Seroprevalencia de la influenza A (H1N1) pandémica 2009 en trabajadores del Instituto Mexicano del Seguro Social

Abstract

Influenza viruses type A were responsible for pandemics in 1918, 1957, 1968, and for the first pandemic of the 21st century in 2009. Anti-HA antibodies are able to block the viral entry and prevent infection; these neutralizing antibodies (NAbs) can be detected by microneutralization assays (MN). Few reports had been published about the seroprevalence of influenza A(H1N1)pdm09 in healthcare workers, although they are a strategic group in the health care system. Therefore, the aim of this study was to analyze the seroprevalence among healthworkers from the IMSS, before the vaccination campaign against pandemic influenza of 2009, by MN assays using retroviral pseudotypes carrying the HA from the influenza virus A(H1N1)pdm09. These retroviral vectors transfer a reporter gene to cells whose receptors are recognized by the HA, as a result, antibodies capable to neutralize the function of this protein, prevent the expression of the reporter gene. Additionally, due the low stability which has the HA from the influenza virus A(H1N1)pdm09 affecting its biotechnological applications, we looked for substitutions sought to increase its stability, performing bioinformatic studies involving molecular dynamics simulation of wild-type and mutated HA to evaluate structurally the effect of such substitutions. We found seven mutations in the stem of the pandemic virus HA that increase the stability of the protein without impacting its antigenicity. According to the results, the seroprevalence in the healthworkers (IMSS) was not significantly higher than in general population (26.71% vs 20%, p = 0.872). When we made a more detailed analysis of the factors that favored seroconversion in the group of study, we found that the workplace (p<0.001), number of cases of pandemic influenza that the worker was in contact (p<0.031) and use of an antivirals (p<0.011), were associated with an increased risk of the worker to seroconvert. However, none of these variables contributed to enhance the titer of NAbs against the HA of the influenza virus A(H1N1)pdm09. This work presents an indication of the spread of the virus in hospitals of the IMSS, the protection used during the pandemic and the status of the seroprevalence before the vaccination campaign against the influenza virus A(H1N1)pdm09. It is important to notice that the identification of risk factors associated with seroconversion will be useful for the IMSS to implement health strategies at work, for decreasing the risk to acquire infections such as influenza type scenarios epidemic or pandemic.