Protective immunity in human Bancroftian filariasis: inverse relationship between antibodies to microfilarial sheath and circulating filarial antigens.
The existence and the nature of protective immunity in human filariasis continues to be a subject of intense debate. While there is no broad consensus on functional immunity against larval and adult stage parasites, anti-microfilarial immunity has been demonstrated to be mediated by antibodies to the microfilarial sheath. In the present study, circulating filarial antigens (CFA), a marker of active filarial infection in human Bancroftian filariasis, was found to be inversely associated with antibodies to microfilarial sheath in a cohort of 411 subjects representing all categories of filariasis across the clinical spectrum of the disease. Approximately 80% of humans of all age groups (5-65 years) were found to have either CFA or anti-sheath antibodies. The inverse relationship observed between these two parameters was found to be independent of the clinical manifestation; both symptomatic and asymptomatic cases were found to display similar inverse association between CFA and anti-sheath antibodies. The prevalence of anti-sheath antibodies in the paediatric group was found to be very high as compared to adults; 78% of children below the age of 10 years tested positive for anti-sheath antibodies although the mf rate and CFA rate were only 4.5% and 22.7%, respectively, in this age group, indicating that developing larvae or juvenile adult stage parasites could have been the source of antigenic stimulus for induction of antibodies to the microfilarial sheath.
Ravindran
B
B
Division of Immunology, Regional Medical Research Centre, ICMR, Bhubaneswar, India. immunol@dte.vsnl.net.in
Satapathy
A K
AK
Sahoo
P K
PK
Babu Geddam
J J
JJ
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood*; D000947:Antigens, Helminth / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004604:Elephantiasis / Q000276:immunology; D005368:Filariasis / Q000276:immunology*; D006801:Humans; D007109:Immunity; D007194:India / Q000453:epidemiology; D014958:Wuchereria bancrofti / Q000276:immunology*
D000909:Antibodies, Helminth; D000947:Antigens, Helminth