Abstract:Objective To explore the correlation between the degree of Helicobacter pylori (HP) infection and the expression levels of programmed death-1 (PD-1) and its ligand PD-L1 in gastric cancer patients. Methods A total of 118 patients with gastric cancer who were treated in Changsha First Hospital from November 2019 to November 2021 was selected prospectively and divided into mild group ( n=42), moderate group ( n=40) and Severe group ( n=36) according to the degree of HP infection. Real-time fluorescence quantitative detection was used to detect the expression levels of PD-1, PD-L1, and Spearman correlation was used to analyze the correlation between the degree of HP infection and the expression levels of PD-1 and PD-L1. The factors affecting the degree of HP infection were screened by ordinal logistic regression. Results There were significant differences in the expression levels of PD-L1 and PD-1, the course of gastric cancer, and smoking history among the three groups (P<0.05). Spearman correlation analysis showed that the degree of HP infection was positively correlated with the expression levels of PD-1 and PD-L1 (r=0.546, r=0.582, P<0.05). The ordinal logistic showed PD-L1 (OR=2.004,95%CI：1.726-2.326), PD-1 (OR=3.347, 95%CI: 2.694-4.158), gastric cancer course (OR=3.007,95%CI：2.547-3.550), with smoking history (OR=1.634,95%CI： 1.547-2.431) were risk factors for the degree of HP infection in patients with gastric cancer (P<0.05).Conclusions The degree of HP infection in gastric cancer patients was positively correlated with the expression of PD-1 and PD-L1, and PD-1 and PD-L1 were risk factors for the degree of HP infection.