title: Low Level of Cross-Reactive Antibodies to Pandemic Influenza (H1N1) 2009 Virus in Humans in Pre-Pandemic Period in Maharashtra, India.
abstract: In India, the first outbreak of pandemic influenza (H1N1) 2009 (H1N1pdm) was reported from Panchgani, Maharashtra, in June 2009. Studies from several countries have revealed different levels of pre-existing immunity to H1N1pdm 2009 in various age groups. This study was undertaken using age-stratified pre-pandemic human sera to understand baseline cross-reactivity of antibodies against H1N1pdm. Using cut off antibody titers 20 and 40, overall cross-reactivity was 2.1 and 0.9% respectively by microneutralization assay; 1.2% and 0.7% by haemagglutination inhibition assay, respectively. Results showed higher baseline antibodies and cross-reactive antibodies in the 0-19 age group whereas the elderly age group (≥60) showed no cross-reactivity to H1N1pdm. The higher baseline and cross-reactive antibodies in 0-19 years age group could be because of higher positivity to seasonal H1N1 in that age group. Overall, low level of cross-reactive antibodies to H1N1pdm virus were found in humans in pre-pandemic period in Maharashtra, India.
authors.affiliation: National Institute of Virology (NIV)-Microbial Containment Complex (MCC), 130/1, Sus Road, Pashan, Pune, 411021 India.
authors.forename: Sadhana S
authors.initials: SS
authors.lastname: Kode
authors.forename: Shailesh D
authors.initials: SD
authors.lastname: Pawar
authors.forename: Babasaheb V
authors.initials: BV
authors.lastname: Tandale
authors.forename: Saurabh S
authors.initials: SS
authors.lastname: Parkhi
authors.forename: Tanaji D
authors.initials: TD
authors.lastname: Barde
authors.forename: Akhilesh C
authors.initials: AC
authors.lastname: Mishra
keywords: Cross-reactive antibodies; Hemagglutination inhibition assay; Microneutralization assay; Pandemic influenza (H1N1) 2009