Hwang Wontae, Wantuch Paeton L, Bernshtein Biana, Zhiteneva Julia, Slater Damien, Vater Kian Hutt, Sridhar Sushmita, Oliver Elizabeth, Roach David J, Rao Sowmya, Turbett Sarah E, Knoot Cory J, Harding Christian M, Amin Mohammed Nurul, Cross Alan S, LaRocque Regina C, Rosen David A, Harris Jason B
bioRxiv. 2024 May 3:2024.05.01.591958. doi: 10.1101/2024.05.01.591958.
(Kpn) is the fourth leading cause of infection-related deaths globally, yet little is known about human antibody responses to invasive Kpn. In this study, we sought to determine whether the O-specific polysaccharide (OPS) antigen, a vaccine candidate, is immunogenic in humans with Kpn bloodstream infection (BSI). We also sought to define the cross-reactivity of human antibody responses among structurally related Kpn OPS subtypes and to assess the impact of capsule production on OPS-targeted antibody binding and function.
We measured plasma antibody responses to OPS (and MrkA, a fimbrial protein) in a cohort of patients with Kpn BSI and compared these with controls, including a cohort of healthy individuals and a cohort of individuals with BSI. We performed flow cytometry to measure the impact of Kpn capsule production on whole cell antibody binding and complement deposition, utilizing patient isolates with variable levels of capsule production and isogenic capsule-deficient strains derived from these isolates.
We enrolled 69 patients with Kpn BSI. Common OPS serotypes accounted for 57/69 (83%) of infections. OPS was highly immunogenic in patients with Kpn BSI, and peak OPS-IgG antibody responses in patients were 10 to 30-fold higher than antibody levels detected in healthy controls, depending on the serotype. There was significant cross-reactivity among structurally similar OPS subtypes, including the O1v1/O1v2, O2v1/O2v2 and O3/O3b subtypes. Physiological amounts of capsule produced by both hyperencapsulated and non-hyperencapsulated Kpn significantly inhibited OPS-targeted antibody binding and function.
OPS was highly immunogenic in patients with Kpn BSI, supporting its potential as a candidate vaccine antigen. The strong cross-reactivity observed between similar OPS subtypes in humans with Kpn BSI suggests that it may not be necessary to include all subtypes in an OPS-based vaccine. However, these observations are tempered by the fact that capsule production, even in non-highly encapsulated strains, has the potential to interfere with OPS antibody binding. This may limit the effectiveness of vaccines that exclusively target OPS.
National Institute of Allergy and Infectious Diseases at the National Institutes of Health.
Despite the potential of O-specific polysaccharide (OPS) as a vaccine antigen against (Kpn), the immunogenicity of OPS in humans remains largely unstudied, creating a significant knowledge gap with regard to vaccine development. A search of PubMed for publications up to March 18, 2024, using the terms " " and "O-specific polysaccharide" or "O-antigen" or "lipopolysaccharide" revealed no prior studies addressing OPS antibody responses in humans with Kpn bloodstream infections (BSI). One prior study evaluated antibody response to a single lipopolysaccharide (which contains one subtype of OPS) in humans with invasive Kpn infection; however, in this study OPS typing of the infecting strains and target antigen were not described. Our investigation into OPS immunogenicity in a human cohort marks a significant advance. Analyzing plasma antibody responses in 69 patients with Kpn BSI, we found OPS to be broadly immunogenic across all the types and subtypes examined, and there was significant cross-reactivity among structurally related OPS antigens. We also demonstrated that Kpn capsule production inhibit OPS antibody binding and the activation of complement on the bacterial surface, even in classical Kpn strains expressing lower levels of capsule. While the immunogenicity and broad cross-reactivity of OPS in humans with Kpn BSI suggests it is a promising vaccine candidate, the obstruction of OPS antibody binding and engagement by physiologic levels of Kpn capsule underscores the potential limitations of an exclusively OPS-antigen based vaccine for Kpn. Our study provides insights for the strategic development of vaccines aimed at combating Kpn infections, an important antimicrobial resistant pathogen.
肺炎克雷伯菌（Kpn）是全球感染相关死亡的第四大主要原因，但对于人类针对侵袭性Kpn的抗体反应知之甚少。在本研究中，我们试图确定一种候选疫苗O特异性多糖（OPS）抗原在患有Kpn血流感染（BSI）的人类中是否具有免疫原性。我们还试图确定人类抗体反应在结构相关的Kpn OPS亚型之间的交叉反应性，并评估荚膜产生对以OPS为靶点的抗体结合和功能的影响。
我们测量了一组Kpn BSI患者对OPS（以及菌毛蛋白MrkA）的血浆抗体反应，并将其与对照组进行比较，对照组包括一组健康个体和一组患有BSI的个体。我们进行了流式细胞术，以测量Kpn荚膜产生对全细胞抗体结合和补体沉积的影响，使用具有不同荚膜产生水平的患者分离株以及从这些分离株衍生的同基因荚膜缺陷菌株。
我们招募了69名患有Kpn BSI的患者。常见的OPS血清型占感染的57/69（83%）。OPS在患有Kpn BSI的患者中具有高度免疫原性，患者中OPS-IgG抗体反应峰值比健康对照组中检测到的抗体水平高10至30倍，具体取决于血清型。在结构相似的OPS亚型之间存在显著的交叉反应性，包括O1v1/O1v2、O2v1/O2v2和O3/O3b亚型。高荚膜化和非高荚膜化的Kpn产生的生理量的荚膜均显著抑制以OPS为靶点的抗体结合和功能。
OPS在患有Kpn BSI的患者中具有高度免疫原性，支持其作为候选疫苗抗原的潜力。在患有Kpn BSI的人类中观察到的相似OPS亚型之间的强交叉反应性表明，在基于OPS的疫苗中可能没有必要包含所有亚型。然而，这些观察结果受到以下事实的影响，即即使在非高度荚膜化菌株中，荚膜产生也有可能干扰OPS抗体结合。这可能会限制仅靶向OPS的疫苗的有效性。
美国国立卫生研究院国家过敏和传染病研究所。
尽管O特异性多糖（OPS）作为针对肺炎克雷伯菌（Kpn）的疫苗抗原有潜力，但OPS在人类中的免疫原性在很大程度上仍未得到研究，这在疫苗开发方面造成了重大的知识空白。在PubMed上搜索截至2024年3月18日的出版物，使用“肺炎克雷伯菌”和“O特异性多糖”或“O抗原”或“脂多糖”等术语，未发现之前有研究探讨患有Kpn血流感染（BSI）的人类中的OPS抗体反应。一项先前的研究评估了患有侵袭性Kpn感染的人类对单一脂多糖（其包含一种OPS亚型）的抗体反应；然而，在该研究中未描述感染菌株的OPS分型和靶抗原。我们对人类队列中OPS免疫原性的研究标志着一个重大进展。通过分析69名患有Kpn BSI的患者的血浆抗体反应，我们发现OPS在所检查的所有类型和亚型中具有广泛的免疫原性，并且在结构相关的OPS抗原之间存在显著的交叉反应性。我们还证明，即使在表达较低水平荚膜的经典Kpn菌株中，Kpn荚膜产生也会抑制OPS抗体结合和细菌表面补体的激活。虽然OPS在患有Kpn BSI的人类中的免疫原性和广泛的交叉反应性表明它是一种有前景的候选疫苗，但Kpn荚膜的生理水平对OPS抗体结合和参与的阻碍突出了仅基于OPS抗原的Kpn疫苗的潜在局限性。我们的研究为旨在对抗Kpn感染（一种重要的抗菌耐药病原体）的疫苗的战略开发提供了见解。
