Prime/Boost Delivery Strategy For HIV-1 Vaccine

The human immunodeficiency virus-1 (HIV-1) is a single chain RNA retrovirusbelonging to the lentivirus family that selectively infects and kills CD4+ T-cells andmacrophages resulting in immune system failure. After the immunity system wasdestroyed by the AIDS virus, the human body lose the ability of resistance to eachkind of pathogen, thus it is easy cause many kinds of infections or the tumor, finallycaused the death. Because there does not have the special effect treatment, themortality rate is extremely high, therefore AIDS is called 20th century plagues. Indeveloping countries, behavioural changes are difficult to implement in an effectivemanner and the high cost of anti-viral drugs places them beyond the reach ofthepeople. At present, there does not have effective control its popular measure.The ultimate solution for the containment of the AIDS epidemic will require thedevelopment of an effective vaccine strategy. But the traditional vaccine can not takeon this millstone.The role of CD8 T cells in the control of immunodeficiency virus replicationhas been amply demonstrated. Soon after primary infection, activated HIV-specificcytotoxic T lymphocytes, mediated primarily by CD8+ cells, were detected inpatients and so the viral load was controlled. To the chronic AIDS patient whoinfects HIV-1 for a long time low virus load capacity in vivo and the condition slowdevelopment also corresponds. Widely CTL responses have been detected aims atGag, Pol, Nef and so on different conservative region, but once loses these CTLreaction, the patient rapidly changes over. In the monkey AIDS model, removes CTLwhich CD8 T cell mediate causes to be unable to control the load capacity ofmonkey HIV (SIV) and rapidly to be taken bad. All these proved that, effectivelyinduces CTL reaction aims at conservative region as Gag, Pol and so on has thepossibility to develop the effective AIDS vaccine completely.The DNA vaccine is a new technology which delivers DNA constructsencoding for a specific immunogen onto the host. Intramuscular injection of DNAvaccine leads to uptake of the plasmid by host cells and expression of the protein Ag.It can produce both cellular and humoral immune response as attenuated livevaccine, but does not have the very big latent crisis resemble latter.In the animal experiment, the DNA vaccine already succeeded in inducingprotective immunity to Hepatitis B virus,influenza virus,Rabies,SIV, Lymphocytevein clump of meningitis,malaria and tuberculosis. Similar exciting is also in AIDSDNA vaccine research aspect. Newly Boyer reported the DNA vaccine will be ableto protect the monkey free of HIV attacktion.Many vaccine research teams take modified vaccinia Ankara (MVA) as thecarrier of vaccine. It has been widely used in at present the human gene treatmentand the vaccine research, for example in III vice-flu vaccine and measles vaccineinvestigation.Recombinant replication-defective adenoviruses are being developed for use inhuman gene therapy to replace missing or faulty genes.Experiments in animals aswell as in humans using recombinant adenovirus expressing a recombinant geneinitially yielded promising results by showing high expression of theadenovirus-encoded protein either in hepatocytes after intravenous application or incells of the airway mucosa after inhalation.Fowlpox virus(FPV),the prototypic member of avipoxviruses,has also beenextensively used to develop candidate recombinant vaccines for poultrypathogens,including avian influenza virus, Marek's disease virus, Newcastle diseasevirus and infectious bursal disease virus..The basic prime–boost strategy involves priming the immune system to a targetantigen delivered by one vector and then selectively boosting this immunity byreadministration of the antigen in the context of a second and distinct vector. Thekey strength of this strategy is that greater levels of immunity are established byheterologous prime–boost than can be attained by a single vaccine administration orhomologous boost strategies. Prime–boost strategy has been shown to generate highlevels of T-cell memory in animal models. Recently, several papers have highlightedthe power of prime–boost strategies in eliciting protective cellular immunity to avariety of pathogens, including M. tuberculosis, HIV and simian immunodeficiencyvirus (SIV), malaria, Listeria monocytogenes , leishmania, Ebola virus, hepatitis Cvirus, herpes simplex virus, human papillomavirus and hepatitis B virus. Theprime-boost protocals in HIV commonly consist of priming with DNA followed byboosting with a live virus vector, but this protocol need to be further optimized.In this paper we constructed DNA vaccine and recombinant Fowlpox vaccine whichexpress the same extrinsic gene, HIV-1 Gag-Pol. To combine with recombinant MVA and/orrecombinant adenovirus AD5, we take the widespread careful research to prime-boost of HIV.Taking the optimized GagPol sequence of HIV-1 B/C subtype as the goal gene, wesubcloned it into carrier, after identification from nucleic acid and protein level, has obtainedHIV-1 DNA vaccine and rFPV vaccine.We have constructed two trunk of recombinant Fowlpox virus (FPV-PLW22-GP ,FPV-PSC11-GP) under PE/L or P7.5 promoter direction. We check their immunity efficience inBALB/C mice through cellular and humoral immune response. In the present study, we detectedthe use of the PE/L promoter significantly increase the expression and CTL response againstGagPol , but similarly results were not found for P7.5 promoter.Here we systemly compared different HIV vaccine forms: DNA,rFPV,rMVA and rAD5with several kinds of combination. At first we confirmed immunity effect of rFPV,rMVA,rAD5singly;secondly DNA prime/ virus boost was checked also, the result showed rAD5 is moreeffective than rFPV or rMVA. In this foundation, using rAD5 separately with DNA, rFPV andrMVA to carry out prime-boost strategy. We concluded from the results of WESTERN andELISPOT that rAD5 prime/rMVA boost strategy cause stronge immunity response best of all.In brief, the present paper system inspect prime-boost immunity strategy ofHIV vaccine, understand the different reorganization of virus carrier how to affectthe direction and the intensity of immunity, will provide the theory basis for the nextAIDS vaccine immunity procedure improvement.