A Nucleic Acid-Based Orthopoxvirus Vaccine Targeting the Vaccinia Virus L1, A27, B5, and A33 Proteins Protects Rabbits against Lethal Rabbitpox Virus Aerosol Challenge.

In the age of COVID, nucleic acid vaccines have garnered much attention, at least in part, because of the simplicity of construction, production, and flexibility to adjust and adapt to an evolving outbreak. Orthopoxviruses remain a threat on multiple fronts, especially as emerging zoonoses. In response, we developed a DNA vaccine, termed 4pox, that protected nonhuman primates against monkeypox virus (MPXV)-induced severe disease. Here, we examined the protective efficacy of the 4pox DNA vaccine delivered by intramuscular (i.m.) electroporation (EP) in rabbits challenged with aerosolized rabbitpox virus (RPXV), a model that recapitulates the respiratory route of exposure and low dose associated with natural smallpox exposure in humans. We found that 4pox-vaccinated rabbits developed immunogen-specific antibodies, including neutralizing antibodies, and did not develop any clinical disease, indicating protection against aerosolized RPXV. In contrast, unvaccinated animals developed significant signs of disease, including lesions, and were euthanized. These findings demonstrate that an unformulated, nonadjuvanted DNA vaccine delivered i.m. can protect against an aerosol exposure. IMPORTANCE The eradication of smallpox and subsequent cessation of vaccination have left a majority of the population susceptible to variola virus or other emerging poxviruses. This is exemplified by human monkeypox, as evidenced by the increase in reported endemic and imported cases over the past decades. Therefore, a malleable vaccine technology that can be mass produced and does not require complex conditions for distribution and storage is sought. Herein, we show that a DNA vaccine, in the absence of a specialized formulation or adjuvant, can protect against a lethal aerosol insult of rabbitpox virus.

Glycoprotein-Specific Antibodies Produced by DNA Vaccination Protect Guinea Pigs from Lethal Argentine and Venezuelan Hemorrhagic Fever.

UNLABELLED: Several members of the Arenaviridae can cause acute febrile diseases in humans, often resulting in lethality. The use of convalescent-phase human plasma is an effective treatment in humans infected with arenaviruses, particularly species found in South America. Despite this, little work has focused on developing potent and defined immunotherapeutics against arenaviruses. In the present study, we produced arenavirus neutralizing antibodies by DNA vaccination of rabbits with plasmids encoding the full-length glycoprotein precursors of Junín virus (JUNV), Machupo virus (MACV), and Guanarito virus (GTOV). Geometric mean neutralizing antibody titers, as measured by the 50% plaque reduction neutralization test (PRNT(50)), exceeded 5,000 against homologous viruses. Antisera against each targeted virus exhibited limited cross-species binding and, to a lesser extent, cross-neutralization. Anti-JUNV glycoprotein rabbit antiserum protected Hartley guinea pigs from lethal intraperitoneal infection with JUNV strain Romero when the antiserum was administered 2 days after challenge and provided some protection (∼30%) when administered 4 days after challenge. Treatment starting on day 6 did not protect animals. We further formulated an IgG antibody cocktail by combining anti-JUNV, -MACV, and -GTOV antibodies produced in DNA-vaccinated rabbits. This cocktail protected 100% of guinea pigs against JUNV and GTOV lethal disease. We then expanded on this cocktail approach by simultaneously vaccinating rabbits with a combination of plasmids encoding glycoproteins from JUNV, MACV, GTOV, and Sabia virus (SABV). Sera collected from rabbits vaccinated with the combination vaccine neutralized all four targets. These findings support the concept of using a DNA vaccine approach to generate a potent pan-arenavirus immunotherapeutic. IMPORTANCE: Arenaviruses are an important family of emerging viruses. In infected humans, convalescent-phase plasma containing neutralizing antibodies can mitigate the severity of disease caused by arenaviruses, particularly species found in South America. Because of variations in potency of the human-derived product, limited availability, and safety concerns, this treatment option has essentially been abandoned. Accordingly, despite this approach being an effective postinfection treatment option, research on novel approaches to produce potent polyclonal antibody-based therapies have been deficient. Here we show that DNA-based vaccine technology can be used to make potently neutralizing antibodies in rabbits that exclusively target the glycoproteins of several human-pathogenic arenaviruses found in South America, including JUNV, MACV, GTOV, and SABV. These antibodies protected guinea pigs from lethal disease when given post-virus challenge. We also generated a purified antibody cocktail with antibodies targeting three arenaviruses and demonstrated protective efficacy against all three targets. Our findings demonstrate that use of the DNA vaccine technology could be used to produce candidate antiarenavirus neutralizing antibody-based products.

Polyclonal antibody cocktails generated using DNA vaccine technology protect in murine models of orthopoxvirus disease.

BACKGROUND: Previously we demonstrated that DNA vaccination of nonhuman primates (NHP) with a small subset of vaccinia virus (VACV) immunogens (L1, A27, A33, B5) protects against lethal monkeypox virus challenge. The L1 and A27 components of this vaccine target the mature virion (MV) whereas A33 and B5 target the enveloped virion (EV). RESULTS: Here, we demonstrated that the antibodies produced in vaccinated NHPs were sufficient to confer protection in a murine model of lethal Orthopoxvirus infection. We further explored the concept of using DNA vaccine technology to produce immunogen-specific polyclonal antibodies that could then be combined into cocktails as potential immunoprophylactic/therapeutics. Specifically, we used DNA vaccines delivered by muscle electroporation to produce polyclonal antibodies against the L1, A27, A33, and B5 in New Zealand white rabbits. The polyclonal antibodies neutralized both MV and EV in cell culture. The ability of antibody cocktails consisting of anti-MV, anti-EV, or a combination of anti-MV/EV to protect BALB/c mice was evaluated as was the efficacy of the anti-MV/EV mixture in a mouse model of progressive vaccinia. In addition to evaluating weight loss and lethality, bioimaging technology was used to characterize the spread of the VACV infections in mice. We found that the anti-EV cocktail, but not the anti-MV cocktail, limited virus spread and lethality. CONCLUSIONS: A combination of anti-MV/EV antibodies was significantly more protective than anti-EV antibodies alone. These data suggest that DNA vaccine technology could be used to produce a polyclonal antibody cocktail as a possible product to replace vaccinia immune globulin.

Endogenous HLA-DQ8αß programs superantigens (SEG/SEI) to silence toxicity and unleash a tumoricidal network with long-term melanoma survival.

BACKGROUND: As the most powerful T cell agonists known, superantigens (SAgs) have enormous potential for cancer immunotherapy. Their development has languished due to high incidence (60%-80%) of seroreactive neutralizing antibodies in humans and tumor necrosis factor-α (TNFα)-mediated cardiopulmonary toxicity. Such toxicity has narrowed their therapeutic index while neutralizing antibodies have nullified their therapeutic effects. METHODS: Female HLA-DQ8 (DQA*0301/DQB*0302) tg mice expressing the human major histocompatibility complex II (MHCII) HLA-DQ8 allele on a high proportion of PBL, spleen and lymph node cells were used. In the established tumor model, staphylococcal enterotoxin G and staphylococcal enterotoxin I (SEG/ SEI) (50 µg each) were injected on days 6 and 9 following tumor inoculation. Lymphoid, myeloid cells and tumor cell digests from tumor tissue were assayed using flow cytometry or quantitated using a cytometric bead array. Tumor density, necrotic and viable areas were quantitated using the ImageJ software. RESULTS: In a discovery-driven effort to address these problems we introduce a heretofore unrecognized binary complex comprizing SEG/SEI SAgs linked to the endogenous human MHCII HLA-DQ8 allele in humanized mice. By contrast to staphylococcal enterotoxin A (SEA) and staphylococcal enterotoxin B (SEB) deployed previously in clinical trials, SEG and SEI does not exhibit neutralizing antibodies in humans or TNFα-mediated toxicity in humanized HLA-DQ8 mice. In the latter model wherein SAg behavior is known to be 'human-like', SEG/SEI induced a powerful tumoricidal response and long-term survival against established melanoma in 82% of mice. Other SAgs deployed in the same model displayed toxic shock. Initially, HLA-DQ8 mediated melanoma antigen priming, after which SEG/SEI unleashed a broad CD4+ and CD8+ antitumor network marked by expansion of melanoma reactive T cells and interferon-γ (IFNy) in the tumor microenvironment (TME). SEG/SEI further initiated chemotactic recruitment of tumor reactive T cells to the TME converting the tumor from 'cold' to a 'hot'. Long-term survivors displayed remarkable resistance to parental tumor rechallenge along with the appearance of tumor specific memory and tumor reactive T memory cells. CONCLUSIONS: Collectively, these findings show for the first time that the SEG/SEI-(HLA-DQ8) empowers priming, expansion and recruitment of a population of tumor reactive T cells culminating in tumor specific memory and long-term survival devoid of toxicity. These properties distinguish SEG/SEI from other SAgs used previously in human tumor immunotherapy. Consolidation of these principles within the SEG/SEI-(HLA-DQ8) complex constitutes a conceptually new therapeutic weapon with compelling translational potential.

Lipid Nanoparticle Formulation Increases Efficiency of DNA-Vectored Vaccines/Immunoprophylaxis in Animals Including Transchromosomic Bovines.

The use of nucleic acid as a drug substance for vaccines and other gene-based medicines continues to evolve. Here, we have used a technology originally developed for mRNA in vivo delivery to enhance the immunogenicity of DNA vaccines. We demonstrate that neutralizing antibodies produced in rabbits and nonhuman primates injected with lipid nanoparticle (LNP)-formulated Andes virus or Zika virus DNA vaccines are elevated over unformulated vaccine. Using a plasmid encoding an anti-poxvirus monoclonal antibody (as a reporter of protein expression), we showed that improved immunogenicity is likely due to increased in vivo DNA delivery, resulting in more target protein. Specifically, after four days, up to 30 ng/mL of functional monoclonal antibody were detected in the serum of rabbits injected with the LNP-formulated DNA. We pragmatically applied the technology to the production of human neutralizing antibodies in a transchromosomic (Tc) bovine for use as a passive immunoprophylactic. Production of neutralizing antibody was increased by >10-fold while utilizing 10 times less DNA in the Tc bovine. This work provides a proof-of-concept that LNP formulation of DNA vaccines can be used to produce more potent active vaccines, passive countermeasures (e.g., Tc bovine), and as a means to produce more potent DNA-launched immunotherapies.

Human polyclonal antibodies produced in transchromosomal cattle prevent lethal Zika virus infection and testicular atrophy in mice.

Zika virus (ZIKV) is rapidly spreading throughout the Americas and is associated with significant fetal complications, most notably microcephaly. Treatment with polyclonal antibodies for pregnant women at risk of ZIKV-related complications could be a safe alternative to vaccination. We found that large quantities of human polyclonal antibodies could be rapidly produced in transchromosomal bovines (TcB) and successfully used to protect mice from lethal infection. Additionally, antibody treatment eliminated ZIKV induced tissue damage in immunologically privileged sites such as the brain and testes and protected against testicular atrophy. These data indicate that rapid development and deployment of human polyclonal antibodies could be a viable countermeasure against ZIKV.

Practical methods for supercoiled pNDA production.

Increased demand for plasmid DNA (pDNA) to be produced to tighter and more exacting specifications, even for early preclinical work, has led to many researchers and manufacturers reevaluating their production methodologies. This chapter is intended to offer realistic methods that may be employed by those wishing to purify between 100 and 200 mg of pDNA in-house based on availability of equipment and other resources. This scale of production typically requires a compromise between techniques used with gravity-flow or vacuum devices and intermediate scale column chromatography. The methodologies described in most instances are unit processes that can be adapted into an appropriate scheme given such considerations as the desired purity level or the quality of the feedstock.

Antiviral Biologic Produced in DNA Vaccine/Goose Platform Protects Hamsters Against Hantavirus Pulmonary Syndrome When Administered Post-exposure.

Andes virus (ANDV) and ANDV-like viruses are responsible for most hantavirus pulmonary syndrome (HPS) cases in South America. Recent studies in Chile indicate that passive transfer of convalescent human plasma shows promise as a possible treatment for HPS. Unfortunately, availability of convalescent plasma from survivors of this lethal disease is very limited. We are interested in exploring the concept of using DNA vaccine technology to produce antiviral biologics, including polyclonal neutralizing antibodies for use in humans. Geese produce IgY and an alternatively spliced form, IgYΔFc, that can be purified at high concentrations from egg yolks. IgY lacks the properties of mammalian Fc that make antibodies produced in horses, sheep, and rabbits reactogenic in humans. Geese were vaccinated with an ANDV DNA vaccine encoding the virus envelope glycoproteins. All geese developed high-titer neutralizing antibodies after the second vaccination, and maintained high-levels of neutralizing antibodies as measured by a pseudovirion neutralization assay (PsVNA) for over 1 year. A booster vaccination resulted in extraordinarily high levels of neutralizing antibodies (i.e., PsVNA80 titers >100,000). Analysis of IgY and IgYΔFc by epitope mapping show these antibodies to be highly reactive to specific amino acid sequences of ANDV envelope glycoproteins. We examined the protective efficacy of the goose-derived antibody in the hamster model of lethal HPS. α-ANDV immune sera, or IgY/IgYΔFc purified from eggs, were passively transferred to hamsters subcutaneously starting 5 days after an IM challenge with ANDV (25 LD50). Both immune sera, and egg-derived purified IgY/IgYΔFc, protected 8 of 8 and 7 of 8 hamsters, respectively. In contrast, all hamsters receiving IgY/IgYΔFc purified from normal geese (n=8), or no-treatment (n=8), developed lethal HPS. These findings demonstrate that the DNA vaccine/goose platform can be used to produce a candidate antiviral biological product capable of preventing a lethal disease when administered post-exposure.

A hantavirus pulmonary syndrome (HPS) DNA vaccine delivered using a spring-powered jet injector elicits a potent neutralizing antibody response in rabbits and nonhuman primates.

Sin Nombre virus (SNV) and Andes virus (ANDV) cause most of the hantavirus pulmonary syndrome (HPS) cases in North and South America, respectively. The chances of a patient surviving HPS are only two in three. Previously, we demonstrated that SNV and ANDV DNA vaccines encoding the virus envelope glycoproteins elicit high-titer neutralizing antibodies in laboratory animals, and (for ANDV) in nonhuman primates (NHPs). In those studies, the vaccines were delivered by gene gun or muscle electroporation. Here, we tested whether a combined SNV/ANDV DNA vaccine (HPS DNA vaccine) could be delivered effectively using a disposable syringe jet injection (DSJI) system (PharmaJet, Inc). PharmaJet intramuscular (IM) and intradermal (ID) needle-free devices are FDA 510(k)-cleared, simple to use, and do not require electricity or pressurized gas. First, we tested the SNV DNA vaccine delivered by PharmaJet IM or ID devices in rabbits and NHPs. Both IM and ID devices produced high-titer anti-SNV neutralizing antibody responses in rabbits and NHPs. However, the ID device required at least two vaccinations in NHP to detect neutralizing antibodies in most animals, whereas all animals vaccinated once with the IM device seroconverted. Because the IM device was more effective in NHP, the Stratis(®) (PharmaJet IM device) was selected for follow-up studies. We evaluated the HPS DNA vaccine delivered using Stratis(®) and found that it produced high-titer anti-SNV and anti-ANDV neutralizing antibodies in rabbits (n=8/group) as measured by a classic plaque reduction neutralization test and a new pseudovirion neutralization assay. We were interested in determining if the differences between DSJI delivery (e.g., high-velocity liquid penetration through tissue) and other methods of vaccine injection, such as needle/syringe, might result in a more immunogenic DNA vaccine. To accomplish this, we compared the HPS DNA vaccine delivered by DSJI versus needle/syringe in NHPs (n=8/group). We found that both the anti-SNV and anti-ANDV neutralizing antibody titers were significantly higher (p-value 0.0115) in the DSJI-vaccinated groups than the needle/syringe group. For example, the anti-SNV and anti-ANDV PRNT50 geometric mean titers (GMTs) were 1,974 and 349 in the DSJI-vaccinated group versus 87 and 42 in the needle/syringe group. These data demonstrate, for the first time, that a spring-powered DSJI device is capable of effectively delivering a DNA vaccine to NHPs. Whether this HPS DNA vaccine, or any DNA vaccine, delivered by spring-powered DSJI will elicit a strong immune response in humans, requires clinical trials.

DNA vaccine-derived human IgG produced in transchromosomal bovines protect in lethal models of hantavirus pulmonary syndrome.

Polyclonal immunoglobulin-based medical products have been used successfully to treat diseases caused by viruses for more than a century. We demonstrate the use of DNA vaccine technology and transchromosomal bovines (TcBs) to produce fully human polyclonal immunoglobulins (IgG) with potent antiviral neutralizing activity. Specifically, two hantavirus DNA vaccines [Andes virus (ANDV) DNA vaccine and Sin Nombre virus (SNV) DNA vaccine] were used to produce a candidate immunoglobulin product for the prevention and treatment of hantavirus pulmonary syndrome (HPS). A needle-free jet injection device was used to vaccinate TcB, and high-titer neutralizing antibodies (titers >1000) against both viruses were produced within 1 month. Plasma collected at day 10 after the fourth vaccination was used to produce purified α-HPS TcB human IgG. Treatment with 20,000 neutralizing antibody units (NAU)/kg starting 5 days after challenge with ANDV protected seven of eight animals, whereas zero of eight animals treated with the same dose of normal TcB human IgG survived. Likewise, treatment with 20,000 NAU/kg starting 5 days after challenge with SNV protected immunocompromised hamsters from lethal HPS, protecting five of eight animals. Our findings that the α-HPS TcB human IgG is capable of protecting in animal models of lethal HPS when administered after exposure provides proof of concept that this approach can be used to develop candidate next-generation polyclonal immunoglobulin-based medical products without the need for human donors, despeciation protocols, or inactivated/attenuated vaccine antigen.

A novel Sin Nombre virus DNA vaccine and its inclusion in a candidate pan-hantavirus vaccine against hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS).

Sin Nombre virus (SNV; family Bunyaviridae, genus Hantavirus) causes a hemorrhagic fever known as hantavirus pulmonary syndrome (HPS) in North America. There have been approximately 200 fatal cases of HPS in the United States since 1993, predominantly in healthy working-age males (case fatality rate 35%). There are no FDA-approved vaccines or drugs to prevent or treat HPS. Previously, we reported that hantavirus vaccines based on the full-length M gene segment of Andes virus (ANDV) for HPS in South America, and Hantaan virus (HTNV) and Puumala virus (PUUV) for hemorrhagic fever with renal syndrome (HFRS) in Eurasia, all elicited high-titer neutralizing antibodies in animal models. HFRS is more prevalent than HPS (>20,000 cases per year) but less pathogenic (case fatality rate 1-15%). Here, we report the construction and testing of a SNV full-length M gene-based DNA vaccine to prevent HPS. Rabbits vaccinated with the SNV DNA vaccine by muscle electroporation (mEP) developed high titers of neutralizing antibodies. Furthermore, hamsters vaccinated three times with the SNV DNA vaccine using a gene gun were completely protected against SNV infection. This is the first vaccine of any kind that specifically elicits high-titer neutralizing antibodies against SNV. To test the possibility of producing a pan-hantavirus vaccine, rabbits were vaccinated by mEP with an HPS mix (ANDV and SNV plasmids), or HFRS mix (HTNV and PUUV plasmids), or HPS/HFRS mix (all four plasmids). The HPS mix and HFRS mix elicited neutralizing antibodies predominantly against ANDV/SNV and HTNV/PUUV, respectively. Furthermore, the HPS/HFRS mix elicited neutralizing antibodies against all four viruses. These findings demonstrate a pan-hantavirus vaccine using a mixed-plasmid DNA vaccine approach is feasible and warrants further development.

Making vaccines "on demand": a potential solution for emerging pathogens and biodefense?

The integrated US Public Health Emergency Medical Countermeasures Enterprise (PHEMCE) has made great strides in strategic preparedness and response capabilities. There have been numerous advances in planning, biothreat countermeasure development, licensure, manufacturing, stockpiling and deployment. Increased biodefense surveillance capability has dramatically improved, while new tools and increased awareness have fostered rapid identification of new potential public health pathogens. Unfortunately, structural delays in vaccine design, development, manufacture, clinical testing and licensure processes remain significant obstacles to an effective national biodefense rapid response capability. This is particularly true for the very real threat of "novel pathogens" such as the avian-origin influenzas H7N9 and H5N1, and new coronaviruses such as hCoV-EMC. Conventional approaches to vaccine development, production, clinical testing and licensure are incompatible with the prompt deployment needed for an effective public health response. An alternative approach, proposed here, is to apply computational vaccine design tools and rapid production technologies that now make it possible to engineer vaccines for novel emerging pathogen and WMD biowarfare agent countermeasures in record time. These new tools have the potential to significantly reduce the time needed to design string-of-epitope vaccines for previously unknown pathogens. The design process-from genome to gene sequence, ready to insert in a DNA plasmid-can now be accomplished in less than 24 h. While these vaccines are by no means "standard," the need for innovation in the vaccine design and production process is great. Should such vaccines be developed, their 60-d start-to-finish timeline would represent a 2-fold faster response than the current standard.

DNA vaccine-generated duck polyclonal antibodies as a postexposure prophylactic to prevent hantavirus pulmonary syndrome (HPS).

Andes virus (ANDV) is the predominant cause of hantavirus pulmonary syndrome (HPS) in South America and the only hantavirus known to be transmitted person-to-person. There are no vaccines, prophylactics, or therapeutics to prevent or treat this highly pathogenic disease (case-fatality 35-40%). Infection of Syrian hamsters with ANDV results in a disease that closely mimics human HPS in incubation time, symptoms of respiratory distress, and disease pathology. Here, we evaluated the feasibility of two postexposure prophylaxis strategies in the ANDV/hamster lethal disease model. First, we evaluated a natural product, human polyclonal antibody, obtained as fresh frozen plasma (FFP) from a HPS survivor. Second, we used DNA vaccine technology to manufacture a polyclonal immunoglobulin-based product that could be purified from the eggs of vaccinated ducks (Anas platyrhynchos). The natural "despeciation" of the duck IgY (i.e., Fc removed) results in an immunoglobulin predicted to be minimally reactogenic in humans. Administration of ≥ 5,000 neutralizing antibody units (NAU)/kg of FFP-protected hamsters from lethal disease when given up to 8 days after intranasal ANDV challenge. IgY/IgYΔFc antibodies purified from the eggs of DNA-vaccinated ducks effectively neutralized ANDV in vitro as measured by plaque reduction neutralization tests (PRNT). Administration of 12,000 NAU/kg of duck egg-derived IgY/IgYΔFc protected hamsters when administered up to 8 days after intranasal challenge and 5 days after intramuscular challenge. These experiments demonstrate that convalescent FFP shows promise as a postexposure HPS prophylactic. Moreover, these data demonstrate the feasibility of using DNA vaccine technology coupled with the duck/egg system to manufacture a product that could supplement or replace FFP. The DNA vaccine-duck/egg system can be scaled as needed and obviates the necessity of using limited blood products obtained from a small number of HPS survivors. This is the first report demonstrating the in vivo efficacy of any antiviral product produced using DNA vaccine-duck/egg system.

A directed molecular evolution approach to improved immunogenicity of the HIV-1 envelope glycoprotein.

A prophylactic vaccine is needed to slow the spread of HIV-1 infection. Optimization of the wild-type envelope glycoproteins to create immunogens that can elicit effective neutralizing antibodies is a high priority. Starting with ten genes encoding subtype B HIV-1 gp120 envelope glycoproteins and using in vitro homologous DNA recombination, we created chimeric gp120 variants that were screened for their ability to bind neutralizing monoclonal antibodies. Hundreds of variants were identified with novel antigenic phenotypes that exhibit considerable sequence diversity. Immunization of rabbits with these gp120 variants demonstrated that the majority can induce neutralizing antibodies to HIV-1. One novel variant, called ST-008, induced significantly improved neutralizing antibody responses when assayed against a large panel of primary HIV-1 isolates. Further study of various deletion constructs of ST-008 showed that the enhanced immunogenicity results from a combination of effective DNA priming, an enhanced V3-based response, and an improved response to the constant backbone sequences.

Effect of trimerization motifs on quaternary structure, antigenicity, and immunogenicity of a noncleavable HIV-1 gp140 envelope glycoprotein.

The external domains of the HIV-1 envelope glycoprotein (gp120 and the gp41 ectodomain, collectively known as gp140) contain all known viral neutralization epitopes. Various strategies have been used to create soluble trimers of the envelope to mimic the structure of the native viral protein, including mutation of the gp120-gp41 cleavage site, introduction of disulfide bonds, and fusion to heterologous trimerization motifs. We compared the effects on quaternary structure, antigenicity, and immunogenicity of three such motifs: T4 fibritin, a GCN4 variant, and the Escherichia coli aspartate transcarbamoylase catalytic subunit. Fusion of each motif to the C-terminus of a noncleavable JRCSF gp140(-) envelope protein led to enhanced trimerization but had limited effects on the antigenic profile and CD4-binding ability of the trimers. Immunization of rabbits provided no evidence that the trimerized gp140(-) constructs induced significantly improved neutralizing antibodies to several HIV-1 pseudoviruses, compared to gp140 lacking a trimerization motif. However, modest differences in both binding specificity and neutralizing antibody responses were observed among the various immunogens.

Preserved anterograde and retrograde memory of rapidly acquired olfactory discrminations after neurotoxic hippocampal lesions.

A forced-choice discrimination paradigm was used in two experiments, to evaluate retrograde and anterograde amnesia in rats after hippocampal ablation. In a within-subjects design (Experiment 1), rats were trained on a set of 10 olfactory discriminations 4 weeks before surgery and on a separate set of 10 discriminations 1 week before surgery. In a mixed design (Experiment 2), rats were trained on olfactory discriminations in one of three conditions: condition 1 (10 discriminations at 4 weeks before surgery); condition 2 (10 discriminations at 1 week before surgery); or condition 3 (10 discriminations at 4 weeks before surgery and 10 discriminations at 1 week before surgery). Discriminations in both experiments were rapidly learned, requiring 7-10 trials to reach criterion. After training, half of the rats in each condition received bilateral neurotoxic lesions of the hippocampus, and the other half received sham surgery. One week after surgery, all rats were given a retention test, consisting of a single critical trial for each discrimination. In both experiments, rats with selective hippocampal lesions exhibited preserved retention of these olfactory discriminations with no observable retention gradient. A postoperative acquisition test for two new discriminations indicated that anterograde memory was also preserved, while a postoperative test of spatial learning in the Morris water maze confirmed that the hippocampal lesions impaired spatial learning. Together, these experiments refute the contention that the hippocampus is requisite for (non-spatial) olfactory memory consolidation, storage, or access, despite the condition that the information be rapidly acquired.