Filarial infection modulates the immune response to Mycobacterium tuberculosis through expansion of CD4+ IL-4 memory T cells

Abstract

Exaggerated CD4(+) T helper 2-specific cytokine producing memory T cell responses developing concomitantly with a T helper 1 response might have a detrimental role in immunity to infection caused by Mycobacterium tuberculosis. To assess the dynamics of Ag-specific memory T cell compartments in the context of filarial infection, we used multiparameter flow cytometry on PBMCs from 25 microfilaremic filarial-infected (Inf) and 14 filarial-uninfected (Uninf) subjects following stimulation with filarial Ag (BmA) or with the M. tuberculosis-specific Ag culture filtrate protein-10 (CFP-10). Our data demonstrated that the Inf group had a marked increase in BmA-specific CD4(+)IL-4(+) cells (median net frequency compared with baseline [Fo] = 0.09% versus 0.01%; p = 0.038) but also to CFP-10 (Fo = 0.16% versus 0.007%; p = 0.04) and staphylococcal enterotoxin B (Fo = 0.49% versus 0.26%; p = 0.04). The Inf subjects showed a BmA-specific expansion of CD4(+)CD45RO(+)IL-4(+) producing central memory (TCM, CD45RO(+)CCR7(+)CD27(+); Fo = 1.1% versus 0.5%; p = 0.04) as well as effector memory (TEM, CD45RO(+)CCR7(-)CD27(-); Fo = 1.5% versus 0.2%; p = 0.03) with a similar but nonsignificant response to CFP-10. In addition, there was expansion of CD4(+)IL-4(+)CD45RA(+)CCR7(+)CD27(+) (naive-like) in Inf individuals compared with Uninf subjects. Among Inf subjects with definitive latent tuberculosis, there were no differences in frequencies of IL-4-producing cells within any of the memory compartments compared with the Uninf group. Our data suggest that filarial infection induces Ag-specific, exaggerated IL-4 responses in distinct T cell memory compartments to M. tuberculosis-specific Ags, which are attenuated in subjects who are able to mount a delayed type hypersensitivity reaction to M. tuberculosis.

Figures

Figure1. Filarial infection is associated with filarial (BmA) as well as mycobacterial antigen (CFP10) and SEB induced increased frequencies of CD4+ cells producing IL-4

Peripheral blood mononuclear cells were cultured overnight with media alone or with BmA or CFP10 or SEB. Representative data are expressed as percent CD4+ cells expressing cytokines are shown as scatter plots in the top panel. Increase in CD4+ T cells producing IL-4 is expressed as net frequency (defined as antigen induced frequency-baseline frequency) in the Inf (n=25) and Uninf (n=14) groups are shown in response to BmA, CFP10 and SEB. Horizontal bars represent the median frequencies. P values were calculated using the Mann-Whitney test.

Figure2. BmA driven IL-4 expansion in filaria infected subjects occurs in TCM and TEM compartments in filaria infected subjects while CFP10 driven IL-4 expansion is primarily noted in NV cells, a pattern distinct from SEB induced expansion primarily in TEM cells

Representative data are expressed as percent CD4+ cells expressing cytokines in the four different memory compartments, Naïve-like (NV), RA+ Effector T cells (TEMRA), Central memory (TCM) and Effector memory (TEM). Box and whisker plots represent median with 95% confidence intervals and individual dots representing each subject. Increase in CD4+ T cells producing IL-4 is expressed as net frequency (defined as antigen induced frequency-baseline frequency) in the Inf (n=25) and Uninf (n=14) groups are shown in response to BmA, CFP10 and SEB. Horizontal bars represent the median frequencies. P values were calculated using the Mann-Whitney test.

Figure3. Filaria infected subjects show preferential IL-4 expansion (compared to IFN-γ and TNF-α) in the TCM and TEM compartments in response to BmA and CFP10. In the NV compartment Inf subjects have a dominant IL-4 response compared to Uninf subjects who have a dominant TNF-α response

Data is represented as pie charts comparing median net frequency in CD4+ cytokine producing (IL-4, IFN-γ and TNF-α) cells as parts of the whole response in the different memory compartments (NV, TEMRA TCM, TEM,) between Inf (n=25) and Uninf (n=14) groups in response to BmA, CFP10 and SEB

Figure 4. LTBI status (defined as a positive QuantiFERON TB Gold test) in filaria-infected subjects abrogates the increased IL-4 response to CFP10 in the NV and TCM compartments

Representative data are expressed as percent CD4+ cells expressing cytokines in the four different memory compartments, Naïve-like (NV), RA+ Effector T cells (TEMRA), Central memory (TCM) and Effector memory (TEM). Box and whisker plots represent median with 95% confidence intervals with individual dots representing each subject. Increase in CD4+ T cells producing IL-4 is expressed as net frequency (defined as antigen induced frequency-baseline frequency). Responses to CFP10 in healthy controls (Q-Uninf, n= 9) who were QuantiFERON TB Gold test negative (n=13) were compared separately with filaria infected subjects with positive (Q+Inf, n=6) and negative (Q-Inf, n= 7) QuantiFERON TB Gold test. Horizontal bars represent the median frequencies. P values were calculated using the Mann-Whitney test