HIV-1 Subtype C Mosaic Gag Expressed by BCG and MVA Elicits Persistent Effector T Cell Responses in a Prime-Boost Regimen in Mice

Abstract

Over 90% of HIV/AIDS positive individuals in sub-Saharan Africa are infected with highly heterogeneous HIV-1 subtype C (HIV-1C) viruses. One of the best ways to reduce the burden of this disease is the development of an affordable and effective prophylactic vaccine. Mosaic immunogens are computationally designed to overcome the hurdle of HIV diversity by maximizing the expression of potential T cell epitopes. Mycobacterium bovis BCG ΔpanCD auxotroph and modified vaccinia Ankara (MVA) vaccines expressing HIV-1C mosaic Gag (GagM) were tested in a prime-boost regimen to demonstrate immunogenicity in a mouse study. The BCG-GagM vaccine was stable and persisted 11.5 weeks post vaccination in BALB/c mice. Priming with BCG-GagM and boosting with MVA-GagM elicited higher Gag-specific IFN-γ ELISPOT responses than the BCG-GagM only and MVA-GagM only homologous vaccination regimens. The heterologous vaccination also generated a more balanced and persistent CD4+ and CD8+ T cell Gag-specific IFN-γ ELISPOT response with a predominant effector memory phenotype. A Th1 bias was induced by the vaccines as determined by the predominant secretion of IFN-γ, TNF-α, and IL-2. This study shows that a low dose of MVA (104 pfu) can effectively boost a BCG prime expressing the same mosaic immunogen, generating strong, cellular immune responses against Gag in mice. Our data warrants further evaluation in non-human primates. A low dose vaccine would be an advantage in the resource limited countries of sub-Saharan Africa and India (where the predominating virus is HIV-1 subtype C).

Chronic schistosomiasis suppresses HIV-specific responses to DNA-MVA and MVA-gp140 Env vaccine regimens despite antihelminthic treatment and increases helminth-associated pathology in a mouse model

“…Cytometric bead array (CBA) assays were carried out as previously described [ 96 ]. Intracellular cytokine staining (ICS) and flow cytometry analysis was performed as previously described [ 12 , 14 ] with minor modifications. Briefly, cells were stained with a viability dye, violet amine reactive dye (ViViD; Invitrogen, USA), at a pre-determined optimal concentration before staining for cell surface molecules with the following fluorochrome-conjugated antibodies: anti-CD3-Alexa 700, anti-CD4-PE-Cy7, anti-αCD8-APC-Cy7, anti-CD62L-APC, and anti-CD44-FITC diluted to 0.2μg in staining buffer (BD Biosciences, USA).…”

Immunogenicity of HIV-1 Vaccines Expressing Chimeric Envelope Glycoproteins on the Surface of Pr55 Gag Virus-Like Particles

“…All DNA vaccines were synthesized by Aldevron (Fargo, North Dakota, USA). Transfer vectors were designed to insert the chimeric envelope genes, under the control of the VACV mH5 promoter, into the genome of MVA-Gag M [19]. The coding sequences were targeted between the G1L and I8R transcriptionally convergent open reading frames (ORFs) ( Figure 1b).…”

“…DNA vaccines that expressed these antigens were constructed using the pTHPCapR plasmid, which contains a porcine circovirus enhancer element known to significantly increase antigen expression [17]. Recombinant MVA was constructed by inserting the chimeric envelope genes into MVA-Gag M [19] between the G1L and I8R ORFs under the control of the mH5 promoter (Figure 1b).…”

Porcine epidemic diarrhea virus virus-like particles produced in insect cells induce specific immune responses in mice

“…After washing twice with RPMI-1640 medium (Gibco, Grand Island, USA)containing 10% fetal bovine serum and 1% penicillin-streptomycin, 5 9 10 5 splenocytes per well were cultured in RPMI-1640 and simultaneously stimulated with inactivated PEDV in a 96-well ELISpot plate (MABtech, Stockholm, Sweden) at 37°C in a 5% CO 2 incubator for 48 h. The other assay was carried out according to the manufacturer's instructions. The amount of splenocytes producing IFN-c and IL-4 was illustrated with spot-forming cells using an ELISpot reader (ELISPOT READER SPECTRUM, AID, Germany) as described previously [28].…”