Filarial infection during pregnancy has profound consequences on immune response and disease outcome in children: A birth cohort study.
PLoS Negl Trop Dis 2018;
12:e0006824. [PMID:
30252839 PMCID:
PMC6173457 DOI:
10.1371/journal.pntd.0006824]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Revised: 10/05/2018] [Accepted: 09/09/2018] [Indexed: 11/19/2022] Open
Abstract
Background
Current Global Program to Eliminate Lymphatic Filariasis (GPELF) that prohibits pregnant mothers and children below two years of age from coverage targeted interruption of transmission after 5–6 rounds of annual mass drug administration (MDA). However, after more than 10 rounds of MDA in India the target has not been achieved, which poses challenge to the researchers and policy makers. Several studies have shown that in utero exposure to maternal filarial infections plays certain role in determining the susceptibility and disease outcome in children. But the mechanism of which has not been studied extensively. Therefore the present study was undertaken to understand the mechanism of immune modulation in children born to filarial infected mother in a MDA ongoing area.
Methodology and principal finding
To our knowledge this is the first study to conduct both cellular and humoral immunological assays and follow up the children until older age in a W bancrofti endemic area,where the microfilariae (Mf) rate has come down to <1% after 10 rounds of MDA. A total 57 (32: born to infected, 25: born to uninfected mother) children were followed up. The infection status of children was measured by presence of Mf and circulating filarial antigen (CFA) assay. Filaria specific IgG1, IgG2, IgG3 and IgG4 responses were measured by ELISA. Plasma level of IL-10 and IFN-γ were evaluated by using commercially available ELISA kit. The study reveals a high rate of acquisition of filarial infection among the children born to infected mother compared to uninfected mothers. A significantly high level of IgG1 and IgG4 was observed in children born to infected mother, whereas high level of IgG3 was marked in children born to uninfected mother. Significantly high level of IL-10 positively correlated with IgG4 have been observed in infected children born to infected mother, while high level of IFN-γ positively correlated with IgG3 was found in infection free children born to mother free from infection at the time of pregnancy. Moreover a negative correlation between IL-10 and IFN-γ has been observed only among the infected children born to infected mother.
Significance conclusion
The study shows a causal association between maternal filarial infection and impaired or altered immune response in children more susceptible to filarial infection during early childhood. As lymphatic damage that commences in childhood during asymptomatic stage has major implications from public health point of view, understanding maternal programming of the newborn immune system could provide a basis for interventions promoting child health by implementing MDA campaigns towards all women of childbearing age and young children in achieving the target of global elimination of LF.
Lymphatic filariasis (LF) has been targeted for elimination by 2020 through a major global initiative. The elimination strategy mainly aims to interrupt the transmission, or spread of infection, through annual mass drug administration (MDA) to entire at-risk population except the pregnant women and children below two years of age. Nevertheless, evidence exists that maternal W bancrofti infection during pregnancy can increase the susceptibility of the offspring to such infection during early childhood, the precise mechanism of which is not clear. Therefore in this study we have made an attempt to elucidate the mechanism of alteration of the foetal immunity due to maternal filarial infection, which may help developing strategy to strengthen the elimination programme. It is known that regulatory T cells are responsible for development of hyporesponsiveness, a condition that supports parasite growth and maternal filarial infection influences the development of T-regulatory cells from infancy to early childhood. Since T-reg cell can induce the production of regulatory cytokine IL-10 that often implicated in induction of IgG4 and we have observed an increased level of IL-10 / IgG4 and decreased levels of IFN- γ/ IgG3 in cord blood of infected mothers, we have thought that the modulation that takes place in utero affects the immune response and eventually disease outcome in early childhood. In order to prove our hypothesis, we have followed up a cohort of 57 children born to infected and uninfected mother in a MDA ongoing area of Odisha, India, where we have found a high rate of acquisition of filarial infection by children born to infected mother. Moreover a significantly high as well as a positive correlation between IgG4 and IL-10 levels in children born to infected mother during early childhood indicates that IL-10 and IgG4 contribute to immune modulation that starts during the period of gestation and continues till the early childhood helping the filarial parasites to evade destruction by their host’s immune system. In contrast a high level of IFN-γ and IgG3 in infection free children irrespective of infection status of mother shows the protective mechanism against the parasite. Additionally the correlation between antibodies and cytokines indicates that susceptibility to filarial infection during early childhood is due to the in utero modulation of T and B responses. Our findings highlights that every effort should be made to advance implementation policies and continue the focus to use the currently available anti-filarial drugs to prevent filarial infection before pregnancy as well as early childhood to achieve the target on time.
Collapse