FbaA- and M protein-based multi-epitope vaccine elicits strong protective immune responses against group A streptococcus in mouse model

We report the construction of a recombinant multivalent vaccine against group A streptococcus (GAS), designated F7M5. It contains seven predominant epitopes of FbaA identified by phage display technology, five non-tissue cross-reactive M protein fragments expressed on four selected serotypes prevalent in China, a Trojan antigen (TA) and a poly-alanine DR epitope (PADRE). BALB/c mice were immunized subcutaneously with F7M5 formulated with Freund's adjuvant, using recombinant FbaA and M protein in parallel as control. Using enzyme-linked immunosorbent assay (ELISA), mouse immune sera were assayed for IgG titers, IgG subclasses, and binding of F7M5 with M1GAS. Results indicated that the multivalent vaccine was highly immunogenic and elicited a balanced IgG1/IgG2a response. We also tested the reactivity of F7M5 to antistreptolysin O (ASO) antibodies in sera of GAS-infected patients and found a 95.8% positive rate, indicating that the epitopes of the vaccine were widely expressed in the prevalent serotypes of GAS. More importantly, the F7M5 vaccine elicited strong protective immune responses against lethal-dose challenge with a survival rate of 90%, but induced no cross-reactions or pathological lesions in mouse model, suggesting that F7M5 can be further developed as an effective and safe anti-GAS vaccine.     

Prophylactic and therapeutic vaccines against sporotrichosis. Feasibility and prospects

Sporotrichosis is an emergent subcutaneous mycosis of humans and some animals caused by dimorphic fungi of the genus Sporothrix. The disease occurs worldwide but is endemic or hyperendemic in tropical and subtropical areas. The epidemiology of the disease is changing dramatically, and it is now considered an important zoonosis with high morbidity rates, principally in Brazil, and an opportunistic infection in immunocompromised patients. Due to the limited options currently available to treat invasive fungal infections, including sporotrichosis, and the emergence of drug resistance and toxicity, the development of anti-Sporothrix vaccines has become an area of great interest. This work provides a brief analysis of the feasibility of the development of prophylactic and therapeutic vaccines against sporotrichosis, the main advances achieved to date, future challenges and prospects.     

Consistency of Bordetella pertussis vaccine seed strains and potency of whole-cell pertussis vaccine still in use in Poland

In Poland, where the wP vaccine has been used since 1960, pertussis rates increased in the mid-1990s. In 2012, the rate of pertussis recognised by surveillance was unexpectedly found to be two-fold higher than in the previous decade. Quality measures on potency and vaccine working seeds were introduced, to confirm the possible impact of manufacturing inconsistency or potency lowering on the observed increase in pertussis. Shewhart charts on potency values for lots released between 2001 and 2013 did not reveal any significant fluctuations. Working seeds of three vaccine strains used within last decade for wP manufacturing belong to the PFGE group III and were highly related. According to PFGE and SDS-PAGE data, all vaccine strains were found consistent according profiling on the genomic and protein levels. According to the sequencing data, they harboured ptxA2, ptxC1, prn1, fim2-1, fim3-1, tcfA2, ptxP1 and were assigned as MLST-2 type. Other factors apart from vaccine manufacturing inconsistency might be responsible for the increase in pertussis noted in 2012 in Poland.     

Epitope-Analyzer: A structure-based webtool to analyze broadly neutralizing epitopes

The antigenic epitope regions of pathogens (e.g., viruses) are recognized by antibodies (Abs) and subsequently cleared by the host immune system, thereby protecting us from disease. Some of these epitopes are conserved among different variants or subgroups of pathogens (e.g., Influenza (FLU) viruses, Coronaviruses), hence can be targeted for potential broad-neutralization. Here we report a web-based tool, Epitope Analyzer (EA), that rapidly identifies conformational epitope and paratope residues in an antigen–antibody complex structure. Furthermore, the tool provides the ways and means to analyze broadly neutralizing epitopes by comparing the equivalent epitope residues in similar antigen structures. The similarity in the epitope residues between (multiple) pairs of similar antigen molecules suggest the presence of conserved epitopes that can be targeted by broadly neutralizing antibodies. These details can be used as a guide in developing effective treatments, such as the design of novel vaccines and formulation of cocktail of broadly neutralizing antibodies, against multiple variants or subgroups of viruses. The web application can be freely accessed from the URL, http://viperdb.scripps.edu/ea.php.     

Regulation of immunity to Plasmodium: Implications from mouse models for blood stage malaria vaccine design

Malaria, a disease caused by the protozoan parasite Plasmodium, remains a serious healthcare problem in developing countries worldwide. While the host-parasite relationship in humans has been difficult to determine, the pliability of murine malaria models has enabled valuable contributions to the understanding of the pathogenesis of disease. Although no single model reflects precisely malaria infection of the human, different models collectively provide important information on the mechanisms of protective immunity and immunopathogenesis. This review summarizes progress towards understanding the broad spectrum of immune responsiveness to the blood stages of the malaria parasite during experimental infections in mice and highlights how examination of murine malarias sheds light on the factors involved in the modulation of vaccine-potentiated immunity.     

In vitro evaluation methods for Clostridium botulinum type C and D vaccines

Reagents were prepared for use in ELISAs to determine the concentration of the antigenic components of Clostridium botulinum type C and D. The results obtained were compared with the L+dose assay and a good correlation was found between the two assays for measurement of the C and D neurotoxin concentration. These ELISAs were also used to determine the concentration of the neurotoxins in toxoid form. The relationship between the C neurotoxin dose, in toxoid form, and the immune response in guinea pigs could be deduced from the data obtained. The relationship for the D neurotoxin was not that clear, as the same concentration of the antigen resulted in variable potency values. However, these ELISAs can be used to formulate the concentration of the C and D components in the final bivalent vaccine. Replacement of the preliminary potency assay on the monovalent components after production with the in vitro assays will shorten the total production time of the vaccine by about 60 days. The economical and ethical implications are the reduction in the use of animals to evaluate the vaccine.     

USDA regulatory guidelines and practices for veterinary Leptospira vaccine potency testing

Batch-release potency testing of leptospiral vaccines licensed by the United States Department of Agriculture (USDA) historically was conducted through animal vaccination-challenge models. The hamster vaccination-challenge assay was Codified in 1974 for bacterins containing Leptospira pomona, Leptospira icterohaemorrhagiae, and Leptospira canicola, and in 1975 for bacterins containing Leptospira grippotyphosa. In brief, 10 hamsters are vaccinated with a specified dilution of bacterin. After a holding period, the vaccinated hamsters, as well as nonvaccinated controls, are challenged with virulent Leptospira and observed for mortality. Eighty percent of vaccinated hamsters must survive in the face of a valid challenge. The high cost of the Codified tests, in terms of monetary expense and animal welfare, prompted the Center for Veterinary Biologics (CVB) to develop ELISA alternatives for them. Potency tests for other serogroups, such as Leptospira hardjo-bovis, that do not have Codified requirements for potency testing continue to be examined on a case-by-case basis.     

Irradiated tumor cells adenovirally engineered to secrete granulocyte/macrophage-colony-stimulating factor establish antitumor immunity and eliminate pre-existing tumors in syngeneic mice

The specific aim of this study was to examine the prophylactic as well as the therapeutic efficacies of irradiated mouse CT26 colon cancer cells, infected with recombinant adenoviruses harboring cDNAs specific for granulocyte macrophage-colony-stimulating factor (GM-CSF), interferon (IFN-γ) and monocyte chemotactic protein1 (MCP-1). Results showed that tumor cells secrete the respective cytokines for several days after infection and subsequent irradiation. Vaccination with irradiated GM-CSF-secreting CT26 cells protected 90% of syngeneic mice challenged with live parental cells. On the other hand, vaccination with irradiated IFNγ or MCP-1-secreting CT26 cells totally failed to protect mice from tumor development after challenge with parental cells. None of the tumor-free mice initially vaccinated with irradiated GM-CSF-producing CT26 cells developed tumor upon repeated challenge with parental cells during the entire observation period. The establishment of specific and long-lasting antitumor immunity following vaccination with GM-CSF-producing tumor cells requires the simultaneous presence of GM-CSF and tumor antigen at the vaccine site. Depletion of CD8⁺ cells, but not CD4⁺ cells, blocked the vaccine efficacy of GM-CSF-producing tumor cells. Subcutaneous injection of irradiated GM-CSF-producing CT26 cells also effectively prevented the growth of a small load of parental tumor that was implanted 3 days earlier or the development of metastatic foci in the lung from intravenously injected parental cells either 7 days before or 3 days after vaccination. Our data thus show that, in these experimental tumor models, subcutaneous injection of irradiated tumor cells adenovirally, transduced with the GM-CSF gene leads not only to prevention of growth of subsequently implanted tumor but also to elimination of pre-existing and metastatic tumors.