Expression of Human Immunodeficiency Virus Type 1 gp120 from Herpes Simplex Virus Type 1-Derived Amplicons Results in Potent, Specific, and Durable Cellular and Humoral Immune Responses

Abstract

Herpes simplex virus type 1 (HSV-1) infects a wide range of cells, including dendritic cells. Consequently, HSV-1 vectors may be capable of eliciting strong immune responses to vectored antigens. To test this hypothesis, an HSV-1 amplicon plasmid encoding human immunodeficiency virus type 1 gp120 was constructed, and murine immune responses to helper virus-free amplicon preparations derived from this construct were evaluated. Initial studies revealed that a single intramuscular (i.m.) injection of 10 6 infectious units (i.u.) of HSV:gp120 amplicon particles (HSV:gp120) elicited Env-specific cellular and humoral immune responses. A potent, CD8؉ -T-cell-mediated response to an H-2D d -restricted peptide from gp120 (RGPGRAFVTI) was measured by a gamma interferon ELISPOT and was confirmed by standard cytotoxic-T-lymphocyte assays. Immunoglobulin G enzyme-linked immunosorbent assay analysis showed the induction of a strong, Envspecific antibody response. An i.m. or an intradermal administration of HSV:gp120 at the tail base elicited a more potent cellular immune response than did an intraperitoneal (i.p.) inoculation, although an i.p. introduction generated a stronger humoral response. The immune response to HSV:gp120 was durable, with robust cellular and humoral responses persisting at 171 days after a single 10 6 -i.u. inoculation. The immune response to HSV:gp120 was also found to be dose dependent: as few as 10 4 i.u. elicited a strong T-cell response. Finally, HSV:gp120 elicited significant Env-specific cellular immune responses even in animals that had been previously infected with wild-type HSV-1. Taken together, these data strongly support the use of helper-free HSV-1 amplicon particles as vaccine delivery vectors.Genetically engineered herpesviruses have been successfully used for the development of vaccines against important animal diseases, including Aujesky's disease (pseudorabies virus), infectious bovine rhinotracheitis, and swine fever (hog cholera virus) (21,56,57). In addition, attenuated herpesviruses have been used for human vaccination (including the Towne strain of human cytomegalovirus and the Oka strain of varicellazoster virus) (5, 24, 38, 52). Both herpes simplex virus type 1 (HSV-1) and varicella-zoster virus have been used for the expression of foreign genes, since these viruses can accommodate large segments of exogenous DNA with little effect on virus replication (15, 43). Replication-competent and replication-defective gene replacement vectors based on both viruses are being explored as possible human immunodeficiency virus (HIV) vaccine delivery systems (32, 45). The appeal of this approach lies in part in the ability of herpesviruses to (i) elicit strong cytotoxic-T-lymphocyte (CTL) responses; (ii) infect mucosal surfaces; (iii) infect a broad range of cell types, including dendritic cells (1,23,30,40); and (iv) establish a state of persistence in the infected cell. The latter property may conceivably result in more durable immune responses to herpesvirus-based vaccines compared to man...

Immune responses to replication-defective HSV-1 type vectors within the CNS: implications for gene therapy

“…The lack of contaminating helper virus in these stocks, and thus loss of immunosuppressive proteins like ICP47, has made the HSV amplicon a powerful delivery platform for infectious disease and cancer vaccines. [53][54][55][56] Similar to recombinant HSV vectors, immune responses arising from infusion of HSV amplicon stocks can arise from several sources and such responses are dependent upon the packaging system employed. Immune response-eliciting sources include viral particle components, copurified packaging cell debris, low-level de novo viral gene product expression (helper virus-based packaging only), and the expressed transgene.…”

HSV-1 amplicon vectors elicit polyfunctional T cell responses to HIV-1 Env, and strongly boost responses to an adenovirus prime

“…pVAX.HSV(cmv)gp120 was created by PCR amplifying syngp120 from the plasmid pHSVgp120 [19] using forward (5′-AvrII-CTCGAGATCCATTGTGCTC-3′) and reverse (5′-SalI-TTACCGCTTCTCGCGCTGCACCAC-3′) primers and then cloning the resulting 1.6kb DNA fragment into NheI and XhoI digested pVAX.HSV(cmv).…”

“…The construction of pHSV(hsv)gp120 has been described [19], as has the process of vector packaging [19,20] …”

“…These advantages include (i) their ability to elicit strong cellular immune responses to encoded antigens [19][20][21], (ii) their broad host cell tropism and ability to directly transduce antigen presenting cells, including dendritic cells (DC), both in vivo and in vitro [21,22]; (iii) their favorable safety profile and lack of expression of virally-encoded immunomodulatory genes; and (iv) their very large transgene capacity (up to 150 kb) [23,24].…”

“…Our laboratory has previously shown that a single injection of a helper-free HSV-1 amplicon vector can elicit potent [19,20] and durable [19] immune responses to an encoded HIV antigen even in the face of preexisting immunity to HSV [19]. While the magnitude of the cellular immune response elicited by amplicon vectors has been extensively studied, little is known about the quality of that response, or the effectiveness of heterologous prime-boost immunization regimens that combine amplicon vectors with another viral vaccine modality.…”