Symbiotic Wolbachia organisms of filarial nematodes have received much attention as possible
chemotherapy targets and disease-causing organisms. In order to further investigate the association between anti-Wolbachia immune responses and chronic filarial disease in humans, antibody responses to Wolbachia
surface protein (WSP) were assayed in serum samples collected from 232 individuals living in Leogane, Haiti, an area where
Wuchereria bancrofti infection is endemic, and from 67 North Americans with no history of
lymphatic filariasis. As opposed to antifilarial antibody responses, which were largely influenced by the patient's
infection status, the prevalence and levels of anti-WSP
immunoglobulin G (
IgG)
antibodies among individuals with
lymphedema or hydrocele were significantly greater than those in gender- and
infection-matched individuals without disease. In at least one case, the anti-WSP
IgG response was coincident with the onset of
lymphedema development, and among anti-WSP-positive women with
lymphedema, anti-WSP
IgG levels were negatively correlated with the duration of
lymphedema. The presence of anti-WSP
IgG was also associated with the severity of inguinal
adenopathy among men with hydrocele. In addition to the presence of anti-WSP
antibodies among Haitians, 15 of 67 (22%) serum samples collected from individuals from North America, where
filariasis is not endemic, were also positive for anti-WSP
antibodies. In comparison to those from Haitians, anti-WSP
antibodies from North Americans primarily recognized a distinct region of WSP located within the highly conserved second transmembrane domain. The results of this study demonstrate that anti-WSP antibody responses are associated with the presence of chronic filarial morbidity and not filarial
infection status in humans and suggest that WSP should be further studied as a potential trigger for the development of filarial disease.