- Th^nh phan hoa hgc va tmh khong thuan nhat: Chi kich thuoc vd tinh la chua du dl xac dinh
1.4.1.3.Ddp ung mien dfch
ị4.ịyirut sm
1.4.1.3.Ddp ung mien dfch
Khdng huylt tiianh xuit hien ngay Idii ban xuit hieiL Xuat hien sdm niidt la IgM, tiep theo la IgG vd IgA trong huylt thanh vd trong dich tilt Ca IgM va IgG dugc sdn sinh ra trudc tien nhung IgM dat dinh cao vdo ngdy thii 7 din ngdy thii 10 sau khi xuat hien ban, sau đ gidm nhanh va khdng ton t£ii sau 4 tudiL Sir cd mdt ciia IgM
chiing td hdnh nhdn bi nhiem Sdi tien ptidt hodc tiem vdcxm. Con IgG dugc tdn tai laụ
Cau tnic vd bao ngodi cua hat virut cd cdc hemaglutinin. Cd vai trd giiip vunit bdm vao receptor cua te bao cdm thụ Sau do protein hod mdng xam nhap phiic hgp tai to hgp, thuc hien su nhdn len cua vinit trong te bao cdm thụ Sau khi vuut dugc nhdn len, giai doan giai phdng ciia vinit thuc hi^n theo phuong thiic nay chdị Vinit Sdi Id vinit đng nhdt, khdng co sir bien di mgi cau tnic cua vmit, do vdy sau khi nhilm vmit Sdi, khdng huyet thanh Sdi se duy tri sudt đị Viriit Sdi chi gdy benh cho ngudị
Tuy nhidn vỉc trung hod virut Sdi trong phdng thi nghiem cd thi bi dnh hudng bdi khdng hityet thanh khdng HẠ Do do de ngdn ngira su lan truyen virut trong cgng ding can cd cd khdng huyet thanh khdng khdng nguyen F. Khdng huyet thanh don đng khdng khdng nguyen F la đc hi§u cho timg chimg. Vai trd quan trgng cua khdng huyet thanh ndy dugc phdng doan tir khi ngudi ta nhdn ra rdng vdcxin Sdi bdt boat khdng mang lai mien dich đy dụ Vdcxin ndy khdng tao ra dugc khdng huylt thanh khdng khdng nguyen F.
Thdnh phin M cua virut Sdi ciing da dugc nghien cuu, đc bỉt trong nhiing b$nh nhdn bi b?nh viem ndo so ciing bdn cap (SSPE). Ngudi ta lihan thdy rdng nhirng b?nh nhan SSPB cd khdng huyet thanh khdng thdnh phin M rat thap. So sdnh 9 chimg vinit khde nhau bdng khdng huyet thanh dcm đng da phdt hien ra rdng protein M thay đi trong cdc quydt dinh khdng nguyen.
Ddnh gid hỉu qud sau khi tidm chung bdng xdc dinh khdng huydt thanh trong mdu va so sdnh trudc khi tidm vdc xin vdi sau klii tiem vdcxin it nhat 4 tuan. Thudng sii dung phdn iing lic che ngdn ngung kit hdng ciu (HI) de xdc dinh hieu gid khang huyet thanh. Hieu gia khdng huylt thanh cao d giai d o ^ diu, nd van tdn tai keo đi tir 1 ->• 1,5 nam sau tiem. Sau do gidm din tir 1/2
-^ 1/3 trong vdng 5 ndm. 1.4.2. Virut Rota 1.42.1. vk hinh thdi hgc
Dudi kinh hiln vi di^n td, vinit Rota cd dang hinh khdi cau dudng kinh khodng 27-30 run bao gom 1 pnrdtein capsit cd cau tnic bin vung bao bgc lay ARN cua virut. Capsit bao gdm 60 tilu dcm vi giong h^t nhau xip dii xiing 20 mdt, mdi tieu dan vi gdm 4 chudi pdlypeptit la VPl;
VP2; Vp3; va VP4. Bdng phuong phdp chilu xa tia X ngudi ta bilt chi tiet cau tnic ciia hat vinit hodn chinh.
1.4.2.2. Ve thanh phan hda hgc ciia virut Rota
Axit nucleic: La ARN mgt sgi duor^, cd chieu đi 2,4imi, trgng lugng phdn tir 2,5 X lÔdalton cugn lai ndm ggn trong vd capsit. Dau 5 cd mgt doan pdlypeptit dugc ggi la VPg gdm 11 axit amin gdn vao cdn diu 3" bi pdlyadenyl hdạ ARN ciia virut dugc chia thdnh 3 vimg chu yeu: Vimg khdng md hda diu 5" bao gdm 740 nucleotit, ciiiem khodng 10% vat lieu di truyen. Khung dgc md dcm bao gdm 6635 nucleotit chiem khodng 89% vat lieu di truyen. Vimg khdng md hda 3 bao gom 75 nucleotit, chiem khoang 1% vat lieu di truyen
• Protein: Prdtein capsit ciia virut Rota bao gdm 4 chudi polypeptit. VPl bao gdm 306 axit amin cd trgng lugng phdn tu 34 kDal; VP2 bao gdm 272 axit amin cd trgng lugng phdn tir 30 kDal; VP3 gom 238 axit amin cd trgng lugng phan tii 26kDal vd VP4 gdm 69 axit amin, trgng lugng phdntii7kDal. Trong đ VPl, VP2,VP3 t^o nen ciu tnic bl mdt cua vkuts cdn VP4 ndm trong vd capsit vd lien kit vdi axit nhdn(ARN). Cdc prdtem bl mat tao nen cdc vi tri khdng nguyen trung hdạ Ngodi ra vd capsit cdn cd tdc dung bdo ve axit nhan vd quylt dinh khd ndng hip phu cua virut Idn bl m^t tl bdo thdng qua cdc thy thi d^c hieụ
• Lipit: Virut Rota khdng chiia lipit nen khdng nhay cam vdi tdc đng ciia ete, cbn, phdnol 1% vd
cdc thu6c tiy thdng thudng. Dya vdo dac tinh ndy ngudi ta sir dung cloroform dl xir 1^ bdnh phdm trudc khi phdn l$p vurut md khdng 1dm mat boat tinh ciia virut.
1.4.2.3. Ve tfnh chit hda 1^
Virut Rota rit nhay cam vdi nhiet dọ d 56°C virut hi bit boat hodn todn trong vdng 30 phiit. d nhỉt dg 20-24**C virut bi bat hoat vdo cudi thdng thii 3. d nhiet dg 37*'C virut giam hieu gid hdng ngdy vdo khodng 0,151ogl 0.
Virut Rota tdng tinh chiu nhiet khi cd mat cua cua ion caxi hoac ion magnie d ndng do IM. Virut Rota ben viing vdi đi pH rdng tir 2-10, nhung pH thich hgp nhit tai pH 6,5-7,2. Ngodi ra virut Rota bi bdt hoat hodn toan bdi formalin nhimg tinh khdng nguyen vdn bao t^n nguydn v?n.
1.4.2.4. Ve cau t^o cua khdng nguySn
Khdng nguyen ciia hat vuut hodn chinh cd khd ndng gdy nhilm triing ggi Id khdng nguyen D(hay cdn ggi Id khdng nguydn N). Khi h?it virut bi dun ndng 50-60°C hinh thdi cua hat virut bi thay doi vd khdng nguydn D chuyin thdnh khdng nguyen C(hay cdn ggi la khang nguyen H). Khdng nguydn D cd hdng s6 Idng Id 160S cdn khdng nguydn C cd hdng sd Idng Id 80-90S.
Khang nguyen D la h^t virut hodn chinh bao gdm cd ARN va vd capsit cdn khdng nguyen C chi la vd capsit khdr^ cd axit nhan vd VP4. Khang nguyen D va C khdng cd phdn iing mien dich cheọ Hai khdng nguyen ndy dugc phdt hien bang phan iing ket hgp bd the vd phan iing ket tiia tren thacJL
Khdng nguydn D cd khd nang tao khdng huyet thanh trung hda dac hieu typ vd bdm vdo thu the cua td bdo cdm thy, nha chiic ndng ndy ma virut cd the xam nhap vao ben trong tl bdo cdm thy de nhdn len.
Khdng nguyen C la khang nguyen chung cho tit ca cac typ, nd kich thích co thi tao ra
khdng huyet thanh kit hgp hh the nhung neu dimg khang nguyen nay dl chl tao khdng huylt thanh
thi se khdng thu dugc khdng huylt thanh trung hdạ 1.4.2.5.VI tinh sinh mien djch
Miln dich thu dgng dugc truyen tir me sang con. Khdng huylt thanh nay chi xuit hien d tre so sinh sau do gidm dan vd biln mdt khi tre dugc 6 thdng tudị
Mien dich chu dgng Id sy dap iing mien dich khi ca thi hi nliilm virut ty niiien hodc sir dyng vdcxin. Ddy Id lô mien dich quan trgng ma lodi ngudi da bilt iing dung dl phdng benh bdng cdh diing vdcxm. Khi bj nhiem vmit Rota hoang dai hodc virut vdcxin, co thi tao ra miln djch đc hỉu chong 1^ virut Rotạ Khdng huylt thanh đc hieu chu ylu Id miln dich dich thi bao gdm IgM, IgG vd IgẠ
Mien dich dich the lidn quan tdi te bdo lypho B vd vdi thi he sau nd la bdo tuong. Bdo tirong sdn xuit cdc globulin miln dich. Khi tl bao B g?.p khdng nguydn Beii lỉt trudc do da dugc khdng huylt thanh tren bl m$t nhdn biet sd kich thich ca thi tang sinh khdng huylt thanh. Khdng huylt tiianh IgM vd IgG phdt hidn dugc sau khi nhilm vinit 2-3 ngdỵ Hieu gid khdng huylt thanh cao d nhiing ngdy diu vd hit sau 2-3 thdng. Hifu gid khdng huylt thanh IgG tang va tdn tai lau nhit trong CO thi cd thi tdi 40 ndm, đy Id khang huyet thanh trung hda cd khd ndng chdng lai virut Rota den h? thin kmh trung uong. Hieu gid khdng huylt thanh IgA phdt hien 2-6 tudn sau khi nhiem virut nhung hifu gid thap, tdng chdm trong 3 thdng dau sau khi nhilm virut va t6n tai trong 6 nam.
1.4.2.6. Ve sy nhdn len cua virut Rota trong te bao cam th^
Nudi ciy tl bdo giir mdt vai trd quan trgng trong nghien ciiu virut Rotạ Tl bao dugc su dyng dl phdn l§p, dinh typ, chudn đ hidu gid, xdc djnh tinh khdng nguyen cua virut dac biet tl bdo sii dyng trong sdn xuit vdcxin Bai lift. Sy nhan len ciia vhut Rota trong tl bdo da dugc bilt tir nam 1913. Dya vdo tinh hudng thin kinh cua virut Rota, cdc nhd nghien cim de nghi dimg md nSo, md tiiy dl phdn l|ip virut. Ndm 1949, lin diu tien Endes da thdnh cdng trong viec nudi ciy vmit Rota
tren te bdo md đng vat cd vii trong phdng thi nghiem. Nam 1954 vdi cdng trinh nghien ciiu dng da khdng (finh vinit Rota cd klia ndng nhan len tdt trong tl bdo md.
Cd 2 loai tl bdo nhay cdm vdi virut Rota: đng te bdo thudng true vd đng te bdo than khi (adsbygoogle = window.adsbygoogle || []).push({});
tien phat. Te bdo thudng true Id loai tl bdo cd the tach nhidu Ian ma khdng thay đi đn đc tinh
cua te bdo nhu te bdo Hep2C cd ngudn gdc ttr tl bao ung thu bieu md ngudi, te bdo vero cd ngudn gdc tir te bao than khi xanh chau Phị Te bdo tien phdt la đng te bdo tdch true tiep tir md dgng vat nhu te bdo than khi, than thd,... Te bdo than khi tien phat la mdt trong cdc loai le bdo nhay cdm iMt vdi virut Rotạ Nhd vdo dac tinh nay cac nha nghien ciiu da sir dung te bao than khi tien phat de sdn xuit vdcxin Bai liet sdng u6ng.
Co che nhan len cua virut Rota trong te bdo: Virut Rota chiia ARN mdt sgi duong. ARN ciia virut vao trong tl bao se hoat dgng nhu nhu ARN thdng trămARN). Qua trinh nay bao gdm 5 giai doan:
• Giai doan hip phy vd xam nhdp: Vhut Rota bam vdo cdc thu till dac hieu tren bl mdt tl bdo cam thu, sau đ chiing xdm nh|ip vdo ben trong te bdo bdng co chl thyc bdo
• Giai dỏm cd do: Giai dogn ndy xdy ra ngay sau khi virut xdm nhdp vdo bdo tuong tl bdọ Viec thdo bd vd capsit dugc thyc hidn dudi sy tham gia cua men proteaza cua tl bdọ ARN gidi phdng ra 1dm khudn mdu tdng hgp cdc thdnh phin ciia h^t virut mdị
• Giai d o ^ ting hgp cdc thanh phin cua cua virut: Sau khi thoat vd, ARN ton tai ty do trong bdọ Chiing hoat đng vhu m^t mARN vd tdng hgp nen mgt polyprotein cd trgng lugng phan tii 220kDal dudi tdc dgng ciia men ARN-polymeraza cd sdn trong tl bdọ Tir polyprotein nay t ^ h ra thdnh cdc protein trung gian P1,P2,P3. Tir protein PI sd ting hgp nen cdc protein ciu tnic cua vurut nhu VPl, VP2, VP3, VP4. Protein P2 se tdng hgp nen protem 2ĂMen proteaza), 2B,2C. Protein P3 tdng hgp nen protein 3A,3C(men proteaza), VPg vd men polymeazạ Ddng thdi, sau khi thodt vd, ARN(+) cua virut dugc dimg 1dm khudn mau tdng hgp nen ARN(-). Tilp tiieo chiing lay ARN(-) ndy lam khudn mdu de tdng hgp nen cdc sgi ARN(+) mdi ciia virut. Qud trinh sao chep nay dugc thyc hien tir dau 3 dudi tdc dgng ciia men sao chep ARN. • Giai dỏin ldp gidp: Cdc sgi ARN(+) mdi dugc tdng hgp se gdn vdi VPg vd dugc bao bgc bdi vd
capsit dl tao thdnh h^t virut mdị Diu tien VP4 dugc lien ket vdi ARN d diu 5". Cdc protein khde VP1,VP2,VP3 tdp hgp lai thdiih ciccpssomẹ Cdc capsomer ndy tdp hgp lai thdnh mdt vd capsit vd bao bgc liy ARN de hinh thanh nen hat virut mdị Cdc hat virut mdi hinh thdnh dugc t|.p trung t?i bdo tucmg cua te bdo tao thanh cdc tieu the nguydn sinh khi ta nhudm va soi tren kinh hiln vị Cdc tilu the ndy diy If ch nhan te bdo ve mdt phia sdt vdi mdng te bdọ
• Giai dôn gidi phong vmit: Virut Rota dugc gidi phong ra ngodi nhd qud trinh phd huy mdng te bdo vd todn bg sd virut dugc gidi phdng ra ngoaị Ngudi ta tinh rang chu ky nhdn len cua virut trong tl bdo keo đi khdng qud 3 gid vd khodng 10^ hat virion tren mdt te bao dugc hinh thanh.