The Primary Study On The Adaptive Mechanism Of Intracellular Infection Of Bartonella Henselae

Bartonella is a fastidious,facultative intracellular,Gram-negative,polymorphism bacteria,which is widely transmitted mainly by blood-sucking arthropods.Bartonella can cause long-lasting,relapsed bacteremia,and bacillary angiomatosis in immunodeficient patients.In this study,the JK33 strain(expressing Bad A pili)from the patient's lymph nodes and the ATCC 49882 strain(without Bad A pili)isolated from blood were used to evaluate their intracellular adaptability.Difference of proteome profile was further investigated to explore the mechanism of intracellular infection and survival of Bartonella henselae.Macrophages and endothelial cells were infected with ATCC 49882 and JK33.The efficiency and intracellular survival characteristics of Bartonella bacilli were studied by immunofluorescence and gentamicin protection experiments.The results showed that the number of intracellular ATCC49882 and JK33 decreased by 89.57% and 28.72% at 8 hours post infection in macrophages.At 1 h post infection,30% and 56% of phagosomes of ATCC 49882 and JK33 were colocalized with Rab7,respectively.At 90 min,59% and 78% of phagosomes of ATCC 49882 and JK33 were colocalized with lysosome,respectively.In endothelial cell infection,number of intracellular bacteria of ATCC 49882 and JK33 reached a peak at 12 h post infection,and then decreased.After 48 h,only 0.016% of total bacteria of JK33 survived in endothelial cells,while 0.14% of input bacteria survived in ATCC 49882 group,The co-localization ratio of ATCC 49882 and JK33 with Rab7 and lysosome is 43% versus 80% and 46% versus 80%,respectively.To better understanding of intracellular infection and adaptability of ATCC 49882,proteomic profile of ATCC 49882 was analysis before and after host cell infection.After 24 hours post infection,the intracellular bacteria and the bacteria grown on plate were collected,and total proteins are subjected to electrophoresis,enzymatic hydrolysis,degumming,desalting,and finally to LC-MS/MS detection.A total of 164 differential proteins were obtained by three replicate experiments,of which,108 proteins were highly expressed in plate-grown bacteria and 56 proteins were specifically expressed in intracellular bacteria.Furthermore,the Trw type ? secretion system associated with adhesion of red blood cells is highly expressed when Bartonella infect endothelial cells.However,the Vir B/D4 type ? secretion system and effector proteins associated known to associate endothelial cell infection are not specifically activated.These results shed light on our understanding of the mechanism how Bartonella infect and survive in host cells.