NS1 protein secretion during the acute phase of West Nile virus infection.
The West Nile virus (WNV) nonstructural protein NS1 is a protein of unknown function that is found within, associated with, and secreted from infected cells. We systematically investigated the kinetics of NS1 secretion in vitro and in vivo to determine the potential use of this protein as a diagnostic marker and to analyze NS1 secretion in relation to the infection cycle. A sensitive antigen capture enzyme-linked immunosorbent assay (ELISA) for detection of WNV NS1 (polyclonal-ACE) was developed, as well as a capture ELISA for the specific detection of NS1 multimers (4G4-ACE). The 4G4-ACE detected native NS1 antigens at high sensitivity, whereas the polyclonal-ACE had a higher specificity for recombinant forms of the protein. Applying these assays we found that only a small fraction of intracellular NS1 is secreted and that secretion of NS1 in tissue culture is delayed compared to the release of virus particles. In experimentally infected hamsters, NS1 was detected in the serum between days 3 and 8 postinfection, peaking on day 5, the day prior to the onset of clinical disease; immunoglobulin M (IgM) antibodies were detected at low levels on day 5 postinfection. Although real-time PCR gave the earliest indication of infection (day 1), the diagnostic performance of the 4G4-ACE was comparable to that of real-time PCR during the time period when NS1 was secreted. Moreover, the 4G4-ACE was found to be superior in performance to both the IgM and plaque assays during this time period, suggesting that NS1 is a viable early diagnostic marker of WNV infection.
Macdonald
Joanne
J
Jerome L. and Dawn Greene Infectious Disease Laboratory, Department of Epidemiology, Mailman School of Public Health, Columbia University, 722 W. 168th St, Rm. 1801, New York, NY 10032, USA.
Tonry
Jessica
J
Hall
Roy A
RA
Williams
Brent
B
Palacios
Gustavo
G
Ashok
Mundrigi S
MS
Jabado
Omar
O
Clark
David
D
Tesh
Robert B
RB
Briese
Thomas
T
Lipkin
W Ian
WI
D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D006224:Cricetinae; D004195:Disease Models, Animal; D015967:Gene Expression Regulation, Viral; D007668:Kidney; D007700:Kinetics; D008647:Mesocricetus; D051381:Rats; D017207:Rats, Sprague-Dawley; D014709:Vero Cells; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000378:metabolism*; D014901:West Nile Fever / Q000503:physiopathology*; D014902:West Nile virus / Q000235:genetics*
D017361:Viral Nonstructural Proteins