Last Updated: 16/02/2023
Serological exposure markers for P. vivax in pregnant women
Objectives
To determine the utility of Serological Exposure Markers (SEM) for P. vivax to identify pregnant women at risk of P. vivax infection during pregnancy and following childbirth.
Over 90 million pregnancies are at risk of P. vivax infection annually, primarily in the Asia-Pacific region. Pregnant and breastfeeding women represent an important reservoir for P. vivax transmission. P. vivax infection during pregnancy is associated with adverse pregnancy outcomes and maternal anaemia. Current rapid diagnostic tests and light microscopy have low sensitivity to detect blood stage infection and there are currently no tests to detect hypnozoites, dormant P. vivax liver stages. Serological exposure markers (SEMs) for P. vivax have potential to identify women at high risk of relapse who can be prioritized for chemoprophylaxis during pregnancy and radical cure after pregnancy. This may reduce adverse pregnancy outcomes in the current and subsequent pregnancy and could reduce the proportion of pregnant and breastfeeding women contributing to malaria transmission. Pregnant women also represent an accessible sentinel population for malaria surveillance. SEMs have not been evaluated in pregnant women.
We will conduct a retrospective cohort study using stored samples from two PNG pregnancy studies. Women were screened for P. falciparum and P. vivax infection by PCR at antenatal enrolment, during pregnancy and at birth. The roll out of malaria control measures that occurred in interval between these studies resulted in substantial declines of P. falciparum and P. vivax prevalence and a shift from microscopic to submicroscopic infections in the study area. We will measure IgG responses to a panel of 8 key P. vivax candidate proteins, including PVX_094255 (RBP2b), at antenatal enrolment and at birth using a published multiplex Luminex assay. The multiplex Luminex assay involves coupling the P. vivax proteins to magnetic beads with different internal colours. This enables antibodies to be measured to all 8 P. vivax SEMs in one assay well, thus using very little of the precious field samples whilst generating large amounts of data. The performance of this panel, to identify women with PCR-confirmed vivax infection during the pregnancy (and who are thus at risk of postpartum relapse), will be determined using receiver-operator curves. The panel will then be applied to identify women at their first antenatal visit as at risk of recurrence.
Aug 2020 — Oct 2023
$15,000
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