Importance of recrudescent avian infection in west nile virus overwintering: Incomplete antibody neutralization of virus allows infrequent vector infection

Sarah S. Wheeler, Meighan P. Vineyard, Chris Barker, William Reisen

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

After the acute infection period, birds persistently infected with West Nile virus (family Flaviviridae, genus Flavivirus, WNV) occasionally shed virus into the bloodstream, but these virions normally are inactivated by neutralizing antibody. The current work tested the hypothesis that these host neutralizing antibodies protect mosquito vectors from WNV infection and reevaluated the minimum WNV infectious dose necessary to infect Culex tarsalis Coquillett. To determine whether host antibodies protect mosquitoes from infection, Cx. tarsalis and Culex stigmatosoma Dyar were fed bloodmeals containing avian blood, WNV, and sera with or without WNV-specific neutralizing antibodies. When viral particles were completely bound by antibody, mosquitoes were protected from infection; however, when incompletely bound, WNV titers as low as 10 2.3 plaque-forming units (pfu)/ml resulted in 5% infection. These data indicated that avian antibodies were protective to mosquito vectors and were not dissociated during digestion. Because recrudescent viremias may not attain the same magnitude as initial acute viremias, Cx. tarsalis vector competence was reevaluated focusing on the fate of low-titered bloodmeals. Females were evaluated for vector competence after ingesting bloodmeals containing 102.2, 103.4, 104.5,10 5.5, or 106.5 WNV pfu/ml. Infection increased with bloodmeal titer, with 1% of the mosquitoes ingesting 103.4 pfu/ml and 45% of the mosquitoes ingesting 106.5 pfu/ml developing disseminated infections. The incomplete neutralization of recrudescent virus may be sufficient to infect a low proportion of competent blood-feeding Culex mosquitoes and perhaps allow persistently infected birds to provide a mechanism for arbovirus overwintering.

Original languageEnglish (US)
Pages (from-to)895-902
Number of pages8
JournalJournal of Medical Entomology
Volume49
Issue number4
DOIs
StatePublished - Jul 1 2012

Fingerprint

West Nile virus
neutralization tests
overwintering
Culicidae
Viruses
antibodies
Antibodies
Culex
Infection
infection
Neutralizing Antibodies
neutralizing antibodies
vector competence
Viremia
viremia
virion
Virion
Mental Competency
Birds
Flaviviridae

Keywords

  • antibody
  • Culex
  • recrudescence
  • vector competence
  • West Nile virus

ASJC Scopus subject areas

  • Insect Science
  • veterinary(all)
  • Infectious Diseases
  • Parasitology

Cite this

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title = "Importance of recrudescent avian infection in west nile virus overwintering: Incomplete antibody neutralization of virus allows infrequent vector infection",
abstract = "After the acute infection period, birds persistently infected with West Nile virus (family Flaviviridae, genus Flavivirus, WNV) occasionally shed virus into the bloodstream, but these virions normally are inactivated by neutralizing antibody. The current work tested the hypothesis that these host neutralizing antibodies protect mosquito vectors from WNV infection and reevaluated the minimum WNV infectious dose necessary to infect Culex tarsalis Coquillett. To determine whether host antibodies protect mosquitoes from infection, Cx. tarsalis and Culex stigmatosoma Dyar were fed bloodmeals containing avian blood, WNV, and sera with or without WNV-specific neutralizing antibodies. When viral particles were completely bound by antibody, mosquitoes were protected from infection; however, when incompletely bound, WNV titers as low as 10 2.3 plaque-forming units (pfu)/ml resulted in 5{\%} infection. These data indicated that avian antibodies were protective to mosquito vectors and were not dissociated during digestion. Because recrudescent viremias may not attain the same magnitude as initial acute viremias, Cx. tarsalis vector competence was reevaluated focusing on the fate of low-titered bloodmeals. Females were evaluated for vector competence after ingesting bloodmeals containing 102.2, 103.4, 104.5,10 5.5, or 106.5 WNV pfu/ml. Infection increased with bloodmeal titer, with 1{\%} of the mosquitoes ingesting 103.4 pfu/ml and 45{\%} of the mosquitoes ingesting 106.5 pfu/ml developing disseminated infections. The incomplete neutralization of recrudescent virus may be sufficient to infect a low proportion of competent blood-feeding Culex mosquitoes and perhaps allow persistently infected birds to provide a mechanism for arbovirus overwintering.",
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AB - After the acute infection period, birds persistently infected with West Nile virus (family Flaviviridae, genus Flavivirus, WNV) occasionally shed virus into the bloodstream, but these virions normally are inactivated by neutralizing antibody. The current work tested the hypothesis that these host neutralizing antibodies protect mosquito vectors from WNV infection and reevaluated the minimum WNV infectious dose necessary to infect Culex tarsalis Coquillett. To determine whether host antibodies protect mosquitoes from infection, Cx. tarsalis and Culex stigmatosoma Dyar were fed bloodmeals containing avian blood, WNV, and sera with or without WNV-specific neutralizing antibodies. When viral particles were completely bound by antibody, mosquitoes were protected from infection; however, when incompletely bound, WNV titers as low as 10 2.3 plaque-forming units (pfu)/ml resulted in 5% infection. These data indicated that avian antibodies were protective to mosquito vectors and were not dissociated during digestion. Because recrudescent viremias may not attain the same magnitude as initial acute viremias, Cx. tarsalis vector competence was reevaluated focusing on the fate of low-titered bloodmeals. Females were evaluated for vector competence after ingesting bloodmeals containing 102.2, 103.4, 104.5,10 5.5, or 106.5 WNV pfu/ml. Infection increased with bloodmeal titer, with 1% of the mosquitoes ingesting 103.4 pfu/ml and 45% of the mosquitoes ingesting 106.5 pfu/ml developing disseminated infections. The incomplete neutralization of recrudescent virus may be sufficient to infect a low proportion of competent blood-feeding Culex mosquitoes and perhaps allow persistently infected birds to provide a mechanism for arbovirus overwintering.

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