Human trophoblast interferon: pattern of response to priming and superinduction of purified term trophoblast and choriocarcinoma cells

Placental interferons

Trophectoderm of ruminant conceptuses (embryo and associated membranes) secrete tau interferons (IFN tau) as the pregnancy recognition signal. Secretion of IFN tau on gestational days 12-13 for sheep and gestation days 14-17 for cows and goats is critical for pregnancy recognition. IFN tau acts on uterine epithelium to suppress estrogen receptor and oxytocin receptor gene expression, which prevents uterine release of luteolytic pulses of prostaglandin F2 alpha (PGF). Expression of the progesterone receptor (PR) gene in uterine endometrium is not affected by oIFN tau. Maintenance of progesterone secretion by the corpus luteum (CL) ensures establishment of pregnancy. Pig conceptuses secrete both IFN alpha and IFN gamma between days 15-21 of gestation, but their role(s) in early pregnancy is unknown. Estrogen secreted by pig trophoblast between gestational days 11-13 and 15-25 increases endometrial receptors for prolactin and causes exocrine secretion of PGF into the uterine lumen to prevent luteolysis. Shared cell-signaling mechanisms by IFNs and lactogenic hormones through Janus kinases (JAK) 1 and 2 may provide a common pathway to abrogate luteolytic mechanisms to ensure establishment of pregnancy. The role(s) of IFNs produced by human and rodent placentae is not known.

Hepatitis C virus infection in pregnancy

OBJECTIVES

To evaluate the clinical aspects of hepatitis C virus (HCV) liver disease in anti-HCV+ve mothers, both during pregnancy and six months after delivery, and to assess the outcome of pregnancy.

SETTING

Obstetric department for high risk pregnancies of the University of Padova, Italy.

PARTICIPANTS

Seventeen hundred consecutive pregnant women were studied.

METHODS

Each woman underwent the following: 1. serological screening for hepatitis surface antigen (HBsAg), antibodies to HCV (anti-HCV), antibodies to human immunodeficiency virus type 1 (HIV1) within the first trimester of pregnancy; and 2. clinico-biochemical assessment in order to ascertain previous or active liver disease and risk factors for viral infections.

RESULTS

Twenty-nine (1.7%) of the 1700 women were found anti-HCV positive. Eight of them had an associated positivity for HIV infection. HCV-RNA was positive in 64.2% of anti-HCV positive women. Liver function tests (included transaminases) were within the normal range in 27 mothers (both during and six months after delivery). Only 2/29 women had a slight increase in AST/ALT; liver biopsy in these cases was compatible with mild chronic active chronic active hepatitis. In all women the outcome of pregnancy was favourable (12/29 anti-HCV positive mothers underwent caesarean delivery for causes independent from HCV infection).

CONCLUSIONS

A substantial proportion of anti-HCV positive pregnant mothers, even if asymptomatic, have circulating HCV-RNA. The pregnancy does not induce a deterioration of liver disease, and vice versa, HCV infection does not increase the risk of obstetric complications.

Human trophoblast interferons enhance major histocompatibility complex class I antigen expression on human term trophoblast cells in culture

The expression and regulation of major histocompatibility complex class I (MHC class I) antigens by virus-induced human trophoblast interferons (tro-IFNs) were examined in term trophoblast cultures. Flow cytometry studies using fluorescence monoclonal antibodies against MHC class I antigens revealed that isolated cytotrophoblasts can express MHC class I antigens. The expression of these antigens increased with stimulation of trophoblast cultures with tro-IFN-alpha and -beta. One hundred IU tro-IFN-alpha and -beta/ml induced no significant higher levels of MHC class I antigens as compared with the control, whereas 1000 IU tro-IFN-alpha and -beta/ml did. The tro-IFN-enhanced expression of MHC class I antigens may be important as it increases the efficiency of local and viral antigen presentation, cytotoxicity by T cell response and local inflammatory processes, thereby preventing virus spread from mother to fetus.

Human trophoblast interferons

The human placental trophoblasts which constitute the first fetal cells and form the major cell layer of the feto-maternal interface are potent producers of interferons (IFNs). The IFN production is dependent on the gestational age of the trophoblast, type of inducer and the stage of differentiation of the trophoblasts. First trimester trophoblast populations produce higher levels (5-6 times) of IFN than the third trimester trophoblasts when stimulated with viruses. Non-viral inducers, such as poly(rl).poly(rC), induce exclusively IFN-beta whereas viruses such as Sendai and Newcastle Disease Virus (NDV) induce mixtures of IFN-alpha subtypes and IFN-beta. Differentiation of mononuclear cytotrophoblasts into syncytiotrophoblasts in vitro increase the IFN production. High-performance and immunoaffinity chromatography of the virus-induced trophoblast IFN preparations resulted in the isolation of three antigenically distinct IFNs, namely, alpha I, alpha II1 (omega 1), and beta with molecular masses of 16, 22 and 24 kDa, respectively, on SDS-PAGE. The human trophoblast IFNs have physical and antiviral activities characteristic of the Type 1 IFNs. The possible roles of the trophoblast IFNs in human placental and fetal development are also discussed in this review.

Differential replication of human immunodeficiency virus type 1 in CD8- and CD8+ subsets of natural killer cells: relationship to cytokine production pattern

CD8+ and CD8- subsets of peripheral blood natural killer (NK) cells were examined for susceptibility to infection with human immunodeficiency virus type 1 (HIV-1) and for the ability to produce various types of interferon (IFN) and tumor necrosis factor (TNF). HIV-1 was preferentially grown in CD8+ NK cells. The ability of CD8- NK cells to suppress HIV-1 replication was related to their ability to produce alpha IFN (IFN-alpha) upon viral induction. Induction with interleukin-2 resulted in IFN-gamma production in both subsets of NK cells. In the CD8+ subset, IFN-gamma and HIV-1 mutually enhanced the production of TNF alpha, leading to hyperactivation of viral replication, whereas in CD8- NK cells IFN-gamma primed HIV-induced IFN-alpha production. The dichotomous effects of IFN-gamma on HIV-1 replication were dependent on the IFN-alpha-producing ability of the cellular targets. These findings can explain the selective depletion of the CD16+ CD8+ subset that begins early in the in vivo HIV-1 infection.

Modulation of interferon secretion by concanavalin A and interleukin-2 in first trimester placental explants in vitro

The human placenta has been demonstrated to be a site of interferon (IFN) production. We report here that early human placental explants in vitro release both type I (IFN-alpha and -beta) and type II (IFN-gamma) immunoreactive IFN. The mitogen concanavalin A (Con A) stimulated immunoreactive (ir-) IFN-gamma secretion in both a dose- and time-dependent manner, but had no significant effect on either ir-IFN-alpha or -beta release. The enhancement of ir-IFN-gamma secretion by Con A, at 2-20 micrograms/ml, was significant at 1 h and persisted until 24 h, but was not significant at 48 h. A high dose of recombinant human interleukin-2 (IL-2) stimulates the release of all three types of ir-IFNs, suggesting that interaction of IL-2 with its receptor might be one cause of the constitutive production of placental IFNs. The patterns of response to Con A and IL-2 were different from those of lymphocytes, providing indirect evidence suggesting that the source of these IFNs might not be lymphocytic. Taken together, these results indicate that first trimester human placental explants in vitro produce both type I and type II IFNs, the major IFN produced depending on the inducer. IL-2 may be one of the physiological inducers of placental IFNs.

Inhibitory effect of natural interferon alpha on human immunodeficiency virus type 1 transmission from epithelial cells to lymphocytes in vitro

The in vitro effect of human natural interferon alpha (IFN-alpha) on cell contact-mediated human immunodeficiency virus type 1 (HIV-1) transmission from epithelial cells to lymphocytes was examined. This type of infection is most likely to occur when the mucosal linings of the reproductive or digestive organs serve as latent viral reservoirs and HIV-1 invades the host through the basolateral surface of polarized epithelia upon contact with intraepithelial lymphocytes. The cell-to-cell infection model consisted of target MOLT-4 T lymphocytes exposed for various time periods to chronically HIV-1-infected intestinal monolayers (I407/YH5) in the presence of log10 dilutions of IFN (range 10(5)-10(-2) IU/ml). Concurrent measurements of resulting productive infection from MOLT-4 revealed that complete inhibition of reverse transcriptase activity was prevented by doses starting from 1 IU, whereas the cessation of p24 production occurred at 1000 IU of IFN present at inoculation. The results indicate that IFN can efficiently prevent not only cell-free but also cell-mediated HIV-1 infection--an important means of viral spread in vivo pertinent to HIV-1 transmission resulting from mucosa-lymphocyte interaction.

Unique features of the trophoblast interferons

The trophoblast interferons (IFN) are Type I IFN with about 50% amino acid sequence identity to the leukocyte IFN (IFN-alpha). They are the major secretory products of the trophoblast of ruminant ungulate species during pregnancy in the period immediately preceding attachment and implantation when they have been implicated in the phenomenon known as maternal recognition of pregnancy. The trophoblast IFN have antiviral and antiproliferative activities typical of other Type I IFN, but unlike IFN-alpha, -beta and -omega are poorly responsive to viral induction and have a highly restricted pattern of expression. Nevertheless, a recombinant bovine IFN-alpha can mimic many of the properties of the trophoblast IFN and has been used pharmacologically to improve pregnancy success in sheep. It still remains unclear, however, whether the trophoblast IFN have unique biological properties or whether they are unusual merely by virtue of the location, magnitude and temporal nature of their expression at a critical time during pregnancy.