RESUMO
Since the SARS-CoV-2 Omicron virus has gained dominance worldwide, its continual evolution with unpredictable mutations and patterns has revoked all authorized immunotherapeutics. Rapid viral evolution has also necessitated several rounds of vaccine updates in order to provide adequate immune protection. It remains imperative to understand how Omicron evolves into different subvariants and causes immune escape as this could help reevaluate the current intervention strategies mostly implemented in the clinics as emergency measures to counter the pandemic and, importantly, develop new solutions. Here, we provide a review focusing on the major events of Omicron viral evolution, including the features of spike mutation that lead to immune evasion against monoclonal antibody (mAb) therapy and vaccination, and suggest alternative durable options such as the ACE2-based experimental therapies superior to mAbs to address this unprecedented evolution of Omicron virus. In addition, this type of unique ACE2-based virus-trapping molecules can counter all zoonotic SARS coronaviruses, either from unknown animal hosts or from established wild-life reservoirs of SARS-CoV-2, and even seasonal alpha coronavirus NL63 that depends on human ACE2 for infection.
Assuntos
COVID-19 , Evasão da Resposta Imune , SARS-CoV-2 , Glicoproteína da Espícula de Coronavírus , SARS-CoV-2/imunologia , SARS-CoV-2/genética , Humanos , COVID-19/imunologia , COVID-19/virologia , Glicoproteína da Espícula de Coronavírus/imunologia , Glicoproteína da Espícula de Coronavírus/genética , Glicoproteína da Espícula de Coronavírus/metabolismo , Enzima de Conversão de Angiotensina 2/metabolismo , Enzima de Conversão de Angiotensina 2/imunologia , Animais , Evolução Molecular , Anticorpos Monoclonais/imunologia , Anticorpos Monoclonais/uso terapêutico , Mutação , Vacinas contra COVID-19/imunologia , Anticorpos Antivirais/imunologiaRESUMO
The capacity of SARS-CoV-2 to evolve poses challenges to conventional prevention and treatment options such as vaccination and monoclonal antibodies, as they rely on viral receptor binding domain (RBD) sequences from previous strains. Additionally, animal CoVs, especially those of the SARS family, are now appreciated as a constant pandemic threat. We present here a new antiviral approach featuring inhalation delivery of a recombinant viral trap composed of ten copies of angiotensin-converting enzyme 2 (ACE2) fused to the IgM Fc. This ACE2 decamer viral trap is designed to inhibit SARS-CoV-2 entry function, regardless of viral RBD sequence variations as shown by its high neutralization potency against all known SARS-CoV-2 variants, including Omicron BQ.1, BQ.1.1, XBB.1 and XBB.1.5. In addition, it demonstrates potency against SARS-CoV-1, human NL63, as well as bat and pangolin CoVs. The multivalent trap is effective in both prophylactic and therapeutic settings since a single intranasal dosing confers protection in human ACE2 transgenic mice against viral challenges. Lastly, this molecule is stable at ambient temperature for more than twelve weeks and can sustain physical stress from aerosolization. These results demonstrate the potential of a decameric ACE2 viral trap as an inhalation solution for ACE2-dependent coronaviruses of current and future pandemic concerns.
Assuntos
Infecções por Coronavirus , Coronavirus , Animais , Camundongos , Humanos , Enzima de Conversão de Angiotensina 2/metabolismo , Ligação Proteica , Infecções por Coronavirus/tratamento farmacológico , Infecções por Coronavirus/prevenção & controle , Infecções por Coronavirus/metabolismo , Glicoproteína da Espícula de CoronavírusRESUMO
The HIV-1 gp41 N-heptad repeat (NHR) region of the prehairpin intermediate, which is transiently exposed during HIV-1 viral membrane fusion, is a validated clinical target in humans and is inhibited by the Food and Drug Administration (FDA)-approved drug enfuvirtide. However, vaccine candidates targeting the NHR have yielded only modest neutralization activities in animals; this inhibition has been largely restricted to tier-1 viruses, which are most sensitive to neutralization by sera from HIV-1-infected individuals. Here, we show that the neutralization activity of the well-characterized NHR-targeting antibody D5 is potentiated >5,000-fold in TZM-bl cells expressing FcγRI compared with those without, resulting in neutralization of many tier-2 viruses (which are less susceptible to neutralization by sera from HIV-1-infected individuals and are the target of current antibody-based vaccine efforts). Further, antisera from guinea pigs immunized with the NHR-based vaccine candidate (ccIZN36)3 neutralized tier-2 viruses from multiple clades in an FcγRI-dependent manner. As FcγRI is expressed on macrophages and dendritic cells, which are present at mucosal surfaces and are implicated in the early establishment of HIV-1 infection following sexual transmission, these results may be important in the development of a prophylactic HIV-1 vaccine.
Assuntos
Proteína gp41 do Envelope de HIV/imunologia , Infecções por HIV/tratamento farmacológico , Receptores de IgG/imunologia , Sequências Repetitivas de Aminoácidos/genética , Sequência de Aminoácidos , Animais , Anticorpos Neutralizantes/imunologia , Anticorpos Neutralizantes/farmacologia , Afinidade de Anticorpos , Cobaias , Anticorpos Anti-HIV/imunologia , Anticorpos Anti-HIV/farmacologia , Proteína gp41 do Envelope de HIV/genética , Infecções por HIV/genética , Infecções por HIV/imunologia , Infecções por HIV/virologia , Soropositividade para HIV/imunologia , HIV-1/efeitos dos fármacos , HIV-1/imunologia , HIV-1/patogenicidade , Humanos , Soros Imunes/imunologia , Soros Imunes/farmacologia , Imunização , Imunoglobulina G/imunologia , Sequências Repetitivas de Aminoácidos/imunologia , Internalização do Vírus/efeitos dos fármacosRESUMO
The COVID-19 pandemic is a stark reminder of the heavy toll that emerging infectious diseases (EIDs) with epidemic and pandemic potential can inflict. Vaccine development, scale-up, and commercialization is a long, expensive, and risky enterprise that requires substantial upfront planning and offers no guarantee of success. EIDs are a particularly challenging target for global health preparedness, including for vaccine development. Insufficient attention has been given to challenges, lessons learned, and potential solutions to support and sustain vaccine industry engagement in vaccine development for EIDs. Drawing from lessons from the most recent Ebola epidemic in the Democratic Republic of the Congo, as well as the 2009 H1N1 influenza, 2014-2016 Ebola, and 2015-16 Zika outbreaks preceding it, we offer our perspective on challenges facing EID vaccine development and recommend additional solutions to prioritize in the near term. The 6 recommendations focus on reducing vaccine development timelines and increasing business certainty to reduce risks for companies. The global health security community has an opportunity to build on the current momentum to design a sustainable model for EID vaccines.
Assuntos
Doenças Transmissíveis Emergentes/prevenção & controle , Infecções por Coronavirus/prevenção & controle , Saúde Global , Vacinas contra Influenza/farmacologia , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Tecnologia Farmacêutica/organização & administração , COVID-19 , Controle de Doenças Transmissíveis/organização & administração , Doenças Transmissíveis Emergentes/epidemiologia , Infecções por Coronavirus/epidemiologia , Aprovação de Drogas , Desenvolvimento de Medicamentos , Indústria Farmacêutica/organização & administração , Feminino , Humanos , Vacinas contra Influenza/administração & dosagem , Masculino , Avaliação das Necessidades , Pandemias/estatística & dados numéricos , Pneumonia Viral/epidemiologia , Saúde Pública , Medidas de SegurançaAssuntos
Hemaglutininas , Influenza Humana , Anticorpos , Humanos , Vírus da Influenza A , Vírus da Influenza BRESUMO
Congenital human cytomegalovirus (HCMV) infection occurs in ~0.64% of infants born each year in the United States and is the leading nongenetic cause of childhood neurodevelopmental disabilities. No licensed HCMV vaccine is currently available. Natural immunity to HCMV in women before pregnancy is associated with a reduced risk of fetal infection, suggesting that a vaccine is feasible if it can reproduce immune responses elicited by natural infection. On the basis of this premise, we developed a whole-virus vaccine candidate from the live attenuated AD169 strain, with genetic modifications to improve its immunogenicity and attenuation. We first restored the expression of the pentameric gH/gL/pUL128-131 protein complex, a major target for neutralizing antibodies in natural immunity. We then incorporated a chemically controlled protein stabilization switch in the virus, enabling us to regulate viral replication with a synthetic compound named Shield-1. The virus replicated as efficiently as its parental virus in the presence of Shield-1 but failed to produce progeny upon removal of the compound. The vaccine was immunogenic in multiple animal species and induced durable neutralizing antibodies, as well as CD4+ and CD8+ T cells, to multiple viral antigens in nonhuman primates.
Assuntos
Infecções por Citomegalovirus/congênito , Infecções por Citomegalovirus/prevenção & controle , Vacinas contra Citomegalovirus/uso terapêutico , Transmissão Vertical de Doenças Infecciosas/prevenção & controle , Animais , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD8-Positivos/citologia , Citomegalovirus , Feminino , Humanos , Imunogenicidade da Vacina , Interferon gama/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Gravidez , Coelhos , Vacinas Atenuadas/uso terapêutico , Proteínas Virais/imunologiaRESUMO
Human cytomegalovirus (HCMV) can cause serious morbidity/mortality in transplant patients, and congenital HCMV infection can lead to birth defects. Developing an effective HCMV vaccine is a high medical priority. One of the challenges to the efforts has been our limited understanding of the viral antigens important for protective antibodies. Receptor-mediated viral entry to endothelial/epithelial cells requires a glycoprotein H (gH) complex comprising five viral proteins (gH, gL, UL128, UL130, and UL131). This gH complex is notably missing from HCMV laboratory strains as well as HCMV vaccines previously evaluated in the clinic. To support a unique vaccine concept based on the pentameric gH complex, we established a panel of 45 monoclonal antibodies (mAbs) from a rabbit immunized with an experimental vaccine virus in which the expression of the pentameric gH complex was restored. Over one-half (25 of 45) of the mAbs have neutralizing activity. Interestingly, affinity for an antibody to bind virions was not correlated with its ability to neutralize the virus. Genetic analysis of the 45 mAbs based on their heavy- and light-chain sequences identified at least 26 B-cell linage groups characterized by distinct binding or neutralizing properties. Moreover, neutralizing antibodies possessed longer complementarity-determining region 3 for both heavy and light chains than those with no neutralizing activity. Importantly, potent neutralizing mAbs reacted to the pentameric gH complex but not to gB. Thus, the pentameric gH complex is the primary target for antiviral antibodies by vaccination.
Assuntos
Anticorpos Monoclonais/imunologia , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , Vacinas contra Citomegalovirus/imunologia , Citomegalovirus/imunologia , Complexos Multiproteicos/imunologia , Proteínas do Envelope Viral/imunologia , Animais , Anticorpos Monoclonais/genética , Anticorpos Neutralizantes/genética , Anticorpos Antivirais/genética , Regiões Determinantes de Complementaridade/genética , Regiões Determinantes de Complementaridade/imunologia , Citomegalovirus/genética , Infecções por Citomegalovirus/genética , Infecções por Citomegalovirus/imunologia , Infecções por Citomegalovirus/prevenção & controle , Vacinas contra Citomegalovirus/genética , Feminino , Humanos , Cadeias Pesadas de Imunoglobulinas/genética , Cadeias Pesadas de Imunoglobulinas/imunologia , Cadeias Leves de Imunoglobulina/genética , Cadeias Leves de Imunoglobulina/imunologia , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/imunologia , Complexos Multiproteicos/genética , Coelhos , Proteínas do Envelope Viral/genéticaRESUMO
Human immunodeficiency virus (HIV), the etiologic agent that causes AIDS, is the fourth largest killer in the world today. Despite the remarkable achievements in development of anti-retroviral therapies against HIV, and the recent advances in new prevention technologies, the rate of new HIV infections continue to outpace efforts on HIV prevention and control. Thus, the development of a safe and effective vaccine for prevention and control of AIDS remains a global public health priority and the greatest opportunity to eventually end the AIDS pandemic. Currently, there is a renaissance in HIV vaccine development, due in large part to the first demonstration of vaccine induced protection, albeit modest, in human efficacy trials, a generation of improved vaccine candidates advancing in the clinical pipeline, and newly defined targets on HIV for broadly neutralizing antibodies. The main barriers to HIV vaccine development include the global variability of HIV, lack of a validated animal model, lack of correlates of protective immunity, lack of natural protective immune responses against HIV, and the reservoir of infected cells conferred by integration of HIV's genome into the host. Some of these barriers are not unique to HIV, but generic to other variable viral pathogens such as hepatitis C and pandemic influenza. Recommendations to overcome these barriers are presented in this document, including but not limited to expansion of efforts to design immunogens capable of eliciting broadly neutralizing antibodies against HIV, expansion of clinical research capabilities to assess multiple immunogens concurrently with comprehensive immune monitoring, increased support for translational vaccine research, and engaging industry as full partners in vaccine discovery and development.
Assuntos
Vacinas contra a AIDS/uso terapêutico , Pesquisa Biomédica/tendências , Infecções por HIV/prevenção & controle , Anticorpos Neutralizantes/imunologia , Saúde Global , Anticorpos Anti-HIV/imunologia , HumanosRESUMO
Maternal immunity to human cytomegalovirus (HCMV) prior to conception is ~70% protective against congenital transmission and in utero infection of HCMV. Both functional antibodies capable of neutralizing virus and effective T-cells are believed to be important for the protection. Previous HCMV vaccines have rarely been shown able to induce neutralizing antibody titers comparable to those seen in naturally infected HCMV seropositive subjects. Recent studies link a glycoprotein H (gH) complex to receptor-mediated viral entry of endothelial/epithelial cells and leukocytes. This pentameric gH complex, composed of five proteins (gH, gL, UL128, UL130 and UL131 proteins), is notably missing in all HCMV vaccine previously evaluated in clinic. Here we showed that a HCMV virus, with restored expression of the pentameric gH complex, can induce 10-fold higher neutralizing antibody titers than an attenuated AD169 virus or a recombinant glycoprotein B vaccine in multiple animal species in which viral replication is not expected. Encouragingly, the peak neutralizing titers post vaccination in rabbits and monkeys were within 2-4-fold of the levels determined in HCMV seropositive subjects. Functional antibodies by vaccination could further be improved when formulated with a novel adjuvant, and the titers of the antiviral antibodies were sustained in rabbits for over a year after vaccination. These results indicate that the pentameric gH complex is associated with greatly improved functional antibodies following vaccination, and support a vaccine concept based on a nonreplicating whole HCMV with the pentameric gH-associated epithelial tropism restored.
Assuntos
Vacinas contra Citomegalovirus/imunologia , Citomegalovirus/imunologia , Citomegalovirus/fisiologia , Células Epiteliais/virologia , Tropismo Viral , Animais , Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Vacinas contra Citomegalovirus/administração & dosagem , Feminino , Macaca mulatta , Camundongos , Camundongos Endogâmicos BALB C , Coelhos , Proteínas Virais/genética , Proteínas Virais/metabolismoRESUMO
It has been suggested that poor immunogenicity may explain the lack of vaccine efficacy in preventing or controlling HIV infection in the Step trial. To investigate this issue we vaccinated eight Indian rhesus macaques with a trivalent replication-incompetent adenovirus serotype 5 vaccine expressing SIV Gag, Pol, and Nef using a regimen similar to that employed in the Step trial. We detected broad vaccine-induced CD8(+) (2-7 pool-specific responses) and CD4(+) (5-19 pool-specific responses) T-cell responses in IFN-γ ELISPOT assays at one week post-boost using fresh PBMC. However, using cryopreserved cells at one and four weeks post-boost we observed a reduction in both the number and magnitude of most vaccine-induced responses. This demonstrates that the time points and conditions chosen to perform immune assays may influence the observed breadth and frequency of vaccine-induced T-cell responses. To evaluate protective efficacy, we challenged the immunized macaques, along with naïve controls, with repeated, limiting doses of the heterologous swarm isolate SIVsmE660. Vaccination did not significantly affect acquisition or control of virus replication in vaccinees compared to naïve controls. Post-infection we observed an average of only two anamnestic CD8(+) T-cell responses per animal, which may not have been sufficiently broad to control heterologous virus replication. While the trivalent vaccine regimen induced relatively broad T-cell responses in rhesus macaques, it failed to protect against infection or control viral replication. Our results are consistent with those observed in the Step trial and indicate that SIV immunization and challenge studies in macaque models of HIV infection can be informative in assessing pre-clinical HIV vaccines.
Assuntos
Vacinas contra a SAIDS/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/prevenção & controle , Vírus da Imunodeficiência Símia/patogenicidade , Replicação Viral , Adenoviridae/imunologia , Animais , Linfócitos T CD8-Positivos/imunologia , Produtos do Gene gag/imunologia , Produtos do Gene nef/imunologia , Produtos do Gene pol/imunologia , Imunidade Celular , Interferon gama/imunologia , Macaca mulatta , Vacinas contra a SAIDS/administração & dosagem , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Vírus da Imunodeficiência Símia/imunologia , Vírus da Imunodeficiência Símia/fisiologia , Carga ViralRESUMO
The Step Trial showed that the MRKAd5 HIV-1 subtype B Gag/Pol/Nef vaccine did not protect men from HIV infection or reduce setpoint plasma viral RNA (vRNA) levels but, unexpectedly, it did modestly enhance susceptibility to HIV infection in adenovirus type 5 (Ad5)-seropositive, uncircumcised men. As part of the process to understand the results of the Step Trial, we designed a study to determine whether rhesus macaques chronically infected with a host-range mutant Ad5 (Ad5hr) and then immunized with a replication defective Ad5 SIVmac239 Gag/Pol/Nef vaccine were more resistant or susceptible to SIV infection than unimmunized rhesus macaques challenged with a series of escalating dose penile exposures to SIVmac 251. The Ad5 SIV vaccine induced CD8(+) T cell responses in 70% of the monkeys, which is similar to the proportion of humans that responded to the vaccine in the Step Trial. However, the vaccine did not protect vaccinated animals from penile SIV challenge. At the lowest SIV exposure dose (10(3) 50% tissue culture infective doses), 2 of 9 Ad5-seropositive animals immunized with the Ad5 SIV vaccine became infected compared to 0 of 34 animals infected in the other animal groups (naive animals, Ad5-seropositive animals immunized with the empty Ad5 vector, Ad5-seronegative animals immunized with the Ad5 SIV vaccine, and Ad5-seronegative animals immunized with the empty Ad5 vector). Penile exposure to more concentrated virus inocula produced similar rates of infection in all animal groups. Although setpoint viral loads were unaffected in Step vaccinees, the Ad5 SIV-immunized animals had significantly lower acute-phase plasma vRNA levels compared to unimmunized animals. Thus, the results of the nonhuman primate (NHP) study described here recapitulate the lack of protection against HIV acquisition seen in the Step Trial and suggest a greater risk of infection in the Ad5-seropositive animals immunized with the Ad5 SIV vaccine. Further studies are necessary to confirm the enhancement of virus acquisition and to discern associated mechanisms.
Assuntos
Vacinas contra a AIDS/imunologia , Produtos do Gene env/imunologia , Produtos do Gene gag/imunologia , Produtos do Gene nef/imunologia , Infecções por HIV/prevenção & controle , Vacinas contra a SAIDS/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/prevenção & controle , Vírus da Imunodeficiência Símia/imunologia , Vacinas contra a AIDS/administração & dosagem , Vacinas contra a AIDS/genética , Adenovírus Humanos/genética , Adenovírus Humanos/fisiologia , Animais , Anticorpos Antivirais/imunologia , Vírus Defeituosos/genética , Vírus Defeituosos/fisiologia , Modelos Animais de Doenças , Produtos do Gene env/administração & dosagem , Produtos do Gene env/genética , Produtos do Gene gag/administração & dosagem , Produtos do Gene gag/genética , Produtos do Gene nef/administração & dosagem , Produtos do Gene nef/genética , Vetores Genéticos/genética , Vetores Genéticos/metabolismo , HIV/genética , HIV/imunologia , Infecções por HIV/imunologia , Infecções por HIV/virologia , HIV-1/genética , HIV-1/imunologia , Humanos , Imunização , Macaca mulatta , Masculino , Vacinas contra a SAIDS/administração & dosagem , Vacinas contra a SAIDS/genética , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/virologia , Vírus da Imunodeficiência Símia/genéticaRESUMO
UNLABELLED: T cell directed HIV vaccines are based upon the induction of CD8+ T cell memory responses that would be effective in inhibiting infection and subsequent replication of an infecting HIV-1 strain, a process that requires a match or near-match between the epitope induced by vaccination and the infecting viral strain. We compared the frequency and specificity of the CTL epitope responses elicited by the replication-defective Ad5 gag/pol/nef vaccine used in the Step trial with the likelihood of encountering those epitopes among recently sequenced Clade B isolates of HIV-1. Among vaccinees with detectable 15-mer peptide pool ELISpot responses, there was a median of four (one Gag, one Nef and two Pol) CD8 epitopes per vaccinee detected by 9-mer peptide ELISpot assay. Importantly, frequency analysis of the mapped epitopes indicated that there was a significant skewing of the T cell response; variable epitopes were detected more frequently than would be expected from an unbiased sampling of the vaccine sequences. Correspondingly, the most highly conserved epitopes in Gag, Pol, and Nef (defined by presence in >80% of sequences currently in the Los Alamos database www.hiv.lanl.gov) were detected at a lower frequency than unbiased sampling, similar to the frequency reported for responses to natural infection, suggesting potential epitope masking of these responses. This may be a generic mechanism used by the virus in both contexts to escape effective T cell immune surveillance. The disappointing results of the Step trial raise the bar for future HIV vaccine candidates. This report highlights the bias towards less-conserved epitopes present in the same vaccine used in the Step trial. Development of vaccine strategies that can elicit a greater breadth of responses, and towards conserved regions of the genome in particular, are critical requirements for effective T-cell based vaccines against HIV-1. TRIAL REGISTRATION: ClinicalTrials.gov NCT00849680, A Study of Safety, Tolerability, and Immunogenicity of the MRKAd5 Gag/Pol/Nef Vaccine in Healthy Adults.
Assuntos
Vacinas contra a AIDS/imunologia , Sequência Conservada/imunologia , Mapeamento de Epitopos , HIV-1/imunologia , Linfócitos T/imunologia , Adulto , Sequência de Aminoácidos , Viés , Ensaios Clínicos Fase I como Assunto , Epitopos de Linfócito T/química , Epitopos de Linfócito T/imunologia , Feminino , Infecções por HIV/imunologia , Infecções por HIV/terapia , Proteínas do Vírus da Imunodeficiência Humana/química , Proteínas do Vírus da Imunodeficiência Humana/imunologia , Humanos , Masculino , Resultado do TratamentoRESUMO
Both Clostridium difficile and Staphylococcus aureus asymptomatically colonize a significant percentage of humans, particularly during the first year of life. The epidemiology of both has been and continues to be quite dynamic; presently, we are in the midst of epidemics of infections by C. difficile and S. aureus. These ancient microbes are now armed with more potent virulence factors, which have extended their reach from the hospital into community settings, and from the elderly and debilitated hosts into the younger and otherwise healthy population. This review presents some emerging concepts that will likely shape efforts to develop active and passive immunization interventions in response to the reemergence of these bacterial pathogens.
Assuntos
Vacinas Bacterianas/imunologia , Clostridioides difficile/imunologia , Infecções por Clostridium/imunologia , Staphylococcus aureus Resistente à Meticilina/imunologia , Infecções Estafilocócicas/imunologia , Vacinas Antiestafilocócicas/imunologia , Animais , Antígenos de Bactérias/imunologia , Infecções por Clostridium/epidemiologia , Feminino , Humanos , Imunidade Celular/imunologia , Masculino , Camundongos , Infecções Estafilocócicas/epidemiologia , Células Th1/imunologia , Células Th17/imunologia , Fatores de Virulência/imunologiaRESUMO
Following the disappointing outcome of the phase IIb test-of-concept step study in which Merck's adenovirus type 5 (Ad5) HIV-1 clade B gag/pol/nef vaccine failed to demonstrate efficacy in HIV high-risk individuals, an extensive review of the trial and preclinical studies which supported the trial is ongoing. One point of interest is how well preclinical nonhuman primate immunogenicity studies predicted what was observed in humans. Here we compare the HIV-1-specific cellular immune responses elicited in nonhuman primates and human clinical trial subjects to several HIV-1 vaccine candidates. We find that although rhesus macaques are immunologically more responsive to vaccination than humans, the hierarchy in potency of single-modality prime-boost regimens using several vector approaches (adenovirus, DNA, and pox vectors) was well predicted. Vaccine approaches using complex formulations such as novel adjuvants (DNA+CRL1005) or mixed-modality prime-boost (DNA/Ad5; Ad5/ALVAC) did not correlate as well between rhesus macaques and humans. Although the immunogenicity of the vaccines and vaccine regimens evaluated were not all accurately predicted, testing in rhesus macaques generally offers an indispensable tool for ranking the immunological potential of HIV-1 vaccine candidates.
Assuntos
Vacinas contra a AIDS/imunologia , Infecções por HIV/prevenção & controle , Imunidade Celular , Linfócitos T/imunologia , Adenoviridae/imunologia , Animais , Ensaios Clínicos Fase I como Assunto , Genes gag , Infecções por HIV/imunologia , Humanos , Imunização Secundária , Interferon gama/imunologia , Macaca mulatta/imunologia , Modelos Animais , Vacinas de DNA/imunologiaRESUMO
PURPOSE OF REVIEW: To consider how nonhuman primate (NHP) model systems can best contribute to HIV vaccine development. RECENT FINDINGS: We review the traditional roles of NHP model systems in vaccine development and compare this with how NHP models have been used in HIV vaccine research and development. Comparisons of the immune responses elicited by cellular immune response-inducing vaccines in macaques and humans illustrate the value of primate studies for the relative ranking of HIV vaccine concepts for their likely immunogenicity in humans. The unusual structures (e.g. long complementarity-determining regions) of known broadly neutralizing HIV antibodies (bNAbs) suggest that it is critical to test candidate env immunogens in NHPs, whose germline antibody repertoires resemble those of humans. Recent clinical efficacy trial results question the utility of existing NHP challenge models in predicting HIV vaccine efficacy in humans, and highlight the need to further develop models in which acquisition of infection can be reliably evaluated. When evaluated in models using low virus dose challenges that better approximate human sexual exposure to HIV - some vaccine and passive NAb interventions appear to protect against acquisition of infection. SUMMARY: NHP models have important roles in the preclinical evaluation, optimization, and ranking of novel HIV immunogens. The apparent vaccine efficacy observed using low virus dose challenge models provides an opportunity to investigate the correlates of protection.
Assuntos
Vacinas contra a AIDS/imunologia , Modelos Animais de Doenças , Avaliação Pré-Clínica de Medicamentos/métodos , Infecções por HIV/imunologia , Infecções por HIV/prevenção & controle , Animais , Indústria Farmacêutica/métodos , Humanos , PrimatasRESUMO
Influenza HA is the primary target of neutralizing antibodies during infection, and its sequence undergoes genetic drift and shift in response to immune pressure. The receptor binding HA1 subunit of HA shows much higher sequence variability relative to the metastable, fusion-active HA2 subunit, presumably because neutralizing antibodies are primarily targeted against the former in natural infection. We have designed an HA2-based immunogen using a protein minimization approach that incorporates designed mutations to destabilize the low pH conformation of HA2. The resulting construct (HA6) was expressed in Escherichia coli and refolded from inclusion bodies. Biophysical studies and mutational analysis of the protein indicate that it is folded into the desired neutral pH conformation competent to bind the broadly neutralizing HA2 directed monoclonal 12D1, not the low pH conformation observed in previous studies. HA6 was highly immunogenic in mice and the mice were protected against lethal challenge by the homologous A/HK/68 mouse-adapted virus. An HA6-like construct from another H3 strain (A/Phil/2/82) also protected mice against A/HK/68 challenge. Regions included in HA6 are highly conserved within a subtype and are fairly well conserved within a clade. Targeting the highly conserved HA2 subunit with a bacterially produced immunogen is a vaccine strategy that may aid in pandemic preparedness.
Assuntos
Escherichia coli/metabolismo , Glicoproteínas de Hemaglutininação de Vírus da Influenza/imunologia , Vírus da Influenza A/imunologia , Vacinas contra Influenza/imunologia , Infecções por Orthomyxoviridae/imunologia , Infecções por Orthomyxoviridae/prevenção & controle , Animais , Anticorpos Neutralizantes/imunologia , Anticorpos Antivirais/imunologia , Sítios de Ligação , Dicroísmo Circular , Escherichia coli/genética , Feminino , Glicoproteínas de Hemaglutininação de Vírus da Influenza/química , Glicoproteínas de Hemaglutininação de Vírus da Influenza/genética , Glicoproteínas de Hemaglutininação de Vírus da Influenza/metabolismo , Concentração de Íons de Hidrogênio , Camundongos , Camundongos Endogâmicos BALB C , Modelos Moleculares , Mutação , Estrutura Quaternária de Proteína , Estrutura Terciária de ProteínaRESUMO
DNA vaccines have undergone important enhancements in their design, formulation, and delivery process. Past literature supports that DNA vaccines are not as immunogenic in nonhuman primates as live vector systems. The most potent recombinant vector system for induction of cellular immune responses in macaques and humans is adenovirus serotype 5 (Ad5), an important benchmark for new vaccine development. Here, we performed a head-to-head evaluation of the Merck Ad5 SIV vaccine and an optimized electroporation (EP) delivered SIV DNA vaccine in macaques. Animals receiving the Ad5 vaccine were immunized three times, whereas the DNA-vaccinated animals were immunized up to four times based on optimized protocols. We observed significant differences in the quantity of IFNgamma responses by enzyme-linked immunosorbent spot (ELISpot), greater proliferative capacity of CD8(+) T cells, and increased polyfunctionality of both CD4(+) and CD8(+) T cells in the DNA-vaccinated group. Importantly, Ad5 immunizations failed to boost following the first immunization, whereas DNA responses were continually boosted with all four immunizations demonstrating a major advantage of these improved DNA vaccines. These optimized DNA vaccines induce very different immune phenotypes than traditional Ad5 vaccines, suggesting that they could play an important role in vaccine research and development.
Assuntos
Adenoviridae/genética , Vetores Genéticos/genética , Vacinas contra a SAIDS/imunologia , Animais , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Macaca mulatta , Plasmídeos/genética , Vacinas de DNA/imunologiaRESUMO
Eliciting a broadly neutralizing polyclonal antibody response against HIV-1 remains a major challenge. One approach to vaccine development is prevention of HIV-1 entry into cells by blocking the fusion of viral and cell membranes. More specifically, our goal is to elicit neutralizing antibodies that target a transient viral entry intermediate (the prehairpin intermediate) formed by the HIV-1 gp41 protein. Because this intermediate is transient, a stable mimetic is required to elicit an immune response. Previously, a series of engineered peptides was used to select a mAb (denoted D5) that binds to the surface of the gp41 prehairpin intermediate, as demonstrated by x-ray crystallographic studies. D5 inhibits the replication of HIV-1 clinical isolates, providing proof-of-principle for this vaccine approach. Here, we describe a series of peptide mimetics of the gp41 prehairpin intermediate designed to permit a systematic analysis of the immune response generated in animals. To improve the chances of detecting weak neutralizing polyclonal responses, two strategies were employed in the initial screening: use of a neutralization-hypersensitive virus and concentration of the IgG fraction from immunized animal sera. This allowed incremental improvements through iterative cycles of design, which led to vaccine candidates capable of generating a polyclonal antibody response, detectable in unfractionated sera, that neutralize tier 1 HIV-1 and simian HIV primary isolates in vitro. Our findings serve as a starting point for the design of more potent immunogens to elicit a broadly neutralizing response against the gp41 prehairpin intermediate.
Assuntos
Anticorpos Neutralizantes/imunologia , Materiais Biomiméticos , Anticorpos Anti-HIV/imunologia , Proteína gp41 do Envelope de HIV/imunologia , HIV-1/imunologia , Soros Imunes/imunologia , Vacinação , Sequência de Aminoácidos , Animais , Cobaias , Proteína gp41 do Envelope de HIV/química , HIV-1/química , HIV-1/isolamento & purificação , Dados de Sequência Molecular , Peptídeos/química , Peptídeos/imunologia , CoelhosRESUMO
The prophylactic efficacies of several multivalent replication-incompetent adenovirus serotype 5 (Ad5) vaccines were examined in rhesus macaques using an intrarectal high-dose simian immunodeficiency virus SIVmac239 challenge model. Cohorts of Mamu-A*01(+)/B*17(-) Indian rhesus macaques were immunized with one of several combinations of Ad5 vectors expressing Gag, Pol, Nef, and Env gp140; for comparison, a Mamu-A*01(+) cohort was immunized using the Ad5 vector alone. There was no sign of immunological interference between antigens in the immunized animals. In general, expansion of the antigen breadth resulted in more favorable virological outcomes. In particular, the order of efficacy trended as follows: Gag/Pol/Nef/Env approximately Gag/Pol > Gag approximately Gag/Pol/Nef > Nef. However, the precision in ranking the vaccines based on the study results may be limited by the cohort size, and as such, may warrant additional testing. The implications of these results in light of the recent discouraging results of the phase IIb study of the trivalent Ad5 HIV-1 vaccine are discussed.
Assuntos
Adenoviridae/imunologia , Vacinas contra a SAIDS/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios , Vírus da Imunodeficiência Símia/imunologia , Vacinas contra a AIDS/imunologia , Adenoviridae/genética , Animais , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/imunologia , Ensaios Clínicos Fase II como Assunto , Humanos , Macaca mulatta/imunologia , Macaca mulatta/virologia , Testes de Neutralização , Síndrome de Imunodeficiência Adquirida dos Símios/imunologia , Síndrome de Imunodeficiência Adquirida dos Símios/prevenção & controle , Vírus da Imunodeficiência Símia/genética , Proteínas do Envelope Viral/genética , Proteínas do Envelope Viral/imunologia , Carga Viral , Viremia/imunologiaRESUMO
BACKGROUND: We report composite results from the Merck phase I program of near-consensus clade B human immunodeficiency virus (HIV) type 1 gag vaccines. METHODS: Healthy HIV-uninfected adults were enrolled in 6 blinded placebo-controlled studies evaluating the immunogenicity of (1) a 4-dose regimen of a DNA vaccine, (2) a 3-dose priming regimen of the DNA vaccine with a booster dose of an adenovirus type 5 (Ad5)-vectored vaccine, or (3) a 3-dose regimen of the Ad5 vaccine. The DNA plasmid was provided with or without an aluminum phosphate or CRL1005 adjuvant. The primary end point was the unfractionated HIV-1 gag-specific interferon gamma enzyme-linked immunospot (ELISpot) response 4 weeks after the final dose. RESULTS: Overall, 254 (83%) of 307 subjects randomized to the vaccine groups were evaluable. Adjuvants did not enhance immunogenicity of the DNA vaccine. Postboost ELISpot responder frequencies were higher for Ad5-containing regimens than for the DNA/DNA regimen (33%) but were similar for DNA/Ad5 (55%) and Ad5/Ad5 (50%). DNA/DNA elicited mainly a CD4 response, whereas Ad5/Ad5 elicited mainly a CD8 response; DNA/Ad5 generated CD4 and CD8 responses comparable to those of DNA/DNA and Ad5/Ad5, respectively. CONCLUSIONS: The DNA vaccine alone or as a priming regimen for the Ad5 vaccine did not increase unfractionated ELISpot responses compared with the Ad5 vaccine alone. Qualitative T cell responses to different vaccine regimens deserve further study.