Intrauterine growth restriction caused by underlying congenital cytomegalovirus infection

Abstract

Background: Human cytomegalovirus (HCMV) is the major viral etiology of congenital infection and birth defects. Fetal transmission is high (30%-40%) in primary maternal infection, and symptomatic babies have permanent neurological, hearing, and vision defects. Recurrent infection is infrequently transmitted (2%) and largely asymptomatic. Congenital infection is also associated with intrauterine growth restriction (IUGR).

Methods: To investigate possible underlying HCMV infection in cases of idiopathic IUGR, we studied maternal and cord sera and placentas from 19 pregnancies. Anti-HCMV antibodies, hypoxia-related factors, and cmvIL-10 were measured in sera. Placental biopsy specimens were examined for viral DNA, expression of infected cell proteins, and pathology.

Results: Among 7 IUGR cases, we identified 2 primary and 3 recurrent HCMV infections. Virus replicated in glandular epithelium and lymphatic endothelium in the decidua, cytotrophoblasts, and smooth muscle cells in blood vessels of floating villi and the chorion. Large fibrinoids with avascular villi, edema, and inflammation were significantly increased. Detection of viral proteins in the amniotic epithelium indicated transmission in 2 cases of IUGR with primary infection and 3 asymptomatic recurrent infections.

Conclusions: Congenital HCMV infection impairs placental development and functions and should be considered as an underlying cause of IUGR, regardless of virus transmission to the fetus.

Keywords: HCMV; IUGR; amnion; blood vessels; chorion; congenital; fetus; placenta; pregnancy; villi.

Figure 1.

Pathology in placentas from cases of IUGR. A, Necrotic, avascular villi embedded in large fibrinoids, case 16. B, No large fibrinoids in seronegative control. C, Edematous villi, case 3. D, Absence of edematous villi in seronegative control. E, Leukocytic infiltration in basal plate and decidua, case 16. F, Increased diameter of villous blood vessel, case 3. G, Accumulation of cytotrophoblasts (cell islands), case 12. Inset, cytokeratin 7 (CK7). Scale bars A and B = 500 µm, C–G = 50 µm. Abbreviation: IUGR, intrauterine growth restriction.

Figure 2.

Quantification of pathological features in cases of IUGR. A, Avascular villi embedded in fibrinoids were counted, and distribution among fibrinoids of various sizes (defined as 5–25, 25–50, or >50 villi) determined. Results shown as average number of villi in fibrinoids of each size class per field (10× objective, approximately 1 mm² area per field). At least four biopsies and more than 100 fields were examined per placenta. B, Edematous villi apparent in IUGR were counted according to severity (3 = most severe, representing a bloated villus with sparse mesenchyme and few visible blood vessels). Average numbers of edematous villi in each class indicated by fill patterns. At least four biopsies and more than 100 fields (10× objective, representing approximately 1 mm²) were examined. C, Leukocytic cell infiltrates in basal plate were counted and the distribution per field presented in a box and whisker format that marks the four quartiles. Median count is indicated by the solid central bar, the second and third quartiles within the boxes below and above, respectively. First quartile is represented by vertical line below the box and fourth (highest) quartile by line above the box. For each placenta, at least four biopsies and between 14 and 37 fields (10× objective, representing approximately 1 mm²) were examined. Abbreviation: IUGR, intrauterine growth restriction.

Figure 3.

HCMV infected cells in the basal plate of primary and recurrent infections detected by immunohistochemistry. A, (left panel) Low power image of a site within the basal plate containing CTBs that express HCMV infected cell proteins. (right panel and inset) High power image of area indicated in panel A (rectangle) showing infected cell proteins in the cytoplasm of invasive CTBs. B, Infected cells in a lymphatic vessel in the decidua. Signal was detected in cytoplasm (upper inset) and nuclei (lower inset) of infected cells at the luminal surface. C, HCMV proteins in cells at the luminal face of an endometrial gland detected in cytoplasm and nuclei. D, Section adjacent to that in C shows cytokeratin 7 (CK7). Scale bars A(left panel) = 200 µm, A(right panel) = 20 µm, B = 50 µm, C–D = 100 µm. Abbreviations: CTB, cytotrophoblast; HCMV, human cytomegalovirus.

Figure 4.

HCMV infected cells in blood vessels of chorion detected by immunohistochemistry in a case of IUGR with primary infection. HCMV proteins (left panels) and smooth muscle (SM) myosin heavy chain (right panels) stained in parallel sections. A and B, Adjacent sections showing HCMV proteins in smooth muscle cells surrounding an artery in the chorion of placenta of IUGR case 16. C and D, Adjacent sections showing absence of viral proteins in smooth muscle cells surrounding an artery in the chorionic plate of placenta #3. E and F, Parallel sections showing HCMV proteins in smooth muscle cells surrounding a vein in the chorionic plate of placenta #16. G and H, Adjacent sections showing absence of viral proteins in smooth muscle cells surrounding a vein in the chorionic plate of placenta #2. Scale bars in B = 200 µm for (A–D). Scale bar in F = 100 µm for E–H. Abbreviations: HCMV, human cytomegalovirus; IUGR, intrauterine growth restriction.

Figure 5.

Immunohistochemical detection of HCMV proteins in epithelial cells of amnion. Viral proteins accumulated in cytoplasmic vesicles of amniotic epithelial cells in placentas from primary and recurrent infections (A–G) but not in a seronegative control (H). F, Grazing section across amniotic epithelial cells revealing the highly vesicular nature of the signal. Scale bar in B = 25 µm for A–E and H. Scale bar in G = 25 µm. Scale bar in F = 15 µm. Abbreviations: HCMV, human cytomegalovirus; IUGR, intrauterine growth restriction.