Naturally acquired antibody kinetics against Plasmodium vivax antigens in people from a low malaria transmission region in western Thailand

Abstract

Plasmodium vivax is the dominant Plasmodium spp. causing the disease malaria in low-transmission regions outside of Africa. These regions often feature high proportions of asymptomatic patients with sub-microscopic parasitaemia and relapses. Naturally acquired antibody responses are induced after Plasmodium infection, providing partial protection against high parasitaemia and clinical episodes. However, previous work has failed to address the presence and maintenance of such antibody responses to P. vivax particularly in low-transmission regions. We followed 34 patients in western Thailand after symptomatic P. vivax infections to monitor antibody kinetics over 9 months, during which no recurrent infections occurred. We assessed total IgG, IgG subclass and IgM levels to up to 52 P. vivax proteins every 2-4 weeks using a multiplexed Luminex assay, and identified protein-specific variation in antibody longevity. Generally, an increase in antibody level was observed within 1-week post symptomatic infection, followed by an exponential decay of different rates. We observed mostly IgG1 dominance and IgG3 sub-dominance in this population. IgM responses followed similar kinetic patterns to IgG, with some proteins unexpectedly inducing long-lived IgM responses. We also monitored antibody responses against 27 IgG-immunogenic antigens in 30 asymptomatic individuals from a similar region. Our results demonstrate that most antigens induced robust and long-lived total IgG responses following asymptomatic infections in the absence of (detected) boosting infections. Our work provides new insights into the development and maintenance of naturally acquired immunity to P. vivax and will guide the potential use of serology to indicate immune status and/or identify populations at risk.

Plasmodium vivax malaria serological exposure markers: assessing the degree and implications of cross-reactivity with P. knowlesi

“…The peak cross-reactive antibody response was at day 7 following infection, which is the same timing as the peak P. knowlesi -antibody response reported previously using a similar sample set from Sabah, Malaysia 24 . This is also in line with the timing of peak IgG antibody responses reported for other species such as P. falciparum and P. vivax (within the first two weeks post-treatment) 36–38 . Antibodies against the P. vivax proteins had reduced in magnitude by day 28 post-infection, and the median IgG levels were below the seropositivity cut-off for all but one P. vivax protein (MSP1-19) at 1-year post- P. knowlesi infection.…”