Very Broadly Effective Hemagglutinin-Directed Influenza Vaccines with Anti-Herpetic Activity

Abstract

A universal vaccine that generally prevents influenza virus infection and/or illness remains elusive. We have been exploring a novel approach to vaccination involving replication-competent controlled herpesviruses (RCCVs) that can be deliberately activated to replicate efficiently but only transiently in an administration site in the skin of a subject. The RCCVs are derived from a virulent wild-type herpesvirus strain that has been engineered to contain a heat shock promoter-based gene switch that controls the expression of, typically, two replication-essential viral genes. Additional safety against inadvertent replication is provided by an appropriate secondary mechanism. Our first-generation RCCVs can be activated at the administration site by a mild local heat treatment in the presence of an antiprogestin. Here, we report that epidermal vaccination with such RCCVs expressing a hemagglutinin or neuraminidase of an H1N1 influenza virus strain protected mice against lethal challenges by H1N1 virus strains representing 75 years of evolution. Moreover, immunization with an RCCV expressing a subtype H1 hemagglutinin afforded full protection against a lethal challenge by an H3N2 influenza strain, and an RCCV expressing a subtype H3 hemagglutinin protected against a lethal challenge by an H1N1 strain. Vaccinated animals continued to gain weight normally after the challenge. Protective effects were even observed in a lethal influenza B virus challenge. The RCCV-based vaccines induced robust titers of in-group, cross-group and even cross-type neutralizing antibodies. Passive immunization suggested that observed vaccine effects were at least partially antibody-mediated. In summary, RCCVs expressing a hemagglutinin induce robust and very broad cross-protective immunity against influenza.

A Broad Influenza Vaccine Based on a Heat-Activated, Tissue-Restricted Replication-Competent Herpesvirus

“…Single-step growth experiments, immunizations, determinations of titers of RCCVs in mouse feet or brains, or challenge viruses in mouse lungs, blood collection, and microneutralization assays as well as HA ELISA tests as well as statistical analyses were performed as described in ref. [12]. Immunized and control mice were challenged by intranasal administration of 20 TCID 50 of influenza virus strain FM47 or 10 TCID 50 of influenza virus strain HK14.…”

“…RCCV HSV-GS19/mKRT1 was derived from HSV-GS19 [12]. It contains a heat-and AP-responsive gene switch that controls ICP4 expression.…”

“…Furthermore, it carries the HA gene of influenza virus strain CA09(H1N1) driven by a cytomegalovirus immediate-early (CMV IE) promoter. Plasmid pIN:37/38-Cal/07/HA [12] was co-transfected with purified 17syn+/mKRT1 virion DNA into HEK293T cells by calcium phosphate precipitation. Plasmid pIN:37/38-Cal/07/HA contains the expressible CA09 HA gene in between sequences from the UL37/38 intergenic region of 17syn+ (nt 83,603-84,417).…”

“…Furthermore, it carries the HA gene of CA09(H1N1) driven by the CMV IE promoter. Plasmid pIN:37/38-Cal/07/HA [12] was co-transfected with purified HSV-GC1 virion DNA into V17gH cells by calcium phosphate precipitation. Picking and amplification of plaques, screening, and plaque purification were performed essentially as described for HSV-GC9.…”

“…The activated RCCVs were far more efficacious in protecting against a lethal challenge by a wild-type HSV-1 strain than not-activated RCCVs or a replication-defective comparison virus. In a recent study, RCCVs expressing a full-length influenza virus subtype H1 or H3 HAs were investigated as potential influenza vaccines [12]. The RCCVs were applied to mice epidermally (to footpads), and the challenge influenza viruses were administered intranasally.…”