['Rheumatoid arthritis (RA) is a complex disease characterized by autoimmune inflammation and joint destruction. Despite recent advances in RA treatment, current therapies require further improvement to overcome adverse events and ineffectiveness in some cases. By targeting different pathways/molecules using drug combinations, a better treatment can be obtained, whereas adverse events are reduced. In order to develop a new treatment option, the present study employs a gene therapy-based combination therapy using doxycycline and human alpha-1 antitrypsin (hAAT).', 'DBA/1 mice were immunized with type II collagen to induce arthritis. Four weeks before immunization, they received a doxycycline containing diet and a single injection of adeno-associated virus vector expressing hAAT under the control of a tetracycline-dependent promoter. Control groups received doxycycline alone or saline. Macroscopic arthritis development as well as histopathological changes in the joint were evaluated. In addition, the effects of hAAT and doxycycline on lipopolysaccharide (LPS)- or tumor necrosis factor-alpha-induced interleukin (IL)-6 production from mouse fibroblast cells were also determined.', 'Combination therapy significantly reduced arthritis development and progression compared to the control group in respect to macroscopic as well as histopathological changes. Doxycycline and hAAT in combination also inhibited IL-6 expression from LPS-stimulated NIH/3T3 mouse fibroblast cells, indicating a contributing mechanism of arthritis inhibition.'] Does combination of alpha-1 antitrypsin and doxycycline suppress collagen-induced arthritis?