Australian Institute of Tropical Health & Medicine, James Cook University, Cairns, QLD, 4870, Australia.
Department of Infection Biology, London School of Hygiene & Tropical Medicine, London, UK.
Malar J. 2019 Oct 1;18(1):334. doi: 10.1186/s12936-019-2975-8.
Mosquito saliva elicits immune responses in humans following mosquito blood feeding. Detection of human antibodies recognizing the Anopheles gambiae salivary gland protein 6 (gSG6) or the gSG6-P1 peptide in residents of Africa, South America and Southeast Asia suggested the potential for these antibodies to serve as a universal marker to estimate human biting rates. Validating the utility of this approach requires concurrent comparisons of anopheline biting rates with antibodies to the gSG6 protein to determine the sensitivity and specificity of the assay for monitoring changes in vector populations. This study investigated whether seroprevalence of anti-gSG6 antibodies in humans reflected the relative exposure to Anopheles farauti bites in the Solomon Islands as estimated from sympatric human landing catches.
Human biting rates by An. farauti were estimated by landing catches at 10 sampling sites in each of 4 villages during the wet and dry seasons. Human serum samples from these same villages were also collected during the wet and dry seasons and analysed for antibody recognition of the gSG6 antigen by the Luminex xMAP platform. Antibody titres and prevalence were compared to HLCs at the sampling sites nearest to participants' residences for utility of anti-gSG6 antibodies to estimate human exposure to anopheline bites.
In this study in the Solomon Islands only 11% of people had very high anti-gSG6 antibody titres, while other individuals did not recognize gSG6 despite nightly exposures of up to 190 bites by An. farauti. Despite clear spatial differences in the human biting rates within and among villages, associations between anti-gSG6 antibody titres and biting rates were not found.
Few studies to date have concurrently measured anopheline biting rates and the prevalence of human antibodies to gSG6. The lack of association between anti-gSG6 antibody titres and concurrently measured human biting rates suggests that the assay for human anti-gSG6 antibodies lacks sufficient sensitivity to be a biomarker of An. farauti exposure at an epidemiologically relevant scale. These findings imply that an improvement in the sensitivity of serology to monitor changes in anopheline biting exposure may require the use of saliva antigens from local anophelines, and this may be especially true for species more distantly related to the African malaria vector An. gambiae.
蚊子在吸食人血后会引起人体的免疫反应。在非洲、南美洲和东南亚的居民中检测到识别冈比亚按蚊唾液腺蛋白 6（gSG6）或 gSG6-P1 肽的人抗体，表明这些抗体有可能成为一种通用标记物，用于估计人类叮咬率。要验证这种方法的有效性，需要将按蚊叮咬率与 gSG6 蛋白抗体进行同时比较，以确定该检测方法监测蚊群变化的敏感性和特异性。本研究调查了人类对 gSG6 抗体的血清阳性率是否反映了在所罗门群岛相对暴露于法鲁按蚊叮咬的情况，这种暴露情况是根据同时进行的人体着陆捕捉法来估计的。
在 4 个村庄的 10 个采样点，在雨季和旱季分别进行人体着陆捕捉，以估计法鲁按蚊的叮咬率。在雨季和旱季，还从这些相同的村庄收集人类血清样本，并使用 Luminex xMAP 平台分析 gSG6 抗原的抗体识别情况。将抗体滴度和流行率与距参与者居住地最近的采样点的 HLC 进行比较，以评估抗 gSG6 抗体估计人类接触按蚊叮咬的效用。
在所罗门群岛进行的这项研究中，只有 11%的人具有非常高的 gSG6 抗体滴度，而其他个体尽管每晚最多被法鲁按蚊叮咬 190 次，却无法识别 gSG6。尽管村庄内和村庄之间的人体叮咬率存在明显的空间差异，但未发现 gSG6 抗体滴度与叮咬率之间存在关联。
迄今为止，很少有研究同时测量按蚊叮咬率和人类对 gSG6 的抗体流行率。抗 gSG6 抗体滴度与同时测量的人类叮咬率之间缺乏关联表明，用于检测人类抗 gSG6 抗体的检测方法缺乏足够的敏感性，无法在流行病学相关的范围内成为法鲁按蚊暴露的生物标志物。这些发现意味着，为了提高监测按蚊叮咬暴露变化的血清学敏感性，可能需要使用来自当地按蚊的唾液抗原，对于与非洲疟疾媒介按蚊关系较远的物种，这可能尤其如此。
