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Nasopharyngeal specimens from 42 children less than one-year old hospitalized with bronchiolitis or pneumonia in El Salvador were analyzed for the presence of subgroup-specific respiratory syncytial virus (RSV) antigens by the indirect immunofluorescence technique. The antigen RSV-A was demonstrated in 28 children, RSV-B in three, and in one child subgroup, specificity could not be determined. The male:female ratio in the RSV-infected children was 1.9:1. The most severe disease, requiring intensive care, was observed in two infants with RSV-B infection. Determination of serum IgG, IgA, and IgM antibodies in acute and convalescent sera showed that none of the tests alone had sufficient sensitivity for routine diagnostic purposes, although, in combination, they provided a correct diagnosis in 86% of the RSV-infected children. A seroprevalence study of IgG, IgA, and IgM antibodies in 206 healthy children showed that a primary RSV infection is usually acquired during the first year of life in El Salvador. These results also indicated that reinfections with RSV frequently occur during the first 3-4 years of life and suggest that the occurrence of serum RSV IgA antibodies may be a marker of reinfection.

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Eosinophil cationic protein (ECP) was assayed in nasopharyngeal secretion (NPS) and serum from 42 infants, hospitalized with acute lower respiratory infection, in El Salvador and the results analyzed in relation to etiology of the infection. ECP concentrations were high in NPS, at an average 50 times higher than those found in serum. Exceedingly high levels of ECP (> 1000 micrograms/L) were found more frequently in wheezing than in non-wheezing children (30% vs 7%) and, accordingly, were more commonly found in children hospitalized with bronchiolitis than in those with pneumonia. Excessive levels were significantly more common in girls than in boys. Of the 42 cases, 28 were found to be caused by respiratory syncytial virus (RSV) subgroup A, and 3 by RSV-B, by means of detection of RSV antigen in nasopharyngeal cells. ECP serum levels were moderately elevated during the acute phase of the respiratory infection and increased slightly but significantly, in cases with RSV antigen-positive bronchiolitis, but not in those with pneumonia. The ECP levels in NPS from patients in Sweden who, by antigen detection in NPS cells, were diagnosed as either RSV or para-influenza 3 infection or none of these, were similar. These results indicate that elevation of ECP in NPS is associated with acute lower respiratory infection in general, but particularly pronounced in cases of bronchiolitis. Elevation of ECP is not an exclusive consequence of RSV infection, but may occur to an equal extent in infections caused by other agents.(ABSTRACT TRUNCATED AT 250 WORDS)

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The occurrence of subgroup A and B strains of respiratory syncytial virus (RSV) was studied during three epidemic years, 1985 to 1987, in Uruguay. A set of monoclonal antibodies was selected according to their reactivity with local RSV isolates and used for the typing of RSV directly in nasopharyngeal cells by indirect immunofluorescence. Of 77 specimens, 69 could be typed as belonging to subgroup A or B, 5 could not be typed with the restricted set of monoclonal antibodies employed, and 3 reacted with both subgroup-specific antibodies. In 1985 and 1986 subgroup A predominated, accounting for 65.7% of all typed specimens, but in 1987 subgroup B surpassed subgroup A, accounting for 82.4% of the samples.

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The characterization of RSV antigenic variants was carried out on 160 nasopharyngeal aspirates from children under 5 years of age, from Argentina and Uruguay, with acute respiratory infection and a previously positive etiological diagnosis for RSV. Results for Argentina were: 20.9% of samples belonged to subtype A, 76.9% to subtype B and the remaining 2.2% to new subtypes as yet uncharacterized. Results for Uruguay were: 5.6% of samples belonged to subtype A, 81% to subtype B and 13.5% to other subtypes. Subtype B was predominant in both countries. The correlation of RSV antigenic variants with the clinical picture and epidemiological profile is currently underway.

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RESUMEN

The characterization of RSV antigenic variants was carried out on 160 nasopharyngeal aspirates from children under 5 years of age, from Argentina and Uruguay, with acute respiratory infection and a previously positive etiological diagnosis for RSV. Results for Argentina were: 20.9

of samples belonged to subtype A, 76.9

to subtype B and the remaining 2.2

to new subtypes as yet uncharacterized. Results for Uruguay were: 5.6

of samples belonged to subtype A, 81

to subtype B and 13.5

to other subtypes. Subtype B was predominant in both countries. The correlation of RSV antigenic variants with the clinical picture and epidemiological profile is currently underway.