Bacterial small RNAs (sRNAs) posttranscriptionally regulate gene expressions involved in various biological processes, including pathogenicity. Our previous study identified sRNAs, the expression of which was up-regulated in
Bordetella pertussis
, the causative agent of whooping cough, upon tracheal colonization of the bacteria; however, their roles in bacterial infection remain unknown. Here, we found that one sRNA, Bpr4, contributes to
B. pertussis
infection by posttranscriptionally up-regulating filamentous hemagglutinin (FHA), a major adhesin of the bacteria. Bpr4 bound to the 5′ untranslated region of
fhaB
mRNA encoding FHA and inhibited its degradation mediated by RNaseE. Our results demonstrated that Bpr4 up-regulation was triggered by the interference of flagellar rotation, which caused the disengagement of MotA, a flagellar stator. Subsequently, MotA activated a diguanylate cyclase to generate cyclic di-GMP, which plays a role in Bpr4 up-regulation through the RisK/RisA two-component system. Our findings indicate that a flagellum-triggered sensory system contributes to
B. pertussis
infection.
In addition to the Gram-negative bacterium
Bordetella pertussis
, the etiological agent of pertussis,
Bordetella parapertussis
also causes respiratory infection in humans, with a mild pertussis-like disease. These bacteria are genetically closely related and share many virulence factors, including adhesins and toxins.
To assess the frequency of SARS-CoV-2 infection enhancing antibodies in the general population, we searched over 64 million heavy chain antibody sequences from healthy and COVID-19 patient repertoires for sequences similar to 11 previously reported enhancing antibodies. Although the distribution of sequence identities was similar in COVID-19 and healthy repertoires, the COVID-19 hits were significantly more clonally expanded than healthy hits. Furthermore, among the tested hits, 17 out of 94 from COVID-19, compared with 2 out of 96 from healthy, bound to the enhancing epitope. A total of 6 of the 19 epitope-binding antibodies enhanced ACE2 receptor binding to the spike protein. Together, this study revealed that enhancing antibodies are far more frequent in COVID-19 patients than in healthy donors, but a reservoir of potential enhancing antibodies exists in healthy donors that could potentially mature to actual enhancing antibodies upon infection.
The pathogenic bacterium
Bordetella bronchiseptica
, which causes respiratory diseases in various mammals, exhibits distinct Bvg
+
and Bvg
−
phenotypes. The former represents the virulent phase, in which the bacteria express a set of virulence factors, while the role of the latter in the bacterial life cycle remains to be understood.
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