LAMP-1 Chimeric to HIV-1 p55Gag in the Immunization of Neonate Mice Induces an Early Germinal Center Formation and AID Expression

Abstract

Neonates have a limited adaptive response of plasma cells, germinal center (GC) B cells, and T follicular helper cells (TFH). As neonatal vaccination can be an important tool for AIDS prevention, these limitations need to be overcome. Chimeric DNA vaccine encoding p55Gag HIV-1 protein conjugated with lysosomal-associated membrane protein 1 (LAMP-1) has been described as immunogenic in the neonate period. Herein, we investigated the immunologic mechanisms involved in neonatal immunization with a LAMP-1/p55Gag (LAMP/Gag) DNA vaccine in a C57BL/6 mouse background. Neonatal LAMP/Gag vaccination induced strong Gag-specific T-cell response until adulthood and elevated levels of anti-Gag IgG antibodies. We also demonstrated for the first time that the immunogenicity of the neonatal period with LAMP/Gag is due to the induction of high-affinity anti-p24 IgG antibodies and long-term plasma cells. Together with that, there is the generation of early TFH cells and the formation of GC sites with the upregulation of activation-induced cytidine deaminase (AID) enzyme mRNA and protein expression in draining lymph nodes after neonatal LAMP/Gag vaccination. These findings underscore that the LAMP-1 strategy in the chimeric vaccine could be useful to enhance antibody production even in the face of neonatal immaturity, and they contribute to the development of new vaccine approaches for other emerging pathogens at an early stage of life.

Enhanced immunogenicity and protective efficacy in mice following a Zika DNA vaccine designed by modulation of membrane-anchoring regions and its association to adjuvants

“…Based on previous studies on the use of molecular adjuvants to boost vaccine efficacy in animal models, a sequence coding for the LAMP molecule and the tPA-SP leader sequence were evaluated. In contrast to other studies where LAMP enhanced vaccine efficacy ( 18 , 24 , 26 , 43 , 50 ), in our vaccine model, association of the LAMP molecule to the target viral proteins did not induce strong protein expression in vitro or strong humoral response in vivo ( Figure 1B and Figure 2B ). Additionally, the combined use of LAMP and tPA-SP on the same constructs did not provide improved vaccine immunogenicity either.…”

“…Similarly, depletion of the E protein stem portion was also described to improve protective nAb production ( 13 , 41 , 42 ). We have previously demonstrated that humoral and cellular responses against viral antigens can be remarkably improved by the modulation of molecular adjuvants added to the expression cassette due to improved antigen presentation ( 23 – 26 , 43 ). In this work, we designed four DNA vaccines coding for the ZIKV prM/M and E proteins along with the tPA-SP leader sequence ( Figure 1A ).…”

“…Formation of GC sites is crucial to ensure effective humoral response, production of long-lived antibody secreting plasma cells and memory B cells ( 56 ). Additionally, the induction of GC response has been associated to improved immunogenicity upon administration of genetic vaccines ( 26 , 57 ).…”

“…Cellular response was assessed in spleens through ELISPOT using the IFN-γ ELISPOT set (BD Biosciences, USA) as previously described ( 26 ) 0.5x10 6 cells/well were stimulated with 2 µg/mL of recombinant ZIKV E protein (Native Antigen, UK). The anti-CD3 and anti-CD28 antibodies (1 µg/mL each) (BD Bioscience, USA) were used as positive control.…”

“…The frequency of GC B cells from iLNs was assessed one week after boost as previously described ( 26 ). 2x10 6 cells were stained with anti-CD3 (PerCP-Cy5.5 – Clone: 17A2), anti-B220 (APC – Clone: RA3-6B2), anti-CD95 (PE-Cy7 – Clone: Jo2) and anti-GL-7 (FITC – Clone: GL-7) antibodies (all from BD Biosciences, USA).…”