Viable R. rickettsii organisms were incubated with naïve serum, anti-rAdr1, -rAdr2, -rOmpW, -rPorin_4, -rTolC, or -WCA (positive control) immune serum for 60 min. After incubation, the mixture was added into EA.hy 926 cells for 6 h. The total number of R. rickettsii that adhered to and invaded the host cells was determined using R. rickettsii-specific qPCR. The results were analyzed using the T test or Wilcoxon two-sample test according to their normality and homogeneity of variance. The statistically significant differences between anti-WCA immune serum and anti-rSEPs immune serum groups were indicated by horizontal lines. The values are presented as mean ± standard deviations (n = 3); *P<0.05, **P<0.01, and ***P<0.001.