Wani macaque HIV model ya sa rare broad antibodies su bayyana da sauri — clue ga vaccine, ba vaccine tukuna ba

Sakamako mai amfani a nan ba wai “an samu rigakafin HIV” ba ne

Binciken rigakafin HIV yana da wata babbar matsala da ke ɓoye a bayan gajeriyar kalma: broadly neutralizing antibodies.

Waɗannan antibodies, waɗanda ake taƙaita sunansu zuwa bNAbs, za su iya gane nau’ikan HIV da yawa maimakon su yi aiki kan ƙaramin rukuni guda ɗaya kawai. Wannan shi ne dalilin muhimmancinsu. Binciken passive transfer ya nuna cewa ba macaques bNAbs masu dacewa na iya kare su daga SHIV challenge, kuma a mutane antibody VRC01 ya ba da kariya daga nau’ikan virus da suke da sauƙin shafuwa da shi. Amma sa jiki ya samar da irin waɗannan antibodies ta hanyar vaccination ya fi wahala sosai.

Dalilin ba wai kawai HIV yana yawan yin mutation ba ne. Babbar matsalar ita ce mafi kyawun bNAbs yawanci ba sa bayyana a mataki guda.

Sau da yawa suna fitowa ne daga dogon tsarin sauye-sauye tsakanin virus da tsarin garkuwar jiki. Da farko, ana buƙatar wata B cell mai wuya samu, wadda receptor ɗinta ya yi kama sosai da abin da zai iya gane siffar da ake nema a virus. Daga nan virus yana sauyawa domin tserewa antibodies da suka bayyana. Layin B cells da ke samar da antibody shi ma yana sauyawa a martani. A zagaye bayan zagaye, virus da antibody suna tura juna ta hanyar mutation da selection.

A natural infection wannan na iya ɗaukar watanni ko shekaru, kuma mutane kaɗan ne kawai suke samar da ƙarfi mai faɗi — wato antibodies da za su iya neutralize nau’ikan HIV da yawa, ba kawai nau’in da ya fara haifar da martanin ba.

Sabuwar takarda a Science daga Ashwin Skelly, Harry Gristick, Hui Li, Edem Gavor da abokan aikinsu ba ta warware wannan matsala a mutane ba. Abin da ta yi ya fi takamaimai amma har yanzu yana da muhimmanci: ta ƙirƙiri wani macaque SHIV model inda wani nau’in bNAbs mai ban sha’awa ya bayyana sau da yawa kuma cikin sauri fiye da yadda aka saba, sannan ta sake gina hanyar matakai biyu da ta kai ga hakan.

Abin da ya dace a ce ba “muna da rigakafin HIV” ba ne. Abin da binciken ya nuna shi ne: marubutan sun gina model da ya sa wata hanyar bunƙasar antibody mai wuya gani ta zama bayyananniya sosai har za a iya nazarinta, kuma wata rana watakila a yi ƙoƙarin kwaikwayonta.

Abin da marubutan suka canza

Manufar ita ce V3-glycan patch a kan envelope protein na HIV.

Wannan suna yana haɗa ra’ayoyi da dama. HIV yana da envelope protein, wanda ake kira Env, da yake amfani da shi wajen shiga cells. Wani sashe na Env shi ne V3 loop. Kusa da gindin wannan loop akwai wani wuri mai rauni da aka lulluɓe da glycans — sugar groups da suke manne da protein. Muhimman glycans biyu a wannan yankin ana kiransu N332 da N301, sunaye da ke nuna wurin da sugars ɗin suke a Env.

Wasu human bNAbs suna iya gane wannan V3-glycan patch kuma su hana HIV aiki da ƙarfi. Marubutan kuma sun lura cewa V3-glycan bNAbs suna da bambancin tsari da na genes fiye da wasu nau’ikan bNAbs. Wannan abu ne mai amfani ga ƙirar rigakafi: idan precursor B cells iri-iri za su iya kai wa wannan target, ba sai an dogara da wani starting point na genetics da yake da matuƙar wuya samu ba.

Marubutan sun yi aiki da simian-human immunodeficiency virus, ko SHIV. SHIV ba HIV kansa ba ne; chimeric virus ne da ake amfani da shi a macaques domin a iya nazarin immune responses ga envelope na HIV a animal model.

Sun ƙera wani virus da suka kira SHIV.5MUT. Sunan fasaha ne, amma ra’ayin mai sauƙi ne: a fara da SHIV da ke ɗauke da envelope na HIV, sannan a gyara ƙaramin ɓangare na envelope ɗin domin a sa V3-glycan target da yake ɓoye ya fi sauƙin isa ga antibodies.

Babban canjin ya kasance a V1 loop na envelope ɗin HIV. Residue a nan yana nufin matsayi guda na amino acid a protein. Idan aka kwatanta da parental SHIV.BG505.N332, 5MUT ya bambanta a residues huɗu na V1 loop: V134Y, N136P, I138L da D140N. Kowane code yana nufin an maye gurbin wani amino acid da wani a takamaiman matsayi. Waɗannan sauye-sauye huɗu sun sa V3-glycan epitope — wato fuskar target da antibody zai gane — ta fi samun damar isa ga sanannun V3-glycan antibodies.

Gwajin dabbobin ya kwatanta yanayi uku.

Wasu macaques an fara yi musu immunization da wasu Env immunogens da aka ƙera tun da farko, sannan daga baya aka infect su da SHIV.5MUT. Wato tsarin garkuwar jikinsu ya riga ya ga Env proteins da aka tsara kafin engineered virus ɗin ya iso.

Wata ƙungiya ba a fara yi mata immunization ba; an infect ta kai tsaye da SHIV.5MUT.

Control group kuwa an infect ta da parental SHIV.BG505.N332, wato virus na kwatance wanda ba ya ɗauke da sauye-sauyen V1-loop na 5MUT.

Wannan tsarin gwajin yana da muhimmanci domin babban sakamakon bai dogara kawai da vaccination na farko ba. Marubutan sun gano cewa engineered virus ɗin, ko wani nau’insa da ya samo asali daga gare shi yayin evolution, shi ne ya fi kama da abin da ya fara tayar da bNAb lineages.

Abin da suka gano

Binciken ya fara da macaques 42 da aka infect, a rukunoni huɗu. Productive infection ya faru a duk 42, ma’ana challenge virus ɗin ya samu damar kafa infection. Daga baya an cire dabbobi shida daga babban nazarin shekara ɗaya: biyar saboda sun ci gaba da samun viral load mai yawa kuma cutar ta yi saurin kai su ga AIDS, ɗaya kuma saboda ya iya sarrafa infection har virus ya yi ƙasa sosai a jini kuma ba a gano autologous neutralization ba — wato antibodies ɗinsa ba su nuna cewa suna neutralize virus ɗin da ya infect shi ba. Hakan ya bar macaques 22 da SHIV.5MUT da controls 14 da parental SHIV.

Marubutan sun ayyana plasma bNAb response a matsayin neutralization na aƙalla viruses uku daga cikin heterologous viruses takwas cikin makonni 48 bayan infection. Heterologous a nan yana nufin viruses da ba su daidai da wanda ya fara infection; saboda haka gwajin yana tambaya ko antibodies sun wuce nau’in virus na farko.

Da wannan ma’auni, 14 daga cikin 22 macaques da SHIV.5MUT suka samar da bNAb responses. A control group na parental SHIV.BG505.N332 kuwa, 0 daga cikin 14 suka yi haka. Bambancin ya yi ƙarfi sosai a gwajin marubutan (P < 0.0001, Fisher’s exact test).

Takwas daga cikin dabbobin SHIV.5MUT sun neutralize aƙalla shida daga cikin heterologous viruses takwas na screening panel, kuma ID50 titers sau da yawa sun haura 1:1000. ID50 ma’aunin dilution ne: idan neutralization har yanzu ana iya ganinsa bayan an diluted plasma fiye da sau dubu, martanin ba ƙarami ba ne. Dukkan breadth na plasma ya koma ga V3-glycan epitope.

Daga nan marubutan suka ware antibody lineages daga dabbobin da suka fi nuna breadth a plasma. Sun gwada monoclonal antibodies 238 daga lineages 106, kuma suka gano V3-glycan bNAb lineages 12 daga macaques takwas.

A kan wani babban global panel mai viruses 130, antibodies ɗin sun bambanta sosai. Neutralization breadth ya kasance daga 6% zuwa 68%. Breadth a nan shi ne kaso na viruses da antibody zai iya neutralize. Geometric mean IC50 ya kasance daga 0.06 zuwa 2.80 micrograms a milliliter; IC50 shi ne concentration na antibody da ake buƙata domin rage infection da rabi a assay, saboda haka ƙaramin IC50 yawanci yana nufin stronger neutralization.

Mafi kyawun antibodies sun kai breadth mai kama da na ƙarfafan V3-glycan bNAbs da aka samo daga mutane. Amma range ɗin yana da muhimmanci: ba kowane antibody ne ya kasance broad ba.

Antibody lineages ɗin ma suna da bambanci. A nan takardar tana duba tsarin antibody: waɗanne variable-heavy-chain gene segments suka yi amfani da su, tsawon wani muhimmin binding loop, da kuma yawan mutation da antibody genes suka tara yayin maturation. Lineages ɗin sun yi amfani da gene-family segments na VH3 da VH4 da dama, CDRH3 loop length ya kasance daga amino acids 14 zuwa 25, kuma matsakaicin VH somatic mutation a matakin nucleotide ya kai 8.4%. Marubutan suna ganin wannan alama ce mai kyau: bayan an fara tayar da waɗannan lineages, wataƙila ba sa buƙatar irin matsanancin mutation burden da ake gani a wasu HIV bNAbs.

Hanyar matakai biyu

Abin da ya fi ban sha’awa a takardar ba wai antibodies sun bayyana kawai ba ne. Muhimmin abu shi ne yadda suka bayyana.

Model ɗin marubutan yana da matakai biyu.

Da farko, SHIV.5MUT yana bayyana wani V1-loop region da aka gyara. Early antibody response yana kai hari ga wannan yankin V1. Daga baya virus yana tserewa ta hanyar rage tsawon V1 loop da canza glycosylation ɗinsa — wato tsarin sugars da ke manne da shi.

A mataki na biyu, waɗannan escape variants masu gajeren V1 suna ƙara bayyana V3-glycan epitope da ke ƙasa. Wannan yana ba precursor B cells na V3-glycan bNAbs damar kama target ɗin. Da zarar waɗannan precursors sun fara aiki, virus da antibody suna ci gaba da coevolution, kuma wasu lineages suna maturation har su samu breadth.

Wannan shi ne babban abin da ya shafi vaccine design. Marubutan ba wai kawai sun ga immune response ba ne; sun tsara jerin abubuwan da suka faru wanda masu ƙirar rigakafi za su iya ƙoƙarin kwaikwaya ba tare da sai sun yi amfani da replicating virus da ke haifar da infection ba.

Takardar kuma ta nuna cewa mutane na iya kasancewa suna da irin precursor material da ake buƙata domin wannan hanyar. VH gene segments da macaque bNAb precursors suka yi amfani da su suna daga cikin common alleles a rhesus macaque da human immunoglobulin databases. Wannan bai tabbatar cewa hanyar za ta yi aiki iri ɗaya a mutane ba. Amma yana sa ta fi zama abin da ya dace da binciken rigakafin mutane, ba wani abin mamaki na macaque kawai ba.

Abin da wannan bai tabbatar ba

• Bai nuna cewa an ƙirƙiri rigakafin HIV ba.
• Bai nuna kariya daga HIV infection a mutane ba.
• Bai nuna cewa vaccination kaɗai zai iya maimaita wannan hanyar ba.
• Bai nuna cewa jikin mutum zai samar da irin waɗannan antibodies cikin aminci da tabbaci ba.
• Bai tabbatar cewa engineered SHIV kansa zai iya zama vaccine platform ba.
• Bai kawar da bukatar clinical trials, gwajin aminci, tsara dosing da tsara immunogens ba.
• Bai nuna cewa duk V3-glycan antibody lineages suna da amfani iri ɗaya ba; antibodies da aka ware sun kasance daga narrow zuwa broad.

Babbar iyaka ita ce wannan infection model ne. SHIV.5MUT ya zama kamar “evolving immunogen” ne saboda yana replication kuma yana sauyawa ƙarƙashin matsin immune system. Wannan yana da amfani sosai ga kimiyya, amma ba hanyar da za a iya ba mutum prophylactic vaccine kai tsaye ba ce.

Aikin fassara wannan zuwa maganin rigakafi ya fi wahala: dole ne a tsara immunogens da za su kwaikwayi jerin exposures masu amfani ba tare da uncontrolled infection shi ne ke motsa tsarin ba.

Yaya ƙarfin shaidar yake?

Ga ikirarin da takardar kanta take yi, shaidar tana da ƙarfi.

Babban kwatancen ya fito fili: 14 daga 22, idan aka kwatanta da 0 daga 14, cikin window ɗin makonni 48 iri ɗaya. Marubutan kuma sun haɗa plasma neutralization, ware monoclonal antibodies, structural analysis, B-cell receptor sequencing da longitudinal viral sequencing. Haɗin waɗannan bayanai ya fi ƙarfi fiye da a dogara da neutralization readout guda ɗaya.

Labarin mechanism ɗin ma ana iya bibiyarsa sosai. Marubutan sun iya ganin early V1 selection, su infer bNAb precursors, su ware mature antibodies, su map epitopes ɗinsu, su kwatanta structures, sannan su bi viral sequence changes tsawon lokaci. Wannan shi ne ɗaya daga cikin dalilan da animal model yake da amfani: yana ba da damar bin wannan tsari daga farko zuwa ƙarshe, abin da ya fi wahalar samu a human infection studies.

Amma akwai iyakoki na gaske. Macaques aka yi amfani da su, ba mutane ba. SHIV tsarin wakilci ne, ba HIV infection na mutum kai tsaye ba. Hanyar ta ƙunshi infection da engineered virus, ba wani kammalallen jadawalin vaccination ba. Kuma duk da cewa antibody response ya fi control yawan faruwa, dabbobi 8 daga cikin 22 na SHIV.5MUT ba su kai ma’aunin bNAb response ba.

Saboda haka shaidar tana da ƙarfi ga model da mechanism. Ga rigakafin mutum kuwa, har yanzu matakin farko ne.

Me ya sa wannan yake da muhimmanci

A binciken rigakafin HIV, sau da yawa ana farawa ne daga rare successful antibodies sannan a koma baya: a gano mature bNAb, a ƙiyasta ancestor ɗinsa, sannan a tsara immunogens da za su jagoranci B-cell lineage ta irin wannan hanya.

Wannan takarda ta ba da wani irin taswira dabam. Ta nuna wata hanya da za a iya maimaitawa inda engineered envelope state na farko yake tura virus zuwa escape, sannan escape ɗin ya ƙara bayyana target na gaba. Ba wai kawai an nuna wa immune system epitope na ƙarshe ba; antigen mai sauyawa ne ya ja tsarin garkuwar jiki mataki-mataki zuwa gare shi.

Idan masu ƙirar rigakafi za su iya maye gurbin replicating-virus ɓangaren da jerin immunogens da ake sarrafawa, wannan na iya taimakawa wajen ɗaya daga cikin matsalolin da suka fi wahala a HIV vaccine work: tayar da precursor cells da suka dace sannan a jagoranci maturation ɗinsu ba tare da martanin ya kauce zuwa wani target ba.

Wannan ci gaba ne na gaske. Amma irin ci gaban da ya kamata a bayyana shi daidai. Takardar ta ba da kyakkyawan blueprint ga vaccine design. Ba ta kawo ginin da aka gama ba.

Taƙaitaccen bayani

Skelly, Gristick, Li, Gavor da abokan aikinsu sun ƙera wani SHIV model da ya sa V3-glycan broadly neutralizing antibodies suka bayyana a macaques sau da yawa fiye da parental control virus. Cikin makonni 48, macaques 14 daga 22 da SHIV.5MUT suka samar da plasma bNAb responses, idan aka kwatanta da 0 daga 14 da parental SHIV.BG505.N332. Marubutan sun ware V3-glycan bNAb lineages 12, sannan suka bi wata hanyar matakai biyu: early antibodies ga altered V1 loop sun zaɓi escape variants masu gajeren V1, waɗanda suka ƙara bayyana V3-glycan epitope kuma suka tayar da bNAb precursors. Wannan muhimmin model ne da kuma alama ga ƙirar HIV immunogens. Ba sakamakon rigakafin HIV a mutane ba ne.

Bincike ba tare da ƙarin gishiri ba

Abin da takardar ta nuna: Engineered macaque SHIV model ya sa wani nau’in HIV broadly neutralizing antibodies ya bayyana sau da yawa fiye da parental control virus, kuma marubutan sun iya bibiyar wata hanya mai yiwuwa ta matakai biyu da ta haifar da su.

Abin da yake yiwuwa amma ba a tabbatar ba: Masu ƙirar rigakafi na iya wata rana kwaikwayon wannan hanyar da jerin immunogens da ake sarrafawa. Wannan shi ne abin da ake fata wajen fassara binciken zuwa rigakafi, amma takardar ba ta nuna shi a mutane ba kuma ba ta bayar da kammalallen vaccination schedule ba.

Abin da ba ta nuna ba: Ba ta nuna rigakafin HIV, kariya ga mutane daga HIV, ko wata hanya mai aminci ta amfani da replicating engineered virus a matsayin vaccine ba. Haka kuma ba ta nuna cewa kowane V3-glycan antibody lineage zai kasance broad ko mai amfani ba.

Babban iyaka ga mai karatu na gama gari: Mechanism mai amfani ya faru ne a cikin infection model. SHIV.5MUT ya yi replication, ya tsere daga matsin immune system, sannan sauyinsa ya ƙara bayyana target na gaba. Ba za a iya kwafin wannan uncontrolled process kai tsaye a prophylactic vaccination na mutum ba; za a buƙaci designed immunogens da za su maimaita jerin matakan cikin aminci.

Yawan amincewar da ya dace: Akwai babban dalilin amincewa cewa macaque model da mechanism ɗin da aka gani suna da gaske a cikin wannan gwaji. Amma amincewar cewa wannan kai tsaye zai haifar da rigakafin mutum ta fi ƙasa sosai. Sakamakon da ya dace a ɗauka shi ne an samu ingantacciyar taswira ga ƙirar HIV immunogens, ba wai an samu vaccine breakthrough ba.