Reemergence of recombinant vaccine-derived poliovirus outbreak in Madagascar.
ABSTRACT After the 2001-2002 poliomyelitis outbreak due to recombinant vaccine-derived polioviruses (VDPVs) in the Toliara province of Madagascar, another outbreak reoccurred in the same province in 2005.
We conducted epidemiological and virological investigations for each polio case patient and for their contacts.
From May to August 2005, a total of 5 cases of acute flaccid paralysis were reported among unvaccinated or partially vaccinated children 2-3 years old. Type-3 or type-2 VDPV was isolated from case patients and from healthy contacts. These strains were classified into 4 recombinant lineages that showed complex mosaic genomic structures originating from different vaccine strain serotypes and probably from human enterovirus C (HEV-C) species. Genetic relatedness could be observed among these 4 lineages. Vaccination coverage of the population was very low (<50%).
The broad distribution of VDPVs in the province and their close genetic relationship indicate intense and rapid cocirculation and coevolution of the vaccine strains and of their related HEV-C strains. The occurrence of an outbreak due to VDPV 3 years after a previous outbreak indicates that a short period with low vaccination coverage is enough to create favorable conditions for the emergence of VDPV in this setting.
Article: Reduced Poliovirus vaccine neutralising-antibody titres in infants with maternal HIV-exposure.[show abstract] [hide abstract]
ABSTRACT: BACKGROUND: Maternally HIV-exposed (mHIV-EU) infants have poor health even without HIV-1 infection. The responses to vaccination are less well defined. Immunity to oral Poliovirus vaccine (OPV) was studied in Zambian infants participating in a randomised controlled trial of micronutrient fortification to improve child health. METHOD: Maternally HIV-unexposed and mHIV-EU infants were recruited at 6 months age and randomised to basal or enriched micronutrient-fortified diets for 12 months. HIV-exposed mother-infant pairs had received perinatal nevirapine to prevent mother-to-child-transmission. In the cohort of 597 infants, neutralising-antibody titres to OPV were analysed at 18 months with respect to micronutrient fortification, maternal or infant HIV-1 infection, and human cytomegalovirus (HCMV) infection detected by antibodies and viraemia (serum DNA). Vaccine protection was defined as log2 titre>3. RESULTS: Compared to uninfected children, HIV-1-infected children had reduced neutralising antibody titres to OPV, irrespective of diet: log2 titre difference (95% confidence interval) -3.44 (-2.41; -4.46), P<0.01. OPV antibody titres were lower in HIV-infected children with HCMV viraemia compared to those without viraemia at 18 months, but did not reach significance: difference -2.55 (-6.10; 1.01), P=0.14. Breastfeeding duration was independently associated with increasing OPV titre (P-value<0.01). In mHIV-EU children there were reduced neutralising antibody titres to Poliovirus compared with maternally HIV-unexposed, irrespective of diet, maternal education and socioeconomic status: log2 titre difference (95% confidence interval) -0.56 (-0.98; -0.15), P<0.01. This difference was noticeably decreased after adjusting for breast-feeding duration, suggesting that in our study population less breast-feeding by HIV-positive mothers could explain the reduced OPV titres in mHIV-EU infants. CONCLUSION: The mHIV-EU infants had reduced polio vaccine antibody titres which were associated with reduced breast-feeding duration. This has important implications for polio eradication and control of vaccine-preventable diseases, in countries where childhood HIV-1 infection and maternal exposure are public health threats.Vaccine 03/2013; · 3.77 Impact Factor
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ABSTRACT: The diversity of nanotechnologies and of the governance challenges that their applications raise calls for exploration and learning across different cases. We present an Upstream Oversight Assessment (UOA) of expected benefits and potential harms of nanoparticles made of a synthetic polymer (PLGA) to improve vaccines for farmed salmon. Suggested by Jennifer Kuzma and colleagues, an UOA may help identify and prioritise research needs, and it may support evaluations of the adequacy of relevant existing regulatory frameworks. In this work, the UOA approach is modified and supported with elements from the uncertainty analysis framework developed by Warren Walker and colleagues. Empirically, we draw on relevant available published literature and insights generated in an ongoing nanoparticle salmon vaccine project, in which one of the authors participates. Nanotechnologies have not previously been encountered in the regulatory context of fish vaccines, which in part raises unique challenges due to prospective large scale vaccine use in semi-open aquatic systems. Strengthened through cooperation between ELSA and technology researchers we found the UOA useful for an early mapping of benefits and concerns, and for identifying areas in need of further research prior to a nanoparticle based salmon vaccine is developed and taken into use. We consider our approach to represent one among several complementing initiatives that seek to contribute to early stage evaluations of possible negative side effects, broadly conceived, in order to facilitate a more robust nanotechnology development.NanoEthics 04/2011; 5(1):57-71.
Article: Recombination between poliovirus and coxsackie A viruses of species C: a model of viral genetic plasticity and emergence.[show abstract] [hide abstract]
ABSTRACT: Genetic recombination in RNA viruses was discovered many years ago for poliovirus (PV), an enterovirus of the Picornaviridae family, and studied using PV or other picornaviruses as models. Recently, recombination was shown to be a general phenomenon between different types of enteroviruses of the same species. In particular, the interest for this mechanism of genetic plasticity was renewed with the emergence of pathogenic recombinant circulating vaccine-derived polioviruses (cVDPVs), which were implicated in poliomyelitis outbreaks in several regions of the world with insufficient vaccination coverage. Most of these cVDPVs had mosaic genomes constituted of mutated poliovaccine capsid sequences and part or all of the non-structural sequences from other human enteroviruses of species C (HEV-C), in particular coxsackie A viruses. A study in Madagascar showed that recombinant cVDPVs had been co-circulating in a small population of children with many different HEV-C types. This viral ecosystem showed a surprising and extensive biodiversity associated to several types and recombinant genotypes, indicating that intertypic genetic recombination was not only a mechanism of evolution for HEV-C, but an usual mode of genetic plasticity shaping viral diversity. Results suggested that recombination may be, in conjunction with mutations, implicated in the phenotypic diversity of enterovirus strains and in the emergence of new pathogenic strains. Nevertheless, little is known about the rules and mechanisms which govern genetic exchanges between HEV-C types, as well as about the importance of intertypic recombination in generating phenotypic variation. This review summarizes our current knowledge of the mechanisms of evolution of PV, in particular recombination events leading to the emergence of recombinant cVDPVs.Viruses 08/2011; 3(8):1460-84. · 1.50 Impact Factor