Role of host immune response and viral load in the differential outcome of pandemic H1N1 (2009) influenza virus infection in Indian patients.
BACKGROUND
An unusually high number of severe pneumonia cases with considerable mortality is being observed with the pandemic H1N1 2009 virus infections globally. In India, all mild as well as critically ill cases were admitted and treated in the government hospitals during the initial phase of the pandemic. The present study was undertaken during this early phase of the pandemic.


METHODS
The role of viral load and host factors in the pathogenesis were assessed by examining 26 mild (MP), 15 critically ill patients (CIP) and 20 healthy controls from Pune, India. Sequential blood and lung aspirate samples were collected from CIP. Viral load and cytokines/chemokine levels were determined from the plasma and lung aspirates of the patients. TLR levels were determined by staining and FACS analysis. Gene profiling was done for both cells in the lung aspirates and PBMCs using TaqMan Low Density arrays. Antibody titres and isotyping was done using HA protein based ELISAs.


RESULTS
13/15 critically ill patients expired. All plasma samples were negative for the virus irrespective of the patient's category. Sequential lung samples from CIP showed lower viral loads questioning association of viral replication with the severity. Anti-rpH1N1-09-HA-IgG titres were significantly higher in critically ill patients and both categories circulated exclusively IgG1 isotype. Critically ill patients exhibited increase in TLR-3, 4, 7 and decrease in TLR-2 expressions. The disease severity correlated with increased plasma levels of IL1RA, IL2, IL6, CCL3, CCL4 and IL10. Majority of the immune-function genes were down-regulated in the PBMCs and up-regulated in the cells from lung aspirates of critically ill patients. No distinct pattern differentiating fatal and surviving patients was observed when sequential samples were examined for various parameters.


CONCLUSIONS
Disease severity was associated with pronounced impairment of host immune response.
National Institute of Virology, Pune, India. varankalle@yahoo.com
Vidya A
VA
Arankalle
Kavita S
KS
Lole
Ravi P
RP
Arya
Anuradha S
AS
Tripathy
Ashwini Y
AY
Ramdasi
Mandeep S
MS
Chadha
Shashi A
SA
Sangle
Deelip B
DB
Kadam
D000293:Adolescent; D000328:Adult; D002469:Cell Separation; D016207:Cytokines / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D006801:Humans; D007194:India / Q000453:epidemiology; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D019562:Viral Load
D016207:Cytokines