Plasmodium falciparum infection during dry season: IgG responses to Anopheles gambiae salivary gSG6-P1 peptide as sensitive biomarker for malaria risk in Northern Senegal

Abstract

BackgroundThe Northern part of Senegal is characterized by a low and seasonal transmission of malaria. However, some Plasmodium falciparum infections and malaria clinical cases are reported during the dry season. This study aims to assess the relationship between IgG antibody (Ab) responses to gSG6-P1 mosquito salivary peptide and the prevalence of P. falciparum infection in children during the dry season in the Senegal River Valley. The positive association of the Ab response to gSG6-P1, as biomarker of human exposure to Anopheles vector bite, and P. falciparum infectious status (uninfected, infected-asymptomatic or infected-symptomatic) will allow considering this biomarker as a potential indicator of P. falciparum infection risk during the dry season.MethodsMicroscopic examination of thick blood smears was performed in 371 and 310 children at the start (January) and at the end (June) of the dry season, respectively, in order to assess the prevalence of P. falciparum infection. Collected sera were used to evaluate IgG response to gSG6-P1 by ELISA. Association between parasitological and clinical data (infected-asymptomatic or infected-symptomatic) and the anti-gSG6-P1 IgG levels were evaluated during this period.ResultsThe prevalence of P. falciparum infection was very low to moderate according to the studied period and was higher in January (23.5%) compared to June (3.5%). Specific IgG response was also different between uninfected children and asymptomatic carriers of the parasite. Children with P. falciparum infection in the dry season showed higher IgG Ab levels to gSG6-P1 than uninfected children.ConclusionsThe results strengthen the hypothesis that malaria transmission is maintained during the dry season in an area of low and seasonal transmission. The measurement of IgG responses to gSG6-P1 salivary peptide could be a pertinent indicator of human malaria reservoir or infection risk in this particular epidemiological context. This promising immunological marker could be useful for the evaluation of the risk of P. falciparum exposure observed during dry season and, by consequences, could be used for the survey of potential pre-elimination situation.

An insight into the sialotranscriptome and virome of Amazonian anophelines

“…This information may be helpful not only for the characterization of novel activities, but also for the identification of salivary biomarkers to evaluate human exposure to malaria vectors in Central and South America. This may be especially relevant since the A. gambiae gSG6, which proved to be a reliable marker of exposure to African [92][93][94], Asian [95], and Melanesian [96] malaria vectors it is not found in New World anopheline species, as suggested earlier [30] and confirmed by the present study. Additionally, we discovered novel viruses following analysis of the transcriptomes, a procedure that should become standard within future RNAseq studies.…”

Evaluation of Malaria Urban Risk Using an Immuno-Epidemiological Biomarker of Human Exposure to Anopheles Bites

“…19 Thereafter, several studies also showed that the gSG6-P1 salivary peptide is a suitable immunological biomarker for assessing low-level human exposure to Anopheles bites. 20,25,29,30 According to the entomological data, it was here observed that the HBR was 1) higher in the rural areas than in the urban areas during both seasons and 2) lower in the dry season than the rainy season for both urban and rural areas. However, the results with the salivary biomarker appeared to be contradictory.…”

“…Enzyme-linked immunosorbent assays were carried out on sera to measure the IgG level to the gSG6-P1 peptide, as previously described. 25 Briefly, Maxisorp plates (Nunc, Roskilde, Denmark) were coated with gSG6-P1 (20 μg/mL) in phosphate-buffered saline (PBS). After washing (demineralized water + Tween 0.1%), each serum sample was incubated in duplicate at 4°C overnight at a 1/320 dilution (in PBS with 1% Tween 20).…”

Operational Assessment of Long-Lasting Insecticidal Nets by Using an Anopheles Salivary Biomarker of Human–Vector Contact

“…19 In addition, the biomarker seemed to be a useful tool for monitoring the risk of malaria transmission in the dry season (similar context than a pre-elimination area presenting very low exposure to Anopheles vector) and discriminating uninfected children to infected ones. 20 Another study evaluated the risk of malaria transmission in children and adults living in Dakar (Senegal) using the salivary biomarker of exposure to Anopheles bites. Results showed considerable variations in anti-gSG6-P1 IgG response levels within and between districts, despite the general context of low exposure to Anopheles.…”