Zoonotic infection of Brazilian primate workers with New World simian foamy virus

Abstract

Simian foamy viruses (SFVs) are retroviruses present in nearly all nonhuman primates (NHPs), including Old World primates (OWP) and New World primates (NWP). While all confirmed human infections with SFV are from zoonotic transmissions originating from OWP, little is known about the zoonotic transmission potential of NWP SFV. We conducted a longitudinal, prospective study of 56 workers occupationally exposed to NWP in Brazil. Plasma from these workers was tested using Western blot (WB) assays containing NWP SFV antigens. Genomic DNA from blood and buccal swabs was analyzed for the presence of proviral SFV sequences by three nested PCR tests and a new quantitative PCR assay. Exposure histories were obtained and analyzed for associations with possible SFV infection. Ten persons (18%) tested seropositive and two persons were seroindeterminate (3.6%) for NWP SFV. Six persons had seroreactivity over 2-3 years suggestive of persistent infection. All SFV NWP WB-positive workers reported at least one incident involving NWP, including six reporting NWP bites. NWP SFV viral DNA was not detected in the blood or buccal swabs from all 12 NWP SFV seroreactive workers. We also found evidence of SFV seroreversion in three workers suggestive of possible clearance of infection. Our findings suggest that NWP SFV can be transmitted to occupationally-exposed humans and can elicit specific humoral immune responses but infection remains well-controlled resulting in latent infection and may occasionally clear.

Fig 1. Detection of simian foamy virus (SFV) antibodies in workers exposed to New World primates.

SFV antigens from a spider monkey (Ateles species, SFVasp) and a common marmoset (Callithrix jacchus, SFVcja) were prepared by expansion in canine thymocyte cells (Cf2Th) and were combined and reacted with test plasma and sera in the upper panel and simultaneously to uninfected Cf2Th antigens in the lower panel to check the specificity of the seroreactivity to the SFV antigens. Worker codes beginning with “C” and “Z” are from the Centro de Primatologia do Rio de Janeiro (CPRJ) and Fundação Jardim Zoológico da Cidade do Rio de Janeiro (RIOZOO), respectively. All human samples were reactive to both Gag proteins except for participants C15H and C18H whose samples were reactive for only the 72 kD Gag protein and which were classified as seroindeterminate. Two seropositive serum controls from an SFV-infected spider monkey (Ateles species) and a capuchin (Cebus apella) and a pedigreed seronegative human plasma sample (negative control) are included in each assay run. Molecular markers in kDa are provided on the left and the location of the 68/72 kDa Gag doublet proteins are shown with blue arrows.