Effect of clinical and virological parameters on the level of neutralizing antibody against pandemic influenza A virus H1N1 2009.
BACKGROUND
Little is known about the antibody response in natural infection by the novel 2009 influenza A (H1N1) virus and its relationship with clinical and virological parameters. The relative lack of background neutralizing antibody against this novel virus provides a unique opportunity for understanding this issue.


METHODS
Case patients presenting with influenza-like illness who were positive for the pandemic H1 gene by reverse transcription polymerase chain reaction were identified. The serum antibody response was assayed by neutralizing antibody titer (NAT) against the virus in 881 convalescent donors. We retrospectively analyzed clinical parameters and viral load.


RESULTS
Ninety percent of the 881 convalescent donors had seroprotective titer of 1:40 or greater. The geometric mean titer of donors with convalescent NAT measured between day 21 and 42 was 1:101.1. Multivariate analysis by ordinal regression showed that pneumonia (odds ratio, 3.39; 95% confidence interval, 1.49-7.61; P = .004) and sputum production (odds ratio, 1.75; 95% CI, 1.01-3.01; P = .046) were the 2 independent factors associated with a higher level of convalescent NAT. Being afebrile on influenza presentation was associated with subsequent poor NAT (<1:40) response (P = .04). A positive correlation between the nasopharyngeal viral load on presentation and the convalescent NAT was demonstrated (Spearman correlation rho, 0.238; P = .026).


CONCLUSIONS
About 10% of these convalescent patients do not have a seroprotective NAT and may benefit from vaccination to prevent reinfection. The convalescent NAT correlated well with the initial viral load and was independently associated with severity of the viral illness, including pneumonia. The findings provide both the clinical and virological markers for identifying potential convalescent plasma donors with high serum NAT, which can be used to produce hyperimmune intravenous immunoglobulin in a randomized treatment trial for patients with severe pandemic H1N1 infection.
Hung
Ivan F N
IF
Department of Microbiology, The University of Hong Kong, Hong Kong.
To
Kelvin K W
KK
Lee
Cheuk-Kwong
CK
Lin
Chi-Kit
CK
Chan
Jasper F W
JF
Tse
Herman
H
Cheng
Vincent C C
VC
Chen
Honglin
H
Ho
Pak-Leung
PL
Tse
Cindy W S
CW
Ng
Tak-Keung
TK
Que
Tak-Lun
TL
Chan
Kwok-Hung
KH
Yuen
Kwok-Yung
KY
D000328:Adult; D057134:Antibodies, Neutralizing / Q000097:blood*; D000914:Antibodies, Viral / Q000097:blood*; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D007251:Influenza, Human / Q000276:immunology* / Q000473:pathology / Q000821:virology; D008297:Male; D012367:RNA, Viral / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019562:Viral Load
D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D012367:RNA, Viral