Objective To study the effect of peripheral blood CD4⁺T lymphocytes of syphilis patients on human immunodeficiency virus type 1 (HIV-1) infection and replication, and explore the molecular mechanism of Treponema pallidum (TP) in facilitating HIV-1 replication. Methods Peripheral blood mononuclear cells (PBMCs) were isolated from syphilis patients and TP-uninfected healthy blood donors, then infected with HIV-1 in vitro. HIV-1 replication level was studied. PBMCs of healthy persons were stimulated with TP and then infected with HIV-1. CD4⁺T lymphocytes were isolated using flow cytometry, and changes in host gene expression profiles were verified using messenger RNA (mRNA) high-throughput sequencing and real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) methods. Results CD4⁺T lymphocytes from TP-infected persons and TP-stimulated CD4⁺T lymphocytes from healthy persons could significantly enhance HIV-1 infection and viral replication levels. The HIV-1 p24 content in the supernatant of cultured cells and intracellular HIV-1 DNA copy number were both higher than those in the control group (both P<0.05). There were significant differences in the mRNA gene expression profiles between the TP stimulation combined with HIV-1 infection group and the HIV-1 infection alone group. Among them, the expression levels of chemokines CXCL5 and CXCL8 were significantly upregulated in the TP stimulation combined with HIV-1 infection group, indicating that chemokines might play an important role in the enhancement of HIV-1 infection and replication by TP. Conclusion TP infection can significantly enhance the susceptibility of peripheral blood CD4⁺T lymphocytes to HIV-1 and promote virus replication, providing new scientific evidences for TP infection promoting HIV-1 infection.