Data from: Helminth interaction with the host immune system: short-term benefits and costs in relation to the infectious environment

Chronic infections imply that the parasite and the host immune system
closely interact for a long time without a fatal outcome. Environmental
changes encountered by hosts and parasites, such as coinfections, can
deeply affect the stability of this apparent equilibrium. Our study aimed
to determine the effect of the infectious environment on the costs and
benefits of chronic infection with the gut nematode Heligmosomoides
polygyrus in mice. Heligmosomoides polygyrus is known for its capacity to
actively interfere with the host immune response by secreting molecules
that can dampen immunity. We simulated bacterial coinfection of H.
polygyrus-infected CBA-strain mice during the chronic phase of the
infection by injecting them with Escherichia coli lipopolysaccharide. We
found that infection by H. polygyrus induced only weak costs for the host
(in terms of reproductive investment) and was characterized by the
upregulation of both Th1 (interferon-γ) and anti-inflammatory
(transforming growth factor-β) cytokines, which is favorable to parasite
persistence. However, when co-occurring with the simulated bacterial
infection, H. polygyrus infection was associated with a pronounced shift
toward a pro-inflammatory status, which was deleterious to both the
parasite and the host. Our study highlights the dynamic equilibrium
reached during chronic infection, where a rapid environmental change, such
as a concomitant bacterial infection, can deeply affect the outcome of the
host-parasite interaction.