Programming the magnitude and persistence of antibody responses with innate immunity

Regulation of B-cell responses by Toll-like receptors

The discovery of host-encoded gene products that sense molecular patterns in infectious microbes, and the demonstration of their role in triggering innate and adaptive immune responses, has been a key milestone in our understanding of immunology. Twenty-three years after Janeway first outlined the fundamental concepts of the 'pattern recognition' model, and 15 years since the identification of Toll-like receptors (TLRs) as pattern recognition receptors (PRRs), new insights continue to be revealed, and questions remain. For example, innate immune responses to microbes that are mediated by PRRs have historically been viewed as the domain of innate immune cell populations such as dendritic cells and macrophages. New evidence, however, has pointed to the role of B-cell-intrinsic TLR activation in shaping antibody responses. These studies have revealed that TLRs regulate a complex transcriptional network that controls multiple steps in the development of antigen-specific antibodies. This review covers these recent developments regarding the role of TLRs in B-cell gene expression and function in vitro and in vivo, and highlights the remaining challenges in the field, with particular emphasis on the role of TLRs in antibody responses to viral infection. A more complete understanding of how TLRs regulate antibody responses will lead to improved vaccine design.

Nano-particle vaccination combined with TLR-7 and -9 ligands triggers memory and effector CD8⁺ T-cell responses in melanoma patients

Optimal vaccine strategies must be identified for improving T-cell vaccination against infectious and malignant diseases. MelQbG10 is a virus-like nano-particle loaded with A-type CpG-oligonucleotides (CpG-ODN) and coupled to peptide(16-35) derived from Melan-A/MART-1. In this phase IIa clinical study, four groups of stage III-IV melanoma patients were vaccinated with MelQbG10, given (i) with IFA (Montanide) s.c.; (ii) with IFA s.c. and topical Imiquimod; (iii) i.d. with topical Imiquimod; or (iv) as intralymph node injection. In total, 16/21 (76%) patients generated ex vivo detectable Melan-A/MART-1-specific T-cell responses. T-cell frequencies were significantly higher when IFA was used as adjuvant, resulting in detectable T-cell responses in all (11/11) patients, with predominant generation of effector-memory-phenotype cells. In turn, Imiquimod induced higher proportions of central-memory-phenotype cells and increased percentages of CD127(+) (IL-7R) T cells. Direct injection of MelQbG10 into lymph nodes resulted in lower T-cell frequencies, associated with lower proportions of memory and effector-phenotype T cells. Swelling of vaccine site draining lymph nodes, and increased glucose uptake at PET/CT was observed in 13/15 (87%) of evaluable patients, reflecting vaccine triggered immune reactions in lymph nodes. We conclude that the simultaneous use of both Imiquimod and CpG-ODN induced combined memory and effector CD8(+) T-cell responses.

Viruses - from pathogens to vaccine carriers

Vaccination is mankind's greatest public health success story. By now vaccines to many of the viruses that once caused fatal childhood diseases are routinely used throughout the world. Traditional methods of vaccine development through inactivation or attenuation of viruses have failed for some of the most deadly human pathogens, necessitating new approaches. Genetic modification of viruses not only allows for their attenuation but also for incorporation of sequences from other viruses, turning one pathogen into a vaccine carrier for another. Recombinant viruses have pros and cons as vaccine carriers, as discussed below using vectors based on adenovirus, herpesvirus, flavivirus, and rhabdovirus as examples.

Cutting edge: TLR13 is a receptor for bacterial RNA

Bacterial RNA (bRNA) can induce cytokine production in macrophages and dendritic cells (DCs) through a previously unidentified receptor. Gene expression analysis of murine DCs showed that bRNA induced gene regulation similar to that induced by stimulation of TLR7 with R848. Although TLR7 was dispensable for cytokine induction by bRNA, TLR-associated proteins MyD88 and UNC93B were required. TLR13 is an endosomal murine TLR that has been described to interact with UNC93B with, so far, no characterized ligand. Small interfering RNA against TLR13 reduced cytokine induction by bRNA in DCs. Moreover, Chinese hamster ovary cells transfected with TLR13, but not with TLR7 or 8, could activate NF-κB in response to bRNA or Streptococcus pyogenes in an RNA-specific manner. TLR7 antagonist IRS661 could, in addition, inhibit TLR13 signaling and reduced recognition of whole Gram-positive bacteria by DCs, also in the absence of TLR7. The results identify TLR13 as a receptor for bRNA.

Long-term and memory immune responses in mice against Newcastle disease virus-like particles containing respiratory syncytial virus glycoprotein ectodomains

Although respiratory syncytial virus (RSV) is a significant human pathogen, no RSV vaccines are available. We have reported that a virus-like particle (VLP) RSV vaccine candidate stimulated, in mice, robust, protective anti-RSV glycoprotein T(H)1 biased immune responses without enhanced respiratory disease upon RSV challenge. We report here an analysis of long-term responses to these VLPs. BALB/c mice immunized, without adjuvant, with VLPs or with infectious RSV generated anti-F and anti-G protein serum antibody responses that were stable over 14 months. Neutralizing antibody titers stimulated by VLPs were robust and durable for 14 months, whereas those of RSV-immunized animals declined significantly by 3 months. F protein-specific antibody-secreting cells were detected in the bone marrows of VLP-immunized mice but not in the marrows of RSV-immunized mice. Adoptive transfer of enriched splenic B cells from VLP-immunized mice into immunodeficient rag(-/-) mice resulted in anti-F and anti-G protein serum IgG antibody responses, in recipient mice, that were protective upon RSV challenge. In contrast, transfer of splenic B cells from RSV-immunized mice produced no detectable serum antibody in the recipients, nor could these mice inhibit RSV replication upon virus challenge. Immunization with VLPs stimulated the formation of germinal center GL7(+) B cells in normal mice. VLP immunization of TCR βδ(-/-) T-cell-deficient mice did not induce anti-RSV IgG antibodies, results consistent with T-cell-dependent immune responses. These results demonstrate that VLPs are effective in stimulating long-lived RSV-specific, T-cell-dependent neutralizing antibody-secreting cells and RSV-specific memory responses.

Subunit vaccines of the future: the need for safe, customized and optimized particulate delivery systems

A major challenge for current vaccine development is the fact that many new subunit vaccines based on highly purified recombinant proteins are poorly immunogenic and mobilize insufficient immune responses for protective immunity. Adjuvants are therefore needed in vaccine formulations to enhance, direct and maintain the immune response to vaccine antigens. Few adjuvants are currently approved for human use that mainly induce humoral immunity, and there is therefore an unmet medical need for development of effective and safe adjuvants that in addition can stimulate cellular or mucosal immunity, or combinations thereof, depending on the requirements for protection against the specific disease. Vaccine delivery systems are important components of adjuvants that allow proper delivery of antigens to antigen-presenting cells. Moreover, they often possess intrinsic immunopotentiating activity and/or can be customized towards a given immunological profile by the appropriate combination with immunopotentiating compounds. This article reviews the current status of human-tailored vaccine delivery with special focus on how to design safe particulate vaccine delivery systems with respect to composition, physicochemical properties, antigen association and choice of administration route, in order to better customize vaccine formulations towards specific diseases in the future.

Contribution of Toll-like receptor signaling to germinal center antibody responses

Toll-like receptors (TLRs) have emerged as one of the most important families of innate immune receptors for initiating inflammation and also for promoting adaptive immune responses. Recent studies have examined the ability of TLRs to promote antibody responses, including T-cell-dependent antibody responses. Initial study suggested that TLR stimulation promotes primarily an extrafollicular antibody response, which rapidly produces moderate affinity antibodies made by short-lived plasma cells. Recent studies, however, have shown that TLRs can also enhance the germinal center response, which produces high affinity class-switched antibody made by long-lived plasma cells. TLR stimulation can increase the magnitude of the latter response and also enhance selection for high affinity IgG. This review summarizes recent advances in understanding the roles of TLRs in B cells and also in other cell types for enhancement of antibody responses, with an emphasis on T-cell-dependent and germinal center antibody responses.

A DNA nanostructure platform for directed assembly of synthetic vaccines

Safe and effective vaccines offer the best intervention for disease control. One strategy to maximize vaccine immunogenicity without compromising safety is to rationally design molecular complexes that mimic the natural structure of immunogenic microbes but without the disease-causing components. Here we use highly programmable DNA nanostructures as platforms to assemble a model antigen and CpG adjuvants together into nanoscale complexes with precise control of the valency and spatial arrangement of each element. Our results from immunized mice show that compared to a mixture of antigen and CpG molecules, the assembled antigen-adjuvant-DNA complexes induce strong and long-lasting antibody responses against the antigen without stimulating a reaction to the DNA nanostructure itself. This result demonstrates the potential of DNA nanostructures to serve as general platforms for the rational design and construction of a variety of vaccines.

Engineering nano- and microparticles to tune immunity

The immune system can be a cure or cause of disease, fulfilling a protective role in attacking cancer or pathogenic microbes but also causing tissue destruction in autoimmune disorders. Thus, therapies aimed to amplify or suppress immune reactions are of great interest. However, the complex regulation of the immune system, coupled with the potential systemic side effects associated with traditional systemic drug therapies, has presented a major hurdle for the development of successful immunotherapies. Recent progress in the design of synthetic micro- and nano-particles that can target drugs, deliver imaging agents, or stimulate immune cells directly through their physical and chemical properties is leading to new approaches to deliver vaccines, promote immune responses against tumors, and suppress autoimmunity. In addition, novel strategies, such as the use of particle-laden immune cells as living targeting agents for drugs, are providing exciting new approaches for immunotherapy. This progress report describes recent advances in the design of micro- and nano-particles for immunotherapies and diagnostics.

Human Toll-like receptor 8 can be cool too: implications for foreign RNA sensing

Recent advances in our understanding of foreign nucleic acid sensing indicate an important role for the human Toll-like receptor (TLR) 8 in the initiation of immune responses to certain pathogens. However, TLR8, far too often grouped together with TLR7 for its common ability to detect RNA, has a function on its own in the initiation of specific proinflammatory responses to viruses and bacteria. Here, we present an overview of what is currently known of human TLR8 biology, from genetic regulation to its function in innate immunity, and discuss how TLR8 could present novel therapeutic opportunities in viral and cancer diseases.

Improved vaccines through targeted manipulation of the body's immunological risk-assessment?

Recent advances have highlighted the outstanding role of the innate immune system for instructing adaptive immunity. Translating this knowledge into successful immunotherapies like vaccines, however, has proven to be a difficult task. This essay is based on the hypothesis that immune responses are tightly scaled to the infectious threat posed by a given microbial stimulus. A meticulous immunological risk-assessment process is therefore instrumental for eliciting well-balanced responses and maintaining immune homeostasis. The immune system makes fine distinctions, for example, between live and dead bacteria, or pathogenic and non-pathogenic microorganisms. Here, I discuss recent evidence for some of the mechanisms underlying these distinctions and speculate on strategies for therapeutically targeting the immunological risk-assessment machinery.

A regulatory dendritic cell signature correlates with the clinical efficacy of allergen-specific sublingual immunotherapy

BACKGROUND

Given their pivotal role in the polarization of T-cell responses, molecular changes at the level of dendritic cells (DCs) could represent an early signature indicative of the subsequent orientation of adaptive immune responses during immunotherapy.

OBJECTIVE

We sought to investigate whether markers of effector and regulatory DCs are affected during allergen immunotherapy in relationship with clinical benefit.

METHODS

Differential gel electrophoresis and label-free mass spectrometry approaches were used to compare whole proteomes from human monocyte-derived DCs differentiated toward either regulatory or effector functions. The expression of those markers was assessed by using quantitative PCR in PBMCs from 79 patients with grass pollen allergy enrolled in a double-blind, placebo-controlled clinical study evaluating the efficacy of sublingual tablets in an allergen exposure chamber over a 4-month period.

RESULTS

We identified several markers associated with DC1 and/or DC17 effector DCs, including CD71, FSCN1, IRF4, NMES1, MX1, TRAF1. A substantial phenotypic heterogeneity was observed among various types of tolerogenic DCs, with ANXA1, Complement component 1 (C1Q), CATC, GILZ, F13A, FKBP5, Stabilin-1 (STAB1), and TPP1 molecules established as shared or restricted regulatory DC markers. The expression of 2 of those DCs markers, C1Q and STAB1, was increased in PBMCs from clinical responders in contrast to that seen in nonresponders or placebo-treated patients.

CONCLUSION

C1Q and STAB1 represent candidate biomarkers of early efficacy of allergen immunotherapy as the hallmark of a regulatory innate immune response predictive of clinical tolerance.

Construction and immunological evaluation of dual cell surface display of HIV-1 gag and Salmonella enterica serovar Typhimurium FliC in Lactobacillus acidophilus for vaccine delivery

Oral vaccines that elicit a mucosal immune response may be effective against human immunodeficiency virus type 1 (HIV-1) because its transmission occurs mainly at the mucosa. The aim of this study was to construct recombinant Lactobacillus for oral delivery of oral vaccines against HIV-1 and to evaluate their immunogenicity. A recombinant Lactobacillus acidophilus strain expressing the HIV-1 Gag on the bacterial cell surface was established by fusion with the signal peptide and anchor motif of a mucus binding protein (Mub) from L. acidophilus with or without coexpression of Salmonella enterica serovar Typhimurium flagellin (FliC) fused to a different Mub signal peptide and anchor. Using HEK293 cells engineered to express Toll-like receptor 5 (TLR5), the biological activity of FliC on the bacterial cell surfaces was determined. The surface-exposed flagellin retained its TLR5-stimulating activity, suggesting that the recombinant strain with Gag and FliC dual display might provide a different immunopotency than the strain expressing only Gag. The immunological properties of the recombinant strains were assessed by coculture with human myeloid dendritic cells (DCs). The heterologous antigens on the cell surface affected maturation and cytokine responses of DCs. Acquired immune responses were also investigated by intragastric immunization of mice. The enzyme-linked immunosorbent spot assay showed induction of gamma interferon-producing cells at local mucosa after immunization of mice with the Gag-producing strain. Meanwhile, the immunization with L. acidophilus displaying both Gag and FliC resulted in an increase of Gag-specific IgA-secreting cells. These results suggested that the Gag-displaying L. acidophilus elicited specific immune responses and the coexistence of FliC conferred an adjuvant effect on local IgA production.

Nanoparticle-mediated codelivery of myelin antigen and a tolerogenic small molecule suppresses experimental autoimmune encephalomyelitis

The immune response is normally controlled by regulatory T cells (Tregs). However, Treg deficits are found in autoimmune diseases, and therefore the induction of functional Tregs is considered a potential therapeutic approach for autoimmune disorders. The activation of the ligand-activated transcription factor aryl hydrocarbon receptor by 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE) or other ligands induces dendritic cells (DCs) that promote FoxP3(+) Treg differentiation. Here we report the use of nanoparticles (NPs) to coadminister ITE and a T-cell epitope from myelin oligodendrocyte glycoprotein (MOG)(35)(-55) to promote the generation of Tregs by DCs. NP-treated DCs displayed a tolerogenic phenotype and promoted the differentiation of Tregs in vitro. Moreover, NPs carrying ITE and MOG(35-55) expanded the FoxP3(+) Treg compartment and suppressed the development of experimental autoimmune encephalomyelitis, an experimental model of multiple sclerosis. Thus, NPs are potential new tools to induce functional Tregs in autoimmune disorders.

Nucleic acid sensing at the interface between innate and adaptive immunity in vaccination

The demand is currently high for new vaccination strategies, particularly to help combat problematic intracellular pathogens, such as HIV and malarial parasites. In the past decade, the identification of host receptors that recognize pathogen-derived nucleic acids has revealed an essential role for nucleic acid sensing in the triggering of immunity to intracellular pathogens. This Review first addresses our current understanding of the nucleic acid-sensing immune machinery. We then explain how the study of nucleic acid-sensing mechanisms not only has revealed their central role in driving the responses mediated by many current vaccines, but is also revealing how they could be harnessed for the design of new vaccines.

Adjuvants for Leishmania vaccines: from models to clinical application

Two million new cases of leishmaniasis occur every year, with the cutaneous leishmaniasis (CL) presentation accounting for approximately two-thirds of all cases. Despite the high incidence rates and geographic expansion of the disease, CL remains a neglected tropical disease without effective intervention strategies. Efforts to address this deficit have given rise to the experimental murine model of CL. By virtue of its simplicity and pliability, the CL model has been used to provide substantial information regarding cellular immunity, as well as in the discovery and evaluation of various vaccine adjuvants. The CL model has facilitated in vivo studies of the mechanism of action of many adjuvants, including the TLR4 agonist monophosphoryl lipid A, the TLR7/8 agonist imiquimod, the TLR9 agonist CpG, adenoviral vectors, and the immunostimulatory complexes. Together, these studies have helped to unveil the requirement for certain types of immune responses at specific stages of CL disease and provide a basis to aid the design of effective second-generation vaccines for human CL. This review focuses on adjuvants that have been tested in experimental CL, outlining how they have helped advance our understanding of the disease and ultimately, how they have performed when applied within clinical trials against human CL.

Analyzing cellular internalization of nanoparticles and bacteria by multi-spectral imaging flow cytometry

Nanoparticulate systems have emerged as valuable tools in vaccine delivery through their ability to efficiently deliver cargo, including proteins, to antigen presenting cells. Internalization of nanoparticles (NP) by antigen presenting cells is a critical step in generating an effective immune response to the encapsulated antigen. To determine how changes in nanoparticle formulation impact function, we sought to develop a high throughput, quantitative experimental protocol that was compatible with detecting internalized nanoparticles as well as bacteria. To date, two independent techniques, microscopy and flow cytometry, have been the methods used to study the phagocytosis of nanoparticles. The high throughput nature of flow cytometry generates robust statistical data. However, due to low resolution, it fails to accurately quantify internalized versus cell bound nanoparticles. Microscopy generates images with high spatial resolution; however, it is time consuming and involves small sample sizes. Multi-spectral imaging flow cytometry (MIFC) is a new technology that incorporates aspects of both microscopy and flow cytometry that performs multi-color spectral fluorescence and bright field imaging simultaneously through a laminar core. This capability provides an accurate analysis of fluorescent signal intensities and spatial relationships between different structures and cellular features at high speed. Herein, we describe a method utilizing MIFC to characterize the cell populations that have internalized polyanhydride nanoparticles or Salmonella enterica serovar Typhimurium. We also describe the preparation of nanoparticle suspensions, cell labeling, acquisition on an ImageStream(X) system and analysis of the data using the IDEAS application. We also demonstrate the application of a technique that can be used to differentiate the internalization pathways for nanoparticles and bacteria by using cytochalasin-D as an inhibitor of actin-mediated phagocytosis.

B cell TLRs and induction of immunoglobulin class-switch DNA recombination

Toll-like receptors (TLRs) are a family of conserved pattern recognition receptors (PRRs). Engagement of B cell TLRs by microbe-associated molecular patterns (MAMPs) induces T-independent (TI) antibody responses and plays an important role in the early stages of T-dependent (TD) antibody responses before specific T cell help becomes available. The role of B cell TLRs in the antibody response is magnified by the synergy of B cell receptor (BCR) crosslinking and TLR engagement in inducing immunoglobulin (Ig) class switch DNA recombination (CSR), which crucially diversifies the antibody biological effector functions. Dual BCR/TLR engagement induces CSR to all Ig isotypes, as directed by cytokines, while TLR engagement alone induces marginal CSR. Integration of BCR and TLR signaling results in activation of the canonical and non-canonical NF-κB pathways, induction of activation-induced cytidine deaminase (AID) and germline transcription of IgH switch (S) regions. A critical role of B cell TLRs in CSR and the antibody response is emphasized by the emergence of several TLR ligands as integral components of vaccines that greatly boost humoral immunity in a B cell-intrinsic fashion.

RNA mediated Toll-like receptor stimulation in health and disease

Besides their well known functions in storage and translation of information nucleic acids have emerged as a target of pattern recognition receptors that drive activation of innate immunity. Due to the paucity of building block monomers used in nucleic acids, discrimination of host and microbial nucleic acids as a means of self/foreign discrimination is a complicated task. Pattern recognition receptors rely on discrimination by sequence, structural features and spatial compartmentalization to differentiate microbial derived nucleic acids from host ones. Microbial nucleic acid detection is important for the sensing of infectious danger and initiating an immune response to microbial attack. Failures in the underlying recognitions systems can have severe consequences: thus, inefficient recognition of microbial nucleic acids may increase susceptibility to infectious diseases. On the other hand, excessive immune responses as a result of failed self/foreign discrimination are associated with autoimmune diseases. This review gives a general overview over the underlying concepts of nucleic acid sensing by Toll-like receptors. Within this general framework, we focus on bacterial RNA and synthetic RNA oligomers.

Immunoprotective activity of a Salmonid Alphavirus Vaccine: comparison of the immune responses induced by inactivated whole virus antigen formulations based on CpG class B oligonucleotides and poly I:C alone or combined with an oil adjuvant

CpG oligonucleotides and polyinosinic:polycytidylic acid (poly I:C) are toll-like receptor (TLR) agonists that mimic the immunostimulatory properties of bacterial DNA and double-stranded viral RNA respectively, and which have exhibited potential to serve as vaccine adjuvants in previous experiments. Here, a combination of CpGs and poly I:C together with water- or oil-formulated Salmonid Alphavirus (SAV) antigen preparations has been used for a vaccine in Atlantic salmon and tested for protection in SAV challenge trial. The results demonstrate that vaccination with a high dose of the SAV antigen induced protection against challenge with SAV which correlated with production of neutralizing antibodies (NAbs). As the high antigen dose alone induced full protection, no beneficial effect from the addition of CpG and poly I:C could be observed. Nevertheless, these TLR ligands significantly enhanced the levels of NAbs in serum of vaccinated fish. Interestingly, gene expression analysis demonstrated that while addition of oil suppressed the CpG/poly I:C-induced expression of IFN-γ, the upregulation of IFNa1 was substantially enhanced. A low dose of the SAV antigen combined with oil did not induce any detectable levels of NAbs either with or without TLR ligands present, however the addition of CpG and poly I:C to the low SAV antigen dose formulation significantly enhanced the protection against SAV suggesting that CpG/poly I:C may have enhanced a cytotoxic response - a process which is dependent on the up-regulation of type I IFN. These results highlight the immunostimulatory properties of the tested TLR ligands and will serve as a ground for further, more detailed studies aimed to investigate their capacity to serve as adjuvants in vaccine formulations for Atlantic salmon.

Memory immune responses against pandemic (H1N1) 2009 influenza virus induced by a whole particle vaccine in cynomolgus monkeys carrying Mafa-A1*052:02

We made an H1N1 vaccine candidate from a virus library consisting of 144 ( = 16 HA×9 NA) non-pathogenic influenza A viruses and examined its protective effects against a pandemic (2009) H1N1 strain using immunologically naïve cynomolgus macaques to exclude preexisting immunity and to employ a preclinical study since preexisting immunity in humans previously vaccinated or infected with influenza virus might make comparison of vaccine efficacy difficult. Furthermore, macaques carrying a major histocompatibility complex class I molecule, Mafa-A1*052:02, were used to analyze peptide-specific CD8(+) T cell responses. Sera of macaques immunized with an inactivated whole particle formulation without addition of an adjuvant showed higher neutralization titers against the vaccine strain A/Hokkaido/2/1981 (H1N1) than did sera of macaques immunized with a split formulation. Neutralization activities against the pandemic strain A/Narita/1/2009 (H1N1) in sera of macaques immunized twice with the split vaccine reached levels similar to those in sera of macaques immunized once with the whole particle vaccine. After inoculation with the pandemic virus, the virus was detected in nasal samples of unvaccinated macaques for 6 days after infection and for 2.67 days and 5.33 days on average in macaques vaccinated with the whole particle vaccine and the split vaccine, respectively. After the challenge infection, recall neutralizing antibody responses against the pandemic virus and CD8(+) T cell responses specific for nucleoprotein peptide NP262-270 bound to Mafa-A1*052:02 in macaques vaccinated with the whole particle vaccine were observed more promptly or more vigorously than those in macaques vaccinated with the split vaccine. These findings demonstrated that the vaccine derived from our virus library was effective for pandemic virus infection in macaques and that the whole particle vaccine conferred more effective memory and broader cross-reactive immune responses to macaques against pandemic influenza virus infection than did the split vaccine.

Type I IFN induced by adenovirus serotypes 28 and 35 has multiple effects on T cell immunogenicity

Recombinant adenovirus (rAd) vectors are being investigated as vaccine delivery vehicles in preclinical and clinical studies. rAds constructed from different serotypes differ in receptor usage, tropism, and ability to activate cells, aspects of which likely contribute to their different immunogenicity profiles. In this study, we compared the infectivity and cell stimulatory capacity of recombinant adenovirus serotype 5 (rAd5), recombinant adenovirus serotype 28 (rAd28), and recombinant adenovirus serotype 35 (rAd35) in association with their respective immunogenicity profiles. We found that rAd28 and rAd35 infected and led to the in vitro maturation and activation of both human and mouse dendritic cells more efficiently compared with rAd5. In stark contrast to rAd5, rAd28 and rAd35 induced production of IFN-α and stimulated IFN-related intracellular pathways. However, the in vivo immunogenicity of rAd28 and rAd35 was significantly lower than that of rAd5. Deletion of IFN-α signaling during vaccination with rAd28 and rAd35 vectors increased the magnitude of the insert-specific T cell response to levels induced by vaccination with rAd5 vector. The negative impact of IFN-α signaling on the magnitude of the T cell response could be overcome by increasing the vaccine dose, which was also associated with greater polyfunctionality and a more favorable long-term memory phenotype of the CD8 T cell response in the presence of IFN-α signaling. Taken together, our results demonstrate that rAd-induced IFN-α production has multiple effects on T cell immunogenicity, the understanding of which should be considered in the design of rAd vaccine vectors.

Characterization of TLR4-mediated auto-antibody production in a mouse model of histidyl-tRNA synthetase-induced myositis

We have previously shown that intramuscular immunization with a recombinant fragment of murine histidyl-tRNA synthetase (HRS) in the absence of exogenous adjuvant generates Ag-specific, IgG class switched Abs a murine model of myositis. Markedly diminished IgG anti-HRS auto-Ab responses in TLR4 signaling-deficient C3H/HeJ mice indicate that TLR4 is required for auto-Ab formation and/or class switching in this system. Comparative time course assessment of HRS-immunized C3H/HeOuJ (wild type) and C3H/HeJ (TLR4 mutant) mice shows here that despite significant impairment of class switched IgG anti-HRS responses in TLR4-deficient C3H/HeJ mice, production of IgM anti-HRS auto-Abs is relatively preserved-suggesting that TLR4-mediated signals modulate IgG class switching rather than auto-Ab formation in this genetic background. In C57BL/6-derived knockout mice lacking either MyD88 (B6.MyD88(-/-)) or TRIF (B6.TRIF(-/-)) adaptor molecules, immunization studies indicate that TRIF exerts a dominant role in the generation of HRS-specific IgG auto-Abs. Complementing these analyses, in vitro stimulation of unfractionated, as well as T cell-depleted, C3H/HeOuJ splenocytes with recombinant murine HRS reveals that TLR4-mediated generation of class switched auto-Abs can occur independently of T cell help. Overall, these findings support a broader role for TLR4 in the breakdown of immune tolerance and development of autoimmunity.

Beyond empiricism: informing vaccine development through innate immunity research

Although a great public heath success, vaccines provide suboptimal protection in some patient populations and are not available to protect against many infectious diseases. Insights from innate immunity research have led to a better understanding of how existing vaccines work and have informed vaccine development. New adjuvants and delivery systems are being designed based upon their capacity to stimulate innate immune sensors and target antigens to dendritic cells, the cells responsible for initiating adaptive immune responses. Incorporating these adjuvants and delivery systems in vaccines can beneficially alter the quantitative and qualitative nature of the adaptive immune response, resulting in enhanced protection.

Trypanosoma cruzi adjuvants potentiate T cell-mediated immunity induced by a NY-ESO-1 based antitumor vaccine

Immunological adjuvants that induce T cell-mediate immunity (TCMI) with the least side effects are needed for the development of human vaccines. Glycoinositolphospholipids (GIPL) and CpGs oligodeoxynucleotides (CpG ODNs) derived from the protozoa parasite Trypanosoma cruzi induce potent pro-inflammatory reaction through activation of Toll-Like Receptor (TLR)4 and TLR9, respectively. Here, using mouse models, we tested the T. cruzi derived TLR agonists as immunological adjuvants in an antitumor vaccine. For comparison, we used well-established TLR agonists, such as the bacterial derived monophosphoryl lipid A (MPL), lipopeptide (Pam3Cys), and CpG ODN. All tested TLR agonists were comparable to induce antibody responses, whereas significant differences were noticed in their ability to elicit CD4(+) T and CD8(+) T cell responses. In particular, both GIPLs (GTH, and GY) and CpG ODNs (B344, B297 and B128) derived from T. cruzi elicited interferon-gamma (IFN-γ) production by CD4(+) T cells. On the other hand, the parasite derived CpG ODNs, but not GIPLs, elicited a potent IFN-γ response by CD8(+) T lymphocytes. The side effects were also evaluated by local pain (hypernociception). The intensity of hypernociception induced by vaccination was alleviated by administration of an analgesic drug without affecting protective immunity. Finally, the level of protective immunity against the NY-ESO-1 expressing melanoma was associated with the magnitude of both CD4(+) T and CD8(+) T cell responses elicited by a specific immunological adjuvant.

Unique contribution of IRF-5-Ikaros axis to the B-cell IgG2a response

IRF-5 is a transcription factor activated by toll like receptor (TLR)7 and TLR9 during innate immune responses. IRF-5 activates not only Type I IFN, but also inflammatory cytokines. Most importantly, a genetic variation in the IRF-5 gene shows a strong association with autoimmune diseases such as Lupus. Here, we report that IRF5-deficient mice have attenuated IgG2a/c responses to T-cell-dependent and -independent antigens and to polyoma virus infection. This defect is due to the intrinsic deletion of IRF-5 in B cells, as SCID mice reconstituted with Irf5-/- B cells show a decrease in IgG2a/c expression after viral infection compared with mice that received wild-type B cells. Irf5-/-B cells in vitro have diminished TLR and cytokine-induced class switching to IgG2a/c. Addressing the molecular mechanism, we show that IRF-5 regulates IgG2a/c expression by decreasing Ikaros expression; reconstitution of IRF-5 in Irf5-/- B cells downregulates Ikaros levels and increases switching to IgG2a/c. The IRF site in ikzf1 promoter binds IRF-5, IRF-4 and IRF-8. We show that IRF-8 but not IRF-4 activates the ikzf1 promoter, and IRF-5 inhibits the transcriptional activity of IRF-8. Collectively, these results identify the IRF-5-Ikaros axis as a critical modulator of IgG2a/c class switching.

An interspecific Nicotiana hybrid as a useful and cost-effective platform for production of animal vaccines

The use of transgenic plants to produce novel products has great biotechnological potential as the relatively inexpensive inputs of light, water, and nutrients are utilised in return for potentially valuable bioactive metabolites, diagnostic proteins and vaccines. Extensive research is ongoing in this area internationally with the aim of producing plant-made vaccines of importance for both animals and humans. Vaccine purification is generally regarded as being integral to the preparation of safe and effective vaccines for use in humans. However, the use of crude plant extracts for animal immunisation may enable plant-made vaccines to become a cost-effective and efficacious approach to safely immunise large numbers of farm animals against diseases such as avian influenza. Since the technology associated with genetic transformation and large-scale propagation is very well established in Nicotiana, the genus has attributes well-suited for the production of plant-made vaccines. However the presence of potentially toxic alkaloids in Nicotiana extracts impedes their use as crude vaccine preparations. In the current study we describe a Nicotiana tabacum and N. glauca hybrid that expresses the HA glycoprotein of influenza A in its leaves but does not synthesize alkaloids. We demonstrate that injection with crude leaf extracts from these interspecific hybrid plants is a safe and effective approach for immunising mice. Moreover, this antigen-producing alkaloid-free, transgenic interspecific hybrid is vigorous, with a high capacity for vegetative shoot regeneration after harvesting. These plants are easily propagated by vegetative cuttings and have the added benefit of not producing viable pollen, thus reducing potential problems associated with bio-containment. Hence, these Nicotiana hybrids provide an advantageous production platform for partially purified, plant-made vaccines which may be particularly well suited for use in veterinary immunization programs.

Imidazoquinoline Toll-like receptor 8 agonists activate human newborn monocytes and dendritic cells through adenosine-refractory and caspase-1-dependent pathways

BACKGROUND

Newborns have frequent infections and manifest impaired vaccine responses, motivating a search for neonatal vaccine adjuvants. Alum is a neonatal adjuvant but might confer a T(H)2 bias. Toll-like receptor (TLR) agonists are candidate adjuvants, but human neonatal cord blood monocytes demonstrate impaired T(H)1-polarizing responses to many TLR agonists caused by plasma adenosine acting through cyclic AMP. TLR8 agonists, including imidazoquinolines (IMQs), such as the small synthetic 3M-002, induce adult-level TNF from neonatal monocytes, but the scope and mechanisms of IMQ-induced activation of neonatal monocytes and monocyte-derived dendritic cells (MoDCs) have not been reported.

OBJECTIVE

We sought to characterize IMQ-induced activation of neonatal monocytes and MoDCs.

METHODS

Neonatal cord and adult peripheral blood monocytes and MoDCs were cultured in autologous plasma; levels of alum- and TLR agonist-induced cytokines and costimulatory molecules were measured. TLR8 and inflammasome function were assayed by using small interfering RNA and Western blotting/caspase-1 inhibitory peptide, respectively. The ontogeny of TLR8 agonist-induced cytokine responses was defined in rhesus macaque whole blood ex vivo.

RESULTS

IMQs were more potent and effective than alum at inducing TNF and IL-1β from monocytes. 3M-002 induced robust TLR pathway transcriptome activation and T(H)1-polarizing cytokine production in neonatal and adult monocytes and MoDCs, signaling through TLR8 in an adenosine/cyclic AMP-refractory manner. Newborn MoDCs displayed impaired LPS/ATP-induced caspase-1-mediated IL-1β production but robust 3M-002-induced caspase-1-mediated inflammasome activation independent of exogenous ATP. TLR8 IMQs induced robust TNF and IL-1β in whole blood of rhesus macaques at birth and infancy.

CONCLUSIONS

IMQ TLR8 agonists engage adenosine-refractory TLR8 and inflammasome pathways to induce robust monocyte and MoDC activation and represent promising neonatal adjuvants.

Mucosal vaccine design and delivery

Mucosal surfaces are a major portal of entry for many human pathogens that are the cause of infectious diseases worldwide. Vaccines capable of eliciting mucosal immune responses can fortify defenses at mucosal front lines and protect against infection. However, most licensed vaccines are administered parenterally and fail to elicit protective mucosal immunity. Immunization by mucosal routes may be more effective at inducing protective immunity against mucosal pathogens at their sites of entry. Recent advances in our understanding of mucosal immunity and identification of correlates of protective immunity against specific mucosal pathogens have renewed interest in the development of mucosal vaccines. Efforts have focused on efficient delivery of vaccine antigens to mucosal sites that facilitate uptake by local antigen-presenting cells to generate protective mucosal immune responses. Discovery of safe and effective mucosal adjuvants are also being sought to enhance the magnitude and quality of the protective immune response.

BCR-signalling synergizes with TLR-signalling for induction of AID and immunoglobulin class-switching through the non-canonical NF-κB pathway

By diversifying antibody biological effector functions, class switch DNA recombination has a central role in the maturation of the antibody response. Here we show that BCR-signalling synergizes with Toll-like receptor (TLR) signalling to induce class switch DNA recombination. BCR-signalling activates the non-canonical NF-κB pathway and enhances the TLR-dependent canonical NF-κB pathway, thereby inducing activation-induced cytidine deaminase (AID), which is critical for class switch DNA recombination. Escherichia coli lipopolysaccharide (LPS) triggers dual TLR4/BCR-signalling and induces hallmarks of BCR-signalling, including CD79a phosphorylation and Ca(2+) mobilization, and activates both the NF-κB pathways to induce AID and class switch DNA recombination in a PI(3)K p85α-dependent fashion. CD40-signalling activates the two NF-κB pathways to induce AID and class switch DNA recombination independent of BCR-signalling. Finally, dual BCR/TLR-engaging NP-lipopolysaccharide effectively elicits class-switched NP-specific IgG3 and IgG2b in mice. Thus, by integrating signals of the non-canonical and canonical NF-κB pathways, BCR and TLRs synergize to induce AID and T-cell-independent class switch DNA recombination.

Age of recipient and number of doses differentially impact human B and T cell immune memory responses to HPV vaccination

Vaccination is one of the most effective medical interventions. However, optimization of existing as well as design of new vaccines is still mostly conducted empirically; a rational approach to vaccine design is largely prohibited by the lack of insight into the relevant mechanisms underlying immune-mediated protection. To delineate the impact of variables on immune memory formation following vaccination, we took advantage of a trial assessing the role of the age of the recipient and the number of administered doses of the quadrivalent HPV vaccine in a well-characterized longitudinal cohort of girls and young women. We found that age of the recipient and the number of doses administered differentially impact the development of B and T cell memory. Specifically, age of the recipient significantly impacted generation of HPV 18-specific B cell memory, while the number of vaccine doses displayed a significant effect on the development of HPV-specific T cell memory. Our data indicate that rational design of vaccines has to be tailored according to the desired induction of B and/or T cell memory.

New strategies for the development of H5N1 subtype influenza vaccines: progress and challenges

The emergence and spread of highly pathogenic avian influenza (H5N1) viruses among poultry in Asia, the Middle East, and Africa have fueled concerns of a possible human pandemic, and spurred efforts towards developing vaccines against H5N1 influenza viruses, as well as improving vaccine production methods. In recent years, promising experimental reverse genetics-derived H5N1 live attenuated vaccines have been generated and characterized, including vaccines that are attenuated through temperature-sensitive mutation, modulation of the interferon antagonist protein, or disruption of the M2 protein. Live attenuated influenza virus vaccines based on each of these modalities have conferred protection against homologous and heterologous challenge in animal models of influenza virus infection. Alternative vaccine strategies that do not require the use of live virus, such as virus-like particle (VLP) and DNA-based vaccines, have also been vigorously pursued in recent years. Studies have demonstrated that influenza VLP vaccination can confer homologous and heterologous protection from lethal challenge in a mouse model of infection. There have also been improvements in the formulation and production of vaccines following concerns over the threat of H5N1 influenza viruses. The use of novel substrates for the growth of vaccine virus stocks has been intensively researched in recent years, and several candidate cell culture-based systems for vaccine amplification have emerged, including production systems based on Madin-Darby canine kidney, Vero, and PerC6 cell lines. Such systems promise increased scalability of product, and reduced reliance on embryonated chicken eggs as a growth substrate. Studies into the use of adjuvants have shown that oil-in-water-based adjuvants can improve the immunogenicity of inactivated influenza vaccines and conserve antigen in such formulations. Finally, efforts to develop more broadly cross-protective immunization strategies through the inclusion of conserved influenza virus antigens in vaccines have led to experimental vaccines based on the influenza hemagglutinin (HA) stem domain. Such vaccines have been shown to confer protection from lethal challenge in mouse models of influenza virus infection. Through further development, vaccines based on the HA stem have the potential to protect vaccinated individuals against unanticipated pandemic and epidemic influenza virus strains. Overall, recent advances in experimental vaccines and in vaccine production processes provide the potential to lower mortality and morbidity resulting from influenza infection.

Polymeric multilayer capsule-mediated vaccination induces protective immunity against cancer and viral infection

Recombinant antigens hold high potential to develop vaccines against lethal intracellular pathogens and cancer. However, they are poorly immunogenic and fail to induce potent cellular immunity. In this paper, we demonstrate that polymeric multilayer capsules (PMLC) strongly increase antigen delivery toward professional antigen-presenting cells in vivo, including dendritic cells (DCs), macrophages, and B cells, thereby enforcing antigen presentation and stimulating T cell proliferation. A thorough analysis of the T cell response demonstrated their capacity to induce IFN-γ secreting CD4 and CD8 T cells, in addition to follicular T-helper cells, a recently identified CD4 T cell subset supporting antibody responses. On the B cell level, PMLC-mediated antigen delivery promoted the formation of germinal centers, resulting in increased numbers of antibody-secreting plasma cells and elevated antibody titers. The functional relevance of the induced immune responses was validated in murine models of influenza and melanoma. On a mechanistic level, we have demonstrated the capacity of PMLC to activate the NALP3 inflammasome and trigger the release of the potent pro-inflammatory cytokine IL-1β. Finally, using DC-depleted mice, we have identified DCs as the key mediators of the immunogenic properties of PMLC.

Modulating immunity as a therapy for bacterial infections

Despite our efforts to halt the increase and spread of antimicrobial resistance, bacteria continue to become less susceptible to antimicrobial drugs over time, and rates of discovery for new antibiotics are declining. Thus, it is essential to explore new paradigms for anti-infective therapy. One promising approach involves host-directed immunomodulatory therapies, whereby natural mechanisms in the host are exploited to enhance therapeutic benefit. The objective is to initiate or enhance protective antimicrobial immunity while limiting inflammation-induced tissue injury. A range of potential immune modulators have been proposed, including innate defence regulator peptides and agonists of innate immune components such as Toll-like receptors and NOD-like receptors.

The long-term potential of biodegradable poly(lactide-co-glycolide) microparticles as the next-generation vaccine adjuvant

Biodegradable polymeric microparticles of poly(lactide-co-glycolide) (PLG) have been extensively evaluated for drug delivery and vaccine applications over the last three decades. Despite a wealth of studies on the use of PLG microparticles in vaccines through controlled release of antigens, there is no commercial PLG-based vaccine as yet. The key challenge that prevented the development of PLG microparticles as commercial vaccines was the instability of encapsulated antigen. Over the years, advancements were made towards maintaining antigen integrity during PLG microparticle preparation and sterilization. In parallel and independently, development of PLG microparticles as therapeutic commercial products established PLG with an excellent safety record in humans, and as a suitable candidate for next-generation vaccines. Through the combination of Toll-like receptor agonist encapsulation and surface adsorption of antigen, PLG microparticles can be used as a vaccine adjuvant to address unmet medical needs, such as vaccines against HIV, malaria and TB. With strategic development of PLG-based vaccines, PLG microparticles can offer advantages over the conventional vaccine adjuvants allowing commercial development of this adjuvant.

IBC's 22nd Annual Antibody Engineering and 9th Annual Antibody Therapeutics International Conferences and the 2011 Annual Meeting of The Antibody Society, December 5-8, 2011, San Diego, CA

The 22nd Annual Antibody Engineering and 9th Annual Antibody Therapeutics international conferences, and the 2011 Annual Meeting of The Antibody Society, organized by IBC Life Sciences with contributions from The Antibody Society and two Scientific Advisory Boards, were held December 5-8, 2011 in San Diego, CA. The meeting drew ~800 participants who attended sessions on a wide variety of topics relevant to antibody research and development. As a preview to the main events, a pre-conference workshop held on December 4, 2011 focused on antibodies as probes of structure. The Antibody Engineering Conference comprised eight sessions: (1) structure and dynamics of antibodies and their membrane receptor targets; (2) model-guided generation of binding sites; (3) novel selection strategies; (4) antibodies in a complex environment: targeting intracellular and misfolded proteins; (5) rational vaccine design; (6) viral retargeting with engineered binding molecules; (7) the biology behind potential blockbuster antibodies and (8) antibodies as signaling modifiers: where did we go right, and can we learn from success? The Antibody Therapeutics session comprised five sessions: (1)Twenty-five years of therapeutic antibodies: lessons learned and future challenges; (2) preclinical and early stage development of antibody therapeutics; (3) next generation anti-angiogenics; (4) updates of clinical stage antibody therapeutics and (5) antibody drug conjugates and bispecific antibodies.

Beyond pattern recognition: five immune checkpoints for scaling the microbial threat

Pattern recognition by the innate immune system enables the detection of microorganisms, but how the level of microbial threat is evaluated - a process that is crucial for eliciting measured antimicrobial responses with minimal inflammatory tissue damage - is less well understood. New evidence has shown that features of microbial viability can be detected by the immune system and thereby induce robust responses that are not warranted for dead microorganisms. Here, we propose five immune checkpoints that, as defined here, collectively determine the gravity of microbial encounters.

Antibody repertoire: embracing diversity

In this Perspective, we discuss two papers that show that the breadth of the antibody response to vaccines could be manipulated by the use of particular vaccine adjuvants that stimulate innate immune mechanisms. The ability to increase the repertoire of antibodies induced by a vaccine may help to control variable pathogens that alter their exposed antigens to evade the immune system.

Superior induction of T cell responses to conserved HIV-1 regions by electroporated alphavirus replicon DNA compared to that with conventional plasmid DNA vaccine

Vaccination using "naked" DNA is a highly attractive strategy for induction of pathogen-specific immune responses; however, it has been only weakly immunogenic in humans. Previously, we constructed DNA-launched Semliki Forest virus replicons (DREP), which stimulate pattern recognition receptors and induce augmented immune responses. Also, in vivo electroporation was shown to enhance immune responses induced by conventional DNA vaccines. Here, we combine these two approaches and show that in vivo electroporation increases CD8(+) T cell responses induced by DREP and consequently decreases the DNA dose required to induce a response. The vaccines used in this study encode the multiclade HIV-1 T cell immunogen HIVconsv, which is currently being evaluated in clinical trials. Using intradermal delivery followed by electroporation, the DREP.HIVconsv DNA dose could be reduced to as low as 3.2 ng to elicit frequencies of HIV-1-specific CD8(+) T cells comparable to those induced by 1 μg of a conventional pTH.HIVconsv DNA vaccine, representing a 625-fold molar reduction in dose. Responses induced by both DREP.HIVconsv and pTH.HIVconsv were further increased by heterologous vaccine boosts employing modified vaccinia virus Ankara MVA.HIVconsv and attenuated chimpanzee adenovirus ChAdV63.HIVconsv. Using the same HIVconsv vaccines, the mouse observations were supported by an at least 20-fold-lower dose of DNA vaccine in rhesus macaques. These data point toward a strategy for overcoming the low immunogenicity of DNA vaccines in humans and strongly support further development of the DREP vaccine platform for clinical evaluation.

Antigen-displaying lipid-enveloped PLGA nanoparticles as delivery agents for a Plasmodium vivax malaria vaccine

The parasite Plasmodium vivax is the most frequent cause of malaria outside of sub-Saharan Africa, but efforts to develop viable vaccines against P. vivax so far have been inadequate. We recently developed pathogen-mimicking polymeric vaccine nanoparticles composed of the FDA-approved biodegradable polymer poly(lactide-co-glycolide) acid (PLGA) “enveloped” by a lipid membrane. In this study, we sought to determine whether this vaccine delivery platform could be applied to enhance the immune response against P. vivax sporozoites. A candidate malaria antigen, VMP001, was conjugated to the lipid membrane of the particles, and an immunostimulatory molecule, monophosphoryl lipid A (MPLA), was incorporated into the lipid membranes, creating pathogen-mimicking nanoparticle vaccines (VMP001-NPs). Vaccination with VMP001-NPs promoted germinal center formation and elicited durable antigen-specific antibodies with significantly higher titers and more balanced Th1/Th2 responses in vivo, compared with vaccines composed of soluble protein mixed with MPLA. Antibodies raised by NP vaccinations also exhibited enhanced avidity and affinity toward the domains within the circumsporozoite protein implicated in protection and were able to agglutinate live P. vivax sporozoites. These results demonstrate that these VMP001-NPs are promising vaccines candidates that may elicit protective immunity against P. vivax sporozoites.

Design considerations for liposomal vaccines: influence of formulation parameters on antibody and cell-mediated immune responses to liposome associated antigens

Liposomes (phospholipid bilayer vesicles) are versatile and robust delivery systems for induction of antibody and T lymphocyte responses to associated subunit antigens. In the last 15 years, liposome vaccine technology has matured and now several vaccines containing liposome-based adjuvants have been approved for human use or have reached late stages of clinical evaluation. Given the intensifying interest in liposome-based vaccines, it is important to understand precisely how liposomes interact with the immune system and stimulate immunity. It has become clear that the physicochemical properties of liposomal vaccines - method of antigen attachment, lipid composition, bilayer fluidity, particle charge, and other properties - exert dramatic effects on the resulting immune response. Here, we present a comprehensive review of the physicochemical properties of liposomal vaccines and how they influence immune responses. A discussion of novel and emerging immunomodulators that are suitable for inclusion in liposomal vaccines is also presented. Through a comprehensive analysis of the body of liposomal vaccine literature, we enumerate a series of principles that can guide the rational design of liposomal vaccines to elicit immune responses of a desired magnitude and quality. We also identify major unanswered questions in the field, pointing the direction for future study.

Respiratory syncytial virus vaccine development

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract viral disease in infants and young children. Presently, there are no explicit recommendations for RSV treatment apart from supportive care. The virus is therefore responsible for an estimated 160,000 deaths per year worldwide. Despite half a century of dedicated research, there remains no licensed vaccine product. Herein are described past and current efforts to harness innate and adaptive immune potentials to combat RSV. A plethora of candidate vaccine products and strategies are reviewed. The development of a successful RSV vaccine may ultimately stem from attention to historical lessons, in concert with an integral partnering of immunology and virology research fields.