Genetic immunization with multiple HIV-1 genes provides protection against HIV-1/MuLV pseudovirus challenge in vivo

Advancing the preclinical study of comorbid neuroHIV and substance use disorders: Current perspectives and future directions

Human immunodeficiency virus (HIV) remains a persistent public health concern throughout the world. Substance use disorders (SUDs) are a common comorbidity that can worsen treatment outcomes for people living with HIV. The relationship between HIV infection and SUD outcomes is likely bidirectional, making clear interrogation of neurobehavioral outcomes challenging in clinical populations. Importantly, the mechanisms through which HIV and addictive drugs disrupt homeostatic immune and CNS function appear to be highly overlapping and synergistic within HIV-susceptible reward and motivation circuitry in the central nervous system. Decades of animal research have revealed invaluable insights into mechanisms underlying the pathophysiology SUDs and HIV, although translational studies examining comorbid SUDs and HIV are very limited due to the technical challenges of modeling HIV infection preclinically. In this review, we discuss preclinical animal models of HIV and highlight key pathophysiological characteristics of each model, with a particular emphasis on rodent models of HIV. We then review the implementation of these models in preclinical SUD research and identify key gaps in knowledge in the field. Finally, we discuss how cutting-edge behavioral neuroscience tools, which have revealed key insights into the neurobehavioral mechanisms of SUDs, can be applied to preclinical animal models of HIV to reveal potential, novel treatment avenues for comorbid HIV and SUDs. Here, we argue that future preclinical SUD research would benefit from incorporating comorbidities such as HIV into animal models and would facilitate the discovery of more refined, subpopulation-specific mechanisms and effective SUD prevention and treatment targets.

Codon optimization and improved delivery/immunization regimen enhance the immune response against wild-type and drug-resistant HIV-1 reverse transcriptase, preserving its Th2-polarity

DNA vaccines require a considerable enhancement of immunogenicity. Here, we optimized a prototype DNA vaccine against drug-resistant HIV-1 based on a weak Th2-immunogen, HIV-1 reverse transcriptase (RT). We designed expression-optimized genes encoding inactivated wild-type and drug-resistant RTs (RT-DNAs) and introduced them into mice by intradermal injections followed by electroporation. RT-DNAs were administered as single or double primes with or without cyclic-di-GMP, or as a prime followed by boost with RT-DNA mixed with a luciferase-encoding plasmid (“surrogate challenge”). Repeated primes improved cellular responses and broadened epitope specificity. Addition of cyclic-di-GMP induced a transient increase in IFN-γ production. The strongest anti-RT immune response was achieved in a prime-boost protocol with electroporation by short 100V pulses done using penetrating electrodes. The RT-specific response, dominated by CD4+ T-cells, targeted epitopes at aa 199–220 and aa 528–543. Drug-resistance mutations disrupted the epitope at aa 205–220, while the CTL epitope at aa 202–210 was not affected. Overall, multiparametric optimization of RT strengthened its Th2- performance. A rapid loss of RT/luciferase-expressing cells in the surrogate challenge experiment revealed a lytic potential of anti-RT response. Such lytic CD4+ response would be beneficial for an HIV vaccine due to its comparative insensitivity to immune escape.

DNA-Encoded Flagellin Activates Toll-Like Receptor 5 (TLR5), Nod-like Receptor Family CARD Domain-Containing Protein 4 (NRLC4), and Acts as an Epidermal, Systemic, and Mucosal-Adjuvant

Eliciting effective immune responses using non-living/replicating DNA vaccines is a significant challenge. We have previously shown that ballistic dermal plasmid DNA-encoded flagellin (FliC) promotes humoral as well as cellular immunity to co-delivered antigens. Here, we observe that a plasmid encoding secreted FliC (pFliC(-gly)) produces flagellin capable of activating two innate immune receptors known to detect flagellin; Toll-like Receptor 5 (TLR5) and Nod-like Receptor family CARD domain-containing protein 4 (NRLC4). To test the ability of pFliC(-gly) to act as an adjuvant we immunized mice with plasmid encoding secreted FliC (pFliC(-gly)) and plasmid encoding a model antigen (ovalbumin) by three different immunization routes representative of dermal, systemic, and mucosal tissues. By all three routes we observed increases in antigen-specific antibodies in serum as well as MHC Class I-dependent cellular immune responses when pFliC(-gly) adjuvant was added. Additionally, we were able to induce mucosal antibody responses and Class II-dependent cellular immune responses after mucosal vaccination with pFliC(-gly). Humoral immune responses elicited by heterologus prime-boost immunization with a plasmid encoding HIV-1 from gp160 followed by protein boosting could be enhanced by use of pFliC(-gly). We also observed enhancement of cross-clade reactive IgA as well as a broadening of B cell epitope reactivity. These observations indicate that plasmid-encoded secreted flagellin can activate multiple innate immune responses and function as an adjuvant to non-living/replicating DNA immunizations. Moreover, the capacity to elicit mucosal immune responses, in addition to dermal and systemic properties, demonstrates the potential of flagellin to be used with vaccines designed to be delivered by various routes.

Rodent models for HIV-associated neurocognitive disorders

Human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) reflect the spectrum of neural impairments seen during chronic viral infection. Current research efforts focus on improving antiretroviral and adjunctive therapies, defining disease onset and progression, facilitating drug delivery, and halting neurodegeneration and viral resistance. Because HIV is species-specific, generating disease in small-animal models has proved challenging. After two decades of research, rodent HAND models now include those containing a human immune system. Antiviral responses, neuroinflammation and immunocyte blood-brain barrier (BBB) trafficking follow HIV infection in these rodent models. We review these and other rodent models of HAND and discuss their unmet potential in reflecting human pathobiology and in facilitating disease monitoring and therapeutic discoveries.

Neutralizing activity and cellular immune responses induced in mice after immunization with apoptotic HIV-1/murine leukemia virus infected cells

Dendritic cells present microbial antigens to T cells after uptake of apoptotic vesicles from infected cells. We previously reported that immunizations with apoptotic HIV-1/murine leukemia virus (MuLV) infected cells lead to induction of both cellular and humoral immune responses as well as resistance to mucosal challenge with live HIV-1/MuLV infected cells. Here we extended those studies and investigated whether apoptotic cells from HIV-1/MuLV infected cells stimulate the production of HIV-1 neutralizing activity. We compared different routes of administration and were able to induce p24- and Nef-specific cellular proliferation after intraperitoneal (i.p.), intranasal (i.n.), subcutaneous (s.c.) and intramuscular (i.m.) immunizations. Serum IgG and IgA antibodies directed against gp160, p24, or Nef were also produced regardless of immunization route used. However, the induction of mucosa-associated IgAs from faeces or vaginal secretions were detected only after either i.p. or i.n. immunizations. We were able to measure neutralizing activity in sera of mice after i.p. and i.n. immunization. Neutralizing reactivity was also detected after s.c. and i.m. immunizations in the presence of the cytokine adjuvant granulocyte macrophage-colony stimulating factor (GM-CSF). Conclusively we show induction of cellular and humoral immune responses including neutralizing activity after immunization with apoptotic HIV-1/MuLV infected cells in mice. The results from this study support further evaluations using apoptotic cells as antigen delivery system for vaccination against HIV-1 in other animal models.

Murine models for HIV vaccination and challenge

HIV-1 only infects humans and chimpanzees. SIV or SHIV are, therefore, used as models for HIV in rhesus, cynomologus and pigtail macaques. Since conducting experiments in primate models does not fully mimic infection or vaccination against HIV-1 and is expensive, there is a great need for small-animal models in which it is possible to study HIV-1 infection, immunity and vaccine efficacy. This review summarizes the available murine models for studying HIV-1 infection with an emphasis on our experience of the HIV-1-infected-cell challenge as a model for evaluating candidate HIV-1 vaccines. In the cell-based challenge model, several important factors that, hopefully, can be related to vaccine efficacy in humans were discovered: the efficiency of combining plasmid DNA representing several of the viral genes originating from multiple clades of HIV-1, the importance of adjuvants activating innate and induced immunity and the enhanced HIV eradication by drug-conjugated antibody.

Safety and immunogenicity, after nasal application of HIV-1 DNA gagp37 plasmid vaccine in young mice

BACKGROUND

There is a need for safe and potent adjuvants capable of delivering vaccine candidates over the mucosal barrier, with good capacity to stimulate both mucosal and systemic cell-mediated and humoral immunity. An adjuvant aimed for intranasal delivery should preferably deliver the antigen and minimize the transfer into the close proximity of the central nervous system, thus avoiding damage on the olfactory tissues. Advantages with a mucosal delivery route would be to provide mucosal and systemic immunity, requiring lower vaccine doses then when given parentally. The aim of this study was to study if the N3 adjuvant intranasally administered with HIV DNA plasmids would be transferred into the olfactory tissues and cause local inflammation and tissue damage.

RESULTS

The N3 adjuvant alone and when combined with HIV-1 DNA gag plasmid and delivered intranasally did not cause detectable damage to the nasal epithelium or the olfactory epithelium or bulb over a period of 3 days after delivery. The intranasal administration of HIV-1 gagp37 DNA induced both a humoral and a cell-mediated immunity against the gag antigen. Significantly higher HIV-1-specific humoral, but not cell-mediated immune responses were seen in DNA/N3-immunized mice in comparison with HIV-1 DNA/saline-immunized animals.

CONCLUSIONS

A safe and convenient intranasal mode of HIV-1 DNA plasmid and adjuvant delivery was shown not to interfere with the tissues in close proximity to the central nervous system. The N3 adjuvant combined with HIV-1 plasmids enhances the HIV-1-specific immunogenicity and merits to be clinically tested.

Clarification of how HIV-1 DNA and protein immunizations may be better used to obtain HIV-1-specific mucosal and systemic immunity

More focused research on a mucosal HIV-1 vaccine is needed urgently. An increasing amount of collected data, using heterologous multimodality prime-booster strategies, suggest that an efficient and protective HIV-1 vaccine must generate broad, long-lasting HIV-specific CD8(+) cytotoxic T-lymphocyte and neutralizing antibody responses. In the mucosa, these responses would be most effective if a preferential stimulus of HIV-1 neutralizing secretory immunoglobulin A and G were obtained. The attractive property of mucosal immunization is the obtained mucosal and systemic immunity, whereas systemic immunization induces a more limited immunity, predominantly in systemic sites. These objectives will require new vaccine regimens, such as multiclade HIV DNA and protein vaccines (nef, tat, gag and env expressed in DNA plasmids) delivered onto mucosal surfaces with needle-free delivery methods, such as nasal drop, as well as oral and rectal/vaginal delivery, and should merit clinical trials.

GTU®-MultiHIV DNA vaccine results in protection in a novel P815 tumor challenge model

A novel animal model for testing the immunogenicity and protective immune response induced by HIV-1 DNA vaccines was developed. DBA/2 mice were immunized with GTU-MultiHIV DNA encoding multigene for Rev, Nef, Tat, optp17/24 and a stretch of Pol/Env epitopes. A single GTU-MultiHIV B-clade specific plasmid or Auxo-GTU-MultiHIV(mix) (mixture of four plasmids with A, B, C and FGH clade specific MultiHIV antigens) were administered via gene gun and cell-mediated and humoral immune responses were analysed. The protective efficacy of the immune response was evaluated by challenging the mice with syngeneic tumor cells (P815) stably transfected with the MultiHIV fusion gene. Our results show that the strong MultiHIV-specific immune response generated by the GTU-MultiHIV vaccines in DBA/2 mice was able to delay the tumor growth substantially, indicating that the CTL response detected in vitro confers protection in vivo. The model described here is a safe and feasible in vivo assay for assessment of the vaccine potency to induce protective cell-mediated immune responses.

Evaluation of immunogenicity and efficacy of combined DNA and adjuvanted protein vaccination in a human immunodeficiency virus type 1/murine leukemia virus pseudotype challenge model

A DNA plasmid encoding human immunodeficiency virus type 1 (HIV-1) env, nef and tat genes was used in mice in a prime-boost immunization regimen with the corresponding recombinant proteins. The genetic immunogen was delivered with a gene gun and the proteins were injected intramuscularly together with the adjuvant AS02A. Immunizations were followed by experimental challenge with pseudotyped HIV-1 subtype A or B virus. In an initial experiment in which animals were challenged four weeks after the final immunization, all single modality and prime-boost vaccinations resulted in a significant level of protection as compared to control animals. There was a trend for DNA-alone immunization yielding the highest protection. In a subsequent study, a late challenge was performed 19 weeks after the final immunization. All groups having received the DNA vaccine, either alone or in combination with adjuvanted protein, exhibited strong protection against HIV replication. The subtype-specific protection against the experimental HIV challenge was significantly stronger than the cross-protection. Cellular and humoral immune responses were assessed during immunization and after challenge, but without clear correlation to protection against HIV replication. The data suggest that either DNA or protein antigens alone provide partial protection against an HIV-1/MuLV challenge and that DNA immunization is essential for achieving very high levels of efficacy in this murine HIV-1 challenge model. While prime-boost combinations were more immunogenic than DNA alone, they did not appear to provide any further enhancement over DNA vaccine mediated efficacy. The DNA immunogen might prime low levels of CD8+ T cells responsible for virus clearance or possibly a yet unidentified mechanism of protection.

Elimination of HIV-1 infection by treatment with a doxorubicin-conjugated anti-envelope antibody

OBJECTIVE

To test the efficacy of an immunoconjugate against HIV-1.

DESIGN

: A murine monoclonal antibody against the envelope antigen of HIV (P4/D10) was conjugated with the conventional anticancer drug, doxorubicin, and tested against infectious virus and infected cells, both in vitro and in vivo.

METHODS

P4/D10 antibody was incubated with free virus (neutralization) or HIV-infected cells (inhibition) and the resulting infection was measured by a p24 capture enzyme-linked immunosorbent assay. In an HIV-1/MuLV murine challenge model, the ability of the conjugate to inhibit infection in vivo was measured.

RESULTS

Doxorubicin-conjugated P4/D10 neutralized HIV-1IIIB and eliminated intercellular spread and HIV replication in infected Jurkat cells in vitro. The conjugate also protected mice from challenge with HIV-1IIIB/MuLV at an eightfold lower concentration than needed for free antibody, whereas no effects were observed for comparable doses of free drug or irrelevant conjugate controls.

CONCLUSION

This indicates that doxorubicin is concentrated to HIV-infected cells by the P4/D10 antibody, significantly (P = 0.0001) contributing to HIV elimination. This concept could also be adapted to eradicate remaining antigen-expressing T cells in patients treated with antiretroviral therapy.

Cross-clade protection induced by human immunodeficiency virus-1 DNA immunogens expressing consensus sequences of multiple genes and epitopes from subtypes A, B, C, and FGH

The correlate of protection in human immunodeficiency virus (HIV) infection is not known, but preclinical and clinical studies support the involvement of both antibodies and cellular immunity. In addition, the existence of multiple HIV clades makes HIV vaccine design especially challenging. We have constructed a vaccine platform with an HIV-1 subtype B DNA immunogen expressing full length consensus sequences from HIV-1 rev, nef, tat, and gag with additional cellular epitope clusters from the env and pol regions. Furthermore, this platform has been extended to three additional plasmids expressing the same immunogens but originating from subtypes A or C consensus or FGH ancestral sequences. Immunogenicity in BALB/c mice, by gene gun or intramuscular delivery, revealed strong IFN-gamma production in response to in vitro re-stimulation with a H-2d restricted gag peptide (AMQMLKETI) or even stronger toward an env epitope (RGPGRAFVTI). Weak humoral immunity was detected. Gene gun immunization with a cocktail of all four plasmids induced pre-challenge cellular immunity in C57Bl6/A2.01 mice and subsequently a robust frequency of protection (11/12 animals) after experimental challenge with subtype A or B HIV-1/Murine Leukemia Virus (HIV-1/MuLV). The cross-clade protection observed in this challenge experiment demonstrates that these multigene/multiepitope HIV DNA immunogens are likely to be potent immunogens also against the HIV-infection of human beings.

A novel DNA adjuvant, N3, enhances mucosal and systemic immune responses induced by HIV-1 DNA and peptide immunizations

AIMS

The study was designed to evaluate a novel cationic lipid DNA adjuvant (N3) and its function for HIV-1gp160/rev DNA plasmid delivered intranasally. The primary N3/HIV-DNA plasmid immunizations were boosted intranasally with a gp41 peptide in a anionic L3 adjuvant. This novel prime-boost strategy of mucosal immunization provided a broad HIV-1 envelope specific immunity, and recognition of viruses of subtypes A, B and C.

CONCLUSIONS

Intranasal N3-adjuvanted gp160/rev DNA prime followed by one L3-peptide boosting immunization, induced broadly neutralizing antibodies against HIV-1 in the mucosa and systemically. The needle-free intranasal prime-boost strategy using two different adjuvant formulations reduced significantly the dose of DNA needed.

A mouse model for study of systemic HIV-1 infection, antiviral immune responses, and neuroinvasiveness

We created a model of HIV-1 infection of conventional mice for investigation of viral replication, control, and pathogenesis. To target HIV-1 to mice, the coding region of gp120 in HIV-1/NL4-3 was replaced with that of gp80 from ecotropic murine leukemia virus, a retrovirus that infects only rodents. The resulting chimeric virus construct, EcoHIV, productively infected murine lymphocytes, but not human lymphocytes, in culture. Adult, immunocompetent mice were readily susceptible to infection by a single inoculation of EcoHIV as shown by detection of virus in splenic lymphocytes, peritoneal macrophages, and the brain. The virus produced in animals was infectious, as shown by passage in culture, and immunogenic, as shown by induction of antibodies to HIV-1 Gag and Tat. A second chimeric virus based on clade D HIV-1/NDK was also highly infectious in mice; it was detected in both spleen and brain 3 wk after tail vein inoculation, and it induced expression of infection response genes, MCP-1, STAT1, IL-1beta, and complement component C3, in brain tissue as determined by quantitative real-time PCR. EcoHIV infection of mice forms a useful model of HIV-1 infection of human beings for convenient and safe investigation of HIV-1 therapy, vaccines, and potentially pathogenesis.