Epidemiological and clinical interaction between HTLV‐1 and Strongyloides stercoralis

Abstract

Strongyloides stercoralis is the most common human parasitic nematode that is able to complete a life cycle and proliferate within its host. The majority of patients with strongyloidiasis have an asymptomatic infection or mild disease. However, when autoinfection occurs, a high number of infecting larvae can gain access to the bloodstream by penetrating the colonic mucosa leading to a severe hyperinfection and the development of disseminated strongyloidiasis. The human T cell lymphotropic virus type 1 (HTLV-1) predominantly infects T cells and induces spontaneous lymphocyte proliferation and secretion of high levels of type 1 cytokines. Strongyloides stercoralis patients with HTLV-1 co-infection have a modified immunological responses against parasite antigens and co-infection has clinical implications for strongyloidiasis. The high production of IFN-gamma observed in patients co-infected with HTLV-1 and Strongyloides stercoralis decreases the production of IL-4, IL-5, IL-13 and IgE, molecules that participate in the host defence mechanism against helminths. Moreover, there is a decrease in the efficacy of treatment of Strongyloides stercoralis in patients co-infected with HTLV-1. Alterations in the immune response against Strongyloides stercoralis and the decrease in the efficacy of anti-parasitic drugs are responsible for the increased prevalence of Strongyloides stercoralis among HTLV-1 infected subjects and make HTLV-1 infection the most important risk factor for disseminated strongyloidiasis.

Effect of treatment of Strongyloides infection on HTLV‐1 expression in a patient with adult T‐cell leukemia

“…The synergistic severity of disease caused by these infections has been suggested to be due to immunocompromise resulting from HTLV-1 as a result of interferon g expression, and shift from Th2 to Th1 responses, resulting in decreased levels of IL4, IL5, IL13, and IgE [4,[16][17][18][19]. Alternatively, a Strongyloides antigen has been postulated to induce a potent polyclonal T-cell mitogenic response, and reactivation of HTLV-1 expression [1,20].…”

Strongyloidiasis – the most neglected of the neglected tropical diseases?

“…26 In contrast, human T cell lymphotropic virus type 1 infection is strongly associated with a higher S. stercoralis prevalence as well as with an increased incidence of hyperinfection. [27][28][29] Although there is a pronounced association between disseminated strongyloidiasis and suppression of the immune system, there are also a significant number of fatal cases in the literature which could not be linked to any known impairment of the immune system. 30 They have tentatively been explained by host factors of intestinal parasite control which act at the interface between the host and the parasite, i.e.…”

O vírus linfotrópico de células T humanos tipo 1 (HTLV-1): Quando suspeitar da infecção?

“…Strongyloides stercoralis hyperinfection of patients infected with HTLV is the result of immunoresponse abnormalities that make systemic dissemination of the infestation possible, leading to recurrent chronic infection and with poor clinical response to the usual treatments. 59,60 Porto et al 61 highlighted a possible protective effect from strongyloides against HAM/TSP, caused by a modulated Th1 response. Patients with tuberculosis have a higher rate of HTLV-1 infection than the general population.…”