Evaluation of the Langat/dengue 4 chimeric virus as a live attenuated tick-borne encephalitis vaccine for safety and immunogenicity in healthy adult volunteers

Department of Pediatrics, Division of Pediatric Infectious Disease, Vanderbilt University Medical Center, Nashville, TN, USA.
Vaccine (Impact Factor: 3.62). 03/2008; 26(7):882-90. DOI: 10.1016/j.vaccine.2007.12.015
Source: PubMed


With the steady rise in tick-borne encephalitis virus (TBEV) infections in Europe, development of a live attenuated vaccine that will generate long-lasting immunity would be of considerable benefit. A chimeric flavivirus, designated LGT/DEN4, was previously constructed to have a genome containing the prM and E protein genes of Langat virus (LGT), a naturally attenuated member of the TBEV complex, and the remaining genetic sequences derived from dengue 4 virus (DEN4). LGT/DEN4 was highly attenuated in rodents and non-human primates, and clinical trials in humans were initiated. Twenty-eight healthy seronegative adult volunteers were randomly assigned in a 4:1 ratio to receive 10(3) plaque-forming units (PFU) of LGT/DEN4 or placebo. Volunteers were closely monitored for clinical responses and for blood chemistry and hematological changes, and the level of viremia and the magnitude and duration of the neutralizing antibody response were determined. The LGT/DEN4 vaccine was safe and viremia was seen in only one vaccinee. Infection induced a neutralizing antibody response to wild-type LGT in 80% of volunteers with a geometric mean titer (GMT) of 1:63 present on day 42 post-immunization; however the antibody response against TBEV was both much less frequent (35%) and lower in magnitude (GMT=1:9). To assess the response to a booster dose, 21 of the original 28 volunteers were re-randomized to receive a second dose of either 10(3) PFU of vaccine or placebo given 6-18 months after the first dose. The immunogenicity against either LGT or TBEV was not significantly enhanced after the second dose of vaccine. Thus, chimerization of LGT with DEN4 yielded a vaccine virus that was highly attenuated yet infectious in humans. The level of replication was sufficiently restricted to induce only a weak cross-reactive antibody response to TBEV. To provide a sufficient level of immunity to widely prevalent, highly neurovirulent strains of TBEV in humans, vaccine candidates will likely need to be based on the TBEV structural protein genes.

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Available from: Anna P Durbin, Nov 21, 2014
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    • "Most chimeric flaviviruses have been developed for vaccine purposes. In these studies, live-attenuated vaccine candidates were created by inserting specific genetic elements (typically the prM-E genes) of the flavivirus of interest into a full-length infectious cDNA backbone of another flavivirus such as the YFV vaccine vector, YFV-17D, or an attenuated strain of DENV [32–38]. The construction and characterization of chimeric flaviviruses has also provided critical information on the genetic elements that modulate the differential vector ranges, transmissibilities and disease phenotypes of divergent flaviviruses. "
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    ABSTRACT: Background Most known flaviviruses, including West Nile virus (WNV), are maintained in natural transmission cycles between hematophagous arthropods and vertebrate hosts. Other flaviviruses such as Modoc virus (MODV) and Culex flavivirus (CxFV) have host ranges restricted to vertebrates and insects, respectively. The genetic elements that modulate the differential host ranges and transmission cycles of these viruses have not been identified. Methods Fusion polymerase chain reaction (PCR) was used to replace the capsid (C), premembrane (prM) and envelope (E) genes and the prM-E genes of a full-length MODV infectious cDNA clone with the corresponding regions of WNV and CxFV. Fusion products were directly transfected into baby hamster kidney-derived cells that stably express T7 RNA polymerase. At 4 days post-transfection, aliquots of each supernatant were inoculated onto vertebrate (BHK-21 and Vero) and mosquito (C6/36) cells which were then assayed for evidence of viral infection by reverse transcription-PCR, Western blot and plaque assay. Results Chimeric virus was recovered in cells transfected with the fusion product containing the prM-E genes of WNV. The virus could infect vertebrate but not mosquito cells. The in vitro replication kinetics and yields of the chimeric virus were similar to MODV but the chimeric virus produced larger plaques. Chimeric virus was not recovered in cells transfected with any of the other fusion products. Conclusions Our data indicate that genetic elements outside of the prM-E gene region of MODV condition its vertebrate-specific phenotype.
    Full-text · Article · Aug 2014 · Virology Journal
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    • "Based on the success of the yellow fever and Japanese encephalitis vaccines, scientists at the Laboratory of Infectious Diseases have developed numerous live attenuated candidate flavivirus vaccines [10] [11] [12] [13] [14] [15]. Many of these were evaluated in clinical trial and were demonstrated to be attenuated and immunogenic in adult flavivirus-naïve subjects [16] [17] [18] [19] [20]. A similar strategy was employed to develop a recombinant live attenuated chimeric WNV vaccine designated rWN/DEN430. "
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    ABSTRACT: WNV has become the leading vector-borne cause of meningoencephalitis in the United States. Although the majority of WNV infections result in asymptomatic illness, approximately 20% of infections result in West Nile fever and 1% in West Nile neuroinvasive disease (WNND), which causes encephalitis, meningitis, or flaccid paralysis. The elderly are at particular risk for WNND, with more than half the cases occurring in persons older than sixty years of age. There is no licensed treatment for WNND, nor is there any licensed vaccine for humans for the prevention of WNV infection. The Laboratory of Infectious Diseases at the National Institutes of Health has developed a recombinant live attenuated WNV vaccine based on chimerization of the wild-type WNV NY99 genome with that of the live attenuated DENV-4 candidate vaccine rDEN4Δ30. The genes encoding the prM and envelope proteins of DENV-4 were replaced with those of WNV NY99 and the resultant virus was designated rWN/DEN4Δ30. The vaccine was evaluated in healthy flavivirus-naïve adult volunteers age 18-50 years in two separate studies, both of which are reported here. The first study evaluated 10(3) or 10(4)PFU of the vaccine given as a single dose; the second study evaluated 10(5)PFU of the vaccine given as two doses 6 months apart. The vaccine was well-tolerated and immunogenic at all three doses, inducing seroconversion to WNV NY99 in 74% (10(3)PFU), 75% (10(4)PFU), and 55% (10(5)PFU) of subjects after a single dose. A second 10(5)PFU dose of rWN/DEN4Δ30 given 6 months after the first dose increased the seroconversion rate 89%. Based on the encouraging results from these studies, further evaluation of the candidate vaccine in adults older than 50 years of age is planned.
    Full-text · Article · Aug 2013 · Vaccine
    • "This can be illustrated by new types of live attenuated vaccines that use mutagenesis of the viral genome or chimerization of 2 different viruses (Mandl et al., 1998; Pletnev et al., 2001; Lai and Monath, 2003; Kofler et al., 2004). Pletnev and Men (1998) have produced a chimeric virus with the prM and E genes encoding structural proteins of LGTV strain TP21 and remaining part of the genome from dengue virus type 4. The attenuation efficacy of the chimera LGT/DEN4 against virulent strains of TBEV has been shown in mice, monkeys, and humans in past years (Pletnev and Men, 1998; Pletnev et al., 2000, 2001; Rumyantsev et al., 2006; Wright et al., 2008; Pripuzova et al., 2009). However, to make a decision about vaccine strain safety, it is required to do more evaluation for the possibility of long-term persistence of attenuated viruses in the recipients and other complications (Pripuzova et al., 2009). "
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    ABSTRACT: Rickettsioses are caused by obligate intracellular bacteria within the genus Rickettsia, mainly transmitted by arthropods. Until recently, Mediterranean spotted fever (MSF) caused by Rickettsia conorii was considered the only tick-borne rickettsiosis in Europe. However, 'new' TBR have been described in Europe during last years. For instance, other subspecies such as R. conorii caspia and R. conorii israelensis have been involved in MSF. Dermacentor-borne necrosis erythema and lymphadenopathy/tick-borne lymphadenopathy (DEBONEL/TIBOLA) cases caused by Rickettsia slovaca, Rickettsia raoultii, and Rickettsia rioja been described in several countries where Dermacentor marginatus ticks (the mainly implicated vector) are present. Rickettsia helvetica has also been involved as a human pathogen in cases of fever with and without rash and in patients with meningitis and carditis. Other TBR such as lymphangitis-associated rickettsioses (LAR), caused by Rickettsia sibirica mongolitimonae, have been diagnosed in different European countries (France, Spain, Portugal and Greece). Rickettsia massiliae is considered an etiological agent of MSF-like illness in the Mediterranean basin. Furthermore, Rickettsia monacensis that is distributed all along Europe has been isolated from patients with MSF-like illness in Spain. Although Rickettsia aeschlimannii has been associated with MSF-like in Africa and is distributed in the Mediterranean area, no autochthonous human cases have been reported for Europe. Other Rickettsia species detected in ticks and unrelated to human disease (Candidatus Rickettsia kotlanii, Candidatus Rickettsia barbariae, Candidatus Rickettsia vini) could be potentially involved in the next years. Climate changes, among other factors, may contribute to the emergence of other rickettsioses or change their distribution. Lastly, African tick-bite fever (ATBF), caused by Rickettsia africae, is frequently diagnosed in Europe in patients returning from endemic areas.
    No preview · Article · Nov 2012 · Ticks and Tick-borne Diseases
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