745. Antibody Response to the Pandemic Influenza A (H1N1) 2009 Virus and Two Porcine Strains Influenza A (H1N1 And H3N2) in A Group of Pediatric Patients, Their Close Contacts and Healthcare Workers in Mexico
Session: Abstracts: Virology: Influenza
Friday, October 22, 2010
Background: Preliminary data lead to the hypothesis that there will be no cross-reactivity between antiserum raised against 2009 pandemic influenza A (H1N1) virus and recent seasonal influenza A. The objective of this study was to analyze the serological response against influenza A (H1N1) 2009 infection and two swine influenza A virus  in a group of influenza-like-illness (ILI) pediatric patients, their  household contacts, and health-care workers (HCWs)  exposed to the virus.   Methods: 159   samples were included:  30 pre-epidemic (December 2008 to March 2009) and 129 samples from April 23 to November 15, 2009.  Serum antibodies were measured using a hemagglutination inhibition assay (HIA) performed with the influenza A/4482/Mexico/2009 (H1N1) strain and two porcine strains; A/swine/Iowa/00239/2004(H1N1), A/swine/Texas/4199-2/98(H3N2). Negative samples were defined as those having HIA titers <10; antibody titers were log-transformed to calculate the Geometric Mean Titers (GMT)  and the 95% confidence intervals;  titers > 40 were considered seroprotective. One-way ANOVA was used to compare GMT between groups.  Results: The analysis by case status (as defined by CDC)  included: 32 confirmed cases, 3 probable cases, 7 not a case patients, 65 household contacts, 22 HCWs and 30 pre-epidemia samples.  A seropositive response was registered in 55.6%  to pandemic 2009 H1N1, and in 83% and 79% to 2004 H1N1 and 1998 H3N2 strains. GMT was higher for confirmed cases in comparison to other groups (p < 0.05). Antibody response to the three strains was higher in the group of children from 6 to 15 y (N= 61), in comparison with the group of 25-44 y (N=76) (p < 0.001).  Secondary attack rate was 26% in household contacts. Seroprotective titers reached 55% in confirmed patients and 51% in household contacts to 2009 pandemic H1N1 virus.  Conclusion: A high seroprevalence to swine strains with similar genetic identity to seasonal influenza A virus was found in all groups. Children seem to develop a higher immunogenic response to 2009 pandemic influenza A strain in comparison to adult subjects.

Subject Category: V. Virology including clinical and basic studies of viral infections, including hepatitis

Speakers:
Guadalupe Miranda-Novales, MD , Hospital Epidemiology Research Unit, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Constantino Lopez-Macias III, PhD , Medical Research Unit on Immunochemistry, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Cristina de Jesus Herrera, MD , Infectious Diseases. Pediatria Hospital, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Irma Zamudio -Lugo, MD , Hospital Epidemiology Division, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Pablo Valero-Pacheco, MSc , Medical Research Unit on Immunochemistry, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Cerbulo Vazquez, PhD , Cellular Biology, Instituto de Perinatologia, Mexico City, Mexico
Lourdes Arrriaga-Pizano, PhD , Medical Research Unit on Immunochemistry, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Eduardo Ferat, MD , Medical Research Unit on Immunochemistry, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Fortino Solorzano-Santos, MD , Infectious Diseases. Pediatria Hospital, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Guillermo Vazquez-Rosales, MSc , Infectious Diseases. Pediatria Hospital, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Marisol Perez-Toledo, MSc , Medical Research Unit on Immunochemistry, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Adriana Núnez-Valencia, MSc , Medical Research Unit on Immunochemistry, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Clara Espitia-Pinzon C , Instituto de Investigaciones Biomedicas, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico
Abigail Meza-Chavez, MD , Hospital Epidemiology Division, Instituto Mexicano del Seguro Social, Mexico City, Mexico
Armando Isibasi, PhD , Medical Research Unit on Immunochemistry, Instituto Mexicano del Seguro Social, Mexico City, Mexico

Disclosures:

G. Miranda-Novales, None

C. Lopez-Macias III, None

C. D. J. Herrera, None

I. Zamudio -Lugo, None

P. Valero-Pacheco, None

C. Vazquez, None

L. Arrriaga-Pizano, None

E. Ferat, None

F. Solorzano-Santos, None

G. Vazquez-Rosales, None

M. Perez-Toledo, None

A. Núnez-Valencia, None

C. Espitia-Pinzon C, None

A. Meza-Chavez, None

A. Isibasi, None

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