Impaired Surfactant Production by Alveolar Epithelial Cells in a SCID-hu Lung Mouse Model of Congenital Human Cytomegalovirus Infection

Abstract

Human cytomegalovirus (HCMV) is the leading viral cause of birth defects and life-threatening lung-associated diseases in premature infants and immunocompromised children. Although the fetal lung is a major target organ of the virus, HCMV lung pathogenesis has remained unexplored, possibly as a result of extreme host range restriction. To overcome this hurdle, we generated a SCID-hu lung mouse model that closely recapitulates the discrete stages of human lung development in utero. Human fetal lung tissue was implanted into severe combined immunodeficient (CB17-scid) mice and inoculated by direct injection with the VR1814 clinical isolate of HCMV. Virus replication in the fetal lung was assessed by the quantification of infectious virus titers and HCMV genome copies and the detection of HCMV proteins by immunohistochemistry and Western blotting. We show that HCMV efficiently replicated in the lung implants during a 2-week period, forming large viral lesions. The virus productively infected alveolar epithelial and mesenchymal cells, imitating congenital infection of the fetal lung. HCMV replication triggered apoptosis near and within the viral lesions and impaired the production of surfactant proteins in the alveolar epithelium. Our findings highlight that congenital and neonatal HCMV infection can adversely impact lung development, leading to pneumonia and acute lung injury. We have successfully developed a small-animal model that closely recapitulates fetal and neonatal lung development and provides a valuable, biologically relevant tool for an understanding of the lung pathogenesis of HCMV as well as other human respiratory viruses. Additionally, this model would greatly facilitate the development and testing of new antiviral therapies for HCMV along with select human pulmonary pathogens.H uman cytomegalovirus (HCMV) infection of the fetus and premature infants is a major global health problem, and in the United States, HCMV is the leading viral cause of birth defects, affecting about 1% of all live births (16). In congenital infection, HCMV spreads extremely efficiently into fetal organs following fetal viremia. Although pneumonitis is rarely the sole manifestation of congenital HCMV disease in the neonate (62), histological examinations of HCMV-infected fetuses identified the lung as a major target organ, with a large number of HCMV-infected cells (8,25). The main burden of lung-associated HCMV diseases occurs during postnatal infection in premature infants (3,22,34,65) and in immunocompromised children (predominantly after organ or bone marrow transplantation) (27,30,67). Some authors reported high rates (up to 37%) of postnatal cytomegalovirus transmission from seropositive breastfeeding mothers to premature infants (31,41,69). A significant proportion of infected infants develop pneumonitis along with hepatosplenomegaly, lymphadenopathy, enteritis, and aseptic meningitis (12, 36). Although breast milk containing HCMV is not considered dangerous to healthy full-term infants, the risk of development of early...

Alveolar Macrophages Are a Prominent but Nonessential Target for Murine Cytomegalovirus Infecting the Lungs

“…This result parallels the HCMV expression of lytic antigens in lung stromal cells more than lung macrophages (7)(8)(9). MCMV was more lytic in AEC2s, and the association of HCMV infection with impaired surfactant production (41,42) suggests that it might be similar to MCMV. The accumulation of MCMV antigens and the expression of reporter genes by macrophages without extensive new virion production suggested that macrophages act as local absorbers of infectivity.…”

Animal models for emerging coronavirus: progress and new insights

“…Lung is the main target organ of coronavirus infection. In 2012, Maidji et al grafted human fetal lung tissues under the kidney capsule of immunodeficient SCID mice [77]. The lung tissues rapidly grew and developed mature structures resembling the normal human lung and were demonstrated to support CMV infection and pathogenesis.…”

Humanized mouse models of human cytomegalovirus infection

“…Maidij et al generated a SCID-hu lung mouse model that closely recapitulates the different stages of human lung development in utero [30]. The authors show that HCMV efficiently replicated in the lung implants forming large viral lesions.…”