Protective Neutralizing Antibody Research Articles

Early development of broadly neutralizing antibodies in HIV-1-infected infants.

Eliciting protective neutralizing antibodies (NAbs) against HIV-1 is daunting because of the extensive genetic and antigenic diversity of HIV-1. Moreover, broad and potent responses are uncommon even during persistent infection, with only a subset of adults developing broadly neutralizing antibodies (bNAbs) that recognize variants from different HIV-1 clades1–8. It is not known whether bNAbs can also arise in HIV-1-infected infants, who typically progress to disease faster than adults9, presumably in part due to an immature immune system10. Here, we show that bNAbs develop at least as commonly in infants as in adults. Cross-clade NAb responses were detected in 20/28 infected infants, in some cases, within 1 year of infection. Among infants with the top quartile of responses, neutralization of Tier 2–3 variants from multiple clades was detected at 20 months post-infection. These findings suggest that, even in early life, there is sufficient B-cell functionality to mount bNAbs against HIV-1. Additionally, the relatively early appearance of bNAbs in infants may provide a unique setting for understanding the pathways of B-cell maturation leading to bNAbs.

Proof of principle for epitope-focused vaccine design

SummaryVaccines prevent infectious disease largely by inducing protective neutralizing antibodies against vulnerable epitopes. Multiple major pathogens have resisted traditional vaccine development, although vulnerable epitopes targeted by neutralizing antibodies have been identified for several such cases. Hence, new vaccine design methods to induce epitope-specific neutralizing antibodies are needed. Here we show, with a neutralization epitope from respiratory syncytial virus (RSV), that computational protein design can generate small, thermally and conformationally stable protein scaffolds that accurately mimic the viral epitope structure and induce potent neutralizing antibodies. These scaffolds represent promising leads for research and development of a human RSV vaccine needed to protect infants, young children and the elderly. More generally, the results provide proof of principle for epitope-focused and scaffold-based vaccine design, and encourage the evaluation and further development of these strategies for a variety of other vaccine targets including antigenically highly variable pathogens such as HIV and influenza.

The Type-Specific Neutralizing Antibody Response Elicited by a Dengue Vaccine Candidate Is Focused on Two Amino Acids of the Envelope Protein

Dengue viruses are mosquito-borne flaviviruses that circulate in nature as four distinct serotypes (DENV1-4). These emerging pathogens are responsible for more than 100 million human infections annually. Severe clinical manifestations of disease are predominantly associated with a secondary infection by a heterotypic DENV serotype. The increased risk of severe disease in DENV-sensitized populations significantly complicates vaccine development, as a vaccine must simultaneously confer protection against all four DENV serotypes. Eliciting a protective tetravalent neutralizing antibody response is a major goal of ongoing vaccine development efforts. However, a recent large clinical trial of a candidate live-attenuated DENV vaccine revealed low protective efficacy despite eliciting a neutralizing antibody response, highlighting the need for a better understanding of the humoral immune response against dengue infection. In this study, we sought to identify epitopes recognized by serotype-specific neutralizing antibodies elicited by monovalent DENV1 vaccination. We constructed a panel of over 50 DENV1 structural gene variants containing substitutions at surface-accessible residues of the envelope (E) protein to match the corresponding DENV2 sequence. Amino acids that contribute to recognition by serotype-specific neutralizing antibodies were identified as DENV mutants with reduced sensitivity to neutralization by DENV1 immune sera, but not cross-reactive neutralizing antibodies elicited by DENV2 vaccination. We identified two mutations (E126K and E157K) that contribute significantly to type-specific recognition by polyclonal DENV1 immune sera. Longitudinal and cross-sectional analysis of sera from 24 participants of a phase I clinical study revealed a markedly reduced capacity to neutralize a E126K/E157K DENV1 variant. Sera from 77% of subjects recognized the E126K/E157K DENV1 variant and DENV2 equivalently (<3-fold difference). These data indicate the type-specific component of the DENV1 neutralizing antibody response to vaccination is strikingly focused on just two amino acids of the E protein. This study provides an important step towards deconvoluting the functional complexity of DENV serology following vaccination.

A global approach to HIV‐1 vaccine development

SummaryA global human immunodeficiency virus-1 (HIV-1) vaccine will have to elicit immune responses capable of providing protection against a tremendous diversity of HIV-1 variants. In this review, we first describe the current state of the HIV-1 vaccine field, outlining the immune responses that are desired in a global HIV-1 vaccine. In particular, we emphasize the likely importance of Env-specific neutralizing and non-neutralizing antibodies for protection against HIV-1 acquisition and the likely importance of effector Gag-specific T lymphocytes for virologic control. We then highlight four strategies for developing a global HIV-1 vaccine. The first approach is to design specific vaccines for each geographic region that include antigens tailor-made to match local circulating HIV-1 strains. The second approach is to design a vaccine that will elicit Env-specific antibodies capable of broadly neutralizing all HIV-1 subtypes. The third approach is to design a vaccine that will elicit cellular immune responses that are focused on highly conserved HIV-1 sequences. The fourth approach is to design a vaccine to elicit highly diverse HIV-1-specific responses. Finally, we emphasize the importance of conducting clinical efficacy trials as the only way to determine which strategies will provide optimal protection against HIV-1 in humans.

B Cell Infection and Activation by Rabies Virus-Based Vaccines

Replication-deficient rabies viruses (RABV) are promising rabies postexposure vaccines due to their prompt and potent stimulation of protective virus neutralizing antibody titers, which are produced in mice by both T-dependent and T-independent mechanisms. To promote such early and robust B cell stimulation, we hypothesized that live RABV-based vaccines directly infect B cells, thereby activating a large pool of antigen-presenting cells (APCs) capable of providing early priming and costimulation to CD4(+) T cells. In this report, we show that live RABV-based vaccine vectors efficiently infect naive primary murine and human B cells ex vivo. Infection of B cells resulted in the significant upregulation of early markers of B cell activation and antigen presentation, including CD69, major histocompatibility complex class II (MHC-II), and CD40 in murine B cells or HLA-DR and CD40 in human B cells compared to mock-infected cells or cells treated with an inactivated RABV-based vaccine. Furthermore, primary B cells infected with a live RABV expressing ovalbumin were able to prime and stimulate naive CD4(+) OT-II T cells to proliferate and to secrete interleukin-2 (IL-2), demonstrating a functional consequence of B cell infection and activation by live RABV-based vaccine vectors. We propose that this direct B cell stimulation by live RABV-based vaccines is a potential mechanism underlying their induction of early protective T cell-dependent B cell responses, and that designing live RABV-based vaccines to infect and activate B cells represents a promising strategy to develop a single-dose postexposure rabies vaccine where the generation of early protective antibody titers is critical.

Deciphering the protective role of adaptive immunity to CHIKV/IRES a novel candidate vaccine against Chikungunya in the A129 mouse model

Chikungunya virus (CHIKV), a mosquito-borne alphavirus, recently re-emerged in Africa and spread to islands in the Indian Ocean, the Indian subcontinent, and to South East Asia. Viremic travelers have also imported CHIKV to the Western hemisphere highlighting the importance of CHIKV in public health. In addition to the great burden of arthralgic disease, which can persist for months or years, epidemiologic studies have estimated case-fatality rates of ∼0.1%, principally from neurologic disease in older patients. There are no licensed vaccines or effective therapies to prevent or treat human CHIKV infections. We have developed a live CHIKV vaccine (CHIKV/IRES) that is highly attenuated yet immunogenic in mouse models, and is incapable of replicating in mosquito cells. In this study we sought to decipher the role of adaptive immunity elicited by CHIKV/IRES in protection against wild-type CHIKV infection. A single dose of vaccine effectively activated T cells with an expansion peak on day 10 post immunization and elicited memory CD4+ and CD8+ T cells that produced IFN-γ, TNF-α and IL-2 upon restimulation with CHIKV/IRES. Adoptive transfer of CHIKV/IRES-immune CD4+ or CD8+ T cells did not confer protection against wtCHIKV-LR challenge. By contrast, passive immunization with anti-CHIKV/IRES immune serum provided protection, and a correlate of a minimum protective neutralizing antibody titer was established. Overall, our findings demonstrate the immunogenic potential of the CHIKV/IRES vaccine and highlight the important role that neutralizing antibodies play in protection against an acute CHIKV infection.

A consensus envelope protein domain III can induce neutralizing antibody responses against serotype 2 of dengue virus in non-human primates

We have previously demonstrated that vaccination with a subunit dengue vaccine containing a consensus envelope domain III with aluminum phosphate elicits neutralizing antibodies against all four serotypes of dengue virus in mice. In this study, we evaluated the immunogenicity of the subunit dengue vaccine in non-human primates. After vaccination, monkeys that received the subunit vaccine with aluminum phosphate developed a significantly strong and long-lasting antibody response. A specific T cell response with cytokine production was also induced, and this correlated with the antibody response. Additionally, neutralizing antibodies against serotype 2 were detected in two of three monkeys. The increase in serotype-2-specific antibody titers and avidity observed in these two monkeys suggested that a serotype-2-biased antibody response occurs. These data provide evidence that a protective neutralizing antibody response was successfully elicited in non-human primates by the dengue subunit vaccine with aluminum phosphate adjuvant.

An inactivated vaccine from a field strain of bovine herpesvirus-1 (BoHV-1) has high antigenic mass and induces strong efficacy in a rabbit model

Bovine Herpesvirus-1 (BoHV-1) is a DNA virus belonging to the family Herpesviridae, subfamily Alfaherpesvirinae; it is a worldwide pathogen, causing serious economic losses in livestock. In Colombia there have been multiple isolates of BoHV-1 that have been subjected to molecular characterization, classifying most of the country isolates as BoHV-1.1. In the present study we developed and evaluated an ethyleneimine binary inactivated isolate from the native BoHV-1 strain (Córdoba-2) in a rabbit model of vaccination and infection. The vaccine was evaluated in two phases, one of immunogenicity with vaccination and a booster after 21 days, and an evaluation phase of protection against challenge with a highly virulent reference strain. The results demonstrate optimum serum-conversion, with protective neutralizing antibody titers 28 days post vaccination and optimal protection against challenge with the reference strain with decreased clinical signs of infection, protection against the onset of fever and decrease of virus excretion post challenge. In conclusion, our results show the enormous potential that an immunogenic inactivated vaccine has produced from the native BoHV-1.1 strain, which produces a high antigen mass to the vaccine to induce optimal immunity and protection, and it is a strong candidate for evaluation and possible future use in different cattle populations.

Reduced neutralizing antibody titer against genotype I virus in swine immunized with a live-attenuated genotype III Japanese encephalitis virus vaccine

A shift in prevalence from Japanese encephalitis virus (JEV) genotype III (GIII) to GI virus has been observed in several Asian countries. Genotype I virus was first detected in Taiwan in 2008, and became the dominant JEV island-wide within a year. We conducted a serosurvey using swine serum specimens from multiple counties in Taiwan following the transmission season in 2009 and results showed 67-100% of JEV seropositive swine showed evidence of GI virus infection. The envelope (E) protein is a structural protein that elicits protective neutralizing antibodies (Nt Ab). The GIII at222 (a live-attenuated swine vaccine) virus E protein differs at eight amino acid residues (E-123, E-129, E-138, E-176, E-209, E-222, E-327 and E-366) from that of the GI TC2009-1 strain (isolated in Taiwan in 2009). Twenty piglets were vaccinated with two doses of at222 vaccine, and serum specimens were collected to evaluate the strain-specific Nt Ab titer against GIII at222, GIII CJN, and GI TC2009-1 viruses. Seropositivity rates (Nt Ab titer≥1:10) and geometric mean titers (GMT) were similar against at222 and CJN viruses. However, sera from swine vaccinated with at222 were least potently neutralizing against GI TC2009-1 virus. The estimated protective threshold against GI virus was observed only when the PRNT50 against at222 virus was ≥1:320. Thus, our current study indicates that the live-attenuated at222 swine vaccine can be partially protective against GI virus, and suggests that the efficacy of GIII swine vaccines currently used may require a comprehensive reevaluation in the field.

CryoEM Visualization of an Adenovirus Capsid-Incorporated HIV Antigen

Adenoviral (Ad) vectors show promise as platforms for vaccine applications against infectious diseases including HIV. However, the requirements for eliciting protective neutralizing antibody and cellular immune responses against HIV remain a major challenge. In a novel approach to generate 2F5- and 4E10-like antibodies, we engineered an Ad vector with the HIV membrane proximal ectodomain region (MPER) epitope displayed on the hypervariable region 2 (HVR2) of the viral hexon capsid, instead of expressed as a transgene. The structure and flexibility of MPER epitopes, and the structural context of these epitopes within viral vectors, play important roles in the induced host immune responses. In this regard, understanding the critical factors for epitope presentation would facilitate optimization strategies for developing viral vaccine vectors. Therefore we undertook a cryoEM structural study of this Ad vector, which was previously shown to elicit MPER-specific humoral immune responses. A subnanometer resolution cryoEM structure was analyzed with guided molecular dynamics simulations. Due to the arrangement of hexons within the Ad capsid, there are twelve unique environments for the inserted peptide that lead to a variety of conformations for MPER, including individual α-helices, interacting α-helices, and partially extended forms. This finding is consistent with the known conformational flexibility of MPER. The presence of an extended form, or an induced extended form, is supported by interaction of this vector with the human HIV monoclonal antibody 2F5, which recognizes 14 extended amino acids within MPER. These results demonstrate that the Ad capsid influences epitope structure, flexibility and accessibility, all of which affect the host immune response. In summary, this cryoEM structural study provided a means to visualize an epitope presented on an engineered viral vector and suggested modifications for the next generation of Ad vectors with capsid-incorporated HIV epitopes.

Modifying the NSs gene to improve live-attenuated vaccine for Rift Valley fever

Vaccines for exotic emerging diseases are considered for populations concerned about economic loss or social panic by natural or intentional introduction of those pathogens into their countries. In particular, zoonotic diseases transmitted by native mosquitoes may cause devastating economic loss and public health impact in the absence of effective countermeasures. A number of countries are at risk of potential spread of Rift Valley fever virus (RVFV; family Bunyaviridae, genus Phlebovirus) from endemic areas in Africa. RVFV establishes vertical transmission in floodwater Aedes species, a primary vector of RVFV, and is also maintained by horizontal transmission between mosquito vectors and animals [1]. RVFV infection results in more than 90% death in newborn lambs, 40–100% of abortion or fetal malformation in pregnant ewes, and causes a similar abortion in cattle, goat or other ruminants [2]. Most of the human patients of RVF typically show a biphasic febrile illness and less than 1% of patients suffer from lethal hemorrhagic fever, thrombosis or neurological disorder, while 1–10% of patients develop partial or complete blindness [3]. After 82 years since the first recognized RVF outbreak in Kenya in 1930, RVF is now endemic to most of sub-Saharan Africa and has spread into Egypt, Madagascar and Yemen [4]. In the USA, RVFV is classified as a Category A Priority Pathogen by the NIH/the National Institute of Allergy and Infectious Diseases, and an overlap select agent by the US Department of Agriculture and Health and Human Service. RVFV is a negative-stranded RNA virus with a tripartite genome named small (S)-, medium (M)- and large (L)-segments; S-segment encodes N and nonstructural NSs proteins in an ambisense manner, M-segment encodes envelope Gn and Gc proteins, nonstructural NSm proteins and the less-characterized 78-kD protein, and L-segment encodes L protein (RNA-dependant RNA polymerase) [4]. Effective vaccines will minimize the impact of RVFV introduction into nonendemic countries. Past studies demonstrated that neutralizing antibodies play an important role in protection from lethal RVFV challenge [5]. Considering that a large number of ruminants are infected during RVF outbreaks, RVF vaccines should rapidly induce high levels of protective neutralizing antibodies in both ruminant and humans with a single dose. Currently, only a formalin-inactivated The Salk Institute-Government Service Division (TSI-GSD)-200 vaccine is available with an Investigational New Drug status in the USA. TSI-GSD-200 is produced from the Entebbe strain (a wild-type [wt] RVFV isolate from mosquitoes in the 1940s) at high containment facilities, and there is a limitation in available doses, while at least three doses are required for inducing a protective level of neutralizing antibody [5,6]. A live-attenuated vaccine strain, Smithburn vaccine, generated by numerous intracerebral passages in suckling mice, has been used in endemic countries since the 1950s. Smithburn vaccine causes abortion in vaccinated pregnant ruminants, and recent sequencing analysis showed a potential reassortment with the wt RVFV strain [7]. A live-attenuated candidate vaccine, MP-12, was generated in the 1980s from an Egyptian isolate, ZH548 strain, by 12 serial passages in human diploid lung MRC-5 cells in the presence of a chemical mutagen, 5-fluorouracil [8]. Ruminants vaccinated with a single dose of MP-12 elicit high levels of neutralizing antibodies [5]. MP-12 has 23 mutations compared with the parental ZH548 strain, among which some of the 19 mutations in M- and L-segments are considered to be responsible for its attenuation, while the S-segment still has a virulent phenotype [5,9]. A study suggested that MP-12 retains residual virulence in pregnant ewes during early pregnancy [10], whereas the safety in pregnant ruminants at later stages and newborn lambs has been demonstrated [5]. Furthermore, more than 100 human volunteers were successfully vaccinated with MP-12 vaccine without notable adverse effects [5]. Thus, MP-12 is much safer than the Smithburn strain, and is considered one of the most promising candidate vaccines for RVF in humans and ruminants in the USA [5]. In addition, MP-12 is the RVFV strain exempted from select agent rule, and can be handled in a biosafety level 2 laboratory.

An adjuvanted respiratory syncytial virus fusion protein induces protection in aged BALB/c mice

BackgroundRespiratory Syncytial Virus (RSV) causes significant disease in the elderly, in part, because immunosenescence impairs protective immune responses to infection in this population. Despite previous and current efforts, there is no RSV vaccine currently licensed in infants or elderly adults. Adjuvanted RSV subunit vaccines have the potential to boost waning immune responses and reduce the burden of RSV disease in the elderly population.ResultsWe used an aged BALB/c mouse model to evaluate immune responses to RSV Fusion (F) protein in the absence and presence of an alum adjuvant. We demonstrate that aged BALB/c mice immunized with alum-adjuvanted RSV F protein had significantly reduced lung viral titers at day 4 following challenge with wild-type (wt) RSV. Serum neutralizing antibody titers measured on day 27 correlated with protection in both young and aged vaccinated mice, although the magnitude of antibody titers was lower in aged mice. Unlike young mice, in aged mice, alum-adjuvanted RSV F did not induce lung TH2-type cytokines or eosinophil infiltration compared to non-adjuvanted F protein following wt RSV challenge.ConclusionOur studies demonstrate that neutralizing anti-RSV antibody titers correlate with protection in both young and aged BALB/c mice vaccinated with RSV F protein vaccines. The F + alum formulation mediated greater protection compared to the non-adjuvanted F protein in both young and aged mice. However, while alum can boost F-specific antibody responses in aged mice, it does not completely overcome the reduced ability of a senescent immune system to respond to the RSV F antigen. Thus, our data suggest that a stronger adjuvant may be required for the prevention of RSV disease in immunosenescent populations, to achieve the appropriate balance of protective neutralizing antibodies and effective TH1-type cytokine response along with minimal lung immunopathology.

Comparison of immune responses against FMD by a DNA vaccine encoding the FMDV/O/IRN/2007 VP1 gene and the conventional inactivated vaccine in an animal model

Foot-and-mouth disease virus (FMDV) is highly contagious and responsible for huge outbreaks among cloven hoofed animals. The aim of the present study is to evaluate a plasmid DNA immunization system that expresses the FMDV/O/IRN/2007 VP1 gene and compare it with the conventional inactivated vaccine in an animal model. The VP1 gene was sub-cloned into the unique Kpn I and BamH I cloning sites of the pcDNA3.1+ and pEGFP-N1 vectors to construct the VP(1) gene cassettes. The transfected BHKT7 cells with sub-cloned pEGFP-N1-VP1 vector expressed GFP-VP1 fusion protein and displayed more green fluorescence spots than the transfected BHKT7 cells with pEGFP-N1 vector, which solely expressed the GFP protein. Six mice groups were respectively immunized by the sub-cloned pcDNA3.1(+)-VP1 gene cassette as the DNA vaccine, DNA vaccine and PCMV-SPORT-GMCSF vector (as molecular adjuvant) together, conventional vaccine, PBS (as negative control), pcDNA3.1(+) vector (as control group) and PCMV-SPORT vector that contained the GMCSF gene (as control group). Significant neutralizing antibody responses were induced in the mice which were immunized using plasmid vectors expressing the VP1 and GMCSF genes together, the DNA vaccine alone and the conventional inactivated vaccine (P<0.05). Co-administration of DNA vaccine and GMCSF gene improved neutralizing antibody response in comparison with administration of the DNA vaccine alone, but this response was the most for the conventional vaccine group. However, induction of humeral immunity response in the conventional vaccine group was more protective than for the DNA vaccine, but T-cell proliferation and IFN-γ concentration were the most in DNA vaccine with the GMCSF gene. Therefore the group that was vaccinated by DNA vaccine with the GMCSF gene, showed protective neutralizing antibody response and the most Th1 cellular immunity.

Evaluation of Japanese encephalitis virus polytope DNA vaccine candidate in BALB/c mice

Vaccination is the most important measure available to control the spread of Japanese encephalitis virus. We have previously described the in silico design, in vitro and primary in vivo analyses of polytope construct (P-JEV). Present study indicates that, P-JEV induces significant specific humoral and cellular immune responses in BALB/c mice. Mice were immunized intra-dermally with 1μg plasmid DNA using gene gun and boosted twice. After the second booster, all the mice seroconverted and developed JEV neutralizing antibodies. Enhancement of post-challenge neutralizing antibody titres indicates the dominant role of anamnestic antibody-mediated protection in the mice JEV challenge model. Our study provides an insight demonstrating, intra-dermal DNA administration led to higher seroconversion rates and potentiated TH2 type of immune responses. The P-JEV construct is thus capable of generating protective neutralizing antibodies in mice and prime the immune system effectively against subsequent exposure to the virus.

Vaccine Induced Protection of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Infection in swine (113.3)

Abstract PRRSV is an economically significant Arterivirus of swine health industry. High genetic diversity (up to 20% strain variability), high mutation rate and various immune evasion strategies pose major challenges in the development of an efficacious broadly protective vaccine. One evasion strategy is the presence of non-conserved immunodominant decoy epitopes that divert the immune response towards non-protective, type-specific ones. We hypothesize that masking decoy epitopes with PRRSV specific antibodies, Antibody Immune Masking (AIM), can redirect immune response towards broadly protective neutralizing antibodies. Presented here is the development of an efficacious AIM PRRSV vaccine model capable of inducing sterilizing immunity in some vaccinated pigs and reduction of viremia as well as PRRSV associated pathology in infected pigs. Pigs were vaccinated with AIM or autologous vaccine and later challenged with a homologous/heterologous virus. Results from a trial with 10 pigs per group demonstrated that AIM vaccination was effective in prevention of heterologous infection in 33% of pigs, while others had significant reduction in peak viremia as compared to the autogenous vaccination control pigs (p=0.0034) and unvaccinated controls (p=0.0001); as well as reduction in pulmonary viral loads compared to unvaccinated controls (p=0.0126). Current research is focused on determination and characterization of correlates of immune protection and confirmation of immune refocusing.

Hepatitis C virus and neutralizing antibodies

Neutralizing antibodies represent a key component of immune control in many viral infections. For a long time, these antibodies were thought to play a marginal role in hepatitis C virus (HCV) infection, and that cellular immune responses are more critical in immune control. The development of model systems to study HCV entry and significant advances in our understanding of viral entry and escape, have reenergized interest in the potential of protective neutralizing antibodies against HCV. Yet further investigations are needed to completely elucidate the role of neutralizing antibodies, recent data on their clinical impact during HCV infection and recent development of monoclonal antibodies capable of neutralizing autologous and heterologousHCVstrains, represent our best hope for the development of novel therapeutic or preventive vaccine.

Destruction of lymphoid organ architecture and hepatitis caused by CD4+ T cells.

Immune responses have the important function of host defense and protection against pathogens. However, the immune response also causes inflammation and host tissue injury, termed immunopathology. For example, hepatitis B and C virus infection in humans cause immunopathological sequel with destruction of liver cells by the host's own immune response. Similarly, after infection with lymphocytic choriomeningitis virus (LCMV) in mice, the adaptive immune response causes liver cell damage, choriomeningitis and destruction of lymphoid organ architecture. The immunopathological sequel during LCMV infection has been attributed to cytotoxic CD8+ T cells. However, we now show that during LCMV infection CD4+ T cells selectively induced the destruction of splenic marginal zone and caused liver cell damage with elevated serum alanin-transferase (ALT) levels. The destruction of the splenic marginal zone by CD4+ T cells included the reduction of marginal zone B cells, marginal zone macrophages and marginal zone metallophilic macrophages. Functionally, this resulted in an impaired production of neutralizing antibodies against LCMV. Furthermore, CD4+ T cells reduced B cells with an IgMhighIgDlow phenotype (transitional stage 1 and 2, marginal zone B cells), whereas other B cell subtypes such as follicular type 1 and 2 and germinal center/memory B cells were not affected. Adoptive transfer of CD4+ T cells lacking different important effector cytokines and cytolytic pathways such as IFNγ, TNFα, perforin and Fas-FasL interaction did reveal that these cytolytic pathways are redundant in the induction of immunopathological sequel in spleen. In conclusion, our results define an important role of CD4+ T cells in the induction of immunopathology in liver and spleen. This includes the CD4+ T cell mediated destruction of the splenic marginal zone with consecutively impaired protective neutralizing antibody responses.

A pan-HPV vaccine based on bacteriophage PP7 VLPs displaying broadly cross-neutralizing epitopes from the HPV minor capsid protein, L2.

BackgroundCurrent human papillomavirus (HPV) vaccines that are based on virus-like particles (VLPs) of the major capsid protein L1 largely elicit HPV type-specific antibody responses. In contrast, immunization with the HPV minor capsid protein L2 elicits antibodies that are broadly cross-neutralizing, suggesting that a vaccine targeting L2 could provide more comprehensive protection against infection by diverse HPV types. However, L2-based immunogens typically elicit much lower neutralizing antibody titers than L1 VLPs. We previously showed that a conserved broadly neutralizing epitope near the N-terminus of L2 is highly immunogenic when displayed on the surface of VLPs derived from the bacteriophage PP7. Here, we report the development of a panel of PP7 VLP-based vaccines targeting L2 that protect mice from infection with carcinogenic and non-carcinogenic HPV types that infect the genital tract and skin.Methodology/Principal FindingsL2 peptides from eight different HPV types were displayed on the surface of PP7 bacteriophage VLPs. These recombinant L2 VLPs, both individually and in combination, elicited high-titer anti-L2 IgG serum antibodies. Immunized mice were protected from high dose infection with HPV pseudovirus (PsV) encapsidating a luciferase reporter. Mice immunized with 16L2 PP7 VLPs or 18L2 PP7 VLPs were nearly completely protected from both PsV16 and PsV18 challenge. Mice immunized with the mixture of eight L2 VLPs were strongly protected from genital challenge with PsVs representing eight diverse HPV types and cutaneous challenge with HPV5 PsV.Conclusion/SignificanceVLP-display of a cross-neutralizing HPV L2 epitope is an effective approach for inducing high-titer protective neutralizing antibodies and is capable of offering protection from a spectrum of HPVs associated with cervical cancer as well as genital and cutaneous warts.

HPV Pseudovirions As DNA Delivery Vehicles

"The ability of HPV pseudovirions to efficiently deliver DNA into cells suggests several potential applications in basic biology, including the characterization of virion biology and measurement of protective neutralizing antibody titers in vitro and in vivo, as well as their employment for more direct medical applications".

Heterotypic Dengue Infection with Live Attenuated Monotypic Dengue Virus Vaccines: Implications for Vaccination of Populations in Areas Where Dengue Is Endemic

Because infection with any of the 4 Dengue virus serotypes may elicit both protective neutralizing antibodies and nonneutralizing antibodies capable of enhancing subsequent heterotypic Dengue virus infections, the greatest risk for severe dengue occurs during a second, heterotypic Dengue virus infection. It remains unclear whether the replication of live attenuated vaccine viruses will be similarly enhanced when administered to Dengue-immune individuals. We recruited 36 healthy adults who had previously received a monovalent live Dengue virus vaccine 0.6-7.4 years earlier. Participants were assigned to 1 of 4 cohorts and were randomly chosen to receive placebo or a heterotypic vaccine. The level of replication, safety, and immunogenicity of the heterotypic vaccine virus was compared with that of Dengue virus immunologically naive vaccinees. Vaccine virus replication and reactogenicity after monovalent Dengue virus vaccination in naive and heterotypically immune vaccinees was similar. In contrast to naive vaccinees, the antibody response in heterotypically immune vaccinees was broadly neutralizing and mimicked the response observed by natural secondary Dengue virus infection. Enhanced replication of these live attenuated Dengue virus vaccines was minimal in heterotypically immune vaccinees and suggests that the further evaluation of these candidate vaccines in populations with preexisting DENV immunity can proceed safely.