Immune Responses to Filarial Nematodes: A Mechanistic Evaluation of Evasion and Modulation Strategiesitle

Filarial parasites are long-lived organisms that cause extreme morbidity due to pathological manifestations, including lymphedema, hydrocele, and elephantiasis. Understanding the hosts’ immune responses to filarial parasites is crucial to developing new and effective anti-filarial treatments. The review thoroughly examines and summarizes immunological modulation, evasion strategies, and filarial-host immune interactions to provide an updated knowledge of the immune evasion maneuvers used by filarial parasites. An extensive literature search was conducted using databases such as PubMed, Google Scholar, ScienceDirect, Web of Science, and Scopus to identify articles published between 2005 and 2025 that focus on the crucial molecular, cellular, and immunomodulatory strategies of filarial parasites. The immune evasion mechanisms include effector T cell modulation, induction of apoptosis in immune cells, release of immunomodulatory proteins, etc., ensuring the mutual survival of both the parasite and the host. An antigen-specific Th2 response and an increase in IL-10-producing CD4+T cells, along with a suppressed Th1 response, are the key immunological characteristics of filarial pathogenesis. This antigen-specific T-cell hyporesponsiveness seems necessary for keeping the long-term infection going, which often involves large parasite densities. This review summarizes filarial parasites' mechanisms and strategies in regulating host immune responses and will facilitate future studies on the filarial pathogenesis, leading to the development of novel anti-filarial therapeutics.