Role of neutralizing antibodies in controlling simian foamy virus transmission and infection

BACKGROUND: Human infections with simian foamy viruses (SFVs) have been reported after occupational and nonoccupational exposure to infected animals and their tissues, blood, and body fluids, although there is no evidence for human-to-human transmission. We previously demonstrated SFV transmission in monkeys by blood transfusion with whole blood from one donor animal that had a low neutralizing antibody (NAb) endpoint titer, whereas blood transfusion from a second donor monkey that had a high NAb titer failed to transmit virus. These results suggested a role for NAbs in SFV transmission and establishment of infection. STUDY DESIGN AND METHODS: Whole blood and antibody-reduced blood were transfused into SFV-negative rhesus macaques. SFV infection in recipient animals was monitored by detection of virus sequences using polymerase chain reaction assays with nucleotide sequence confirmation, by analysis for antibody development in Western blots, and by virus isolation in coculture assays. NAb titer was evaluated by endpoint dilution assays. RESULTS: SFV transmission by whole blood transfusion from a donor monkey with high NAb endpoint titer failed to establish infection in SFV-negative monkeys, whereas virus transmission was successful with transfer of antibody-reduced blood cells. CONCLUSIONS: Passive transfer of high-titer NAbs blocked SFV cell-associated transmission, indicating that NAbs may play a role in virus transmission to individuals exposed to SFV-infected blood and tissues.