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1.  Applications and challenges of multivalent recombinant vaccines 
The exceptional discoveries of antigen/gene delivery systems have allowed the development of novel prophylactic and therapeutic vaccine candidates. The vaccine candidates employ various antigen-delivery systems, particularly recombinant viral vectors. Recombinant viral vectors are experimental vaccines similar to DNA vaccines, but they use attenuated viruses or bacterium as a carrier “vector” to introduce microbial DNA to cells of the body. They closely mimic a natural infection and therefore can efficiently stimulate the immune system. Although such recombinant vectors may face extensive preclinical testing and will possibly have to meet stringent regulatory requirements, some of these vectors (e.g. measles virus vectors) may benefit from the profound industrial and clinical experience of the parent vaccine. Most notably, novel vaccines based on live attenuated viruses combine the induction of broad, strong and persistent immune responses with acceptable safety profiles. We assess certain technologies in light of their use against human immunodeficiency virus (HIV).
doi:10.4161/hv.23220
PMCID: PMC3891700  PMID: 23249651
vaccines; DNA; live attenuated viruses; HIV; measles; SIV; reverse genetics; recombinant vectors
2.  Relevance of a pre-existing measles immunity prior immunization with a recombinant measles virus vector 
Measles virus (MV) vectors are promising candidates for designing new recombinant vaccines since the parental live vaccines have a well-known safety and efficacy record. Like all viral vectors, the MV vector efficacy in inducing a protecting immune answer could be affected by the pre-existing immunity among the human population. In order to determine the optimal immunization route and regimen, we mimicked a MV pre-immunity by passively administrating MV neutralizing antibodies (MV-nAb) prior intramuscular (i.m.) and/or intranasal (i.n.) immunization with recombinant MV expressing the SIV-gag antigen (rMV-SIVgag). Our results revealed that 500 mIU of MV-nAb allowed the induction of a humoral and cellular immune response against the vector and the transgene, while higher titers of the MV-nAb were significantly inhibitory. In a prime-boost regimen, in the presence of MV-nAb, the intranasal-intramuscular (i.n.-i.m.) or intramuscular-intramuscular (i.m.-i.m.) routes induced higher humoral immune responses against the vector and the transgene (SIV-gag). In naive animals, cellular immune response was significantly higher by i.m. immunization; however, MV pre-immunity did not seem to affect the cellular immune response after an i.n. immunization.
In summary, we show that a pre-existing immunity of up to 500 mIU anti-MV neutralizing antibodies had little effect on the replication of rMV and did not inhibit the induction of significant humoral and cellular immune responses in immune-competent mice.
doi:10.4161/hv.23241
PMCID: PMC3891717  PMID: 23324399
vaccine; pre-existing immunity; immunization route; measles; SIV; recombinant virus; reverse genetics; immune competent mice
3.  Sequence and immunogenicity of a clinically approved novel measles virus vaccine vector 
The measles virus vaccine (MVbv) is a clinically certified and well-tolerated vaccine strain that has been given both parenterally and mucosally. It has been extensively used in children and has proven to be safe and effective in eliciting protective immunity. This specific strain was therefore chosen to generate a measles viral vector. The genome of the commercial MVbv vaccine strain was isolated, sequenced and a plasmid, p(+)MVb, enabling transcription of the viral antigenome and rescue of MVb, was constructed. Phylogenic and phenotypic analysis revealed that MVbv and the rescued MVb constitute another evolutionary branch within the hitherto classified measles vaccines. Plasmid p(+)MVb was modified by insertion of artificial MV-type transcription units (ATUs) for the generation of recombinant viruses (rMVb) expressing additional proteins. Replication characteristics and immunogenicity of rMVb vectors were similar to the parental MVbv and to other vaccine strains. The expression of the additional proteins was stable over 10 serial virus transfers, which corresponds to an amplification greater than 1020. The excellent safety record and its efficient application as aerosol may add to the usefulness of the derived vectors.
doi:10.4161/hv.23242
PMCID: PMC3891718  PMID: 23324616
recombinant measles virus; viral vectors; live-attenuated vaccines
4.  Attenuated Measles Virus as a Vaccine Vector 
Vaccine  2007;25(16):2974-2983.
Live attenuated measles virus (MV) vaccines have an impressive record of safety, efficacy and ability to induce life-long immunity against measles infection. Using reverse genetics technology, such negative-strand RNA viruses can now be rescued from cloned DNA. This technology allows the insertion of exogenous genes encoding foreign antigens into the MV genome in such a way that they can be expressed by the MV vaccine strain, without affecting virus structure, propagation and cell targeting. Recombinant viruses rescued from cloned cDNA induce immune responses against both measles virus and the cloned antigens. The tolerability of MV to gene(s) insertion makes it an attractive flexible vector system, especially if broad immune responses are required. The fact that measles replication strictly occurs in the cytoplasm of infected cells without DNA intermediate has important biosafety implications and adds to the attractiveness of MV as a vector. In this article we report the characteristics of reporter gene expression (GFP, LacZ and CAT) and the biochemical, biophysical and immunological properties of recombinant MV expressing heterologous antigens of simian immunogeficiency virus (SIV).
doi:10.1016/j.vaccine.2007.01.064
PMCID: PMC3707277  PMID: 17303293
recombinant vaccines; viral vectors; protein expression
5.  Recombinant measles virus-HPV vaccine candidates for prevention of cervical carcinoma 
Vaccine  2009;27(25-26):3385-3390.
Cervical cancer is mainly associated with HPV genotype 16 infection. Recombinant measles virus (rMV) expressing HPV genotype 16 L1 capsid protein was generated by construction of an antigenomic plasmid, followed by rescue using the human “helper” cell line 293-3-46. In cell cultures the recombinant MV-L1 virus replicated practically as efficiently as the standard attenuated MV established as commercial vaccine, devoid of the transgene. The high genetic stability of MVb2-L1 was confirmed by 10 serial viral transfers in cell culture. In transgenic mice expressing the MV receptor CD46 the recombinant induced strong humoral immune responses against both MV and HPV; the antibodies against L1 exhibited mainly neutralizing capacity. Our data suggest that MV is a promising vehicle for development of inexpensive and efficient vaccines protecting from HPV infection.
doi:10.1016/j.vaccine.2009.01.061
PMCID: PMC3487399  PMID: 19200837
Recombinant MV; Reverse genetics; HPV-L1
6.  Measles Virus Spreads in Rat Hippocampal Neurons by Cell-to-Cell Contact and in a Polarized Fashion 
Journal of Virology  2002;76(11):5720-5728.
Measles virus (MV) can infect the central nervous system and, in rare cases, causes subacute sclerosing panencephalitis, characterized by a progressive degeneration of neurons. The route of MV transmission in neurons was investigated in cultured rat hippocampal slices by using MV expressing green fluorescent protein. MV infected hippocampal neurons and spread unidirectionally, in a retrograde manner, from CA1 to CA3 pyramidal cells and from there to the dentate gyrus. Spreading of infection depended on cell-to-cell contact and occurred without any detectable release of infectious particles. The role of the viral proteins in the retrograde MV transmission was determined by investigating their sorting in infected pyramidal cells. MV glycoproteins, the fusion protein (F) and hemagglutinin (H), the matrix protein (M), and the phosphoprotein (P), which is part of the viral ribonucleoprotein complex, were all sorted to the dendrites. While M, P, and H proteins remained more intracellular, the F protein localized to prominent, spine-type domains at the surface of infected cells. The detected localization of MV proteins suggests that local microfusion events may be mediated by the F protein at sites of synaptic contacts and is consistent with a mechanism of retrograde transmission of MV infection.
doi:10.1128/JVI.76.11.5720-5728.2002
PMCID: PMC137054  PMID: 11992000
7.  Mutations in the Middle of the Transmembrane Domain Reverse the Polarity of Transport of the Influenza Virus Hemagglutinin in MDCK Epithelial Cells  
The Journal of Cell Biology  1998;142(1):51-57.
The composition of the plasma membrane domains of epithelial cells is maintained by biosynthetic pathways that can sort both proteins and lipids into transport vesicles destined for either the apical or basolateral surface. In MDCK cells, the influenza virus hemagglutinin is sorted in the trans-Golgi network into detergent-insoluble, glycosphingolipid-enriched membrane domains that are proposed to be necessary for sorting hemagglutinin to the apical cell surface. Site- directed mutagenesis of the hemagglutinin transmembrane domain was used to test this proposal. The region of the transmembrane domain required for apical transport included the residues most conserved among hemagglutinin subtypes. Several mutants were found to enter detergent-insoluble membranes but were not properly sorted. Replacement of transmembrane residues 520 and 521 with alanines converted the 2A520 mutant hemagglutinin into a basolateral protein. Depleting cell cholesterol reduced the ability of wild-type hemagglutinin to partition into detergent-insoluble membranes but had no effect on apical or basolateral sorting. In contrast, cholesterol depletion allowed random transport of the 2A520 mutant. The mutant appeared to lack sorting information but was prevented from reaching the apical surface when detergent-insoluble membranes were present. Apical sorting of hemagglutinin may require binding of either protein or lipids at the middle of the transmembrane domain and this normally occurs in detergent-insoluble membrane domains. Entry into these domains appears necessary, but not sufficient, for apical sorting.
PMCID: PMC2133032  PMID: 9660862
polarized epithelia; apical; sorting; protein traffic; lipid domain
8.  Chimeric Measles Viruses with a Foreign Envelope 
Journal of Virology  1998;72(3):2150-2159.
Measles virus (MV) and vesicular stomatitis virus (VSV) are both members of the Mononegavirales but are only distantly related. We generated two genetically stable chimeric viruses. In MGV, the reading frames of the MV envelope glycoproteins H and F were substituted by a single reading frame encoding the VSV G glycoprotein; MG/FV is similar but encodes a G/F hybrid in which the VSV G cytoplasmic tail was replaced by that of MV F. In contrast to MG/FV, MGV virions do not contain the MV matrix (M) protein. This demonstrates that virus assembly is possible in the absence of M; conversely, the cytoplasmic domain of F allows incorporation of M and enhances assembly. The formation of chimeric viruses was substantially delayed and the titers obtained were reduced about 50-fold in comparison to standard MV. In the novel chimeras, transcription and replication are mediated by the MV ribonucleoproteins but the envelope glycoproteins dictate the host range. Mice immunized with the chimeric viruses were protected against lethal doses of wild-type VSV. These findings suggest that it is feasible to construct MV variants bearing a variety of different envelopes for use as vaccines or for gene therapeutic purposes.
PMCID: PMC109510  PMID: 9499071
9.  Measles Viruses with Altered Envelope Protein Cytoplasmic Tails Gain Cell Fusion Competence 
Journal of Virology  1998;72(2):1224-1234.
The cytoplasmic tail of the measles virus (MV) fusion (F) protein is often altered in viruses which spread through the brain of patients suffering from subacute sclerosing panencephalitis (SSPE). We transferred the coding regions of F tails from SSPE viruses in an MV genomic cDNA. Similarly, we constructed and transferred mutated tail-encoding regions of the other viral glycoprotein hemagglutinin (H) gene. From the mutated genomic cDNAs, we achieved rescue of viruses that harbor different alterations of the F tail, deletions in the membrane-distal half of the H tail, and combinations of these mutations. Viruses with alterations in any of the tails spread rapidly through the monolayer via enhanced cell-cell fusion. Double-tail mutants had even higher fusion competence but slightly decreased infectivity. Analysis of the protein composition of released mutant viral particles indicated that the tails are necessary for accurate virus envelope assembly and suggested a direct F tail-matrix (M) protein interaction. Since even tail-altered glycoproteins colocalized with M protein in intracellular patches, additional interactions may exist. We conclude that in MV infections, including SSPE, the glycoprotein tails are involved not only in virus envelope assembly but also in the control of virus-induced cell fusion.
PMCID: PMC124600  PMID: 9445022

Results 1-9 (9)