It remains a great challenge to develop an effective HIV vaccine against the most prevalent HIV-1 clade, B′/C recombinant, in China. Our objective was to test the influence of a new modification of the V1/V2 loops of HIV-1CN54 gp140 on the immunogenicity of Env. HIV-1CN54 gp140 was deglycosylated by replacing all six N residues in V1/V2 loops with six Q residues (gp140dG) or partially deleted on V1/V2 loops (gp140dV). gp140, gp140dG, and gp140dV were transferred into plasmid vector and recombinant Tiantan vaccinia (rTTV) vector to generate three DNA vaccines and three rTTV vaccines for vaccination of female BALB/c mice in a prime–boost regimen. An Elispot assay was used to read out the T cell immunity and ELISA and a poly-l-leucine (PLL) ELISA was employed to assess humoral immune responses. Surprisingly, gp140dV (1570 ± 1569 SFCs/106 splenocytes) and gp140dG (731 ± 471 SFCs/106 splenocytes) could elicit significantly higher Env-specific T cells than gp140 (224 ± 140 SFCs/106 splenocytes). Three T cell epitopes were newly identified in BALB/c mice at the N terminus of C1, C terminus of C4, and N terminus of HR, respectively. Env-specific binding antibodies and linear antibodies elicited by gp140 tended to be higher than that stimulated by gp140dG and gp140dV but did not reach statistical difference. Our data demonstrated that the deglycosylation and partial deletion of V1/V2 loops of B′/C recombinant gp140 could lead to improvement of specific T cell immune responses.
