Influenza is a major concern across healthcare environments. Annual vaccination of healthcare workers (HCWs) remains essential for maintaining the health and availability of HCWs, as well as influenza prevention in healthcare environments. Yet, annual vaccination coverage among HCWs continues to be below recommended standards during pandemic (pH1N1) and non-pandemic (sINFLU) influenza seasons. The primary aim of this research is to inform the design and implementation of effective HCW targeted influenza vaccination campaigns via a 1) systematic review of the existing literature on HCW pH1N1 vaccination, 2) qualitative content analysis of motivators and barriers to HCW pH1N1 and sINFLU vaccination, as well as 3) quantitative regression analysis of modifiable factors predicting pH1N1 and sINFLU vaccination. The qualitative and quantitative analysis processes were applied to data collected from a large-scale multi-professional sample of HCWs. Findings from all analysis sections were found to be consistent. Most attitudes, beliefs, motivators, and barriers influencing HCW influenza vaccination were similar for pH1N1 and sINFLU vaccinations. Yet, a number of notable differences were also identified. HCWs were likely to accept vaccination if they perceived, 1) vaccination to be safe, 2) vaccination to be protective against influenza for self, loved ones, patients or communities, and 3) influenza to be a serious and severe infection to self and others. Additionally, encouragement from supervisors and colleagues, physicians, and loves ones also enhanced vaccine uptake. Most HCWs avoided vaccination because of 1) limited knowledge or misinformation about vaccination, 2) concern for vaccine induced side-effects and 3) assuming vaccination was not a requirement for healthy adults. With respect to pH1N1 vaccination, mass media communications, perceptions of novel vaccinations, and rapid vaccine development processes especially deterred HCW pH1N1 vaccination. Future vaccination programs targeting HCWs should look towards influencing HCWs’ vaccination attitudes and promoting pro-vaccination cultures in healthcare workplaces.

Influenza is a major concern across healthcare environments. Annual vaccination of healthcare workers (HCWs) remains essential for maintaining the health and availability of HCWs, as well as influenza prevention in healthcare environments. Yet, annual vaccination coverage among HCWs continues to be below recommended standards during pandemic (pH1N1) and non-pandemic (sINFLU) influenza seasons. The primary aim of this research is to inform the design and implementation of effective HCW targeted influenza vaccination campaigns via a 1) systematic review of the existing literature on HCW pH1N1 vaccination, 2) qualitative content analysis of motivators and barriers to HCW pH1N1 and sINFLU vaccination, as well as 3) quantitative regression analysis of modifiable factors predicting pH1N1 and sINFLU vaccination. The qualitative and quantitative analysis processes were applied to data collected from a large-scale multi-professional sample of HCWs. Findings from all analysis sections were found to be consistent. Most attitudes, beliefs, motivators, and barriers influencing HCW influenza vaccination were similar for pH1N1 and sINFLU vaccinations. Yet, a number of notable differences were also identified. HCWs were likely to accept vaccination if they perceived, 1) vaccination to be safe, 2) vaccination to be protective against influenza for self, loved ones, patients or communities, and 3) influenza to be a serious and severe infection to self and others. Additionally, encouragement from supervisors and colleagues, physicians, and loves ones also enhanced vaccine uptake. Most HCWs avoided vaccination because of 1) limited knowledge or misinformation about vaccination, 2) concern for vaccine induced side-effects and 3) assuming vaccination was not a requirement for healthy adults. With respect to pH1N1 vaccination, mass media communications, perceptions of novel vaccinations, and rapid vaccine development processes especially deterred HCW pH1N1 vaccination. Future vaccination programs targeting HCWs should look towards influencing HCWs’ vaccination attitudes and promoting pro-vaccination cultures in healthcare workplaces.

BACKGROUND: The widespread use of vaccines led to significant decline in multiple potentially fatal infectious diseases. Recently, there has been an increase in vaccine hesitancy. Measles and pertussis outbreaks throughout the United States have put a spotlight on this urgent healthcare issue. Motivational interviewing is a counseling tactic that is gaining popularity and is being studied for its efficacy in preventative medicine and psychological disorders. It aims to inspire people to make behavioral changes through collaborative relationships with their provider by understanding how current actions do not translate into their health goals. LITERATURE REVIEW FINDINGS: Vaccine hesitancy is growing. Communities with decreased immunization rates are associated with a higher risk of disease outbreak. Increasing rates of undervaccinated children are likely due to increases in non-medical exemptions. Many parents, regardless of their vaccine hesitancy status, are concerned about vaccine safety. Vaccine hesitant parents refuse vaccines due to philosophical and religious beliefs, conspiracy theories, and safety concerns. Parents feel that providers do not adequately address their concern. Providers report not having the training to discredit parental concerns. The majority of parents describe their child’s pediatrician as their most trusted source of vaccine information. Parents who receive vaccine information from a provider are more likely to comply with the recommended childhood vaccine schedule. The most efficient way to discuss vaccines with parents has yet to be determined. PROPOSED PROJECT: This is a proposed QI research project for the Pediatric Clinic at Boston Medical Center. Providers would be trained in motivational interviewing during several sessions that included lectures and small group practice sessions with systematic feedback. During the intervention, parents who refuse vaccines for their child, aged 0-6 years old, will receive motivational interviewing from the provider. The proportion of the vaccine hesitant parents who accept the offered vaccine after will be analyzed. The pre and post intervention vaccination rates for the entire clinic will also be assessed. Data collection will be preformed through retrospective chart review. The project aims to increase provider confidence on vaccine counseling, educate providers on reasons for hesitancy, and improve compliance with the CDC recommended vaccine schedule. CONCLUSION: While most Americans continue to vaccinate their children according to the CDC’s recommended schedule, constant vigilance is required to maintain high immunization rates to protect our communities. Motivational interviewing is goal-oriented to alter a specific behavior and would allow providers to engage in an open, persuasive dialogue about parental vaccine concerns.

The seasonal influenza (flu) vaccine has been shown to prevent flu outbreaks that can cause debilitating effects on the body and even death. Underserved members of Black communities are more likely to refuse the flu vaccine than are persons of other ethnicities. The purpose of the project was to determine from a needs assessment the reasons for flu vaccine refusal in the Black population of an inner city clinic in order to develop tailored communication and nursing actions that promote awareness of the flu vaccine's importance and safety. The health belief model constructs (perceived susceptibility, perceived severity, perceived benefits, and perceived barriers) were used to guide the project. A survey based on the constructs of the health belief model was administered to a convenience sample of 40 adult patients in an inner city clinic who completed the anonymous survey while they waited for the physician. Descriptive statistics showed that adults ages 18 to 36, who were the largest group of respondents (n = 33), agreed to be vaccinated and believed the flu to be a serious disease for their age group. Reported barriers to vaccination included finding time to get vaccinated and the belief that the vaccine causes the flu. The findings supported development of an annual seasonal flu vaccine campaign that included verbal and written education, informational posters, social media messages, and a standing order to offer and administer the injection to all adults served by the practice. Social change implications are expected to include decreased morbidity and mortality from flu among the Black inner city patients and closer alignment of the clinic with the Healthy People 2020 vaccination goals.

Human rotavirus (HRV) is a major causative agent of acute gastroenteritis (AGE), which causes severe dehydrating diarrhea in children under the age of five and results in up to 215,000 deaths worldwide each year. There are two live oral attenuated vaccines licensed for use in the United States that are highly effective in high-income countries but much less so in low-and middle-income countries (LMICs). Several factors contributing to decreased efficacy in these areas include chronic malnutrition, gut dysbiosis, and concurrent viral infection. Along with this, currently used vaccines require constant cold-chain storage to maintain vaccine stability, and those resources can be scarce in LMICs. These areas continue to maintain a high burden of HRV morbidity and mortality, and more efficacious vaccines are needed. The gnotobiotic (Gn) pig model of HRV infection and diarrhea has long been used in the evaluation of novel HRV vaccines due to Gn pigs' susceptibility to HRV infection, development of clinical signs, histopathological changes in the intestine, and the infection kinetics that mimic those seen in human infants. The first project in this dissertation used the Gn pig model to evaluate a thermostable live oral attenuated vaccine administered as a dissolvable film. Two doses of the tetravalent dissolvable film vaccine conferred significant protection from virus shedding by delaying its onset and reducing peak titers in feces. It also significantly delayed the onset of diarrhea and reduced the duration and area under the curve (AUC) of diarrhea. The dissolvable film was highly immunogenic, inducing high titers of serum virus neutralizing (VN) antibodies specific to each of the four G-types included in the vaccine formulation, HRV-specific serum IgA and IgG, and intestinal IgA. These data confirm the thermostable platform as a useful alternative to liquid vaccines that require cold-chain. The second project evaluated three mRNA-based nonreplicating vaccine candidates in the Gn pig model. All three mRNA candidates encoded a universal CD4+ T cell epitope, P2, derived from tetanus toxoid, fused with the encoded VP8* from P[4], P[6], and P[8] HRVs. Two candidates also encoded for a lumazine synthase (LS) domain fused with the P2-VP8*. A dose response study of the LS-P2-VP8* candidates was conducted simultaneously. Significant protection against virus shedding was induced by all three candidates, with LS-P2-VP8* candidates inducing significantly higher VP8*-specific serum IgG. All three candidates induced significantly higher numbers of P[8]-VP8*-specific IgG antibody-secreting cells (ASCs) and IFN-γ-producing T cells in the ileum, spleen and blood. These data provide guidance for further development of the relatively new mRNA-based technology for use in HRV vaccine development. In the final study of this dissertation, we used the Gn pig model of both P[8] and P[6] HRV infection to evaluate a cocktail nanoparticle-based HRV vaccine. This vaccine was made up of an S60 nanoparticle, self-assembled from the S domain of the human norovirus capsid protein. The exposed C-termini on the S60 nanoparticle were utilized as an antigen display platform, where VP8* from P[4], P[6] and P[8] HRVs was fused. This vaccine was tested as both a two-dose intramuscular (IM) regimen, or as an IM booster preceded by an oral priming immunization with commercial monovalent Rotarix®. Pigs were challenged with either P[6] or P[8] HRV to evaluate cross-protection of the nanoparticle vaccine. Both regimens were highly immunogenic, inducing high titers of serum VN, IgG and IgA antibodies. Furthermore, the prime-boost regimen conferred significant protection against virus shedding in P[8] HRV-challenged pigs as evidenced by the shortened duration of fecal virus shedding. There was also significant protection in P[6] HRV-challenged pigs vaccinated with the prime-boost regimen, as evidenced by the shortened duration, reduced mean peak titer and AUC of virus shedding. Prime-boost-vaccinated pigs challenged with P[8] HRV had significantly higher P[8]-specific IgG ASCs in the spleen post-challenge. Prime-boost-vaccinated pigs challenged with P[6] HRV had significantly higher numbers of P[6] and P[8]-specific IgG ASCs in the ileum, as well as significantly higher numbers of P[8]-specific IgA ASCs in the spleen post-challenge. Oral priming followed by parenteral boosting appears to be a promising vaccination strategy for HRV and these data warrant further investigation into this regimen. Through these studies, we improved our understanding of the effect of different vaccination routes and formulations in the effectiveness of conferring protection against an enteric virus. The knowledge will facilitate the development of more effective vaccination strategies against HRV, the leading cause of infantile diarrhea in LMICs, as well as other enteric viruses. / Doctor of Philosophy / Human rotavirus (HRV) is a major causative agent of acute gastroenteritis (AGE) in children under the age of five. Acute gastroenteritis is characterized by nausea, vomiting, and potentially deadly dehydrating diarrhea. There are two highly effective vaccines licensed for use in the United States; however, these vaccines are much less effective in low- and middle-income countries (LMICs), where HRV disease burden is the highest. There are several reasons thought to be responsible for the decrease in effectiveness seen in these areas, including chronic malnutrition and gut dysbiosis. Non-biological reasons for decreased efficacy may include the breakdown of cold-chain storage for these vaccines, which require constant low temperature storage that is often unavailable in LMICs. Thermostable vaccines are necessary for increasing vaccine distribution and efficacy in these areas. Because many of the biologic factors thought to interfere with the effectiveness of these vaccines appear to be confined to the gastrointestinal tract, development of next generation HRV vaccines has focused on the parenteral route of administration. The gnotobiotic (Gn) pig model is a highly relevant animal model that has been used for decades to evaluate novel HRV vaccine efficacy. Our first study evaluated a thermostable, dissolvable live oral vaccine administered as a dissolvable film in our Gn pig model. Two doses of this vaccine significantly reduced the severity of diarrhea and virus shedding in the stool. Our second study evaluated three mRNA-based intramuscular (IM) vaccines in the Gn pig model. Three doses of all mRNA candidates provided significant protection from virus shedding in the stool, as well as inducing the production of strong HRV-specific antibodies in the serum and high numbers of virus-specific T cells in the tissues. In our final study, we evaluated a nanoparticle-based vaccine as a two-dose IM regimen or as an IM booster preceded by an oral immunization using the commercially available Rotarix® vaccine. The prime-boost regimen significantly shortened the duration and severity of virus shedding in the stool. We also detected more cross-strain HRV-specific antibody-secreting cells in the tissues. All three vaccines evaluated in this dissertation offer differing novelty in the field of HRV vaccine development, and the Gn pig model has been instrumental in the evaluation of these vaccines.

A major obstacle to the development of dengue virus (DENV) vaccines has been the need to immunise concurrently against each of the four DENV serotypes in order to avoid sensitising recipients to developing severe DENV infections. A problem already encountered with live attenuated tetravalent DENV vaccines has been the difficulty in eliciting adequate immune responses against all four DENV serotypes in human hosts. This could have been due to variations in the antigenicity and/or the replication rates of the four DENV serotypes. Non-replicating DNA vaccines avoid the issue of different replication rates. Currently, only DENV-1 and DENV-2 DNA vaccines have been evaluated. In this study, a number of DNA vaccines for each of the four DENV serotypes were developed and their immunogenicity was evaluated in outbred mice. These vaccines included DNA vaccines encoding the DENV prM-E protein genes derived from the four DENV serotypes (pVAX-DEN1, -DEN2, -DEN3 and -DEN4), and DNA vaccines encoding DENV prM and hybrid-E protein genes derived from multiple DENV serotypes. The hybrid-E protein genes were constructed by substituting either domains I and II, domain III, and/or the stem-anchor region from the E protein of one DENV serotype with the corresponding region from another DENV serotype. A number of superior DNA vaccines against each of the four DENV serotypes were identified based on their ability to elicit high titres (≥40, FFURNT50) of neutralising antibodies against the corresponding DENV in mice. The superior DNA vaccines against DENV-1 were pVAX-DEN1, pVAX-C2M2E211, pVAX-C2M2E122 and pVAX-C2M1E122. The superior DNA vaccine against DENV-2 was pVAX-C2M1E122 and the superior DNA vaccines against DENV-3 were pVAX-DEN3 and pVAX-C2M3E344. The superior DNA vaccines against DENV-4 were pVAX-C2M3E344, pVAX-C2M4E434 and pVAX-C2M4E433. Each of these DNA vaccines could provide effective protection against infection by the corresponding DENV serotypes. This is the first study to describe the development of DNA vaccines against DENV-3 and DENV-4. However, mice immunised with a tetravalent DENV DNA vaccine, composed of a DNA vaccine encoding the prM-E protein genes from each of the four DENV serotypes (pVAX-DEN1-4), elicited high titres of neutralising antibodies against DENV-1 and DENV-3 only. Nevertheless, the results from this study suggested that a tetravalent DENV DNA vaccine, composed of pVAX-DEN1, pVAX-C2M1E122, pVAX-DEN3 and pVAX-C2M4E434, may provide effective concurrent protection against infection by each of the four DENV serotypes. In addition, mice immunised with pVAX-C2M1E122, which encoded a hybrid-E protein gene derived from DENV-1 and DENV-2, elicited high titres of anti-DENV-1 and anti-DENV-2 neutralising antibodies, and mice immunised with pVAX-C2M3E344, which encoded a hybrid-E protein gene derived from DENV-3 and DENV-4, elicited high titres of anti-DENV-3 and anti-DENV-4 neutralising antibodies. This result suggested that the co-immunisation of these two hybrid-E DNA vaccines also may provide effective concurrent protection against infection by each of the four DENV serotypes. Extracellular E proteins, believed to be in the form of recombinant subviral particles (RSPs), were recovered from the tissue culture supernatant of all DNA vaccine-transfected mammalian cells by ultracentrifugation, except for cells transfected with the pVAX-C2M2E122 hybrid-E DNA vaccine. Western blotting with the monoclonal antibody 4G2 (flavivirus cross-reactive) demonstrated that the extracellular E proteins expressed by the DNA vaccines were synthesized and cleaved in a manner similar to that of native DENV E proteins. In addition, mammalian cells transfected with pVAX-DEN1, pVAX-DEN2 or pVAX-DEN3 secreted higher amounts of extracellular E proteins than cells transfected with pVAX-DEN4. The amount of extracellular E protein secreted by pVAX-DEN4-transfected cells increased when the c-region of the prM/E signal peptidase cleavage site was made more polar. In contrast, decreasing the polarity of the c-region of the C/prM signal peptidase cleavage site of pVAX-DEN4 resulted in no detectable extracellular E proteins from pVAX-DEN4-transfected cells. This result suggested that the amount of extracellular E proteins secreted by cells transfected with DNA expressing the DENV prM-E protein genes may be dependent of the efficiency of C/prM and prM/E protein cleavages by host-derived signal peptidases. Mice immunised with the mutated pVAX-DEN4, which was capable of expressing large amounts of extracellular E proteins in vitro, produced significantly higher concentrations of Th1-type anti-DENV-4 antibodies than mice immunised with the unmodified pVAX-DEN4, but failed to produce detectable levels of anti-DENV-4 neutralising antibodies. In contrast, increasing the ratio of CpG-S to CpG-N motifs in the pVAX-DEN2 DNA vaccine by incorporating either an additional CpG-S motif, or an antibiotic resistance gene with a high ratio of CpG-S to CpG-N motifs, resulted in a significant increase in both the concentration of Th1-type anti-DENV-2 antibodies and the titres of anti-DENV-2 neutralising antibodies in immunised mice. This result suggested that increasing the amount of CpG-S motifs in DENV DNA vaccines may present an simple and effective approach to increasing the immunogenicity of the DENV DNA vaccines.

abstract: Zika virus (ZIKV) outbreaks have been linked to several neurological pathologies in the developing fetus, which can progress to spontaneous abortion and microcephaly in newborns whose mothers were infected with the virus during pregnancy. ZIKV has also been correlated with neurological complications in adults such as Guillain-Barré Syndrome (GBS). ZIKV outbreaks often occur in low income areas with limited access to healthcare. Therefore, there is a need to create a low-cost preventative vaccine against the virus. Mature ZIKV particles contain a lipid bilayer, a positive sense single stranded RNA genome and three structural proteins: the envelope (E), membrane (M) and capsid (C) proteins. Congruently, to other members of the Flaviviridae family, ZIKV proteins are synthesized as a polyprotein precursor which needs to be processed to release the mature structural and non-structural viral proteins. Past studies have determined the ZIKV precursor protein is cleaved by a host furin protease which separates the Pr peptide and the M protein, while the host signal peptidase separates the M and E protein. Processing is important for correct folding of the E protein. In turn, the most important neutralizing antibodies upon infection are directed against epitopes of the E protein. In this work, we used a Bean Yellow Dwarf Viral vector system to transiently express, in Nicotiana benthamiana plants, a portion of the ZIKV polyprotein encoding the Pr, M and E proteins. I further demonstrate that plants can proteolytically process the polyprotein to yield the two integral membrane proteins M and E. These proteins can be shown to co-partition into a soluble membrane-particulate fraction, consistent with formation of enveloped virus-like particles (VLPs). This work provides the first step in creating a low-cost sustainable plant-based production system of ZIKV VLPs that can be explored as a potential component 0f a low-cost prophylactic vaccine against ZIKV. / Dissertation/Thesis / Masters Thesis Molecular and Cellular Biology 2018

Even though influenza vaccinations were provided free to all healthcare workers in the United States, healthcare workers were not 100% compliant. The non-compliance with influenza vaccinations may expose their patients, their families, and the public at large to a high-risk source of influenza infection. This study's research questions included how registered nurses perceived influenza and influenza vaccination; registered nurses' self-reported incidents with influenza vaccination; and factors that contributed to registered nurses' non-compliance with influenza vaccination. Guided by the theory of reasoned action and the theory of planned behavior, the purpose of this qualitative study was to determine the factors that contributed to the non-compliance of registered nurses with receiving the influenza vaccination. Twenty participants from a healthcare facility in Florida were interviewed using an interview guide. Audio data was transcribed to text data; text data was coded and thematically analyzed by using ATLAS.ti software. Results revealed that 70% of registered nurses were afraid of influenza vaccination, while 80% of them saw influenza vaccination as ineffective; 90% of them had bad experiences or have seen colleagues/friends who have had bad experiences after influenza vaccination. In addition, 40% of registered nurses claimed that they already had good immunity, while 20% of them declined influenza vaccination because of personal choices. Research findings from this study may be utilized to bring positive social change to society at large. The findings may be utilized to enhance existing strategies or policies or even help formulate new policies and strategies that would address the concerns of HCWs, especially registered nurses.

Master of Science / Department of Animal Sciences and Industry / David M. Grieger / Mares in estrus can exhibit erratic and fractious behavior that may adversely affect their ease of handling. Current treatments for suppression of estrus in the mare include an oral progestin, Regu-mate® (Hodgson et al., 2005), uterine insertion of a glass ball (Nie et al., 2003), fetal crushing through rectal palpation (Lefranc, 2004) and surgical sterilization (McCue, 2003). Although effective, all of these procedures are problematic for different reasons. Immunization against an endogenous hormone critical to fertility is an attractive alternative in suppressing estrus; especially if it is less intrusive and reversible. This strategy has been demonstrated by targeting gonadotropin-releasing hormone (GnRH) in gilts (Esbenshade and Britt, 1985), ewes (Clarke et al., 1978), mares (Garza et al., 1986), and heifers (Johnson et al., 1988). The antigen developed for this study was produced using the sequence of the bacterial protein, glutathione-S-transferase (GST) linked to three in-tandem repeats of the mammalian GnRH gene coding sequence (GST-GnRH3). Six reproductively sound mares, between the ages of 3 and 8 years, were used in this study. The anti-GnRH group (n=4) received 1 mg of GST-GnRH3 in 2ml of incomplete Freund’s adjuvant (IFA) as the primary injection. Four weeks later, mares received a single booster injection of 0.5mg of GST-GnRH3 in 1ml of IFA. The control mares (n=2) received similar doses of GST protein only, in identical injection volumes of IFA as the anti-GnRH group. The entire duration of the study ran for 22 weeks from early May through September. Ovaries were monitored three times weekly to track follicular growth and ovulation via transrectal ultrasonography. In addition, all mares were exposed to a stallion twice weekly and observed for estrous behavior. Weekly blood samples were collected to evaluate progesterone levels and serum binding of GnRH. The GST-GnRH3 antigen suppressed follicular activity in all treatment mares within 45 days following the second injection. Estrous behavior was suppressed in all but one mare in the anti-GnRH group. When exposed to the stallion, this mare displayed strong estrous behavior for seven weeks despite her lack of ovarian cyclicity. Follicular activity and estrous behavior remained normal in one of the control mares (avg. cycle length = 20 days). For the final 10 weeks of the study, however, the other control mare developed large follicles but failed to ovulate according to the ultrasound data. This mare did not display estrous behavior during this period, and her progesterone levels remained greater than 2 ng/ml for most of the final 10 weeks of the study. Approximately 2 weeks after the booster injection all anti-GnRH mares had progesterone levels of <1ng/ml. GnRH antibody binding peaked two weeks following booster immunization in all treated mares and remained undetectable in control mares throughout the study. The GST-GnRH3 treatment induced GnRH binding, suppressed follicular activity and reduced progesterone concentrations in all four mares. Although estrous behavior was abolished in 3 of the 4 treated mares, one did continue to demonstrate estrous behavior in the presence of a stallion. This dissociation of ovarian activity and estrous behavior was evident in our study with a limited number of animals, but the vaccine does show promise in reducing unwanted estrous behavior.

Filarial infections are major causes of morbidity in the tropics and sub-tropics, afflicting over 150 million people in about 80 countries, causing debilitating symptoms such as elephantiasis (lymphatic filariasis), dermatitis and blindness (onchocerciasis or river blindness). Current control of lymphatic filariais relies on mass drug treatment with diethylcarbamazine（DEC) and albendazole while ivermectin is used against onchocerciasis. Repeat treatment is frequently required and this highlights the possibility of development of drug resistance. In addition, risk of adverse reactions following treatment excludes some patients from control programmes. Such circumstances urgently call for the development of complementary control measures such as vaccination. DNA vaccines are novel type of subunit vaccine in which production of the immunizing antigen is induced in host cells after introduction of a plasmid or recombinant viral vector containing the gene that encodes the antigen. DNA vaccines are relatively simple and cheap to produce and their stability makes them particularly suitable for use in remote regions that lack the cold-chain storage facilities required of conventional vaccines. Filarial nematodes are tissue-dwelling parasites that survive for many years in immunocompetent hosts. It is proposed that this longevity is, in part, due to the capacity of the parasites to modulate potentially lethal Th2 responses of their hosts. Consequently, the efficiency of a filarial vaccine may depend on how well it circumvents filarial-driven immunosuppression. To test this hypothesis, a series of DNA vaccines were developed and tested in the Litomosoides sigmodontis-mouse model of filarial infections. The L. sigmodontis Abundant Larval Transcript-1 (Ls-ALT) and Cysteine Protease Inhibitor (Ls-CPI) genes were cloned and genetically engineered to ablate their immunomodulatory properties by deleting the acid domain and by site mutation, respectively. In addition, the L. sigmodontis Venom Allergen Homologue (Ls-VAH) and Thioredoxin Peroxidase (Ls-TPX) were used in their native forms as vaccine targets. To improve immunisation and antigen processing by the host, these parasite genes were fused to a DNA sequence encoding an antibody that specifically binds dendritic cell surface protein (αDEC205 single chain Fv). DNA plasmids carrying mutated forms and/or anti-DEC205 were then co-administered with plasmids encoding the Th2 promoting cytokine IL4, and/or antigen-presenting cell activating MIP1α and Flt3L. Mice immunized with mutated forms (ADDALT and CPImu) of parasite antigens produced more specific antibody post-challenge and showed strongly increased lymphocyte stimulation above controls immunized with the native form. The immune response was further enhanced when plasmids encoding IL4, MIP1α, Flt3L and anti-DEC-205 forms were co-administered, resulting in production of a Th2/IgG1 phenotype. Significant reduction of worm burden (82.3%) was achieved by a cocktail vaccination which combined the ADDALT and CPImu candidates. Mice immunized with Ls-VAH and Ls-TPX DNA carried by αDEC205 elicited Th2-biased responses with up-regulated IgG1 and IgE antibodies as well as enhanced IL5, IL4, and IL13 and diminished IFNγ production compared to controls. The immune responses were further driven towards the Th2/IgG1 phenotype when Ls-VAH and Ls-TPX were injected with plasmids encoding ADDALT and CPImu and with the adjuvants Flt3L, MIP1α and IL4. This resulted in reduction in worm burden of 55.7% (cocktail vaccine containing Ls-VAH) and 41.6% (cocktail vaccine containing Ls-TPX) respectively in vaccinated animals.