Cytokine immune response profiles during 5 intestinal helminths and Mycobacterium 6 tuberculosis coinfection: An in vitro and human ex vivo study in KwaZulu-Natal.
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Date
2023
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Abstract
Background: There is a striking geographic overlap between helminths and tuberculosis (TB),
particularly in developing countries like Africa. Underprivileged communities are more
susceptible to these illnesses due to poverty, poor sanitation, and other environmental factor Helminth and tuberculosis infections exhibit distinct immune responses, which may be
antagonistic in coinfected hosts and lead to poor prognosis. Helminth infections induce anti422
inflammatory Th2/Treg responses contrary to the pro-inflammatory Th1 responses triggered
by Mycobacterium tuberculosis (Mtb) infection. Reduced TB protection has been associated
with a strong Th2 response. Uncertainty exists on how helminth infection affects the host’s
resistance to TB. This necessitates further investigation of immune responses in helminths and
TB coinfection cases, particularly in KwaZulu-Natal (KZN).
Aim: To determine the cytokine response profiles during intestinal helminth and TB coinfection
using lymphocytic Jurkat and monocytic THP-1 cell lines for the in vitro study and TB and
helminth coinfected South African adults for the human ex vivo study.
Methods: Lymphocytic Jurkat and monocytic THP-1 cell lines were stimulated for 24 and 48
hours with Mtb H37Rv and Ascaris lumbricoides (A. lumbricoides) excretory-secretory protein
extracts for the in vitro study. A cross-sectional study on consenting adult participants (≥18
years) (n = 414) recruited from primary health care clinics was conducted between March 2020
and August 2021 in Durban, KwaZulu Natal, for the pilot human ex vivo study. Blood and stool
samples were collected from the recruited participants. The Kato-Katz and Mini-Parasep faecal
parasite concentration techniques were used to detect intestinal parasite infections in stool
samples. Blood samples were analysed to determine A. lumbricoides-specific immunoglobulin
E (IgE) and immunoglobulin G4 (IgG4) levels to improve microscopy sensitivity.
In this study, cytokine analysis was undertaken for 164 participants; 96 were HIV infected and
had to be excluded, leaving 68 eligible participants. The eligible individuals were subdivided
into uninfected controls (no helminth and TB infection) (n = 18), helminth only infected (n =
TB only infected (n = 6), and TB and helminth co-infected (n = 6) groups. Thereafter, for
both the in vitro and ex vivo study, the gene expression profiles of the T helper type 1(Th1) and
transcription factors [Interferon-γ (IFN-γ), Tumour necrosis factor-α (TNF-α), Interleukin-2 (ILxvii
2), Nuclear factor of activated T cells 2 (NFATC2), Eomesodermin 446 (eomes), T helper 2 (Th2) and
transcription factors (Interleukin-4 (IL-4), Interleukin5 (IL-5, Transforming growth factor-β
(TGF-β), T helper type 17 (Th17) (Interleukin-17 (IL-17), immune protein and proteases
(Granzyme B, Perforin), Regulatory T cells (Tregs) (Interleukin-10 (IL-10) and Fork head box
P3 (FoxP3)] and the uninfected controls, TB alone, helminth alone and coinfected groups were
determined using RT-qPCR.
Results: (i) In vitro study: TB-stimulated Jurkat cells had significantly higher levels of IFN-γ,
TNF-α, Granzyme B, and perforin compared to unstimulated controls, LPS, A. lumbricoides,
and A. lumbricoides plus TB costimulated cells (p<0.0001). IL-2, IL-17, Eomes, and NFATC2
levels were also higher in TB-stimulated Jurkat cells (p<0.0001). TB alone stimulated cells had
lower IL-5 and IL-4 levels compared to A. lumbricoides alone stimulated and TB plus A.
lumbricoides costimulated Jurkat and THP-1 cells (p<0.0001. A. lumbricoides alone stimulated
cells had higher IL-4 levels compared to TB plus A. lumbricoides costimulated Jurkat and THP-
1 cells (p<0.0001). TGF-β levels were also lower in TB alone stimulated cells compared to TB
plus A. lumbricoides costimulated cells. IL-10 levels were lower in TB stimulated Jurkat and
THP-1 cells compared to TB plus A. lumbricoides costimulated cells (p<0.0001. (ii) Ex vivo
study: Similar results were noted for both the in vitro and the ex vivo study, although the human
study had a smaller sample size.
Conclusion: Data suggest that helminths induce a predominant anti-inflammatory Th2 and
Treg response which may downregulate critical proinflammatory Th1 responses crucial for TB
protection.
Description
Masters Degree. University of KwaZulu-Natal, Durban.