Naturally acquired opsonic antipneumococcal antibodies are commonly found in nonvaccinated adults and confer protection against infection and colonization. Despite this, only limited data exist regarding the adaptive immune response after pneumococcal exposure. To investigate the dynamics of naturally acquired antipneumococcal immunity in relation to an episode of infection, opsonic antibody activity was studied with paired acute-phase and convalescent-phase sera obtained from 54 patients with pneumococcal community-acquired pneumonia (CAP) using an opsonophagocytic assay (OPA). Results were compared with clinical characteristics and anticapsular immunoglobulin (Ig) concentrations. Interestingly, a nonfunctional opsonic antibody response (characterized by a decreased convalescent-phase serum OPA titer compared to that of the acute-phase serum or undetectable titers in both sera) was observed in 19 (35%) patients. A nonfunctional convalescent-phase response was significantly more common among patients with invasive pneumococcal disease (i.e., bacteremia) than in patients without invasive disease (53%; P = 0.019). Remaining individuals exhibited either an increased convalescent-phase OPA titer (n = 24 [44%]) or a detectable, but unchanged, titer at both time points (n = 11 [20%]). No correlation was found between anticapsular Ig concentrations and OPA titers. Our findings indicate that an episode of pneumococcal infection may act as an immunizing event, leading to an improved antipneumococcal adaptive immune status. However, in some cases, when patients with CAP also suffer from bacteremia, a nonfunctional opsonic antibody response may occur. Furthermore, the results suggest that factors other than anticapsular Ig concentrations are important for opsonic antibody activity in serum.IMPORTANCE Numerous reports on the dynamics of antipneumococcal immunity in relation to immunization with pneumococcal vaccines and on the prevalence of naturally acquired immunity in various populations have been published. In contrast, studies on the dynamics of the humoral immune response triggered by pneumococcal infection are scarce. This study provides valuable information that will contribute to fill this knowledge gap. Our main results indicate that a functional immune response frequently fails to occur after CAP, predominantly among patients with simultaneous bacteremia.

中文翻译：

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肺炎球菌性肺炎后常发生非功能性调理抗体反应，并与浸润性疾病相关。

天然获得的调理素抗肺炎球菌抗体通常在未接种疫苗的成年人中发现，可防止感染和定植。尽管如此，关于肺炎球菌暴露后的适应性免疫反应只有有限的数据。为了研究与感染发作有关的自然获得性抗肺炎球菌免疫力的动态变化，使用调理吞噬细胞分析法，从54例肺炎球菌社区获得性肺炎（CAP）患者中获得了成对的急性期和恢复期血清，研究了调理素抗体活性（ OPA）。将结果与临床特征和抗荚膜免疫球蛋白（Ig）浓度进行比较。有趣的是 在19名（35％）患者中观察到无功能性调理抗体反应（与急性期血清相比，恢复期血清OPA滴度降低或两种血清均未检测到滴度）。侵袭性肺炎球菌疾病（即菌血症）患者的无功能恢复期应答明显高于无侵袭性疾病的患者（53％； P = 0.019）。其余个体在两个时间点均显示出恢复期OPA效价增加（n = 24 [44％]）或可检测但未改变的效价（n = 11 [20％]）。在抗荚膜Ig浓度和OPA滴度之间未发现相关性。我们的发现表明，肺炎球菌感染可能是一种免疫事件，导致抗肺炎球菌的适应性免疫状态得到改善。但是，在某些情况下，当CAP患者也患有菌血症时，可能会发生功能性调理抗体反应。此外，结果表明除抗荚膜Ig浓度外的其他因素对于血清中的调渗抗体活性也很重要。重要的报告涉及抗肺炎球菌免疫与肺炎球菌疫苗免疫相关的动力学以及各种人群中自然获得性免疫的普遍性。发表。相反，关于由肺炎球菌感染引发的体液免疫反应动力学的研究很少。这项研究提供了宝贵的信息，将有助于填补这一知识空白。我们的主要结果表明，CAP后，功能性免疫反应通常无法发生，主要是在同时发生菌血症的患者中。