Antibody‐Dependent Cellular Cytotoxicity and Natural Killer Activity Against HTLV‐1 Infected Cells

Abstract

Antibody‐dependent cellular cytotoxicity (ADCC) and natural killer (NK) ativity were examined using MT‐2 cells persistently infected by HTLV‐1 as target cells, and mononuclear cells as effector cells, from helathy one‐week‐old newborn babies, infants, children and adults. More than 10% of ADCC was observed in 17 newborn babies out of 22 (77.3%) and in all 67 healthy one‐month‐old babies to adults, by adding serum from anti‐HTLV‐1 positive carriers. When anti‐HTLV‐1 negative serum was added, less than 10% of ADCC was observed. If infants without anti‐HTLV‐1 antibodies were breast‐fed they had the possibility of HTLV‐1 vertical transmission. There was no significant decrease in NK activity between 90 healthy newborn babies, infants, children, or adults. These results suggest that ADCC and NK activity protect against the transmission of HTLV‐1 from mother to child.

Natural Killer Cytotoxicity and Antibody-Dependent Cellular Cytotoxicity of Human Immunodeficiency Virus–Infected Cells by Leukocytes from Human Neonates and Adults

“…Alternatively, interferon-a production induced by HIV-infected targets (26) may enhance NKC selectively in the neonate (16). Indeed, neonates' PBMC have been found to be as effective as adults' in NKC of human T-cell lymphotrophic virus-1-infected target cells (23). However, the striking difference we observed between adults and neonates in ADCC capacity suggests that a developmental defect in this mode of antiviral activity may exist in the human neonate.…”

“…Because developmental defects in antiviral cytotoxicity have been observed toward cells infected with viruses other than HIV (17,23), we compared the effector cell capacity of leukocytes from healthy infants and adults in the NKC and ADCC HIV assay. Umbilical cord blood samples collected at the same time as blood samples from healthy adult volunteers were tested in pairs in the cytotoxicity assay to minimize artifacts from interassay variability.…”

Complete Rescue of HTLV-1p12KO Infectivity by Depletion of Monocytes Together with NK and CD8+ T Cells

“…Viral infection significantly alters T-cell and dendritic cell functions, increases the frequency of intermediate and non-classical monocytes (pro-inflammatory monocytes), and decreases the frequency of classical monocytes that mediate apoptotic cell clearance and maintain tissue homeostasis [ 79 , 81 , 82 ]. The continuous but ineffective attempts of the immune system to clear HTLV-1 may result in chronic inflammation with exhaustion of both NK and CD8 cells, as reported in infected individuals with high virus burden [ 74 , 83 , 84 , 85 , 86 , 87 , 88 , 89 ]. Although, in the current study, the depletion of monocytes in the blood was minimal, it is possible that tissue macrophage depletion was more pronounced, as has been reported [ 90 , 91 ].…”

Hijacking Host Immunity by the Human T-Cell Leukemia Virus Type-1: Implications for Therapeutic and Preventive Vaccines

“…Thus, eliciting anti-HTLV-1 antibodies may be important for clearance by antibody-dependent cellular cytotoxicity (ADCC). An early study examining ADCC and NK cell activity from newborns, infants and adults suggests that these activities can protect against the transmission of mother-to-child [ 242 ]. A more recent study found that a neutralizing anti-Env antibody, LAT-27, induced ADCC, eliminating Tax positive cells and can contribute to the control of infection [ 243 ].…”