Molecular Epidemiology And Pathogenesis Of Measles Virus Infection In Shanghai Adults

In 2005,the Regional Committee for Western Pacific,of which China is a member state,endorsed the plan to eliminate measles by 2012.However,measles outbreak and epidemic still took place in several provinces of China.In 2005,there was a significant increase in measles patients in Shanghai compared with that of the previous years.The case survey data suggested that more than 70%of patients were adults,and the majority of patients displayed severe disease symptoms.To elucidate the causes of such phenomenon,we planed to identify the genetic characterization of measles virus circulated in Shanghai,as well as to study the immuno-pathogenesis of adult measles cases.The current research conducted an epidemiologic survey on the adult measles patients admitted into 3 different hospitals in Shanghai first.The case investigation data suggested that 3.3%(2/61)or 9.8%(6/61)patients had or had not vaccinated with measles vaccine before,the rest 86.9%(53/61) of cases did not know their previous measles vaccination history.At the same time,we collected the blood,urine,and throat swab samples from patients.Then we isolated MV from clinical samples and titrated them with Vero-SLAM cell line.Cultures were confirmed with Immuno-fluorescent Assay by using a monoclonal antibody to measles virus H protein or by viewing the electronic microscope.The sequences of the 450 nucleotides coding for the COOH-terminus of the nucleoprotein from all clinical isolates were detected.Sequences were analyzed,and phylogenetic trees were constructed.The phylogenetic analysis based on both nucleotide and amino acid homology showed that all 21 isolates formed three small clusters within Hla.To illucidate the immuno-pathology caused by measles virus in adult measles patients,we collected blood samples from healthy adults admitted to the blood bank and adult measles patients from 3 hospitals in Shanghai,and isolated the plasma and PBMC;moreover,we using a wild type measles virus we isolated in 2006 to stimulate the normal PBMC,collected the culture supernatant and cells post infection.Then we detected the IL-2,IL-4,IL-5,IL-10,TNFα,IFNγand IFNαgene expression in patients' PBMC as well as in-vitro cultured cells by RT-PCR,as well as checked the protein level in patients' plasma and in-vitro culture supernatant by CBA technique; We also quantified the CD14~+,CD4~+,CD4~+ CD25~+ cell population and the number of cells expression TLR2/4 in PBMC.Our results showed that in acute measles phase, the innate immune system of the adult patients was marked suppressed with significant reduction of TLR2/4 expressing cells and blocked typeⅠinterferon secretion;For adaptive immune,there was a mixed Th1 and Th2 immune response with down-regulated CD 14~+,CD4~+ cell population but up-regulated CD4~+ CD25~+ percentile in adult patients.Statistic analysis showed that,in adult measles patients,CD4~+ CD25~+ cell population positively correlated to plasma IL-10 production.Taken together,our data identified all 21 clinical isolates gotten from 2006 to 2007 as H1a genotype viruses,which suggested that virus mutation may not be the main cause of severe disease symptoms observed in adult measles patients in Shanghai.Our data also confirmed that in acute measles infection,the innate immune system of the adult patients was marked suppressed with significant reduction of TLR2/4 expressing cells and blocked typeⅠinterferon secretion;There was a mixed Thl(characterized by the elevated IL-2/IFNγproduction) and Th2 immune response (characterized by an elevated IL-10),but the number of CD 14~+,CD4~+ T cell population were down-regulated with the up-regulated CD4~+ CD25~+ T percentile.Our results suggested that the robust IFNγand IL-10 production,and the marked elevated CD4~+ CD25~+ T cell population may related to the severe disease symptoms observed in adult measles patients in Shanghai;and CD4~+ CD25~+ T cell might be the cellular source of the robust IL-10 production in adult measles patients.The above study provides laboratory evidences and epidemiologic clue for the police makers to construct appropriate measles control strategies,which may help to better handle the measles outbreaks and epicemic in our country.