Control of HTLV-1 Infection by Eliminating Envelope Protein-Positive Cells with Recombinant Vesicular Stomatitis Viruses Encoding HTLV-1 Primary Receptor

Human T-cell leukemia virus type 1 (HTLV-1) infection causes adult T-cell leukemia (ATL), which is frequently resistant to current available therapies and has a very poor prognosis. To prevent the development of ATL among carriers it is important to control HTLV-1–infected cells in infected individuals. Therefore, the establishment of novel therapies with drugs specifically targeting infected cells is urgently required. This study aimed to develop a potential therapy by generating recombinant vesicular stomatitis viruses (rVSVs) that lack an envelope glycoprotein G and instead encode HTLV-1 receptor(s) with human glucose transporter 1 (GLUT1), neuropilin 1 (NRP1), or heparan sulfate proteoglycans (HSPGs) including syndecan 1 (SDC1), designated as VSVΔG-GL, VSVΔG-NP, or VSVΔG-SD, respectively. In an attempt to enhance the infectivity of rVSV against HTLV-1–infected cells, we also constructed rVSVs with a combination of two or three receptor genes, designated as VSVΔG-GLN and VSVΔG-GLNS, respectively. The current study demonstrated VSVΔG-GL, VSVΔG-NP, VSVΔG-GLN, and VSVΔG-GLNS have tropism for HTLV-1 envelope (Env) expressing cells. Notably, the inoculation of VSVΔG-GL or VSVΔG-NP significantly eliminated HTLV-1–infected cells in the culture conditions. Furthermore, in an HTLV-1–infected humanized mouse model, VSVΔG-NP was capable of efficiently preventing HTLV-1–induced leukocytosis in the periphery and eliminating HTLV-1–infected Env-expressing cells in the lymphoid tissues. In summary, an rVSV engineered to express HTLV-1 primary receptor, especially human NRP1, may represent a drug candidate that has potential for the development of unique virotherapy against HTLV-1de novoinfection.IMPORTANCEAlthough several anti-ATL therapies are currently available, ATL is still frequently resistant to therapeutic approaches and its prognosis remains poor. Control ofde novoHTLV-1 infection or expansion of HTLV-1–infected cells in the carrier holds considerable promise for the prevention of ATL development. In this study, we developed rVSVs that specifically target and kill HTLV-1 Env-expressing cells (not ATL cells, which generally do not express Envin vivo) through replacement of the G gene with HTLV-1 receptor gene(s) in the VSV genome. Notably, an rVSV engineered to express human NRP1 controlled the number of HTLV-1–infected Env-expressing cellsin vitroandin vivo, suggesting the present approach may be a promising candidate for novel anti-HTLV-1 virotherapy in HTLV-1 carriers, including as a prophylactic treatment against the development of ATL.

Creation of Matrix Protein Gene Variants of Two Serotypes of Vesicular Stomatitis Virus as Prime-Boost Vaccine Vectors

ABSTRACTTo take advantage of live recombinant vesicular stomatitis viruses (rVSVs) as vaccine vectors for their high yield and for their induction of strong and long-lasting immune responses, it is necessary to make live vaccine vectors safe for use without losing their immunogenicity. We have generated safer and highly efficient recombinant VSV vaccine vectors by combining the M51R mutation in theMgene of serotype VSV-Indiana (VSVInd) with a temperature-sensitive mutation (tsO23) of the VSVIndOrsay strain. In addition, we have generated two new serotype VSV-New Jersey (VSVNJ) vaccine vectors by combining M48R and M51R mutations with G22E and L110F mutations in theMgene, rVSVNJ(G22E M48R M51R) [rVSVNJ(GMM)] and VSVNJ(G22E M48R M51R L110F) [rVSVNJ(GMML)]. The combined mutations G21E, M51R, and L111F in the M protein of VSVIndsignificantly reduced the burst size of the virus by up to 10,000-fold at 37°C without affecting the level of protein expression. BHK21cells and SH-SY5Y human neuroblastoma cells infected with rVSVInd(GML), rVSVNJ(GMM), and rVSVNJ(GMML) showed significantly reduced cytopathic effectsin vitroat 37°C, and mice injected with 1 million infectious virus particles of these mutants into the brain showed no neurological dysfunctions or any other adverse effects. In order to increase the stability of the temperature-sensitive mutant, we have replaced the phenylalanine with alanine. This will change all three nucleotides from UUG (leucine) to GCA (alanine). The resulting L111A mutant showed the temperature-sensitive phenotype of rVSVInd(GML) and increased stability. Twenty consecutive passages of rVSVInd(GML) with an L111A mutation did not convert back to leucine (UUG) at position 111 in the M protein gene.IMPORTANCERecombinant vesicular stomatitis viruses as live vaccine vectors are very effective in expressing foreign genes and inducing adaptive T cell and B cell immune responses. As with any other live viruses in humans or animals, the use of live rVSVs as vaccine vectors demands the utmost safety. Our strategy to attenuate rVSVIndby utilizing a temperature-sensitive assembly-defective mutation of L111A and combining it with an M51R mutation in the M protein of rVSVIndsignificantly reduced the pathogenicity of the virus while maintaining highly effective virus production. We believe our new temperature-sensitiveMgene mutant of rVSVInd(GML) andMgene mutants of rVSVNJ(GMM) and rVSVNJ(GMML) add excellent vaccine vectors to the pool of live viral vectors.

Stimulation of Human Dendritic Cells by Wild-Type and M Protein Mutant Vesicular Stomatitis Viruses Engineered To Express Bacterial Flagellin

ABSTRACT Vesicular stomatitis viruses (VSVs) containing wild-type (wt) or mutant matrix (M) proteins are being developed as candidate vaccine vectors due to their ability to induce innate and adaptive immunity. Viruses with wt M protein, such as recombinant wild-type (rwt) virus, stimulate maturation of dendritic cells (DC) through Toll-like receptor 7 (TLR7) and its adaptor molecule MyD88. However, M protein mutant viruses, such as rM51R-M virus, stimulate both TLR7-positive and TLR7-negative DC subsets. The goal of this study was to determine whether the ability of rwt and rM51R-M viruses to induce maturation of human DC can be enhanced by engineering these vectors to express bacterial flagellin. Flagellin expressed from the rwt virus genome partially protected human DC from VSV-induced shutoff of host protein synthesis and promoted the production of interleukin 6 (IL-6) and IL-1β. In addition, DC infected with rwt virus expressing flagellin were more effective at stimulating gamma interferon (IFN-γ) production from CD8+ allogeneic T cells than DC infected with rwt virus. Although rM51R-M virus effectively stimulated human DC, flagellin expressed from the rM51R-M virus genome enhanced the production of cytokines. Furthermore, mice immunized with both rwt and rM51R-M viruses expressing flagellin had enhanced anti-VSV antibody responses in vivo. Therefore, rwt and rM51R-M viruses expressing flagellin may be promising vectors for the delivery of foreign antigen due to their potential to stimulate DC function.