Perfil eletroforético de antígenos de Haemonchus placei e de Oesophagostomum radiatum e suas reatividades aos soros de bovinos naturalmente infectados

Abstract

Livestock farming continues to be a crucial economic activity for Brazil, playing a significant role in the national economy. However, the bovine population faces a challenge in combating gastrointestinal nematode infections. Haemonchus placei and Oesophagostomum radiatum stand out as species known for their high infection rates and reproductive capacity, along with their resistance to many predominant control methods. Despite chemical formulations serving as the primary tool for parasite control, they face limitations in consumer markets due to the residues they leave in meat. Additionally, these formulations promote the selection of organisms resistant to their active components. Therefore, new control strategies must be explored. Considering these strategies, the present study aimed to characterize the profiles of total antigens from gastrointestinal nematode specimens in cattle (Haemonchus placei and Oesophagostomum radiatum) and compare the humoral immune response via Western Blot using Immunoglobulin G (IgG Total), employing sera from animals characterized by fecal egg count (EPG) sampled from commercial beef cattle herds, seeking to relate the immune status in animals of different ages to their respective EPG’s. In this study, a total of 1147 animals were sampled and categorized into four groups: pre-weaning, weaned, yearlings, and adults. Fecal and blood samples were collected and subjected to the McMaster technique and ELISA, respectively. Total antigens (TAs) were extracted from disintegrated adult specimens of Haemonchus placei and Oesophagostomum radiatum obtained through induced mixed infections. The study also involved the characterization of TAs from both species by SDS-PAGE electrophoresis and subsequent immunoblotting. The results revealed significant variations in fecal egg counts (EPG) among these categories, with pre-weaning calves having the highest EPG values, followed by weaned calves. All sera showed reactivity to total immunoglobulin G (IgG) when exposed to Haemonchus placei and Oesophagostomum radiatum antigens. Younger cattle had higher EPG’s and lower reactivity indices, while older cattle exhibited the opposite trend. Regarding the electrophoretic profile of total extracts from Haemonchus placei and Oesophagostomum radiatum, different protein fractions were identified in both antigens. Although some size similarities among fractions were observed, the profiles differed. In Western Blot, reactivity was observed for some proteins from Oesophagostomum radiatum, especially in older animals with lower EPG’s. However, no reactions were observed for Haemonchus placei fractions. In conclusion, this research provides a comprehensive analysis of gastrointestinal nematode infections in cattle, highlighting the influence of age, immune response, and the complexity of antigenic fractions of these parasites, emphasizing naturally acquired resistance in animals, and providing a succinct overview of TA electrophoretic profiles, which identifies fractions recognized by immunoglobulins G in sera —particularly in animals displaying lower EPG’s, indicative of higher resistance.