Onchocerca volvulus: molecular cloning, primary structure, and expression of a microfilarial surface-associated antigen.
Although the filarial nematode parasite Onchocerca volvulus is an important human pathogen in large areas of Africa and Latin America, little is known of the molecular interactions that govern the clinical status of patients with this chronic, debilitating disease. As a step toward defining the parasite molecules important to the immunobiology of host-parasite interactions, we have identified and cloned a major surface-associated antigen expressed by O. volvulus microfilariae. Radiolabeling experiments demonstrated that O. volvulus microfilariae have a limited repertoire of peptides at the surface. Prominent among these labeled peptides is an 18-kDa component. Immunological cross-reactivity between a surface-associated component of Dirofilaria immitis microfilariae and the 18-kDa surface-associated molecule from O. volvulus was exploited in a strategy to clone this potentially important O. volvulus microfilarial antigen. The cross-reacting antibodies were used to immunoscreen O. volvulus cDNA expression libraries. One clone, M2f.e, contained an open reading frame of 495 bp encoding an 18.1-kDa protein (OVMS18). Antibodies produced against the expression product of M2f.e recognized an 18-kDa component in extracts of O. volvulus microfilariae and bound to the surface of intact O. volvulus and D. immitis microfilariae. Southern blot analyses showed that M2f.e-like sequences are present in the genomic DNA of a number of filarial nematode species, but not in DNAs from nonfilarial nematode species.
Department of Immunology and Infectious Diseases, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205.
J D
JD
Dinman
A L
AL
Scott
D000595:Amino Acid Sequence; D000818:Animals; D000909:Antibodies, Helminth / Q000276:immunology; D000947:Antigens, Helminth / Q000096:biosynthesis / Q000235:genetics*; D000954:Antigens, Surface / Q000096:biosynthesis / Q000235:genetics; D001483:Base Sequence; D015139:Blotting, Southern; D015153:Blotting, Western; D003001:Cloning, Molecular; D003429:Cross Reactions; D004247:DNA / Q000235:genetics; D015342:DNA Probes; D004183:Dirofilaria immitis / Q000235:genetics / Q000276:immunology; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation; D015723:Gene Library; D008842:Microfilariae / Q000235:genetics / Q000276:immunology; D008969:Molecular Sequence Data; D009854:Onchocerca / Q000235:genetics* / Q000276:immunology; D012333:RNA, Messenger / Q000235:genetics; D015183:Restriction Mapping
D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D000954:Antigens, Surface; D015342:DNA Probes; D000939:Epitopes; D012333:RNA, Messenger; D004247:DNA