Molecular Epidemiology Of Cryptosporidiosis On Children With Diarrhea Under 2 Years And HIV-1 Tat Impairs Anti-C.parvum Defense Through Modulating The Expression Of KSRP

Cryptosporidium is a protozoan parasite that infects the gastrointestinal epithelium and causes a diarrheal disease.Infection in human is characterized by self-limited diarrhea and abdominal pain that usually last several days,but it can be chronic and life-threatening in immunocompromised patients and young children.Recent studies indicated Cryptosporidium is responsible for moderate to severe diarrhea in children less than 2 years.Infection with Cryptosporidium shows significant association with mortality in this age group and appears to predispose children to lasting deficits in age-appropriate body growth and cognitive development.However,few studies have been performed among children under 2 years in China.The aim of the first study is to determine the prevalence and genotypes of Cryptosporidium among young children with diarrhea in Wuhan,Hubei province.The human stool specimens(n=298)were screened for the presence of Cryptosporidium by nested PCR.The infection rate of Cryptosporidium was 3.02%(9/298).The infection rate of Cryptosporidium was 5.93%(7/118)in infants between 1-2 years old,and the infection rate was 1.11%(2/180)in the infants under 1 year old,and there was a significant difference between the two groups(χ2 = 4.13;P(?)0.05).The nine samples which were positive by nested PCR were successfully sequenced and compared with the reference sequences on GenBank.The results revealed the nine positive specimens were all infected with C.parvum,particularly,and two of them were co-infected with C.hominis.Neighbor-joining trees were constructed from the aligned partial SSU rRNA sequences of these nine isolates,and in the SSU rRNA locus,the nine isolates were grouped with C.parvum.On the other hand,Cryptosporidium infection is one of the important causes of AIDS deaths.HIV Tat is a viral trans-activating protein essential for HIV-1 replication in infected cells.Tat can also be released from HIV-infected macrophages and lymphocytes and taken up by many cell types including epithelial cells.Extracellular Tat acts as a pleiotropic molecule inducing several biological effects on different target cells and is a key player in AIDS pathogenesis.We recently demonstrated thatTat hampers Toll-like receptor 4(TLR4)/NF-kB-mediated innate immunity and increases C.parvum infection burden in cultured epithelial cells.However,mechanisms by which Tat attenuates epithelial anti-microbial immunity are not fully understood.The second part of this paper explored the effect of Tat protein on C.parvum.The results showed that HIV Tat induced epithelial expression of KSRP(KSRP,also known as KHSRP)through down regulation of selected miRNAs,such as miR-27b.As an RNA-binding protein,KSRP could recognize AU-rich elements(AREs)within the 3’UTRs of iNOS mRNA and control their half-life time in the cytoplasm.Results from our studies could provide a rational basis for the implementation of new immunotherapeutic strategies for opportunistic infections in AIDS patients.