Microfilarial clearance in loiasis involves elevation of Th1 and Th2 products and emergence of a specific pattern of T-cell populations

Diethylcarbamazine (DEC) induced clearance of microfilaraemia in loiasis is associated with severe posttreatment reactions. To define the switch from hypo- to hyper-responsiveness associated with DEC treatment, phenotypic alterations of T-lymphocytes, characterized by flow cytometry, and cytokines, determined by enzyme linked immunosorbent assay, were monitored in a microfilaraemic patient. In contrast to reports on onchocerciasis and lymphatic filariases, no elevation of interleukin (IL)-6 and tumour necrosis factor (TNF)-α was observed. The most severe side effects coincided with an elevation of interferon (IFN)-γ on day 3, followed by IL-10, transforming growth factor (TGF)-β2 and macrophage inflammatory protein-1α (MIP-1α) peaking on day 5. Phenotypieally, T-cell activation markers CD38, CD54 and CD25 were significantly expressed before treatment, with high CD38 expression still existing one year after clearance of microfilaraemia. Treatment-related increases were observed with anti-CD 122, anti-HLA-DR and anti-CD69. CD28 was expressed before treatment on almost 100% qf'CD4⁺ and CD8⁺ T cells and dropped to 20% by day 5, reaching again baseline levels on day 21. Furthermore, there emerged 20% TCRαβ^-/CD3⁺ T cells and 10%) anti-βV5(e) ⁺ T cells, altogether indicating a specific pattern of T-helper (Th)1 and Th2 cytokines as well as expansion of certain pauciclonal T-cell populations in response to microfilarial clearance.