Gravity Probe B: final results of a space experiment to test general relativity.

Gravity Probe B, launched 20 April 2004, is a space experiment testing two fundamental predictions of Einstein's theory of general relativity (GR), the geodetic and frame-dragging effects, by means of cryogenic gyroscopes in Earth orbit. Data collection started 28 August 2004 and ended 14 August 2005. Analysis of the data from all four gyroscopes results in a geodetic drift rate of -6601.8±18.3 mas/yr and a frame-dragging drift rate of -37.2±7.2 mas/yr, to be compared with the GR predictions of -6606.1 mas/yr and -39.2 mas/yr, respectively ("mas" is milliarcsecond; 1 mas=4.848×10(-9) rad).

Immunity induced by DNA immunization with herpes simplex virus type 2 glycoproteins B and C.

The complete sequence of herpes simplex virus type 2 (HSV-2) glycoproteins B and C (gB & gC) were cloned into plasmid expression vectors and evaluated in murine and guinea pig genital HSV-2 models. Balb/c mice were immunized with either pgB-2 or pgC-2 plasmids intramuscularly (IM) or intradermally (ID). The vaccines induced HSV-2-specific neutralizing and ELISA IgG antibody, but little or no enhancement of viral clearance from the vagina was detected following intravaginal challenge. Immunization of guinea pigs with pgB-2 or pgC-2 induced ELISA IgG antibody; however, antibody titers were approximately one log(10) unit lower than that seen in HSV-2 convalescent sera. IM immunization of guinea pigs with either plasmid also did not decrease vaginal viral shedding following vaginal challenge, but the severity of the acute disease and the subsequent number of recurrent lesion days were reduced in animals immunized with pgB-2. Lastly, IM immunization of latently infected guinea pigs with a combined gB-2 and gC-2 plasmid vaccine significantly reduced the number of subsequent HSV-2 recurrences. DNA vectors expressing gB-2 or gC-2 were both immunogenic, although the gB-2 plasmid induced higher titers of antibody and significantly reduced primary and recurrent herpetic disease in the guinea pig model. These results also suggest that immunotherapy with plasmid expression vectors may be effective against recurrent genital HSV-2 disease.

Effects of DNA immunization formulated with bupivacaine in murine and guinea pig models of genital herpes simplex virus infection.

The immunogenicity and efficacy of a herpes simplex virus type 2 glycoprotein D (gD2) DNA vaccine formulated with bupivacaine was evaluated using murine and guinea pig models of genital herpes. Animals received three doses of 100 microg of gD2 plasmid or control plasmid intramuscularly prior to intravaginal challenge with HSV-2. Immunization induced HSV ELISA and neutralizing antibody in serum and ELISA antibody in the vaginal secretions of all animals evaluated. Following intravaginal HSV-2 challenge, vaginal viral replication was reduced in both models with peak reductions of greater than 99%. Immunization also decreased the number of animals developing any clinical disease (p < 0.001) and the severity of the acute disease (total lesion score 6.4 versus 0.6 in guinea pigs, p < 0.001). Further recurrent lesion days were reduced from 14.5 to 4.9 days in immunized guinea pigs (p < 0.001). DNA immunization with gD2 + bupivacaine was effective in reducing clinical disease and viral replication in both guinea pigs and mice.

Antiviral activity of herpes simplex virus vectors expressing murine alpha 1-interferon.

Mutant herpes simplex virus type I (HSV-1) vectors were engineered to express murine alpha 1 interferon (IFN) and assessed for their ability to inhibit the replication of challenge viruses in infection of monolayer cell cultures. The alpha 1 IFN gene was placed under control of the Rous sarcoma virus (RSV) long terminal repeat (LTR) region in the thymidine kinase (tk) locus of both the wild-type HSV-1 strain KOS and the replication-defective KOS mutant dl20, in which both copies of the ICP4 immediate-early (IE) gene are deleted. To evaluate IFN expression, vector-infected cell culture media from epithelial, fibroblast and neuronal cells were assayed for alpha IFN release. These cells did not secrete detectable levels of alpha IFN when infected with control KOS or d120-based viruses. Cells infected at a multiplicity of infection (MOI) of 10 with either RSV-LTR-IFN vector produced from approximately 12 to 100 U of alpha 1-IFN per millilitre of culture fluid in 24 h, as determined by a standard vesicular stomatitis virus (VSV) replication inhibition assay. Vector-derived alpha 1-IFN expression did not inhibit the growth of the KOS-RSV-IFN virus in IFN sensitive cell lines. However, pretreatment of murine L cells with IFN produced from the RSV-IFN vectors blocked the replication of HSV-1. Additionally, L cells infected with d120-RSV-IFN (at an MOI of 0.5 to 0.06) were protected from superinfection with VSV. Thus, pre-infection of a small percentage of cells with a nonreplicating HSV-IFN expression vector provided complete protection of tissue culture cell monolayers from the cytopathic effect of a challenge virus infection. These vectors should be useful for in vivo analysis of the antiviral potential of IFN expression from within the nervous system.

The mouse model and understanding immunity to herpes simplex virus.

Investigation of the immune response to herpes simplex virus (HSV) has progressed rapidly, mainly through the use of various animal models of human disease. Murine models of HSV infection have been explored extensively and have yielded a wide array of insights into the mechanisms of antiviral immunity. Current research has focused on defining the role of individual viral envelope glycoproteins in stimulating a protective B and T cell response, with the ultimate goal of identifying the minimum effective immunization unit. This ongoing dissection of the glycoprotein-specific immune response in the mouse has revealed both the values of an animal model that mimics human infection and the limitations inherent in defining the immunopotential of specific viral proteins and peptides in an unnatural host. This article reviews the results of murine studies evaluating the mechanisms of protection against HSV infection and the protective potential of immunization with the viral envelope glycoproteins.

Protection against zosteriform spread of herpes simplex virus by monoclonal antibodies.

The in vivo protective role of herpes simplex virus (HSV-1)-specific antibody was analyzed using monoclonal antibodies (MAbs) reactive with discrete antigenic sites on glycoproteins B, C, and D (gB, gC, gD) in the murine zosteriform spread model of HSV-1. All of the anti-gC and anti-gD MAbs, and one of four anti-gB MAbs (B6) were protective. The in vitro abilities of the MAbs to neutralize HSV-1 and mediate antibody-dependent cellular cytotoxicity (ADCC) against HSV-1-infected cells were examined as potential mechanistic correlates to in vivo protection. All animals given MAbs at high ADCC unit doses were protected. Some but not all mice given MAbs at high ADCC unit doses were protected. These studies designate specific epitopes recognized by protective antibodies and indicate that protection from the neurologic spread of HSV may be related to neutralization, ADCC, or both. The actual contribution of ADCC and neutralization to in vivo antibody-mediated protection remains unclear.

Herpes simplex virus type 1-specific immunity induced by peptides corresponding to an antigenic site of glycoprotein B.

Herpes simplex virus (HSV) envelope glycoproteins are the prime targets of adaptive antiviral immunity. Previous investigation identified a protective, neutralizing, glycoprotein B1 (gB-1)-reactive monoclonal antibody (MAb B6) and localized the linear epitope recognized by the MAb to residue 84 of gB-1. Three overlapping peptides (two 20-mers and one 18-mer), together spanning amino acids 63 to 110 of the wild-type sequence of gB-1, were synthesized and analyzed for their ability to stimulate immunity which cross-reacts with HSV-1. All stimulated some level of response. Two peptides, the gB 18-mer and 20.1-mer, were recognized by MAb B6 and HSV-immune antibody but were unable to stimulate virus-neutralizing antibody or serum able to protect against zosteriform spread in vivo. The 20.2-mer peptide, however, which was not recognized by MAb B6 or HSV-generated immune antibody, stimulated the production of neutralizing antibody and serum able to protect against zosteriform spread. Immunization with all of the peptides was able to enhance viral clearance of a low dose of HSV-1 in an ear challenge model and induce antibody reactive in antibody-dependent complement-mediated lysis of HSV-1-infected cells in vitro. These results are the first report of HSV immunity induced by peptides corresponding to gB and indicate that the best immunogen, in terms of stimulating neutralizing antiserum able to protect in vivo against HSV-1, was a peptide not recognized by HSV-immune mechanisms or by the MAb used to localize it.