OspCrelated

OspC-related refers to proteins and genes that are homologous or functionally connected to the outer surface protein C (OspC) of Borrelia species, particularly Borrelia burgdorferi, the agent of Lyme disease. The term encompasses the canonical ospC gene and a broader set of ospC-like paralogs found on Borrelia plasmids across B. burgdorferi sensu lato and related spirochetes. These lipoproteins share a conserved N-terminal signal peptide for lipid modification and export, but central and C-terminal regions are highly variable, yielding numerous OspC protein variants.

Genetic context and diversity: The ospC locus is located on Borrelia plasmids, and multiple ospC alleles exist within natural populations. This allelic diversity is associated with geographic distribution and host range and is thought to aid immune evasion and adaptation to different mammalian hosts. OspC-related proteins therefore comprise a family of highly variable surface lipoproteins.

Expression and regulation: OspC expression is tightly controlled and is upregulated during the tick-to-mammal transition when conditions shift to mammalian temperatures. Regulators such as RpoS and BosR contribute to its transcriptional activation and subsequent downregulation as infection progresses. The timing of expression is important for establishing early-stage infection.

Function and role in disease: OspC is a surface-exposed lipoprotein implicated in early infection, contributing to initial colonization and dissemination within the mammalian host. It may interact with host components and participate in immune evasion. Although not universally essential, ospC is important in many models for establishing disseminated infection during acute Lyme disease.

Medical relevance: Due to early expression and strong antigenic variation, OspC and related proteins are a focus of serodiagnostic approaches and vaccine research. The diversity of variants can complicate diagnostics and immunization strategies, guiding ongoing research into their functional differences and host interactions.