A Novel Live Pichinde Virus-Based Vaccine Vector Induces Enhanced Humoral and Cellular Immunity after a Booster Dose

Abstract

Pichinde virus (PICV) is a bisegmented enveloped RNA virus that targets macrophages and dendritic cells (DCs) early in infection and induces strong innate and adaptive immunity in mice. We have developed a reverse genetics system to produce live recombinant PICV (strain P18) with a trisegmented RNA genome (rP18tri), which encodes all four PICV gene products and as many as two foreign genes. We have engineered the vector to express the green fluorescent protein (GFP) reporter gene (abbreviated as G in virus designations) and either the hemagglutination (HA [H]) or the nucleoprotein (NP [P]) gene of the influenza A/PR8 virus. The trisegmented viruses rP18tri-G/H and rP18tri-G/P showed slightly reduced growth in vitro and expressed HA and NP, respectively. Mice immunized with rP18tri-G/H were completely protected against lethal influenza virus challenge even 120 days after immunization. These rP18tri-based vectors could efficiently induce both neutralizing antibodies and antigen-specific T cell responses via different immunization routes. Interestingly, the immune responses were significantly increased upon a booster dose and remained at high levels even after three booster doses. In summary, we have developed a novel PICV-based live vaccine vector that can express foreign antigens to induce strong humoral and cell-mediated immunity and is ideal for a primeand-boost vaccination strategy. IMPORTANCE We have developed a novel Pichinde virus (PICV)-based live viral vector, rP18tri, that packages three RNA segments and encodes as many as two foreign genes. Using the influenza virus HA and NP genes as model antigens, we show that this rP18tri vector can induce strong humoral and cellular immunity via different immunization routes and can lead to protection in mice. Interestingly, a booster dose further enhances the immune responses, a feature that distinguishes this from other known live viral vectors. In summary, our study demonstrates a unique feature of this live rP18tri vector to be used as a novel vaccine platform for a prime-and-boost vaccination strategy.A renaviruses are enveloped RNA viruses with a bisegmented genome and mostly use rodents as natural hosts. There are at least 27 members that are geographically, serologically, and phylogenetically divided into Old World and New World arenaviruses (1). The prototypic lymphocytic choriomeningitis virus (LCMV) infection of mice has long been used as a valuable model with which to study viral persistence and virus-induced immunity and immunopathology (2, 3). The arenavirus is composed of a total of four genes on two genomic RNA segments in opposite orientations (1). The Z protein, produced from the large (L) genomic segment, is a small RING domain-containing matrix protein that mediates virus budding, regulates viral RNA synthesis, and mediates host immune suppression (4, 5). The large L protein (ϳ200 kDa), also encoded on the L segment, is the RNA-dependent RNA polymerase (RdRp), which is required for viral RNA synthesis (6). The glycoprotein (GPC), encoded...

Recombinant Tri-Segmented Pichinde Virus as a Novel Live Viral Vaccine Platform

“…Blood cells were collected at 7 days after each dose in heparinized tubes and used immediately for analysis of T cell response (7). Blood was collected at 14 days after each dose into 1.5-ml microtubes.…”

“…After blood clotting at 37°C for 1 h, collect the serum by centrifugation at 6,000 rpm for 10 min in a microfuge. Serum can be stored at −20°C until being used for analysis of neutralizing antibodies (7). …”

“…1B). The rP18tri-based viruses are attenuated in vitro and in vivo , and can effectively induce strong T cell and humoral responses with limited anti-vector neutralizing antibodies (7). Therefore this novel rP18tri vector exhibits multiple features of an ideal live viral vector including safety, immunogenicity, robust antigen-encoding capacity, targeting antigen-presenting cells (APCs), and the lack of a strong anti-vector immunity.…”

Arenaviral vaccine vectors to combat infectious diseases

“…However, this study did not use any bona fide immunogenic antigens in order to evaluate the efficacy of the vaccine vector. In order to further evaluate this concept, we have recently developed a tri-segmented recombinant Pichinde virus (triPICV) as a new vaccine vector [4]. Unlike LCMV, which has the potential to cause diseases in humans and a relatively high seroprevalence in human population, PICV is generally not known to be pathogenic in humans, who would rarely come in contact with this virus due to the fact that it is only found in Colombia, South America.…”

“…We have used the recombinant triPICV to deliver different foreign antigens, including the influenza hemagglutinin (HA) and nucleoprotein (NP) that could provide complete protection against lethal influenza virus challenge in a mouse model [4]. Specifically, this viral vector could mount robust influenza antigen-specific humoral and cellular immune responses and proved ideal for use in a prime-boost vaccination strategy.…”