La coriza infecciosa es una enfermedad del tracto respiratorio de Gallus gallus domesticucs causada por la bacteria Avibacterium paragallinarum (AP), que genera una mortalidad incrementada y una disminución productiva para la industria avícola (1). La prevención de la coriza es dificultosa debido a la diversidad fenotípica de AP, cuyos aislados de campo requieren una identificación larga y costosa (2). Para estudiar la diversidad fenotípica de AP, se han clasificado los aislados de la bacteria en 3 serogrupos que contienen 9 serovariedades, usando un método de inhibición de la hemaglutinación (2). Esta clasificación es altamente demandante e ineficiente para identificar acertadamente todos los aislados (3), lo que es crucial para prevenir los brotes de la enfermedad. Si no se identifica qué serovariedad causa un brote específico, no se puede utilizar la vacuna adecuada, ya que las vacunas tienen una protección específica para cada serovariedad (1, 4). Los esfuerzos previos de serotipificación mediante técnicas moleculares (5, 10-12) y los análisis de la variabilidad genética de las proteínas causantes de la hemaglutinación HagA y HMTp210 (6,7,8) han sido poco exitosos y de baja reproducibilidad. Si bien se ha demostrado la relevancia de HMTp210 (13,14), la investigación reciente se ha enfocado infructuosamente en la secuencia de este único gen (13,15,16). Este enfoque ignora que la serotipificación tradicional se realiza a partir de extractos sonicados de AP (2), por lo que potencialmente podrían interferir otras moléculas inmunorrelevantes como factores de virulencia. Además, los estudios de HMTp210 registrados no contemplan la predicción de las estructuras post-traduccionales que determinan la respuesta inmune, como los epítopes reconocidos por el MHC-II (34). En este trabajo planteamos el análisis genético de los factores de virulencia de AP de 25 genomas para identificar si sus secuencias presentan polimorfismos específicos para cada serovariedad. Además, proponemos la predicción epitópica de 25 secuencias del gen HMTp210 para verificar si existen diferencias los epítopes predichos para cada serovariedad.
Infectious coryza is a disease of the respiratory tract of chickens and hens caused by the bacterium Avibacterium paragallinarum (AP), which causes increased mortality and a relevant decrease in production for the poultry industry (1). The pathogen, AP, has wide phenotypic variability that has prevented the finding of a single prevention method. AP isolates can be classified according to their serological characteristics into 9 Kume serotypes, and the vaccines developed have a restricted range of action specific to each serotype, with some exceptions. Classification into the 9 serotypes is done through hemagglutination inhibition assays. These tests evaluate the hemagglutination capacity (adhesion of the pathogen to blood cells) of each isolate in the presence of standardized inhibitors. Identification is crucial because the usual prevention method uses inactivated whole cell vaccines whose cross protection between different serovars is limited (4). HI assays can identify serovars in the vast majority of isolates, but molecular characteristics related to serotype diversity have not yet been precisely identified. Non-gene specific molecular techniques have been developed to genetically typify the reference strains of the 9 Kume serotypes (5). In addition, from the report and characterization of two AP hemagglutinins - HagA (6) and HMTp210 (7,8) - typing analyzes directed at these genes (9) have been developed. However, the results of these methods are not consistent with the Kume serovars (10–12). It is proven that HMTp210 has the greatest contribution to the haemagglutinating effect of AP (13) and is the main antigen inhibited by protective antibodies (14), so recent research has focused on this gene (9,11,13,15,16 ). However, the structural differences in the proteins expressed by this gene between the different serovars have not been analyzed. Furthermore, the antibodies used for Kume serotyping correspond to the entire mixture of antigens present in a sonicated extract of AP (2), but other antigens have not been considered in previous attempts at molecular serotyping. Likewise, it is known that the degree of virulence of AP varies 5 significantly between serovars (17), a change whose correlation between the virulence genes of AP has not yet been sought. We propose to analyze the joint genetic variability of the virulence genes as potential antigens that interact in the HI assays and are likely responsible for the variations in virulence between serovars.
