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Nancy L Davis

Publications and source records attributed to Nancy L Davis.

13 recordsLinked to original sources
PubMed2006

Mucosal and systemic adjuvant activity of alphavirus replicon particles.

Vaccination represents the most effective control measure in the fight against infectious diseases. Local mucosal immune responses are critical for protection from, and resolution of, infection by numerous mucosal pathogens. Antigen processing across mucosal surfaces is the natural route by which mucosal immunity is generated, as peripheral antigen delivery typically fails to induce mucosal immune responses. However, we demonstrate in this article that mucosal immune responses are evident at multiple mucosal surfaces after parenteral delivery of Venezuelan equine encephalitis virus replicon particles (VRP). Moreover, coinoculation of null VRP (not expressing any transgene) with inactivated influenza virions, or ovalbumin, resulted in a significant increase in antigen-specific systemic IgG and fecal IgA antibodies, compared with antigen alone. Pretreatment of VRP with UV light largely abrogated this adjuvant effect. These results demonstrate that alphavirus replicon particles possess intrinsic systemic and mucosal adjuvant activity and suggest that VRP RNA replication is the trigger for this activity. We feel that these observations and the continued experimentation they stimulate will ultimately define the specific components of an alternative pathway for the induction of mucosal immunity, and if the activity is evident in humans, will enable new possibilities for safe and inexpensive subunit and inactivated vaccines.

Adjuvants, Immunologic↗
PubMed2006

Vaccination of mice with gonococcal TbpB expressed in vivo from Venezuelan equine encephalitis viral replicon particles.

We investigated the immunogenicity of gonococcal transferrin binding protein B (TbpB) expressed with and without a eukaryotic secretion signal from a nonpropagating Venezuelan equine encephalitis virus replicon particle (VRP) delivery system. TbpB was successfully expressed in baby hamster kidney (BHK) cells, and the presence of the eukaryotic secretion signal not only apparently increased the protein's expression but also allowed for extracellular localization and glycosylation. Mice immunized with VRPs produced significant amounts of serum antibody although less than the amounts produced by mice immunized with recombinant protein. The response of mice immunized with VRPs encoding TbpB was consistently more Th1 biased than the response of mice immunized with recombinant protein alone. Boosting with recombinant protein following immunization with TbpB VRPs resulted in higher specific-antibody levels without altering the Th1/Th2 bias. Most of the immunization groups produced significant specific antibody binding to the intact surface of the homologous Neisseria gonorrhoeae strain. Immunization with TbpB VRPs without a eukaryotic secretion signal generated no measurable specific antibodies on the genital mucosal surface, but inclusion of a eukaryotic secretion signal or boosting with recombinant protein resulted in specific immunoglobulin G (IgG) and IgA in mucosal secretions after TbpB VRP immunization. The TbpB VRP system has potential for an N. gonorrhoeae vaccine.

Animals↗
PubMed2005

Vaccination of macaques with SIV immunogens delivered by Venezuelan equine encephalitis virus replicon particle vectors followed by a mucosal challenge with SIVsmE660.

VEE replicon particles (VRP), non-propagating vaccine vectors derived from Venezuelan equine encephalitis virus (VEE), were engineered to express immunogens from the cloned isolate SIVsmH-4, combined in a vaccine cocktail and inoculated subcutaneously to immunize rhesus macaques. The virulent, uncloned challenge stock, SIVsmE660, represented a type of heterologous challenge and the intrarectal challenge modeled infection across a mucosal surface. Prechallenge neutralizing antibodies against SIVsmH-4 were induced in all vaccinates, and a prechallenge cellular immune response could be detected in one of six. Post-challenge, virus loads were reduced at the peak, at set point and at termination (41 weeks post-challenge), although these differences did not reach statistical significance. Significantly elevated levels of CD4+ T cells were observed post-challenge. A strong correlation was noted between a net increase in CD4+ T cell count and lowered virus load at set point.

Animals↗
PubMed2005

A novel viral system for generating antigen-specific T cells.

Dendritic cell (DC)-based vaccines are increasingly used for the treatment of patients with malignancies. Although these vaccines are typically safe, consistent and lasting generation of tumor-specific immunity has been rarely demonstrated. Improved methods for delivering tumor Ags to DCs and approaches for overcoming tolerance or immune suppression to self-Ags are critical for improving immunotherapy. Viral vectors may address both of these issues, as they can be used to deliver intact tumor Ags to DCs, and have been shown to inhibit the suppression mediated by CD4+CD25+ regulatory T cells. We have evaluated the potential use of Venezuelan equine encephalitis virus replicon particles (VRPs) for in vitro Ag delivery to human monocyte-derived DCs. VRPs efficiently transduced immature human DCs in vitro, with approximately 50% of immature DCs expressing a vector-driven Ag at 12 h postinfection. VRP infection of immature DCs was superior to TNF-alpha treatment at inducing phenotypic maturation of DCs, and was comparable to LPS stimulation. Additionally, VRP-infected DC cultures secreted substantial amounts of the proinflammatory cytokines IL-6, TNF-alpha, and IFN-alpha. Finally, DCs transduced with a VRP encoding the influenza matrix protein (FMP) stimulated 50% greater expansion of FMP-specific CD8+ CTL when compared with TNF-alpha-matured DCs pulsed with an HLA-A*0201-restricted FMP peptide. Thus, VRPs can be used to deliver Ags to DCs resulting in potent stimulation of Ag-specific CTL. These findings provide the rationale for future studies evaluating the efficacy of VRP-transduced DCs for tumor immunotherapy.

CD8-Positive T-Lymphocytes↗
PubMed2005

Heterologous gene expression by infectious and replicon vectors derived from tick-borne encephalitis virus and direct comparison of this flavivirus system with an alphavirus replicon.

The flavivirus tick-borne encephaltis virus (TBEV) was established as a vector system for heterologous gene expression. The variable region of the genomic 3' non-coding region was replaced by an expression cassette consisting of the reporter gene enhanced green fluorescent protein (EGFP) under the translational control of an internal ribosomal entry site element, both in the context of an infectious virus genome and of a replicon lacking the genes of the surface proteins prM/M and E. The expression level and the stability of expression were measured by fluorescence-activated cell-sorting analysis and compared to an established alphavirus replicon vector derived from Venezuelan equine encephaltis virus (VEEV), expressing EGFP under the control of its natural subgenomic promoter. On the first day, the alphavirus replicon exhibited an approximately 180-fold higher expression level than the flavivirus replicon, but this difference decreased to about 20- and 10-fold on days 2 and 3, respectively. Four to six days post-transfection, foreign gene expression by the VEEV replicon vanished almost completely, due to extensive cell killing. In contrast, in the case of the TBEV replicon, the percentage of positive cells and the amount of EGFP expression exhibited only a moderate decline over a time period of almost 4 weeks. The infectious TBEV vector expressed less EGFP than the TBEV replicon at all times. Significant expression from the infectious vector was maintained for four cell-culture passages. The results indicate that the VEEV vector is superior with respect to achieving high expression levels, but the TBEV system may be advantageous for applications that require a moderate, but more enduring, gene expression.

Alphavirus↗
PubMed2005

Comparison of immune responses to gonococcal PorB delivered as outer membrane vesicles, recombinant protein, or Venezuelan equine encephalitis virus replicon particles.

Porin (PorB) is a major outer membrane protein produced by all Neisseria gonorrhoeae strains and has been a focus of intense interest as a vaccine candidate. In this study, the immunogenicity of PorB in mice was investigated after several immunization regimens. Outer membrane vesicles (OMV), recombinant renatured PorB (rrPorB), and PorB-expressing Venezuelan equine encephalitis (VEE) virus replicon particles (PorB VRP) were delivered intranasally (i.n.) or subcutaneously (s.c.) into the dorsal area or the hind footpad in three-dose schedules; the PorB VRP-immunized mice were given a single additional booster dose of rrPorB in Ribi adjuvant. Different delivery systems and administration routes induced different immune responses. Mice immunized s.c. with rrPorB in Ribi had the highest levels of PorB-specific serum immunoglobulin G (IgG) by enzyme-linked immunosorbent assay. Surprisingly, there was an apparent Th1 bias, based on IgG1/IgG2a ratios, after immunization with rrPorB in Ribi in the footpad while the same vaccine given in the dorsal area gave a strongly Th2-biased response. PorB VRP-immunized mice produced a consistent Th1 response with a high gamma interferon response in stimulated splenic lymphocytes and very low IgG1/IgG2a ratios. Immunization by OMV delivered i.n. was the only regimen that resulted in a serum bactericidal response, and it generated an excellent mucosal IgA response. Serum from mice immunized with rrPorB preferentially recognized the surface of whole gonococci expressing a homologous PorB, whereas serum from PorB VRP-immunized mice had relatively low whole-cell binding activity but recognized both heterologous and homologous PorB equally. The data resulting from this direct comparison suggested that important aspects of the immune response can be manipulated by altering the form of the antigen and its delivery. This information coupled with an understanding of protective antigonococcal immune responses will enable the design of the optimal vaccine for N. gonorrhoeae.

Animals↗
PubMed2004

A new metric for continuing medical education credit.

The two major continuing medical education (CME) credit systems for allopathic physicians in the United States are administered by the American Medical Association (AMA) and the American Academy of Family Physicians (AAFP). This article explores the history of AMA and AAFP CME credit and its value to physicians and the patients they serve. Historically, CME credit has been awarded as hours for participation, but this approach is inadequate as a measure of CME and its impact on improving physician practice. New credit systems are needed to measure a CME activity by its value in bettering the physician's knowledge base, competence, and performance in practice.

American Medical Association↗
PubMed2003

Evaluation of Venezuelan Equine Encephalitis (VEE) replicon-based Outer surface protein A (OspA) vaccines in a tick challenge mouse model of Lyme disease.

Venezuelan Equine Encephalitis (VEE) virus replicon particles (VRPs) encoding Borrelia burgdorferi Outer surface protein A (OspA) were evaluated for their ability to induce an immune response and provide protection from tick-borne spirochetes. VRPs expressing ospA that accumulated intracellularly (VRP OspA) or that was secreted from host cells (VRP tPA-OspA) were tested. Both VRP OspA and VRP tPA-OspA expressed ospA in immunized mice. Mice vaccinated with VRPs expressing secreted OspA produced significant amounts of anti-OspA antibodies, whereas VRPs expressing intracellular OspA were less immunogenic. The VRP method of delivery induced a Th1 type immune response unlike the recombinant OspA protein in Freund's adjuvant, which induced a mixed (Th1 and Th2) immune response. The VRP tPA-OspA construct induced an immune response that reduced the bacterial load in feeding Ixodes scapularis and blocked transmission to the host. These results indicate that VRPs are capable of providing protection against tick-borne B. burgdorferi, and potentially can be used for developing improved vaccines against Lyme disease.

Adjuvants, Immunologic↗
PubMed2003

Genetically engineered, live attenuated vaccines for Venezuelan equine encephalitis: testing in animal models.

The central objective of this research was to test molecularly defined, live attenuated Venezuelan equine encephalitis virus (VEEV) vaccine candidates that were produced through precise genetic manipulation of rationally selected viral nucleotide sequences. Molecular clones of vaccine candidates were constructed by inserting either three independently attenuating mutations or a PE2 cleavage-signal mutation with a second-site resuscitating mutation into full-length cDNA clones. Vaccine candidate viruses were recovered through DNA transcription and RNA transfection of cultured cells, and assessed in rodent and non-human primate models. Based on results from this assessment, one of the PE2 cleavage-signal mutants, V3526, was determined to be the best vaccine candidate for further evaluation for human use.

Animals↗
PubMed2003

Treatment of medical students during clerkships based on their stated career interests.

BACKGROUND: Clerkship students often face questions from teachers about their career interests and may perceive that their responses change their clerkship experiences significantly. PURPOSE: To explore student experiences with "career interest" inquiries and how responses may influence clerkship experiences. METHODS: A qualitative study of 4th-year medical students by use of focus groups, whose experienced facilitators used a structured interview protocol. Purposeful sampling identified a representative group of participants. Transcribed focus group proceedings were analyzed with a predetermined theme matrix. RESULTS: Participants reported frequently facing career interest inquiries, feeling comfortable with some, and feeling threatened by others. The tone of inquiries ranged from casual to confrontational. Participants perceived that their responses could significantly influence the quality of teaching relationships, access to clinical opportunities, and grades. Students often responded vaguely or deceptively for self-protection. CONCLUSIONS: For clerkship students, career interest inquiries and how students respond can be high-stakes issues, potentially compromising teaching quality, equitable treatment, and fair evaluations. Further quantitative study is essential

Attitude of Health Personnel↗
PubMed2002

Alphavirus replicon particles expressing the two major envelope proteins of equine arteritis virus induce high level protection against challenge with virulent virus in vaccinated horses.

Replicon particles derived from a vaccine strain of Venezuelan equine encephalitis (VEE) virus were used as vectors for expression in vivo of the major envelope proteins (G(L) and M) of equine arteritis virus (EAV), both individually and in heterodimer form (G(L)/M). The immunogenicity of the different replicons was evaluated in horses, as was their ability to protectively immunize horses against intranasal and intrauterine challenge with a virulent strain of EAV (EAV KY84). Horses immunized with replicons that express both the G(L) and M proteins in heterodimer form developed neutralizing antibodies to EAV, shed little or no virus, and developed only mild or inapparent signs of equine viral arteritis (EVA) after challenge with EAV KY84. In contrast, unvaccinated horses and those immunized with replicons expressing individual EAV envelope proteins (M or G(L)) shed virus for 6-10 days in their nasal secretions and developed severe signs of EVA after challenge. These data confirm that replicons that co-express the G(L) and M envelope proteins effectively, induce EAV neutralizing antibodies and protective immunity in horses.

Animals↗
PubMedDate not supplied

Alphavirus replicon particles as candidate HIV vaccines.

Replicon particles based on Venezuelan equine encephalitis virus (VEE) contain a self-replicating RNA encoding the VEE replicase proteins and expressing a gene of interest in place of the viral structural protein genes. Structural proteins for packaging of replicon RNA into VEE replicon particles (VRPs) are expressed from separate helper RNAs. Aspects of the biology of VEE that are exploited in VRP vaccines include 1) expression of very high levels of immunogen, 2) expression of immunizing proteins in cells in the draining lymph node, and 3) the ability to induce mucosal immunity from a parental inoculation. Results of experiments with VRPs expressing green fluorescent protein or influenza virus hemagglutinin (HA) demonstrated that specific mutations in the VRP envelope glycoproteins affect both targeting in the draining lymph node and efficiency of the immune response in mice. VRPs expressing either the matrix-capsid portion of Gag, the full-length envelope gp160, or the secreted gp140 of cloned SIVsm H-4i were mixed in a cocktail and used to immunize macaques at 0, 1, and 4 months. Neutralizing antibodies against SIVsm H-4 were induced in 6 of 6 vaccinates and CTL in 4 of 6. An intrarectal challenge with the highly pathogenic SIVsm E660 was given at 5 months. A vaccine effect was seen in reduced peak virus loads, reduced virus loads both at set point and at 41 weeks postchallenge, and preserved or increased CD4 counts compared to controls. A candidate VRP HIV vaccine expressing Clade C Gag contains a sequence that is very close to the South African Clade C consensus and was selected from a recent seroconverter in the Durban cohort to represent currently circulating genotypes in South Africa. A GMP lot of this vaccine has been manufactured and tested for a phase I trial in the first months of 2002.

AIDS Vaccines↗