PubMed · 7464831
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X Fen, S Feng-Xin, Z Zeng-Bian. 1980. The complement hemolytic intermediate EAC1q4.. https://doi.org/10.1016/0161-5890(80)90024-3
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A comparison was made of the agglutination and lysis of three strains of Trypanosoma cruzi in gut extracts and hemolymph of Rhodnius prolixus and the results obtained were correlated with the success or failure of the parasite strain to infect the digestive tube or to survive in the hemocel after inoculation. Both T. cruzi strains Dm28c and Cl urine 35 days after feeding with parasites. Concomitantly, both of these strains were agglutinated but not lysed by the crop extracts. In contrast, T. cruzi Y strain parasites rapidly disappeared from the gut and showed no agglutination, but some lysis, in the crop extract. Following inoculation into the hemocel, only the Cl strain survived at high levels and was also the only strain agglutinated significantly in the hemolymph. Both Dm28c and Y strains rapidly disappeared from the hemocel with the former parasite being removed more slowly than the latter, probably due to clearance by the cellular defenses. The rapid clearance of the Y strain was correlated with the presence of a high titer lysin in the hemolymph. Subsequent experiments using FITC-labeled lectins and FACS to probe the carbohydrates on the parasite surfaces showed significant differences between the three strains. Thus, only Dm28c was stained strongly by Arachis hypogea (PNA) lectin, indicating the presence of galactose/N-acetylgalactosamine residues, and Dm28c and Y strains by Phytolacca lectin for N-acetyl glucosamine moieties. Finally, the fact that, in contrast to Dm28c and Y, the Cl strain strongly interacted with Triticum vulgaris (WGA) but not with Phytolacca lectin may be due to the presence of N-acetyl neuraminic acid residues on these organisms. These surface carbohydrate differences may be correlated both to the behavior and agglutination variations between the three strains recorded in this work.
A direct agglutination test (DAT) for the detection of post-kala azar dermal leishmaniasis (PKDL) was evaluated in conditions that simulate the disease clinically or immunologically. A reference strain of Leishmania donovani (LEM 1399), and antigen preparations from Leishmania isolates from Bangladeshi patients with post-kala azar dermal leishmaniasis or visceral leishmaniasis were used. A titre of at least 51,200 was obtained in tests of patients with PKDL with all three antigens, whereas a maximum titre of 1600 was recorded in patients with cutaneous leishmaniasis, mucocutaneous leishmaniasis or leprosy. Antigens from dermal isolates of L. tropica (LV 140) and L. braziliensis (LV 65) yielded titres of 1600-6400 in patients with PKDL. The lowest titre recorded in 70 patients tested with the homologous PKDL antigen was 409,600. In patients with leprosy, cutaneous leishmaniasis, syphilis, onchocerciasis, tuberculosis, blastomycosis or vitiligo, titres ranged from 100 to 1600. Tha DAT is better than current parasitological and histopathological methods for the diagnosis of PKDL in areas in which leprosy is co-endemic.
Previously, we reported on the properties of a monoclonal antibody, 2B10, which has the same determinant on the human erythrocyte as MSA-1 of Plasmodium falciparum (FCR3 strain); the binding of both ligands to erythrocyte receptors was totally sialic acid dependent. In this work, rabbit anti-2B10 idiopathic antibodies were generated. The anti-idiotypic antibodies recognized both the erythrocyte binding site of 2B10 and the C-terminal region of MSA-1 (amino acids 1047 to 1640); they were able to inhibit 2B10 and MSA-1 binding to erythrocytes and partially prevent P. falciparum merozoites from invading erythrocytes. The utility of 2B10 in the study of the interaction between MSA-1 and human erythrocytes prompted us to determine the nucleotide and deduced amino acid sequences of its VH and VL regions. The data show that the 2B10 VH region is part of the J558 family and is especially homologous to BALB/c anti-nitrophenyl monoclonal antibody 21.1.43; the VL region belongs to the VK1 subgroup and comes from the same genomic locus as (NZB x W)F1 anti-DNA and C57BL anti-dextran monoclonal antibodies BXW-14 and 42.48.12.2, respectively. Most of the differences among the VH and VL segments are located in CDR1 and -3. The binding site of 2B10 contains both negatively and positively charged amino acid residues. The amino acid sequences of the 2B10 VH region and a region of MSA-1 from the Wellcome strain of P. falciparum (amino acids 1002 to 1115) share 43% similarity, and the amino acid sequences between the 2B10 VL region and another segment of the same MSA-1 (amino acids 1247 to 1394) share 48% similarity. We conclude that the interactions between erythrocyte receptors and their ligands, 2B10 and MSA-1, are related and that the C-terminal region of MSA-1 is the erythrocyte binding domain.