Borrelia burgdorferi sensu lato (Bbsl), the causative agent of Lyme disease, establishes an initial infection in the host’s skin following a tick bite, and then disseminates to distant organs, leading to multisystem manifestations. Tick-to-vertebrate host transmission requires that Bbsl survives during blood feeding. Complement is an important innate host defense in blood and interstitial fluid. Bbsl produces a polymorphic surface protein, CspA, that binds to a complement regulator, Factor H (FH) to block complement activation in vitro. However, the role that CspA plays in the Bbsl enzootic cycle remains unclear. In this study, we demonstrated that different CspA variants promote spirochete binding to FH to inactivate complement and promote serum resistance in a host-specific manner. Utilizing a tick-to-mouse transmission model, we observed that a cspA-knockout B. burgdorferi is eliminated from nymphal ticks in the first 24 hours of feeding and is unable to be transmitted to naïve mice. Conversely, ectopically producing CspA derived from B. burgdorferi or B. afzelii, but not B. garinii in a cspA-knockout strain restored spirochete survival in fed nymphs and tick-to-mouse transmission. Furthermore, a CspA point mutant, CspA-L246D that was defective in FH-binding, failed to survive in fed nymphs and at the inoculation site or bloodstream in mice. We also allowed those spirochete-infected nymphs to feed on C3-/- mice that lacked functional complement. The cspA-knockout B. burgdorferi or this mutant strain complemented with cspA variants or cspA-L246D was found at similar levels as wild type B. burgdorferi in the fed nymphs and mouse tissues. These novel findings suggest that the FH-binding activity of CspA protects spirochetes from complement-mediated killing in fed nymphal ticks, which ultimately allows Bbsl transmission to mammalian hosts.

KRAS is one of the most commonly mutated oncogenes in cancer, enabling tumor proliferation and maintenance. After various approaches to target KRAS have failed over the past decades, the first specific inhibitor of the p.G12C mutation of KRAS was recently approved by the FDA after showing promising results in adenocarcinomas of the lung and other solid tumors. Lung cancer, the most common cancer worldwide, is a promising use case for these new therapies, as adenocarcinomas in particular frequently harbor KRAS mutations. However, in squamous cell carcinoma (SCC) of the lung, KRAS mutations are rare and their impact on clinical outcome is poorly understood. In this review, we discuss the current knowledge on the prevalence and prognostic and predictive significance of KRAS mutations in the context of SCC.

Little is known about the cellular immune response to SARS‐CoV‐2 vaccination in patients after HSCT and B‐NHL with iatrogenic B‐cell aplasia. In nonseroconverted HSCT patients, induction of specific T‐cell responses was assessed. The majority of allogeneic HSCT patients not showing humoral responses to vaccination also fail to mount antigen‐specific T‐cell responses.