West Nile virus activity in Latin America and the Caribbean

Komar, Nicholas; Clark, Gary G.

doi:10.1590/s1020-49892006000200006

Cited by 206 publications

(181 citation statements)

References 32 publications

(37 reference statements)

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“…Our results are consistent with prior reports of retrospective studies that indicate that approximately 10% of WNV-infected horses develop clinical disease [5,7,16], which is markedly greater than the occurrence (< 1%) of severe disease in WNV-infected humans [4,7]. In contrast to the reported attenuation of virulence of WNV in the tropical ecosystems in Latin America and the Caribbean [14], there was no evidence that the virus circulating in California had attenuated following transcontinental spread from the original incursion to New York in 1999 because the frequency of clinical WND in the horses in our study population was similar to that of prior reports. Interestingly, WNV was only sporadically detected by PCR analysis of mosquitoes that were intensively trapped at the site throughout both the 2004 and 2005 WNV seasons, and there was minimal mortality of susceptible bird species at the site (data not shown).…”

Section: Discussionsupporting

confidence: 92%

“…In 1999, WNV was first detected in North America in New York, and subsequently the virus spread throughout Canada, the USA, Mexico and the Caribbean [13,14,21]. Horses have been the mammalian species most impacted during the current epidemic of WNV infection in North America, with attendant high morbidity and mortality [20,22,[25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%

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Incidence and effects of West Nile virus infection in vaccinated and unvaccinated horses in California

et al. 2007

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Incidence and effects of West Nile virus infection in vaccinated and unvaccinated horses in California

et al. 2007

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“…In addition, more recent findings show evidence of WNV human and equine infection in several countries of tropical America [3]. While WNV disease generally results in moderate to severe flu-like symptoms in approximately 20% of infected individuals, about 1 out of 150 progress to severe neurological disease [4].…”

Section: Introductionmentioning

confidence: 99%

Preparation and immunogenic properties of a recombinant West Nile subunit vaccine

Lieberman

Clements

Ogata

et al. 2007

Vaccine

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While several West Nile vaccines are being developed, none are yet available for humans. In this study aimed at developing a vaccine for humans, West Nile virus (WNV) envelope protein (E) and non-structural protein 1 (NS1) were produced in the Drosophila S2 cell expression system. The Cterminal 20% of the E protein, which contains the membrane anchor portion, was deleted, thus allowing for efficient secretion of the truncated protein (80E) into the cell culture medium. The proteins were purified by immunoaffinity chromatography (IAC) using monoclonal antibodies that were flavivirus envelope protein group specific (for the 80E) or flavivirus NS1 group specific (for NS1). The purified proteins were produced in high yield and used in conjunction with adjuvant formulations to vaccinate mice. The mice were tested for both humoral and cellular immune responses by a plaque reduction neutralization test and ELISA, and by lymphocyte proliferation and cytokine production assays, respectively. The results revealed that the 80E and the NS1 proteins induced both high-titered ELISA and neutralizing antibodies in mice. Splenocytes from immunized mice, cultured in vitro with the vaccine antigens as stimulants, showed excellent proliferation and production of cytokines . The level of antigen-stimulated lymphocyte proliferation and cytokine production was comparable to the level obtained from mitogen (phytohemagglutinin or pokeweed) stimulation, indicating a robust cellular response as well. These findings are encouraging and warrant further in vivo studies to determine the protective efficacy of the WNV vaccine candidate.

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“…The hypothesis that species especially vulnerable to WNV are particularly numerous in the Nearctic avifauna might explain observations suggesting lesser susceptibility of wild birds in the Neotropics, even though WNV infecting tropical America presumably originated in North America (Komar and Clark 2006). One possible factor in this difference in susceptibility between Nearctic and Neotropical birds may be the reduced genetic diversity of the former, evidently an effect of glaciation on effective population sizes of North American birds .…”

Section: Discussionmentioning

confidence: 99%

Rapid fixation of a distinctive sequence motif in the 3′ noncoding region of the clade of West Nile virus invading North America

Hughes

Piontkivska

Foppa

2007

Gene

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Phylogenetic analysis of complete genomes of West Nile virus (WNV) by a variety of methods supported the hypothesis that North American isolates of WNV constitute a monophyletic group, together with an isolate from Israel and one from Hungary. We used ancestral sequence reconstruction in order to obtain evidence for evolutionary changes that might be correlated with increased virulence in this clade (designated the N.A. clade). There was one amino acid change (I→T at residue 356 of the NS3 protein) that occurred in the ancestor of the N.A. clade and remained conserved in all N.A. clade genomes analyzed. There were four changes in the upstream portion of the 3′ noncoding region (the AT-enriched region) that occurred in the ancestor of the N.A. clade and remained conserved in all N.A. clade genomes analyzed, changes predicted to alter RNA secondary structure. The AT-enriched region showed a higher rate of substitution in the branch ancestral to the N.A. clade, relative to polymorphism, than did the remainder of the non-coding regions, synonymous sites in coding regions, or nonsynonymous sites in coding regions. The high rate of occurrence of fixed nucleotide substitutions in this region suggests that positive Darwinian selection may have acted on this portion of the 3′NCR and that these fixed changes, possibly in concert with the amino acid change in NS3, may underlie phenotypic effects associated with increased virulence in North American WNV.

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West Nile virus activity in Latin America and the Caribbean

Abstract: The sparse reports of equine, human and avian disease in Latin America and the Caribbean is puzzling. Isolates are needed to evaluate viral attenuation or other possible explanations for reduced disease burden in tropical ecosystems.

Cited by 206 publications

References 32 publications

Incidence and effects of West Nile virus infection in vaccinated and unvaccinated horses in California

Incidence and effects of West Nile virus infection in vaccinated and unvaccinated horses in California

Preparation and immunogenic properties of a recombinant West Nile subunit vaccine

Rapid fixation of a distinctive sequence motif in the 3′ noncoding region of the clade of West Nile virus invading North America

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