title: HIV-1 at the placenta: immune correlates of protection and infection.
abstract: Mother-to-child transmission (MTCT) of HIV-1 remains a significant global health concern despite implementation of maternal combination antiretroviral therapy for treatment as prevention to offset transmission. The risk of in-utero HIV-1 transmission in the absence of interventions is ∼7%. This low rate of transmission points to innate and adaptive mechanisms to restrict lentiviral infection within the placenta.
  
  
  
  Placental macrophages (Hofbauer cells) are key mediators in in-utero transmission of HIV-1. Hofbauer cells constitutively express elevated concentrations of regulatory cytokines, which inhibit HIV-1 replication in vitro, and possess intrinsic antiviral properties. Hofbauer cells sequester HIV-1 in intracellular compartments that can be accessed by HIV-1-specific antibodies and may occur in vivo to offset MTCT. Intriguingly, studies have reported strong associations between maternal human cytomegalovirus (HCMV) viremia and MTCT of HIV-1. HCMV infection at the placenta promotes inflammation, chronic villitis, and trophoblast damage, providing potential HIV-1 access into CD4CCR5 target cells. The placenta exhibits a variety of mechanisms to limit HIV-1 replication, yet viral-induced activation with maternal HCMV may override this protection to facilitate in-utero transmission of HIV-1.
  
  
  
  Understanding immune correlates of protection or transmission at the placenta during on-going HIV-1 exposure may contribute to understanding HIV pathogenesis and the development of effective immunotherapies.
authors.affiliation: aDepartment of Pediatrics, Division of Infectious Diseases, Emory University School of Medicine bChildren's Center for Immunology and Vaccines, Children's Healthcare of Atlanta, Atlanta, Georgia, USA.
authors.forename: Erica L
authors.initials: EL
authors.lastname: Johnson
authors.forename: Rana
authors.initials: R
authors.lastname: Chakraborty
mesh_terms: D005260:Female; D015658:HIV Infections / Q000276:immunology / Q000517:prevention & control; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D018445:Infectious Disease Transmission, Vertical; D010920:Placenta / Q000166:cytology / Q000276:immunology; D011247:Pregnancy