Vaccines — Open Access Journal

Sub-Saharan Africa carries the biggest burden of the human immunodeficiency virus type 1 (HIV-1)/AIDS epidemic and is in an urgent need of an effective vaccine. CD8⁺ T cells are an important component of the host immune response to HIV-1 and may need to be harnessed if a vaccine is to be effective. CD8⁺ T cells recognize human leukocyte antigen (HLA)-associated viral epitopes and the HLA alleles vary significantly among different ethnic groups. It follows that definition of HIV-1-derived peptides recognized by CD8⁺ T cells in the geographically relevant regions will critically guide vaccine development. Here, we study fine details of CD8⁺ T-cell responses elicited in HIV-1/2-uninfected individuals in Nairobi, Kenya, who received a candidate vaccine delivering conserved regions of HIV-1 proteins called HIVconsv. Using 10-day cell lines established by in vitro peptide restimulation of cryopreserved PBMC and stably HLA-transfected 721.221/C1R cell lines, we confirm experimentally many already defined epitopes, for a number of epitopes we define the restricting HLA molecule(s) and describe four novel HLA-epitope pairs. We also identify specific dominance patterns, a promiscuous T-cell epitope and a rescue of suboptimal T-cell epitope induction in vivo by its functional variant, which all together inform vaccine design. Full article

Human papillomavirus (HPV)-induced cancers continue to affect millions of women around the world, and the five year survival rate under the current standard of care for these cancers is less than 60% in some demographics. Therefore there is still an unmet need to develop an effective therapy that can be easily administered to treat established HPV cervical cancer lesions. We sought to investigate the potential of an intranasal HPV peptide therapeutic vaccine incorporating the combination of α-Galactosylceramide (α-GalCer) and CpG-ODN adjuvants (TVAC) against established HPV genital tumors in a syngeneic C57BL/6J mouse model. We obtained evidence to show that TVAC, delivered by the mucosal intranasal route, induced high frequencies of antigen-specific CD8 T cells concurrent with significant reduction in the immunosuppressive regulatory T cells and myeloid derived suppressor cells in the tumor microenvironment (TME), correlating with sustained elimination of established HPV genital tumors in over 85% of mice. Inclusion of both the adjuvants in the vaccine was necessary for significant increase of antigen-specific CD8 T cells to the tumor and antitumor efficacy because vaccination incorporating either adjuvant alone was inefficient. These results strongly support the utility of the TVAC administered by needle-free intranasal route as a safe and effective strategy for the treatment of established genital HPV tumors. Full article

Virulent strains of West Nile virus (WNV) are highly neuro-invasive and human infection is potentially lethal. However, no vaccine is currently available for human use. Here, we report the immunogenicity and protective efficacy of a vaccine derived from a chimeric virus, which was constructed using the structural proteins (prM and E) of the Kunjin strain of WNV (WNV_KUN) and the genome backbone of the insect-specific flavivirus Binjari virus (BinJV). This chimeric virus (BinJ/WNV_KUN-prME) exhibits an insect-specific phenotype and does not replicate in vertebrate cells. Importantly, it authentically presents the prM-E proteins of WNV_KUN, which is antigenically very similar to other WNV strains and lineages. Therefore BinJ/WNV_KUN-prME represents an excellent candidate to assess as a vaccine against virulent WNV strains, including the highly pathogenic WNV_NY99. When CD1 mice were immunized with purified BinJ/WNV_KUN-prME, they developed robust neutralizing antibody responses after a single unadjuvanted dose of 1 to 5 μg. We further demonstrated complete protection against viremia and mortality after lethal challenge with WNV_NY99, with no clinical or subclinical pathology observed in vaccinated animals. These data suggest that BinJ/WNV_KUN-prME represents a safe and effective WNV vaccine candidate that warrants further investigation for use in humans or in veterinary applications. Full article

Immunoassays are among the frontline methods used for disease diagnosis and surveillance. Despite this, there are no immunoassays developed for the Chinese soft-shelled turtle (Pelodiscus sinensis), which has expanded into large scale commercial production in several Asian countries. One of the critical factors delaying the development of immunoassays is the lack of characterized soft-shelled turtle immunoglobulins. Herein, we used mass spectrometry together with the ProtQuest software to identify the soft-shelled turtle IgM heavy chain in serum, which again was used to produce a polyclonal anti-turtle-IgM in rabbits. Thereafter, the polyclonal anti-turtle-IgM was used as a secondary antibody in an indirect ELISA to evaluate antibody responses of soft-shelled turtles injected with the bovine serum albumin (BSA) model antigen. Our findings show that only turtle immunized with a water-in-oil BSA plus ISA 763A VG adjuvant (SEPPIC, France) emulsion had antibodies detected at 42 days post vaccination (dpv) while turtles injected with phosphate buffered saline (PBS) only as well as turtle injected with BSA dissolved in PBS had no significant antibody levels detected in serum throughout the study period. In summary, our findings show that rabbit polyclonal anti-turtle-IgM produced can be used in ELISA to measure serum antibody responses in immunized soft-shelled turtles. Future studies should explore its application in other immunoassays needed for the disease diagnosis and vaccine development for soft-shelled turtles. Full article

West Nile virus (WNV) is an emerging neurotropic flavivirus that naturally circulates between mosquitoes and birds. However, WNV has a broad host range and can be transmitted from mosquitoes to several mammalian species, including humans, through infected saliva during a blood meal. Although WNV infections are mostly asymptomatic, 20% to 30% of cases are symptomatic and can occasionally lead to severe symptoms, including fatal meningitis or encephalitis. Over the past decades, WNV-carrying mosquitoes have become increasingly widespread across new regions, including North America and Europe, which constitutes a public health concern. Nevertheless, mosquito and human innate immune defenses can detect WNV infection and induce the expression of antiviral effectors, so-called viral restriction factors, to control viral propagation. Conversely, WNV has developed countermeasures to escape these host defenses, thus establishing a constant arms race between the virus and its hosts. Our review intends to cover most of the current knowledge on viral restriction factors as well as WNV evasion strategies in mosquito and human cells in order to bring an updated overview on WNV–host interactions. Full article

Repeated reactivations of latent herpes simplex virus type-1 (HSV-1) in the central nervous system (CNS) may contribute to neurodegeneration in Alzheimer’s disease (AD) patients. Immune response is a key element for the control of viral reactivation. HSV-1 uses a number of strategies to evade immune recognition, Immunoglobulin G 3 (IgG₃) alone counteracts humoral immunoevasion, as it is the only IgG subclass that is not blocked by the HSV-1 Fc receptor, a protein that protects virion and infected cells from antibody-mediated effector mechanisms. We examined HSV-1-specific IgG₃ titers in serum of AD (n = 70) and mild cognitive impairment (MCI) (n = 61) subjects comparing the results to those of 67 age- and sex-matched healthy controls (HC); associations between MRI-determined brain cortical health and HSV-1-specific IgG₃ were analyzed in a subgroup of AD and MCI subjects. HSV-1-specific IgG₃ were more frequently detected in MCI compared to AD and HC subjects. Significant inverse correlations were found between IgG₃ titers and brain cortical thickness in areas typically involved in dementia and HSV-1 encephalitis in AD patients; interestingly, this negative correlation was much less important in MCI subjects. All together these results suggest that in AD an inefficient IgG₃ humoral immune response, failing to block viral replication, contributes to progressive neurodegeneration. Full article

Currently available commercial foot-and-mouth disease (FMD) vaccines have various limitations, such as the slow induction and short-term maintenance of antibody titers. Therefore, a novel FMD vaccine that can rapidly induce high neutralizing antibody titers to protect the host in early stages of an FMD virus infection, maintain high antibody titers for long periods after one vaccination dose, and confer full protection against clinical symptoms by simultaneously stimulating cellular and humoral immunity is needed. Here, we developed immunopotent FMD vaccine strains A-3A and A-HSP70, which elicit strong initial cellular immune response and induce humoral immune response, including long-lasting memory response. We purified the antigen (inactivated virus) derived from these immunopotent vaccine strains, and evaluated the immunogenicity and efficacy of the vaccines containing these antigens in mice and pigs. The immunopotent vaccine strains A-3A and A-HSP70 demonstrated superior immunogenicity compared with the A strain (backbone strain) in mice. The oil emulsion-free vaccine containing A-3A and A-HSP70 antigens effectively induced early, mid-term, and long-term immunity in mice and pigs by eliciting robust cellular and humoral immune responses through the activation of co-stimulatory molecules and the secretion of proinflammatory cytokines. We successfully derived an innovative FMD vaccine formulation to create more effective FMD vaccines. Full article

Pneumonia is the most frequent severe medical complication after stroke. An overactivation of the cholinergic signaling after stroke contributes to immunosuppression and the development of spontaneous pneumonia caused by Gram-negative pathogens. The α7 nicotinic acetylcholine receptor (α7nAChR) has already been identified as an important mediator of the anti-inflammatory pathway after stroke. However, whether the α2, α5 and α9/10 nAChR expressed in the lung also play a role in suppression of pulmonary innate immunity after stroke is unknown. In the present study, we investigate the impact of various nAChRs on aspiration-induced pneumonia after stroke. Therefore, α2, α5, α7 and α9/10 nAChR knockout (KO) mice and wild type (WT) littermates were infected with Streptococcus pneumoniae (S. pneumoniae) three days after middle cerebral artery occlusion (MCAo). One day after infection pathogen clearance, cellularity in lung and spleen, cytokine secretion in bronchoalveolar lavage (BAL) and alveolar-capillary barrier were investigated. Here, we found that deficiency of various nAChRs does not contribute to an enhanced clearance of a Gram-positive pathogen causing post-stroke pneumonia in mice. In conclusion, these findings suggest that a single nAChR is not sufficient to mediate the impaired pulmonary defense against S. pneumoniae after experimental stroke. Full article

Many vaccine candidates against visceral leishmaniasis (VL) have been proposed; however, to date, none of them have been efficacious for the human or canine disease. On this basis, the design of leishmaniasis vaccines has been constantly changing, and the use of approaches to select specific epitopes seems to be crucial in this scenario. The ability to predict T cell-specific epitopes makes immunoinformatics an even more necessary approach, as in VL an efficient immune response against the parasite is triggered by T lymphocytes in response to Leishmania spp. immunogenic antigens. Moreover, the success of vaccines depends on the capacity to generate long-lasting memory and polyfunctional cells that are able to eliminate the parasite. In this sense, our study used a combination of different approaches to develop potential chimera candidate vaccines against VL. The first point was to identify the most immunogenic epitopes of Leishmania infantum proteins and construct chimeras composed of Major histocompatibility complex (MHC) class I and II epitopes. For this, we used immunoinformatics features. Following this, we validated these chimeras in a murine model in a thorough memory study and multifunctionality of T cells that contribute to a better elucidation of the immunological protective mechanisms of polyepitope vaccines (chimera A and B) using multicolor flow cytometry. Our results showed that in silico-designed chimeras can elicit polyfunctional T cells producing T helper (Th)1 cytokines, a strong immune response against Leishmania antigen, and the generation of central and effector memory T cells in the spleen cells of vaccinated animals that was able to reduce the parasite burden in this organ. These findings contribute two potential candidate vaccines against VL that can be used in further studies, and help in this complex field of vaccine development against this challenging parasite. Full article

Vaccination is one of the most successful strategies to prevent human infectious diseases. Combinatorial adjuvants have gained increasing interest as they can stimulate multiple immune pathways and enhance the vaccine efficacy of subunit vaccines. We investigated the adjuvanticity of Aluminum (alum) in combination with rASP-1, a protein adjuvant, using the Middle East respiratory syndrome coronavirus MERS-CoV receptor-binding-domain (RBD) vaccine antigen. A highly enhanced anti-MERS-CoV neutralizing antibody response was induced when mice were immunized with rASP-1 and the alum-adjuvanted RBD vaccine in two separate injection sites as compared to mice immunized with RBD + rASP-1 + alum formulated into a single inoculum. The antibodies produced also significantly inhibited the binding of RBD to its cell-associated receptor. Moreover, immunization with rASP-1 co-administered with the alum-adjuvanted RBD vaccine in separate sites resulted in an enhanced frequency of TfH and GC B cells within the draining lymph nodes, both of which were positively associated with the titers of the neutralizing antibody response related to anti-MERS-CoV protective immunity. Our findings not only indicate that this unique combinatorial adjuvanted RBD vaccine regimen improved the immunogenicity of RBD, but also point to the importance of utilizing combinatorial adjuvants for the induction of synergistic protective immune responses. Full article

Vaccines against Porcine circovirus type 2 (PCV2) have been studied intensely and found to be effective in decreasing mortality and improving growth in swine populations. In this study, interleukin-23 (IL-23) gene was cloned from peripheral blood mononuclear cells (PBMCs) of Tibetan pigs and inserted into a eukaryotic VR1020 expression vector-VRIL23. Coated with chitosan (CS), the VRIL23-CS was intramuscularly injected into 3-week-old piglets with PCV2 vaccine. The blood was collected after vaccination at 0, 1, 2, 4, 8, and 12 weeks, respectively, to detect the immunological changes. The IgG2a and specific PCV2 antibodies were detected using ELISA, and blood CD4+ and CD8+ T cells were quantified by flow cytometry. Quantitative fluorescence PCR was used to evaluate the expression of immune genes. The results indicate that leukocytes, erythrocytes, and CD4+ and CD8+ T cells increased significantly in the blood of VRIL23-CS inoculated piglets in comparison with the control (p < 0.05) and so did the IgG2a and PCV2 antibodies. In addition, the expressions of Toll-like receptor (TLR) 2, TLR7, cluster of differentiation (CD) 45, IL-15, IL-12, signal transducer and activator of transcription (STAT)1, STAT2, STAT3, STAT4, and B-cell lymphoma (Bcl)-2 genes were also obviously higher in the VRIL23-CS inoculated pigs at different time points (p < 0.05). Overall, the results demonstrated that VRIL23-CS can enhance the comprehensive immune responses to PCV2 vaccine in vivo and has the promising potential to be developed into a safe and effective adjuvant to promote the immunity of pig against PCV disease. Full article

Background: The yellow fever (YF) vaccination is recommended by the WHO for people traveling or living in endemic areas at risk for yellow fever infections in Africa and South America. Although the live attenuated yellow fever vaccine is a safe and efficient vaccine, rare serious adverse events after vaccination have been reported. Case presentation: We present the case of a 74-year-old male with multiorgan failure after yellow fever vaccination for a trip to Brazil. The patient required admission to the intensive care unit with a prolonged stay due to severe organ dysfunction. Five days after the YF vaccination, the patient experienced nausea, vomiting, diarrhea, and general illness. Three days later he sought medical attention and was transferred to the University Hospital Heidelberg with beginning multiorgan failure and severe septic shock, including hypotonia, tachypnea, thrombopenia, and acute renal failure the same day. Within one week after vaccination, antibodies against YF virus were already detectable and progressively increased over the next two weeks. Viral RNA was detected in serum on the day of admission, with a viral load of 1.0 × 10⁵ copies/mL. The YF virus (YFV) RNA was also present in tracheal secretions for several weeks and could be detected in urine samples up to 20 weeks after vaccination, with a peak viral load of 1.3 × 10⁶ copies/mL. After 20 weeks in the ICU with nine weeks of mechanical ventilation, the patient was transferred to another hospital for further recovery. Conclusions: The risk for severe adverse events due to the YF vaccination should be balanced against the risk of acquiring a severe YF infection, especially in elderly travelers. Full article

Background: In Italy, the loss of confidence towards vaccination resulted in low vaccine coverage, also among healthcare workers (HCWs). Indeed, low vaccination coverage among HCWs can lead to dangerous outbreaks of disease, reduce productivity, and increase absenteeism. The aim of this study was to investigate the vaccine coverage and attitudes toward vaccination among HCWs. Methods: A multicenter cross-sectional study was conducted among HCWs referred to all hospitals of the Local Health Authority 02 of Abruzzo Region, Italy. The survey was based on the questionnaire proposed by the H-ProImmune Project. Results: A total of 347 HCWs were enrolled in the study. Of these, 57.3% reported missing diphtheritis-tetanus-pertussis (DTP) vaccination, 50.1% reported missing measles-mumps-rubella (MMR) vaccination, and 62.5% reported missing flu vaccination. Regarding attitudes, other healthcare professionals reported to believe more in natural immunization compared to vaccination (26.5%; p < 0.001), and they were worried about long-term effects of vaccination (10.2%; p = 0.044). Conclusions: This survey showed all vaccination coverage considered resulted below the 95% threshold. Training on vaccination and mandatory measures may be needed in order to achieve better coverage. Full article

A majority of hepatocellular carcinoma (HCC) develops in the setting of persistent chronic inflammation as immunological mechanisms have been shown to play a vital role in the initiation, growth and progression of tumours. The index review has been intended to highlight ongoing immunological changes in the hepatic parenchyma responsible for the genesis and progression of HCC. The in-situ vaccine effect of radiofrequency (RF) is through generation tumour-associated antigens (TAAs), following necrosis and apoptosis of tumour cells, which not only re-activates the antitumour immune response but can also act in synergism with checkpoint inhibitors to generate a superlative effect with intent to treat primary cancer and distant metastasis. An improved understanding of oncogenic responses of immune cells and their integration into signaling pathways of the tumour microenvironment will help in modulating the antitumour immune response. Finally, we analyzed contemporary literature and summarised the recent advances made in the field of targeted immunotherapy involving checkpoint inhibitors along with RF application with the intent to reinstate antitumour immunity and outline future directives in very early and early stages of HCC. Full article

African Animal Trypanosomiasis (AAT) is a disease caused by pathogenic trypanosomes which affects millions of livestock every year causing huge economic losses in agricultural production especially in sub-Saharan Africa. The disease is spread by the tsetse fly which carries the parasite in its saliva. During the disease progression, the cattle are prominently subjected to anaemia, weight loss, intermittent fever, chills, neuronal degeneration, congestive heart failure, and finally death. According to their different genetic programs governing the level of tolerance to AAT, cattle breeds are classified as either resistant or susceptible. In this study, we focus on the cattle breeds N’Dama and Boran which are known to be resistant and susceptible to trypanosomiasis, respectively. Despite the rich literature on both breeds, the gene regulatory mechanisms of the underlying biological processes for their resistance and susceptibility have not been extensively studied. To address the limited knowledge about the tissue-specific transcription factor (TF) cooperations associated with trypanosomiasis, we investigated gene expression data from these cattle breeds computationally. Consequently, we identified significant cooperative TF pairs (especially $DBP-PPARA$ and $DBP-THAP1$ in N’Dama and $DBP-PAX8$ in Boran liver tissue) which could help understand the underlying AAT tolerance/susceptibility mechanism in both cattle breeds. Full article

Background: Recent studies have shown preliminary evidence that vaccination against human papillomavirus (HPV) could decrease the risk of persistent/recurrent HSIL in women treated for high-grade cervical intraepithelial lesion (HSIL). We aimed to determine the benefits of HPV vaccination in patients undergoing conization for HSIL in real-life conditions and evaluate vaccination compliance associated with different funding policies. Methods: From January 2013 to July 2018, 265 women underwent conization in our center. From January 2013 to July 2017, treated patients (n = 131) had to pay for the vaccine, whereas after July 2017 the vaccine was publicly funded and free for treated women (n = 134). Post-conization follow-up controls were scheduled every six months with a Pap smear, HPV testing, and a colposcopy. Results: 153 (57.7%) women accepted vaccination (vaccinated group), and 112 (42.3%) refused the vaccine (non-vaccinated group). Persistent/recurrent HSIL was less frequent in vaccinated than in non-vaccinated women (3.3% vs. 10.7%, p = 0.015). HPV vaccination was associated with a reduced risk of persistent/recurrent HSIL (OR 0.2, 95%CI: 0.1–0.7, p = 0.010). Vaccination compliance increased when the vaccine was publicly funded (from 35.9% [47/131] to 79.1% [106/134], p < 0.001). Conclusions: HPV vaccination in women undergoing conization is associated with a 4.5-fold reduction in the risk of persistent/recurrent HSIL. Vaccination policies have an important impact on vaccination compliance. Full article

Myxoma virus (MYXV) is the prototypic member of the Leporipoxvirus genus of the Poxviridae family of viruses. In nature, MYXV is highly restricted to leporids and causes a lethal disease called myxomatosis only in European rabbits (Oryctologous cuniculus). However, MYXV has been shown to also productively infect various types of nonrabbit transformed and cancer cells in vitro and in vivo, whereas their normal somatic cell counterparts undergo abortive infections. This selective tropism of MYXV for cancer cells outside the rabbit host has facilitated its development as an oncolytic virus for the treatment of different types of cancers. Like other poxviruses, MYXV possesses a large dsDNA genome which encodes an array of dozens of immunomodulatory proteins that are important for host and cellular tropism and modulation of host antiviral innate immune responses, some of which are rabbit-specific and others can function in nonrabbit cells as well. This review summarizes the functions of one such MYXV host range protein, M029, an ortholog of the larger superfamily of poxvirus encoded E3-like dsRNA binding proteins. M029 has been identified as a multifunctional protein involved in MYXV cellular and host tropism, antiviral responses, and pathogenicity in rabbits. Full article

We recently described a cytotoxic CD8⁺ T lymphocyte (CTL) vaccine platform based on the intramuscular (i.m.) injection of DNA eukaryotic vectors expressing antigens of interest fused at the C-terminus of HIV-1 Nef^mut, i.e., a functionally defective mutant that is incorporated at quite high levels into exosomes/extracellular vesicles (EVs). This system has been proven to elicit strong CTL immunity against a plethora of both viral and tumor antigens, as well as inhibit both transplantable and orthotopic tumors in mice. However, a number of open issues remain regarding the underlying mechanism. Here we provide evidence that hindering the uploading into EVs of Nef^mut-derived products by removing the Nef^mut N-terminal fatty acids leads to a dramatic reduction of the downstream antigen-specific CD8⁺ T-cell activation after i.m. injection of DNA vectors in mice. This result formally demonstrates that the generation of engineered EVs is part of the mechanism underlying the in vivo induced CD8⁺ T-cell immunogenicity. Gaining new insights on the EV-based vaccine platform can be relevant in view of its possible translation into the clinic to counteract both chronic and acute infections as well as tumors. Full article

Introduction: Diverse algorithms for signal detection exist. However, inconsistent results are often encountered among the algorithms due to different levels of specificity used in defining the adverse events (AEs) and signal threshold. We aimed to explore potential safety signals for two pneumococcal vaccines in a spontaneous reporting database and compare the results and performances among the algorithms. Methods: Safety surveillance was conducted using the Korea national spontaneous reporting database from 1988 to 2017. Safety signals for pneumococcal vaccine and its subtypes were detected using the following the algorithms: disproportionality methods comprising of proportional reporting ratio (PRR), reporting odds ratio (ROR), and information component (IC); empirical Bayes geometric mean (EBGM); and tree-based scan statistics (TSS). Moreover, the performances of these algorithms were measured by comparing detected signals with the known AEs or pneumococcal vaccines (reference standard). Results: Among 10,380 vaccine-related AEs, 1135 reports and 101 AE terms were reported following pneumococcal vaccine. IC generated the most safety signals for pneumococcal vaccine (40/101), followed by PRR and ROR (19/101 each), TSS (15/101), and EBGM (1/101). Similar results were observed for its subtypes. Cellulitis was the only AE detected by all algorithms for pneumococcal vaccine. TSS showed the best balance in the performance: the highest in accuracy, negative predictive value, and area under the curve (70.3%, 67.4%, and 64.2%). Conclusion: Discrepancy in the number of detected signals was observed between algorithms. EBGM and TSS calibrated noise better than disproportionality methods, and TSS showed balanced performance. Nonetheless, these results should be interpreted with caution due to a lack of a gold standard for signal detection. Full article