Elevated levels of soluble CD8 molecule in patients with lymphatic filariasis

Highlighting the Relevance of CD8+ T Cells in Filarial Infections

The T cell immune responses in filarial infections are primarily mediated by CD4+ T cells and type 2-associated cytokines. Emerging evidence indicates that CD8+ T cell responses are important for anti-filarial immunity, however, could be suppressed in co-infections. This review summarizes what we know so far about the activities of CD8+ T cell responses in filarial infections, co-infections, and the associations with the development of filarial pathologies.

Epidemiology and immunopathology of bancroftian filariasis

Human lymphatic filariasis affects 120 million people worldwide. Although the disease is considered to be potentially erradicable by the World Health Organization, comprehensive studies on epidemiological aspects as well as mechanisms of pathology development are still premature. The following review summarizes currently available data on these topics and ends by discussing the latest control strategies.

Differences in the frequency of cytokine-producing cells in antigenemic and nonantigenemic individuals with bancroftian filariasis

Individuals with clinical manifestations of lymphatic filariasis may be currently infected or not. Twenty-five individuals from a Wuchereria bancrofti-endemic area of Brazil were classified as being asymptomatic microfilaremic individuals, antigenemic individuals with clinical filariasis, or nonantigenemic individuals with clinical filariasis. Intracellular cytokine staining of mitogen-stimulated peripheral blood mononuclear cells (PBMC) showed that the frequency of either gamma interferon (IFN-gamma)- or interleukin-4 (IL-4)-producing cells was higher in the nonantigenemic individuals with clinical filariasis than in the asymptomatic microfilaremic individuals (geometric means, 22.1 versus 10.7% [P = 0.02] and 2.9 versus 1.4% [P = 0.01], respectively). When the asymptomatic microfilaremic individuals and antigenemic individuals with clinical filariasis were grouped together to constitute all actively infected individuals, the frequency of IFN-gamma-producing cells was also lower than in the nonantigenemic individuals with clinical filariasis (P = 0.04). Likewise, the frequency of IL-4-producing cells in the actively infected individuals was also lower than in the nonantigenemic individuals with clinical filariasis (P = 0.02). No differences in the frequency of IFN-gamma-, IL-4-, or IL-5-producing cells in purified CD4 T lymphocytes were found among the groups. These findings suggest that the presence of antigenemia, which is an indicator of current active infection, is closely associated with the frequency of IFN-gamma- and IL-4-producing cells in lymphatic filariasis. The differences found in the frequency of cytokine-producing cells among the three groups appear to be due to a subset of cells other than CD4 T cells.

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)-alpha was observed. The most severe side effects coincided with an elevation of interferon (IFN)-gamma on day 3, followed by IL-10, transforming growth factor (TGF)-beta 2 and macrophage inflammatory protein-1 alpha (MIP-1 alpha) peaking on day 5. Phenotypically, 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-CD122, anti-HLA-DR and anti-CD69. CD28 was expressed before treatment on almost 100% of CD4+ and CD8+ T cells and dropped to 20% by day 5, reaching again baseline levels on day 21. Furthermore, there emerged 20% TCR alpha beta+/CD3+ T cells and 10% anti-beta V5(c)+ 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.

Soluble (s)CD23 levels in a parasitized population from Papua New Guinea

Levels of sCD23, total and specific IgE were found to be considerably elevated in the plasma of a helminth infected population from Papua New Guinea. Using age-corrected data, a significant negative correlation was seen between sCD23 and total IgE in the young, at a time when hookworms are being rapidly acquired, and total IgE levels are rising most dramatically. It is suggested on the basis of this data that this inverse correlation is due to the stabilizing effect of IgE on the Fc epsilon RII receptor in vivo, and that the high levels of sCD23 seen in hookworm infected individuals are partly responsible for the high levels of IgE recorded in these patients.

C-reactive protein in patients with lymphatic filariasis: increased expression on lymphocytes in chronic lymphatic obstruction

Levels of C-reactive protein (CRP) were evaluated by enzyme immunoassay in patients infected with the filarial parasite Wuchereria bancrofti. Significantly elevated levels of CRP (P less than 0.001) were demonstrated in patients with chronic lymphatic pathology (CP; n = 18) compared to patients with asymptomatic microfilaremia (MF; n = 13) and normal volunteers (NV; n = 29). Serum levels of CRP showed an inverse correlation (rs = -0.37; P less than 0.05) with phosphocholine (PC)-containing filarial antigen that was present in the circulation of patients with bancroftian filariasis. Marked elevations in the percentage of CRP-binding lymphocytes were observed in patients with CP (mean = 44%; P less than 0.001) compared to those with MF (mean = 18%) or NV (mean = 3%). The increased percentage of surface CRP was not due to an abnormal change in major lymphocyte subset (CD5, CD4, CD8, or CD19). No significant correlation was noted between surface CRP and serum CRP; however, an inverse correlation was observed between surface CRP and PC-bearing circulating filarial Ag (rs = -0.64; P less than 0.001). Biosynthetic labeling and immunoprecipitation with anti-CRP antibodies indicated quantitative differences in the synthesis of CRP in patients with CP compared to MF and CP. Complexing of CRP with PC-containing Brugia malayi antigen (CRP-BmA) caused increased binding to normal lymphocytes (less than 8%), but not close to the extent seen in patients with CP (44%), suggesting de novo synthesis of CRP in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)