title: Characterization of immunoglobulin G and its subclass response to Indian kala-azar infection before and after chemotherapy.
abstract: Serologic parameters of kala-azar were evaluated by Western blot analysis. Sera from kala-azar patients with confirmed diagnoses were screened for immunoglobulin G (IgG) and IgG subclass-specific reactivity against Leishmania donovani membrane antigen (LAg). Heterogeneous LAg-specific IgG reactivity with numerous proteins with molecular masses ranging from 18 to 190 kDa was observed. Though the individual band patterns were varied, seven polypeptides of approximately 31, 34, 51, 63, 72, 91, and 120 kDa were immunoreactive with all the sera tested from kala-azar patients. The band patterns of the immunoblots of sera from patients after treatment and clinical cure with sodium antimony gluconate revealed a decrease in the frequency of the bands. Still, recognition of the 63- and 120-kDa bands was 100%, and the 55- and 91-kDa fractions were recognized in 93% of the sera from cured individuals. Among the IgG subclasses, IgG1 reacted with the greatest number of polypeptides. The 63-kDa protein was again detected by all of the IgG subclasses of all the sera tested. Other fractions recognized by the subclasses of more than 70% of the serum samples included those of 47, 51, 55, and 78 kDa. Following treatment, 63- and 51-kDa bands were the most reactive with the IgG subclasses. LAg-associated cross-reaction with other reference human antisera revealed a mild reactivity of the 63-kDa polypeptide with some of the serum samples from leprosy, malaria, typhoid, tuberculosis, and healthy controls. Western blot analysis of LAg entrapped in liposomes, strong vaccine candidates against experimental visceral leishmaniasis, revealed a more restricted band pattern. The 63-kDa fraction revealed by all pre- and posttreatment sera showed almost negligible levels of cross-reaction with sera from patients with other diseases or from healthy controls. These observations provide insight into induced immunity during kala-azar infection for future application.
authors.affiliation: Infectious Diseases Group, Indian Institute of Chemical Biology, Calcutta 700032, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Ravindran
authors.forename: Khairul
authors.initials: K
authors.lastname: Anam
authors.forename: Bibhas C
authors.initials: BC
authors.lastname: Bairagi
authors.forename: Bibhuti
authors.initials: B
authors.lastname: Saha
authors.forename: Netai
authors.initials: N
authors.lastname: Pramanik
authors.forename: Subhasis K
authors.initials: SK
authors.lastname: Guha
authors.forename: Rama P
authors.initials: RP
authors.lastname: Goswami
authors.forename: Dwijadas
authors.initials: D
authors.lastname: Banerjee
authors.forename: Nahid
authors.initials: N
authors.lastname: Ali
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D000953:Antigens, Protozoan / Q000032:analysis / Q000276:immunology; D002648:Child; D006801:Humans; D015151:Immunoblotting; D007074:Immunoglobulin G / Q000097:blood* / Q000145:classification; D007893:Leishmania donovani / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000188:drug therapy* / Q000276:immunology; D008081:Liposomes; D008875:Middle Aged; D008970:Molecular Weight
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D007074:Immunoglobulin G; D008081:Liposomes