Background

Some strains of Bacillus Calmette–Guérin (BCG) vaccine not only confer protection against disseminated forms of tuberculosis, but also reduce all-cause mortality by the induction of protection against infections with non-related pathogens.

Objectives

We review evidence for non-specific protection induced by BCG vaccination against viral infections, discuss possible mechanisms of action, and summarize implications for vaccination policies and vaccine discovery.

Sources

Relevant studies retrieved from PubMed and clinicaltrials.gov.

Content

Numerous epidemiological, clinical and immunological studies demonstrate that BCG vaccination impacts the immune response to subsequent infections, resulting in reduced morbidity and mortality. Important lines of evidence indicating that BCG protects against viral pathogens comes from experimental studies in mice showing that BCG offers protection against various DNA and RNA viruses, including herpes and influenza viruses. Recently, the effect of BCG on an experimental viral infection in humans has been demonstrated. These effects are thought to be mediated via the induction of innate immune memory and heterologous lymphocyte activation, resulting in enhanced cytokine production, macrophage activity, T-cell responses and antibody titres.

Implications

The discovery of innate immune memory has greatly improved our understanding of the mechanisms underlying the non-specific effects induced by BCG vaccination. However, a full understanding of the molecular mechanisms that underlie this phenomenon is still evolving. By identifying the factors that impact the non-specific effects of BCG, we will take an important step towards novel therapeutic options and vaccination strategies, which might lead to a reduction in severe morbidity and mortality associated with viral infections.

中文翻译：

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卡介苗疫苗对病毒感染的非特异性作用

背景

某些卡介苗（BCG）疫苗不仅可以预防传播的结核病，而且可以通过诱导针对非相关病原体的感染来降低全因死亡率。

目标

我们审查了BCG疫苗对病毒感染诱导的非特异性保护的证据，讨论了可能的作用机制，并概述了疫苗接种政策和疫苗发现的意义。

资料来源

从PubMed和Clinicaltrials.gov检索到的相关研究。

内容

大量的流行病学，临床和免疫学研究表明，卡介苗接种会影响对随后感染的免疫反应，从而降低发病率和死亡率。表明BCG可以抵抗病毒病原体的重要证据来自对小鼠的实验研究，表明BCG可以抵抗各种DNA和RNA病毒，包括疱疹和流感病毒。最近，已经证明了卡介苗对人实验性病毒感染的作用。这些作用被认为是通过诱导先天免疫记忆和异源淋巴细胞活化而介导的，从而导致细胞因子产生，巨噬细胞活性，T细胞反应和抗体滴度的提高。

含意

固有免疫记忆的发现大大提高了我们对BCG疫苗诱导的非特异性作用的潜在机制的理解。但是，对这种现象背后的分子机制的全面理解仍在发展中。通过确定影响卡介苗非特异性作用的因素，我们将朝着新的治疗选择和疫苗接种策略迈出重要的一步，这可能会导致与病毒感染相关的严重发病率和死亡率降低。