DISCUSSION
The data obtained in this investigation indicate that there is a direct statistically and clinically significant relationship between the levels of specific immunoglobulin A against Respiratory Syncytial Virus in respiratory samples (nasopharyngeal exudate) and the level of severity of the clinical picture presented by pediatric patients infected with this agent, the presence of serious clinical variables such as thoraco-abdominal dissociation and dry cough which are more common in those whose antibody levels are lower. The afore mentioned agrees with what was published by Walsh et al (2018), who measured IgG antibodies against RSV F protein in infected patients, finding in a multivariate analysis adjusted for age, a significant correlation between the decrease in clinical severity and the increase in titers of the antibodies, with greater benefit, in the first 2 months of age, also finding that the greater antibodies titers at birth are correlated with delayed RSV infection, thus suggesting the benefits of maternal vaccination during pregnancy. 28
Likewise, in 2017, Jans et al, also correlated the levels of antibodies against the RSV G protein and the presence of severity markers such as oxygen therapy need, tachypnea, oxygen saturation, admission to the intensive care unit and days of hospitalization, finding that the avidity of RSV-specific IgG antibodies was lower in vitro in infected infants than in uninfected controls, though, they found no relationship between the titers of these antibodies and the severity data.10 However, Falsey, Koval, DeVincenzo and Walsh (2017), demonstrated that high titers of neutralizing antibodies against RSV bring benefits in the survival of immunocompromised patients infected with this virus 7 also Nyiroet al. (2016), reported the association between high titers of neutralizing antibodies against RSV, measured in the umbilical cord of pediatric patients with severe infection and the decrease in the probability of acquiring the infection over time in controls. 18 However, they mention a wide variation in antibody levels, which is why further studies will follow in this regard. 10,7, 18
These investigations support that, the greater the number of specific antibodies against the respiratory syncytial virus, (both IgG and IgA), the clinical data on the severity of said infection in pediatric populations will be lower.
Previous research regarding RSV antibody levels are all measured in serum, Vissers, Ahout, de Jonge and Ferwerda (2016), supported that elevated levels of IgG in infected infants mucosa are correlated with a lower viral load than plasma IgG levels, suggesting focusing humoral immunity studies on mucosae of patients affected by this virus, corroborating in this study what was stated by these authors.27
Likewise, there was also found a relationship between the presence of clinical signs of repetitive respiratory tract infections in pediatric patients whose RSV-specific immunoglobulin A titers were lower.
Jounai et al. (2017), examined the responses of total IgG antibodies, subclasses and antibodies against the neutralizing epitopes of patients in acute and convalescent stages of RSV infection, also evaluated the serum neutralizing activity, finding that children antibody responses against RSV matured over time in terms of titer, neutralization levels, increased affinity, and increased overall IgG response in repeat virus infections (Jounai et al., 2017). (12)
On the other hand, another of the results obtained in this research indicates that there is a relationship between breastfeeding for 6 months and the decrease in the presence of clinical severity data in RSV infection, such as low oxygenation index, presence of crackles and wheezes on physical examination. This is recently supported by what was published in January of this year in Nepal by scientists who carried out a clinical study where the concentration of immunoglobulins A and G against RSV F fusion protein was measured in breast milk, finding that patients with active RSV infection had lower IgG concentrations than controls, ,being the comparison of means statistically significant. This supports the important role played by the antibodies present in breast milk as a protective measure against infections and symptoms of this virus. 17
In regard to the clinical characteristics epidemiology of Mexican pediatric patients, data that are not updated in Mexico, it was found that there was a predominance of males, the median age was 12 months, this in contrast to what was reported by Rodríguez-Auadetal., in 2012, where it is mentioned that the median age in their study population was 22 months. Most of the patients presented incomplete vaccination schedule, which, at present, represents a real public health problem, probably due to the social stereotypes focused on vaccination, a situation which, focused on the infection context by RSV, predisposes to situations of co-infections, increased mortality and risk of RSV infection, making visible the lack of optimization of vaccination tools and strategies. 11,22
Also, it was documented in this investigation that the patients presented as important pathological personal history, exposure to tobacco smoke, repeated respiratory tract infections, previous wheezing, gastroesophageal reflux disease and asthma. 18 patients who had some underlying disease were treated in the intensive care unit and mechanically intervened for breathing, data that is consistent with that published by Vissers, Ahout, de Jonge, and Ferwerda (2016), who also mention the predominance of these conditions in patients younger than 6 months of age. 27
This study showed that the main coinfections identified among the included patients were essentially viral, with Rhinovirus being the main responsible agent, followed by seasonal influenza and Parainfluenza 1 virus, this coinciding with what was reported by Robledo-Acevedo et at ., last year. 22 A high exposure to cigarette smoke was also found in the population of patients included in this research, as was also found by these authors. About the coinfections found, Pneumococcus was the most frequently isolated bacterium in this population, as well as the H1N1 influenza virus, whose association RSV-Influenza H1N1 was already reported by Taylor et al. (2017).26 Finally Aspergillus spp. it was the only isolated fungus considered as a fungal coinfection in this study.
The clinical relevance of the findings in this research lies in the importance of promoting breastfeeding as a preventive method to avoid severe RSV infections in pediatric patients, since currently there is no effective vaccine or treatment. and standardized to prevent and treat such infection. Likewise, the medical importance of the information produced by this research updates the epidemiological data of the population affected by this infection and its clinical characteristics and outcomes.
The limitations of this research are related to the methodological procedure for measuring specific immunoglobulin A against RSV, since when trying to measure these levels in a poorly studied medium (nasopharyngeal exudate), it is a priority to standardize this process and to indicate by means of ROC curves, the cut points of said concentrations, opening a chain of subsequent investigations that can determine specific concentrations of specific IgA and even propose it as a diagnostic or monitoring method in infected patients.