokines that may be produced by EC (IL1, IL6, IL8, TNF, IFN-beta) failed to modify virus adsorption and replication, whereas treatment with IL1-beta plus TNF-alpha stimulated both virus binding and virus release. As seen by gag polymerase chain reaction (PCR), the viral genome persisted up to 15 days in untreated EC cultures, but over 20 days in cultures exposed to IL1-beta plus TNF-alpha. This study shows that: (a) CD4-negative HUVEC are capable of binding substantial amounts of HIV-1; (b) binding is enhanced by proinflammatory cytokines; (c) the establishment of productive infection is favored by cell proliferation; and (d) exposure to IL1-beta plus TNF-alpha enhances virus replication.

Regulation of human immunodeficiency virus type 1 and cytokine gene expression in myeloid cells by NF-kappa B/Rel transcription factors

CD4+ macrophages in tissues such as lung, skin, and lymph nodes, promyelocytic cells in bone marrow, and peripheral blood monocytes serve as important targets and reservoirs for human immunodeficiency virus type 1 (HIV-1) replication. HIV-1-infected myeloid cells are often diminished in their ability to participate in chemotaxis, phagocytosis, and intracellular killing. HIV-1 infection of myeloid cells can lead to the expression of surface receptors associated with cellular activation and/or differentiation that increase the responsiveness of these cells to cytokines secreted by neighboring cells as well as to bacteria or other pathogens. Enhancement of HIV-1 replication is related in part to increased DNA-binding activity of cellular transcription factors such as NF-kappa B. NF-kappa B binds to the HIV-1 enhancer region of the long terminal repeat and contributes to the inducibility of HIV-1 gene expression in response to multiple activating agents. Phosphorylation and degradation of the cytoplasmic inhibitor I kappa B alpha are crucial regulatory events in the activation of NF-kappa B DNA-binding activity. Both N- and C-terminal residues of I kappa B alpha are required for inducer-mediated degradation. Chronic HIV-1 infection of myeloid cells leads to constitutive NF-kappa B DNA-binding activity and provides an intranuclear environment capable of perpetuating HIV-1 replication. Increased intracellular stores of latent NF-kappa B may also result in rapid inducibility of NF-kappa B-dependent cytokine gene expression. In response to secondary pathogenic infections or antigenic challenge, cytokine gene expression is rapidly induced, enhanced, and sustained over prolonged periods in HIV-1-infected myeloid cells compared with uninfected cells. Elevated levels of several inflammatory cytokines have been detected in the sera of HIV-1-infected individuals. Secretion of myeloid cell-derived cytokines may both increase virus production and contribute to AIDS-associated disorders.

Simian immunodeficiency virus infection of macaque primary placental cells

We have characterized the ability of a simian immunodeficiency virus, SIVmne strain E11S, to infect macaque placental trophoblast and Hofbauer cells. These primary placental cells were permissive to SIVmne infection, regardless of gestational age. Virus production by the infected cells was determined as time-dependent viral core antigen p27 production, followed by verification of the proviral gag/LTR DNA sequences in the infected cells using a polymerase chain reaction assay. Of more than six placentas tested, SIVmne infection of placental cells at an early gestational age (i.e., days 55 or 78) produced more than 10-fold the amount of virus core antigen p27 than did placental cells infected at a late gestational age (i.e., days 135 or 165). In addition, SIVmne infection of trophoblast cells was inhibited by SIVmac neutralizing macaque serum but not by normal serum, indicating the specificity of virus infection. Furthermore, the amount of SIV core antigen p27 produced by the virus-infected trophoblast and Hofbauer cells was shown to be dependent on the multiplicity of virus infection. Collectively, our results indicate that macaque trophoblast and Hofbauer cells can be infected by SIV and that both gestational age and viral dose may play a role in the extent of viral infection.

Levels of the circulating cell adhesion molecule E-selectin and disease progression in HIV infection

The levels of soluble form of E-Selectin (sEs), or endothelial-leukocyte adhesion molecule-1, were measured in 96 sera derived from 72 HIV-infected patients at different stages of the disease, 60 healthy blood donors, and 50 HIV-negative patients with infections, using a quantitative ELISA. Levels of sEs in HIV-infected individuals without AIDS, according to the 1993 classification system of the Centers for Disease Control, were higher than normal (mean +/- SEM 48 +/- 4 versus 35 +/- 3 ng/ml, p = 0.003). Patients with established AIDS, who were afebrile and had no evidence of acute concurrent infection, had even higher sEs serum levels (70 +/- 9 ng/ml, p = 0.009, compared to those without AIDS). A significant increase in clinical category disease progression was present. Individual concentrations of sEs correlated directly with levels of soluble intercellular adhesion molecule-1 (p < 0.00001) and IL-2 receptor (p = 0.001), but not with CD4+ T-cell counts. Zidovudine treatment was not associated with changes in sEs serum levels. Elevated sEs levels were also found in HIV-seronegative patients with other bacterial and protozoal infections. Since sEs is a biologically active molecule, further studies should investigate the pathogenetic significance of circulating sEs in HIV-related disease progression, and assess the prognostic value of sEs determination for these patients.

Protective effect of interferon-alpha against cell-mediated human immunodeficiency virus transmission resulting from coculture of infected lymphocytes with fetal trophoblasts

The hypothesis that the low transmission rate of HIV in utero may be due, in part, to the protective effect of IFN-producing placental trophoblasts was explored in vitro. The model consisted of H9 lymphocytes, as surrogates of maternal HIV-infected T cells, incubated for 3 h with JEG-3 trophoblasts in the presence of 10-fold dilutions of leukocyte-derived IFN-alpha (from 1000 to 0.1 IU/ml). The dose effect was monitored either directly, by measuring the levels of proviral DNA by PCR after a single round of infection, or indirectly, by coculturing infected JEG-3 with cord blood-derived MT-4 lymphocytes and determining the levels of p24 production by ELISA. Both assays revealed a dose-dependent blocking effect of IFN-alpha on cell-mediated HIV transmission. The complete inhibition of HIV infection was observed in the presence of 100 IU IFN-alpha. The efficacy of such a low dose could not be attributed to insufficient viral load because up to 10(8) infectious particles could be transmitted during cell-cell contact. An adhesion assay ruled out the possibility that IFN-alpha acts through prevention of lymphocyte-trophoblast contact. The results suggest that physiologic levels of IFN-alpha, present in the placental environment, may contribute to the protection of the fetus against HIV infection.

Similarity in env and gag genes between genomic RNAs of human immunodeficiency virus type 1 (HIV-1) from mother and infant is unrelated to time of HIV-1 RNA positivity in the child

Variation in the env (V3 region) and gag (p17 region) genes of genomic RNA of human immunodeficiency virus type 1 was studied in three mother-child pairs. One infant was human immunodeficiency virus type 1 RNA positive at birth (pair 114), one became positive 6 weeks after birth (pair 127), and one became positive 30 months after birth (pair 564). The first two children were born to seropositive mothers, and the last child was infected by breast-feeding following seroconversion of the mother after delivery. In both V3 and p17gag, intrasample variability was much higher in the maternal samples, including the first seropositive sample of the seroconverted mother, than in the infants' samples. Variability was less in p17gag than in V3, except in the postnatally infected child. In all three cases, infection of the child was established by variants representing a minority of the cell-free virus population in the maternal samples. For the two infants born to seropositive mothers, V3 sequences were more similar to the sequence populations of maternal samples collected during pregnancy than to those of samples collected at delivery or thereafter. However, in pair 114 a V3 variant identical to the child's virus was also detected in the sample collected at delivery. In contrast to the V3 region, p17gag sequences of maternal samples of the first trimester of pregnancy and at delivery had comparable resemblance to the child's sequences in pair 114, while in pair 127, similarity to sequences of the sample collected at delivery was higher than that to sequences of the sample from early in pregnancy. In the last pair, V3 and p17gag sequences from a maternal sample collected 18 months prior to the first RNA-positive sample of the child resembled the infant's sequences as much as the sample collected close to the presumed time of infection. Taken together, the evolutionary characteristics for genomic RNA env and gag genes did not point to a particular time of mother-to-child transmission.

Aids em crianças: considerações sobre a transmissão vertical

Trata-se de uma revisão sobre os aspectos epidemiológicos da síndrome de imunodeficiência adquirida em crianças e sobre a transmissão vertical do vírus da imunodeficiência humana (HIV). Discutem-se as diversas vias pelas quais o HIV pode transmitir-se de mãe para filho, abordando questões inerentes à fisiopatologia da infecção intra-útero, periparto e/ou pós-parto.

Adherence of human immunodeficiency virus-infected lymphocytes to fetal placental cells: a model of maternal --> fetal transmission

The precise timing and mechanism of in utero human immunodeficiency virus (HIV) infection are unknown, but transplacental transmission is likely. Term placentas from HIV+ pregnancies contain only rare HIV-infected cells whose origins and phenotypes remain controversial, and no correlation has been found between the presence of HIV in term placentas and transmission to offspring. Reports of trophoblast infectibility have not been reproducible and do not address the question of infection in the placental stroma, the cells in direct contact with fetal circulation. We report that primary cultures of fetal placental chorionic villus stromal cells, while not infectable in vitro, do support lethally irradiated HIV-infected peripheral blood mononuclear cells (PBMCs) in a form that permits rescue of HIV by activated PBMCs weeks later. Infected PBMCs adhere and become intimately associated with placental cells by a mechanism that is LFA-1 and CD4 independent but can be blocked by antibodies or soluble CD4 binding to cell surface-expressed HIV envelope. The ability to sustain infected irradiated cells was not shared by several trophoblast, fibroblast, or epithelial cell lines. This model has several features that are compatible with in utero transmission and allow testing of various agents proposed as interventions to block maternal-->fetal transmission. Placental stromal cells appear to inhibit apoptosis of HIV-infected, irradiated lymphocytes.

Concurrence of high levels of interferons alpha and beta in cord and maternal blood and simultaneous presence of interferon in trophoblast in an African population

A high concentration of interferon-alpha (IFN-alpha) (> 5 U/ml) in cord blood was used as the criterion for establishing our study group. In a collection from deliveries by 269 Kenyan women, 16 such cord samples with matching maternal blood and placental biopsies were identified. These 16 were studied in detail together with 23 randomly selected among those with low cord IFN-alpha levels. The levels of IFN- in retal blood correlated with levels in their mothers for both IFN-alpha and beta but not for IFN-gamma. IFN-alpha was furthermore demonstrated in villous and decidual trophoblast from 15 (94%) placentae from donors with high IFN-alpha in the cord blood but not in the placenta of any low IFN level donors. In contrast, IFN-beta was not demonstrated in any placenta. These observations suggest simultaneous IFN induction in the three compartments, transplacental IFN transport, or trophoblast production of IFN to both circulations. Looking for IFN inducers, we did serologic tests for nonspecific indicators of inflammation and for specific virus and protozoan infections, but these showed no relation to elevated IFN levels. Immunohistology also revealed no evidence of a number of placental infections. The cause of the high levels of IFN-alpha could still be infectious but remains unexplained and may be noninfectious.

[Maternal-fetal transmission of HIV]

HIV infection in children is mainly the result of a mother-to-child transmission. The contamination during pregnancy is well known but intrapartum vertical transmission may also occur through ascending infection, blood exchange between mother and child, or direct contact with vaginal or cervical secretions. In addition HIV can be transmitted via breast milk. The reported rates of vertical transmission are highly variable: 14.4% in a European study, 18.3% in a French survey, 20 to 25% in the USA, 35 to 50% in Africa. It is unclear whether such a large variation of the rate of transmission is due to methodological differences or to different distributions of risk factors in the populations. There are some known predictive factors of HIV transmission such as low CD4 cells count, positive p24 antigenaemia and elevated concentrations of virus. The role of other factors is still debated: prematurity, virus (CMV, HTLV-1, HVB, HVC), C section prior labour, rupture of membranes. The prevention of HIV infection in infants is mainly based on contra-indication of pregnancy in infected women, desinfection of the vagina at the beginning of labour, early protection of the newborn by avoiding skin lesions and immediate washing, preventive treatment by zidovudin during pregnancy.

Mother-to-infant HIV transmission: timing, risk factors and prevention

Identifying when--during pregnancy, delivery or the postnatal period--transmission of human immunodeficiency virus (HIV) from mother to infant usually takes place is critical to the development of methods to prevent maternal-infant transmission. Evidence is reviewed in this paper as to whether transmission occurs prepartum (early or late in gestation), intrapartum, or postpartum with breast feeding. Evidence in support of the notion of prepartum transmission has come from isolation of HIV from aborted fetal organs, comparison of maternal-child viral genotypes and study of neonatal cell-mediated immune responses. Evidence against prepartum transmission is that fewer than half of the children later known to be HIV-infected can be identified by virological tests carried out close to birth. A reduced rate of transmission in infants delivered by Caesarean section, and a reduced risk of transmission to second-born twins delivered vaginally, offers support to the view that intrapartum factors influence the risk of HIV transmission. Transmission through breast feeding can occur if a mother is infected postpartum and seems to pose some additional risk if she is already infected at parturition. The risk of infection increases with the stage of maternal HIV disease, but specific immunological, clinical and viral characteristics need to be investigated further. A clinical trial of zidovudine, used during late pregnancy and delivery and given to the infant at birth, has reported a significant reduction in transmission. Primary prevention of HIV infection in women remains a principal priority.

Vertical transmission of feline immunodeficiency virus

We studied vertical transmission of feline immunodeficiency virus (FIV) to determine whether it might provide a model with which to study intervention strategies for mother-to-offspring transmission of human immunodeficiency virus (HIV). We found that pregnant cats acutely infected with FIV (FIV-CSU-2771) transmitted the virus to their offspring via both prenatal and postnatal routes. In utero transmission led to several pathogenic consequences including arrested fetal development, abortion, stillbirth, subnormal birth weights, and birth of viable, virus-infected, and asymptomatic but T cell-deficient kittens. Postnatal milk-borne FIV transmission was demonstrated by the presence of cell-free and cell-associated virus in colostrum and milk and through a foster-nursing experiment. The potential for intrapartum FIV transmission was documented by frequent virus isolation from vaginal wash cells in both the pre- and postpartum periods. FIV transmission was efficient during acute maternal infection, leading to an overall infection rate of 70%. We conclude that FIV vertical transmission may be a useful model with which to evaluate intervention strategies for HIV transmission from mother to child.

Perinatal transmission of HIV type 1: associations with maternal anti-HIV serological reactivity. Mothers and Infants Cohort Study and the HIV-1 Perinatal Serology Working Group

As a hypothesis-generating study of large regions of the human immunodeficiency virus type 1 (HIV-1) envelope, we collaborated with several laboratories to test sera from subgroups of 65 HIV-1-positive pregnant women, 18 (28%) of whom transmitted the virus to their infants. Assays included neutralizing antibodies to HIVLAI and reactivity to 102 HIV-1 Env peptides with sequences based on strains LAI, MN, SC, RF, and WMJ-2 as well as several clinical isolates, spanning about 65% of gp120 and about 80% of gp41. Results for the V3 loop and for neutralizing activity were conflicting and for the most part did not reach statistical significance. Transmission risk appeared lower with reactivity to a few gp41 epitopes (amino acids 571-585, 736-750, and perhaps 650-663), whereas risk appeared higher with reactivity to two gp120 epitopes (amino acids 466-480 and 475-486) and one gp41 epitope (amino acids 547-576). However, these associations could have occurred simply by chance because such a large number of peptides was tested. With independently synthesized peptides, results between laboratories often were inconsistent. However, reproducibility was good (rank correlation coefficient > or = 0.78) when the same protocols and peptides were used. Although this study could not identify a humoral immune response to linear Env peptides that consistently and broadly protected against perinatal transmission of HIV-1, there were regions of gp120 and gp41 that should be evaluated in larger cohorts and with techniques to investigate potential conformational epitopes and neutralization to autologous or clinical isolates of HIV-1 from the community.

Epidemiology of HIV infection in children in Europe

In Europe the Human Immunodeficiency Virus (HIV) epidemic in children is an important public health problem. Reliable epidemiological information varies widely among countries, and there is no standard method to document the pandemia. By September 1992, a total of 81,849 AIDS cases were identified. France had 21,487, Spain 15,678 and Italy 14,784 (63% of all cases). The highest rate per 100,000 inhabitants occurred in Spain (88.9), France had 70.6 and Italy 63.5. The numbers of HIV+ newborns (NB) in Spain were 4673, in Italy 2,693, in Belgium 368, in Scotland 79 and in Holland 11. The highest rate of HIV+ NBs per 100,000 inhabitants occurred in Spain (120.1), the lowest in Holland (0.73). In Western Europe, 82% of all cases were due to vertical transmission. Mothers' venous drug use was the most common form of HIV transmission.

Metabolism of 3'-azido-3'-deoxythymidine (AZT) in human placental trophoblasts and Hofbauer cells

3'-Azido-3'-deoxythymidine (AZT) is currently under clinical investigation to assess its potential to inhibit maternal-fetal HIV transmission. To determine the activation of AZT to its phosphorylated metabolites by placental cells, we characterized the intracellular phosphorylation of AZT in two major cell types of the placenta, namely trophoblasts and Hofbauer cells. Although phosphorylation of AZT in trophoblast and Hofbauer cells is 50- to 100-fold lower than that in human lymphocytic cell lines or activated lymphocytes, both cell types are capable of activating AZT to AZT triphosphate (AZTTP) at a level comparable to that of resting lymphocytes. We found that AZT monophosphate (AZTMP) was the major phosphorylated AZT metabolite, while AZT diphosphate (AZTDP) and AZTTP constituted less than 4% of the intracellular phosphorylated AZT pool. This result was independent of AZT concentration and exposure time in both types of placental cells. The rate-limiting step in the conversion of AZT to AZTTP was determined to be thymidylate kinase-catalyzed conversion of AZTMP to AZTDP. Trophoblasts and Hofbauer cells exhibited different time-course and concentration-dependent profiles of intracellular AZT phosphorylation, suggesting that these two placental cells may have anabolic or catabolic enzymes of different composition or efficiency. AZTTP decayed in both trophoblasts and Hofbauer cells with a half-life of 4-6 hr. These results should be useful in rationally designing AZT dosage regimens to treat HIV-infected women for prevention of maternal-fetal HIV transmission.

Feline immunodeficiency virus can be experimentally transmitted via milk during acute maternal infection

Postnatal transmission of feline immunodeficiency virus (FIV) in neonates nursed by acutely infected mothers and infection resulting from oral inoculation of kittens with FIV were evaluated. Ten of 16 kittens nursed by four queens with FIV infection established immediately postpartum developed FIV infection. Five of 11 neonates orally administered cell-free FIV culture supernatant developed FIV infection. Kittens that developed FIV infection had greater proportions of CD4+ and Pan-T+ lymphocytes at birth than negative kittens. Infectious virus was recovered from the milk of acutely infected mothers. We conclude that FIV may be experimentally transmitted via milk from queens with acute infections and that oral administration of FIV to neonatal kittens results in infection.

Detection of congenital cytomegalovirus infection by using chorionic villi of the early pregnancy and polymerase chain reaction

OBJECTIVE

To detect congenital cytomegalovirus (CMV) infection of chorionic villi in early pregnancy.

METHODS

Extraction of DNA of chorionic villi and amplification of the gene of major immediate-early (MIE) antigen of CMV using a polymerase chain reaction (PCR).

RESULTS

Sixty-eight specimens of chorionic villi and 16 specimens were positive for CMV infection by PCR. The incidence of congenital CMV infection in the first trimester of pregnancy was 23.5%.

CONCLUSIONS

The risk of transmission of CMV from mother to fetus in early pregnancy is very high and potential CMV carriers may transmit CMV to their fetus in early pregnancy.

Primary cultures of rhesus placental syncytiotrophoblasts are permissive for SIV infection

Primary cultures of rhesus syncytiotrophoblasts incubated with SIVdeltaB670, SIVmac251, or SIVmac239 produced readily detectable virus in the supernatant for up to three weeks after infection. At four weeks, cells generally failed to release virus but placental cell lysates and placental cells cocultured for 24 hours with uninfected CEM x 174 cells were able to transmit infection. The presence of virus was confirmed by electron microscopy and PCR amplification of viral sequences from trophoblast genomic DNA. SIV p27 antigen was localized by immunostaining primarily in syncytiotrophoblasts.

Studies on the placental transfer of cell-free human immunodeficiency virus and p24 antigen in an ex vivo human placental model

OBJECTIVE

We studied whether the human placenta has the structural integrity to impede transplacental passage of cell-free human immunodeficiency virus (HIV)-1 or p24 antigen from the maternal to the fetal circulation.

METHODS

Nine term human placentas from uncomplicated vaginal or cesarean section deliveries were studied ex vivo with a placental perfusion apparatus to determine whether cell-free HIV-1 at 200-2000 tissue culture infectious dose (TCID50/mL) would pass to the fetal circulation. Passage of virus or p24 was assessed by infectivity titration and/or p24 antigen capture enzyme immunoassay.

RESULTS

Infectious HIV-1 was not detected in any of the fetal perfusate samples taken periodically during experiments. Low concentrations of HIV-1 p24 antigen, however, were detected in fetal perfusate samples from three placentas.

CONCLUSIONS

The term human placenta effectively impedes passage of cell-free HIV-1 from the maternal to the fetal circulation. However, it may be permeable to passage of p24 antigen.

Maternally acquired immunity in newborns from women infected by the human immunodeficiency virus

Maternally acquired immunity was studied in 16 pairs of human immunodeficiency virus (HIV)-seropositive women and their newborns, and was compared to 18 control mother-newborn pairs. The HIV-infected women had higher IgG levels than the control subjects, but no difference was observed between newborn samples, presumably due to the limited placental IgG transfer in the HIV group. A poor type 2 poliovirus antibody transfer was also noted in this group. The population of newborns lacking demonstrable measles antibodies was higher in the HIV group than in the control group, probably because many of the HIV-infected mothers lacked measles antibodies also. These results show that maternally acquired immunity may be affected to newborns from HIV-infected women, either because of low maternal serum antibody levels or deficient transplacental transfer. If so, the measles vaccine schedule should be revised for these children and the same should be done for future passive immunization regarding fetus protection in pregnant HIV-seropositive women.

Human immunodeficiency virus infection of early passage cervical epithelial cultures

Women are infected with HIV in increasing numbers; the predominant mode of spread is through heterosexual transmission. Little is known regarding the mechanism of HIV transit through the female genital tract. We investigated whether early passage cervical epithelial cells could be directly infected with HIV-1LAI. Virus production was measured using the reverse transcriptase (RT) assay and direct assay for syncytia-forming units. In-situ hybridization was performed on infected cervical cell cultures. Immunostaining was carried out using a monoclonal antibody to leukocyte common antigen (LCA). Virus was recovered in the supernatants of all infected cervical cultures. Localization of HIV infection using in-situ hybridization identified rare cells in the population which gave a strong signal. These infected cells had a lymphoid morphology and were also detected using immunostaining for LAC. Cervical epithelial cells were uninfected in this in vitro model; cells in this population which supported viral replication were most likely of the macrophage/monocyte lineage.

The foamy virus family: molecular biology, epidemiology and neuropathology

The family of foamy viruses designates a group of retroviruses which share a specific morphology and provoke characteristic cytopathic effects in cultured cells. Like HTLV and HIV, foamy viruses are complex viruses encoding a number of ancillary genes in addition to gag, pol and env, including a transcriptional transactivator. Foamy viruses are endemic in various primate species, and human foamy viruses (HFV) have been isolated from patients with various neoplastic and degenerative diseases. Despite a growing body of knowledge on the biology of foamy viruses, it has not yet been possible to identify a disease specifically caused by foamy virus infection. After reviewing the epidemiology and molecular biology of the various animal foamy viruses, this article focuses on the pathogenic properties of HFV in transgenic mouse systems. HFV transgenes exhibit a striking neurotropism and elicit a progressive degenerative disease of the central nervous system and striated muscle. Similarly to patients with HIV-associated encephalopathy, HFV transgenic mice develop accumulations of syncytial giant cells in their brains. The relevance of these findings for human neuropathology is discussed.

Pediatric infection with the human immunodeficiency virus (HIV): head, neck, and oral manifestations

The increasing incidence of HIV infection in the pediatric population is of concern for the practicing dentist. Long incubation periods of the virus, combined with difficulty in detection, results in many undiagnosed cases of prenatal and natal infections with HIV. As a result, many dentists will unknowingly treat HIV-positive children. This article presents most common features of pediatric HIV infection, placing special emphasis on manifestations which affect the head, neck, and oral tissues.

Human immunodeficiency virus infection in pregnancy

Human immunodeficiency virus (HIV) infection in women is an increasing problem. World wide, at least 25% of all infections occur in adolescent or adult women, most of whom are of child-bearing age. The commonest modes of acquisition of HIV infection are sexual contact with an HIV-infected male and sharing needles during injecting drug use. Vertical transmission is the major route of HIV infection in infants and children and can occur in utero, intrapartum, through exposure to infected blood or secretions, or post partum, via breast milk. HIV infection has not been demonstrated to affect fertility, or to influence the outcome of pregnancy unless there is evidence of significant immune dysfunction, with CD4 counts below 400/mm3. Though data are limited, pregnancy does not appear to affect the course of HIV infection. Low CD4 counts predispose women to the opportunistic infectious complications of HIV. Pathogens include Candida sp., Mycobacterium tuberculosis, Pneumocystis carinii, Toxoplasma gondii, Cryptococcus neoformans and Cryptosporidium. These pathogens require early recognition and diagnosis if optimal treatment and outcome are to be attained. Treatment with zidovudine and prophylaxis against Pneumocystis carinii are appropriate when CD4 counts are less than 200/mm3, though the safety of zidovudine in early pregnancy is not known. Similarly it is not known whether zidovudine treatment of the mother prevents transmission of HIV infection to her baby. Caesarean section does not prevent peripartum transmission of HIV and should be undertaken only for other appropriate indications. The utility of antenatal screening for HIV depends upon the seroprevalence in the population. Such programmes must be supported by comprehensive clinical care as well as sensitive and non-judgemental counselling.

High levels of 2',5'-oligoadenylate synthetase and 2',5'-oligoadenylate-dependent endonuclease in human trophoblast

Human placenta contains a high level of 2',5'-oligoadenylate (2-5A) synthetase activity of the 100-kD form of the enzyme. About 20% of the placental 2-5A synthetase activity was found to be cytosolic, whereas the remaining 80% was released by 0.5 M KCl in the presence of detergent. Most of the enzyme activity was localized in trophoblast cells, which also contain a high level of 2-5A-dependent RNase L activity. The purified trophoblast 100-kD 2-5A synthetase was shown to be activated by human immunodeficiency virus type 1 (HIV-1) 5' RNA 1-311 and 1-707, which both contain the TAR and primer binding site (PBS) structured regions. These two HIV-1 RNAs activated human trophoblast 2-5A synthetase at the same level as poly(I).poly (C), a standard highly efficient activator of the enzyme, and at the same optimal concentration. On the contrary, HIV-1 RNA 311-618, a poorly structured region missing TAR and PBS, was shown to be a poor activator of the enzyme. The specific cellular location of the 2-5A synthetase and its efficient activation by HIV 5' RNA favors the idea that the trophoblast 2-5A system negatively controls HIV replication in trophoblasts.

The distribution of factor XIIIa-positive cells in the human fetus and placenta

Immunohistochemical staining for factor XIIIa, a transglutaminase, revealed a variety of positively stained cells in human fetal tissues. Factor XIIIa-positive cells were most numerous in the dermis and connective tissues. Numerous large, stellate cells in placental villi, decidua, and chorionic membranes also expressed factor XIIIa at 7-9 weeks gestational age, before the onset of fetal hematopoiesis. There was heterogeneity in the staining for factor XIIIa in the early and late fetal tissues, in both rounded and in dendritic cells. In preparations of consecutive sections and in double-labelling experiments, some cells expressed both factor XIIIa and certain monocyte markers and were identified in close association with blood vessels and lymphoid organs in the late fetus and in the placental villi at the end of gestation. Other rounded and dendritic cells expressed factor XIIIa but not monocyte markers, and were found in adult and fetal connective tissues at all gestational ages. These results suggest that there are two factor XIIIa-positive cell populations. One population is present at all developmental stages, does not express monocyte markers, and probably differentiates in situ from primitive mesenchyme. The other population appears mainly after the onset of fetal hematopoiesis, coexpresses some monocyte markers, is HLA-DR positive and may be capable of antigen presentation.

Cytomegalovirus infection of the human placenta: an immunocytochemical study

In congenital cytomegalovirus (CMV) infection histologic evaluation of the placenta is often unrevealing. In the present study immunocytochemistry to CMV immediate early and early nuclear antigens was used to characterize placental involvement in six cases of symptomatic intrauterine CMV infection. Histologic examination had demonstrated diagnostic viral inclusions in one placenta and non-specific villitis in another. However, immunocytochemistry revealed CMV infection in five of the six placentas, including three with no pathologic changes on routine histologic evaluation. Infected cells were located primarily in the villous stroma. In one case immunoperoxidase staining showed infection in the syncytiotrophoblast. Infected endothelial cells were demonstrated by double staining for CMV and factor VIII antigen. No double-stained cells were seen in tissue sections stained for CMV immediate early nuclear antigen or the human macrophage-associated CD68 antigen, which is expressed in Hofbauer cells. In conclusion, specific immunoperoxidase staining was more sensitive for demonstrating placental CMV infection than was histologic examination and it aided in the characterization of infected cells.

Demonstration of HIV-1 infected cells in human placenta by in situ hybridisation and immunostaining

AIMS

To show the presence of HIV infected cells in the placentas and membranes exposed to HIV during pregnancy, and to trace the possible transmission routes from mother to fetus.

METHODS

Twenty three therapeutic abortions and 11 term placentas were investigated for the presence of HIV antigen by immunostaining with HIV core protein specific antibodies and HIV nucleic acids by in situ hydridisation (ISH) with a 35S-labelled HIV specific RNA probe.

RESULTS

HIV antigen as well as HIV RNA positive cells were rarely found in placental tissue and membranes. In therapeutic abortions HIV antigen was shown in 10 out of 23 placentas, HIV RNA in two. HIV antigen was detected in five out of 11 term placentas and HIV RNA in two. Infected cell types comprised syncytiotrophoblasts, Hofbauer cells, amnionic epithelium, chorionic macrophages as well as maternal lymphocytes in the intervillous space and decidua.

CONCLUSION

These data suggest that the transmission routes are: (1) a haematogenous route from the maternal intervillous space to villous stromal cells; (2) from chorion laeve to amnionic fluid and vice versa. Two additional transmission routes are partly suggested by the data: (1) in early gestation by direct extension from basal decidua to budding trophoblastic cells; (2) from the capsular decidua to chorion laeve and chorionic plate, entering the fetal circulation via the small veins.

Cytotoxic T lymphocyte responses in the peripheral blood of children born to human immunodeficiency virus-1-infected mothers

Cytotoxic T lymphocytes (CTL) are present at high activities in adult patients infected with the human immunodeficiency virus (HIV). In this report, CTL effectors were identified in peripheral blood mononuclear cells (PBMC) of children born to HIV-1-infected mothers. These CTL killed HLA-matched HIV-1-infected H9 target cells or doubly transfected P815-A2-env, gag or nef mouse tumor cells, which expressed the viral antigens in association with HLA-A1/A3 or HLA-A2, respectively. HIV-1-specific CTL were detected early after birth (less than 2 months) and remained present during the asymptomatic phase of the infection. As in HIV-1-infected adults, HIV-specific CTL declined with disease progression. Surprisingly, HIV-1-specific CTL were detected in the PBMC of three children who subsequently became seronegative.