Chondrocytes are the sole cellular constituents of normal cartilage. The degeneration and apoptosis of these cells are considered the main cause of osteoarthritis (OA). Previous studies have suggested that the enhancement of autophagy in chondrocytes can delay the progression of osteoarthritis by affecting intracellular metabolic activity, i.e., by regulating the metabolism of nutrients, which can delay cell aging and death. In this review, we explored the relationship between autophagy and chondrocyte metabolism and provided new ideas for the prevention and treatment of OA.

A partial gene sequence encoding the 56-kD scrub typhus antigen (Sta56) was amplified from genomic DNA of the Orientia tsutsugamushi Karp strain by a polymerase chain reaction (PCR). The PCR product was ligated with the 47-kD scrub typhus antigen (Sta47) gene in the pQE30/47 expression vector, and the resulting recombinant expression vector was designated pQE30/56-47. A fusion antigen (Sta56-47) was expressed in Escherichia coli cells transformed with pQE30/56-47 after induction with isopropyl-beta-d-thiogalactopyranoside. The Sta56-47 antigen was recognized by both Sta47 and Sta56 immune sera and by immune serum to Sta56-47 in an immunoblot assay. This antigen was purified and used to immunize BALB/c mice. The animals immunized with Sta56-47 exhibited profound humoral and cellular immune responses, as well as increased resistance to O. tsutsugamushi Karp compared with mice immunized with Sta56 or Sta47. These results strongly suggest that Sta56-47 contains antigenic epitopes of the Sta56 and Sta47 antigens of O. tsutsugamushi Karp, and is a more suitable candidate for replacing whole-cell antigen of O. tsutsugamushi Karp to induce protective immunity against scrub typhus.

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The gene fragments encoding outer membrane protein 1 (P1) and heat-shock protein B (HspB) amplified from genomic DNA of Coxiella burnetii Xinqiao by PCR were inserted into prokaryotic expression vector pQE30 to construct recombinant expression plasmids pQE30/p1 and pQE30/hspB, respectively. The p1 fragment from pQE30/p1 was ligated with hspB of pQE30/hspB to construct pQE30/p1-hspB. Recombinant proteins, P1, HspB, and P1-HspB, were expressed in Escherichia coli cells transformed with pQE30/p1, pQE30/hspB, and pQE30/p1-hspB, respectively. The purified recombinant proteins and whole-cell antigen (WCA) of C. burnetii were used to immunize BALB/c mice. The antibody detection, T-cell proliferation assay, and cytokine detection demonstrated that the animals immunized with P1-HspB or WCA exhibited stronger humoral and cellular immune responses compared with animals immunized with P1 or HspB individually. Seven days after challenge of 10-fold 50% infection dose of C. burnetii, mice were euthanized and their spleens were collected. The splenic weights of mice immunized with P1-HspB or WCA were significantly lighter than that of mice immunized with P1 or HspB. By real-time PCR assay, the coxiella loads of spleens of mice immunized with P1-HspB or WCA were also significantly lower than that of mice immunized with P1 or HspB. The data from this study indicate that fusion antigen P1-HspB is a good immunogen for eliciting immunoresponses against C. burnetii, and it may be a more suitable candidate for preparing subunit vaccine against Q fever.