Onchocerciasis modulates the immune response to mycobacterial antigens

Abstract

Chronic helminth infection induces a type-2 cellular immune response. In contrast to this, mycobacterial infections commonly induce a type-1 immune response which is considered protective. Type-2 responses and diminished type-1 responses to mycobacteria have been previously correlated with active infection states such as pulmonary tuberculosis and lepromatous leprosy. The present study examines the immune responses of children exposed to both the helminth parasite Onchocerca volvulus and the mycobacterial infections, Mycobacterium tuberculosis and M. leprae. Proliferation of peripheral blood mononuclear cells (PBMC) and production of IL-4 in response to both helminth and mycobacterial antigen (PPD) decreased dramatically with increasing microfilarial (MF) density. Although interferon-gamma (IFN-gamma) production strongly correlated with cellular proliferation, it was surprisingly not related to MF density for either antigen. IL-4 production in response to helminth antigen and PPD increased with ascending children's age. IFN-gamma and cellular proliferation to PPD were not related to age, but in response to helminth antigen were significantly higher in children of age 9-12 years than children of either the younger age group (5-8 years) or the older group (13-16 years). Thus, there was a MF density-related down-regulation of cellular responsiveness and age-related skewing toward type 2 which was paralleled in response to both the helminth antigen and PPD. This parasite-induced immunomodulation of the response to mycobacteria correlates with a previous report of doubled incidence of lepromatous leprosy in onchocerciasis hyperendemic regions. Moreover, this demonstration that helminth infection in humans can modulate the immune response to a concurrent infection or immunological challenge is of critical importance to future vaccination strategies.

Enteroparasitosis prevalence and parasitism influence in clinical outcomes of tuberculosis patients with or without HIV co-infection in a reference hospital in Rio de Janeiro (2000-2006)

“…Recent in vitro studies showed significant correlations between helminthic infections and tuberculosis [10, [18][19][20][21]. In this study, initially, we evaluated the prevalence of enteroparasitosis in tuberculosis patients, HIV-infected or non infected, and we found a prevalence of helminthes similar to that observed by other authors, Strongyloides stercoralis being the most frequent parasite [10,20].…”

Risk of Intestinal Helminth and Protozoan Infection in a Refugee Population

“…34,35 A. lumbricoides and Onchocerca volvulus, parasites commonly found in immigrant populations, have been found to impair immune response to both acute (Vibrio) and chronic (Mycobacteria) infection. 36,37 High rates of latent TB infection have been noted in a number of refugee screening studies. 5,8,26,30,38,39 With reactivation of latent TB often occurring within the first few years of immigration, it is conceivable that untreated helminth infections contribute to this important public health problem.…”

Prolonged infection byFonsecaea pedrosoiafter antigenic co-stimulation at different sites in experimental murine chromoblastomycosis

“…[3][4][5][6] This promiscuous immunity probably occurs because once the suppressive response is activated, it seems to be nonspecific. 7 More recently, however, a link between T suppressor cells and peripheral tolerance prolonged infection by Fonsecaea pedrosoi after antigenic co-stimulation at different sites in experimental murine chromoblastomycosis alexandre paulo Machado, 1 Maria Regina Regis silva 2 and Olga Fischman 8,9 Over the past 15 years, evidence has accumulated that suppressor cells such as CD4 + CD25 + T regulatory cells (T regs) are important for peripheral tolerance and downregulation of various immune responses.…”