Applied Biology

Vaccine

Break in cold chain mainly results in:

Break in cold chain defined as temperature excursion outside recommended range due to equipment failure, power outage, improper conditioning of ice packs causing freezing, transport delays, human error leaving vaccines outside refrigerator. Consequences mainly vaccine failure due to irreversible potency loss. Heat exposure accelerates physico-chemical degradation: proteins unfold aggregating via hydrophobic interactions, deamidation of asparagine residues altering epitopes, hydrolysis of phosphodiester bonds in mRNA vaccines producing fragmented inactive RNA, replication titer of live attenuat

Ref: Matthias et al. Bull WHO 2007 85:400 Break cold chain vaccine failure; WHO VVM guidance.

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Vaccine

The cold chain in vaccination refers to:

Cold chain in vaccination encompasses system ensuring vaccines maintained within manufacturer recommended temperature range during storage and transport from production facility through national, regional, district stores to health centers and outreach vaccination sessions preserving potency until moment administration. Term refers to low temperature preservation, not manufacturing or injection method. Typical vaccines requiring 2 to 8C refrigeration include DTP, hepatitis B, pentavalent, IPV, BCG; some lyophilized vaccines stable at ambient during transport but reconstituted require immediate

Ref: WHO Cold chain storage transport low temperature 2-8C; WHO PQS devices catalog; CDC storage.

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Vaccine

BCG vaccine is administered via:

BCG vaccine is administered via intradermal route which is uniquely specified among routine childhood immunizations. Technique involves injection of small volume 0.05 ml for infants under 12 months and 0.1 ml for older children into superficial dermis of lower insertion of deltoid muscle left arm using 26G or 27G needle inserted bevel upward at approximately 10-15 degree angle pushing needle 2 mm subepidermal creating characteristic peau d orange wheal 6-8 mm bleb that disappears within 30 minutes indicating correct placement. Dermis abundant in Langerhans cells expressing langerin CD207 and d

Ref: WHO BCG vaccine position paper 2018 intradermal; Plotkin BCG route; CDC intradermal.

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Vaccine

Edible vaccines should preferably be consumed:

Edible vaccines rely on oral exposure to gut associated lymphoid tissue, so preservation of antigen structural integrity is crucial. Cooking, drying at high temperature, roasting, fermentation involving microbial proteases and acidic boiling denatures protein tertiary structure, unfolding alpha helices and beta sheets, disrupting disulfide bonds essential for conformational B cell epitopes required for neutralizing antibody induction, aggregating proteins into insoluble forms, destroying T cell epitopes via hydrolysis. For example HBsAg virus like particles dissociate into monomers losing part

Ref: Mason et al. 2002 Trends Biotech Edible consumption raw; Streatfield Kwon 2007 Should be raw.

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Vaccine

Which plant was engineered to produce edible Hepatitis B vaccine?

Banana was specifically engineered to produce edible Hepatitis B vaccine demonstrating fruit-based oral immunization feasibility. Hepatitis B surface antigen HBsAg 226 amino acid small surface protein self-assembles into 22 nm virus like particles highly immunogenic protective against HBV infection. Early work by Thanavala 1995 expressed HBsAg in transgenic tobacco plants showing assembly. Subsequent collaboration by Arntzen, Mason and colleagues introduced HBsAg gene under fruit specific promoter E8 and constitutive CaMV 35S with endoplasmic reticulum retention signal KDEL into Cavendish bana

Ref: Thanavala et al. PNAS 1995 92:3358 Banana HBsAg; Arntzen 1997 Edible Hepatitis B banana; Lancet.

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Vaccine

Edible vaccines are produced using:

Edible vaccines utilize transgenic plants as low-cost production and oral delivery systems synthesizing recombinant immunogens in edible tissues. Concept pioneered by Charles Arntzen 1990 proposing foods containing antigens could be eaten eliminating purification, cold chain, sterile needles, medical personnel and hazardous waste associated with injections. Plant transformation via Agrobacterium tumefaciens binary vector carrying antigen gene driven by constitutive CaMV 35S promoter or tissue specific patatin, glutelin for seed accumulation, plus signal peptide targeting to endoplasmic reticul

Ref: Ma et al. Nat Rev Genet 2003 Plant vaccines; Rybicki Adv Virus Res 2014 Edible transgenic.

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Vaccine

DNA vaccines deliver genes in the form of:

DNA vaccines deliver genetic instructions as circular plasmid DNA rather than protein antigen or RNA. Plasmid constructs typically contain bacterial origin pUC, antibiotic resistance for selection during manufacturing, and eukaryotic expression cassette comprising strong promoter cytomegalovirus CMV immediate early with intron A enhancing transcription, codon optimized antigen gene, polyadenylation signal bovine growth hormone BGH or SV40 preventing mRNA degradation. Plasmids produced in Escherichia coli fermentation high copy number, purified supercoiled isoform removing endotoxin via chromat

Ref: Wolff et al. Science 1990 DNA vaccines plasmid; Plotkin DNA vaccines; WHO DNA plasmid.

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Vaccine

Which of the following is an mRNA vaccine?

Pfizer-BioNTech BNT162b2 Comirnaty exemplifies messenger RNA vaccine success. It contains 30 microgram dose of nucleoside modified mRNA encoding full length SARS-CoV-2 spike protein stabilized in prefusion conformation by double proline substitution K986P V987P preventing post fusion transition, retaining epitopes for neutralizing antibodies. mRNA produced by cell free transcription, purified to remove dsRNA impurities that trigger innate over activation. LNP formulation enables efficient transfection without electroporation. After emergency use authorization December 2020, phase three trial i

Ref: Polack et al. NEJM 2020 383:2603 Pfizer-BioNTech mRNA; CDC mRNA vaccines list; FDA Comirnaty.

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Vaccine

mRNA vaccines work by:

Messenger RNA vaccines represent nucleic acid platform delivering synthetic mRNA encoding pathogen antigen directly to host cytoplasm where host ribosomal machinery translates it transiently. Manufacturing involves in vitro transcription using T7 RNA polymerase from linearized plasmid DNA template encoding spike protein, incorporation of modified nucleoside N1 methylpseudouridine replacing uridine reducing TLR7 mediated inflammation and increasing translation half-life, addition of 5' cap 7-methylguanosine via vaccinia capping enzyme and 2'O-methylation, and 3' polyadenine tail 100 nt for stab

Ref: Pardi et al. Nat Rev Drug Discov 2018 mRNA mechanism; Polack NEJM mRNA; CDC mRNA work.

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Vaccine

AZD1222 (Covishield) vaccine uses which vector?

AZD1222 vaccine known in India as Covishield produced by Serum Institute Pune under license from AstraZeneca Oxford University uses chimpanzee adenovirus vector ChAdOx1. ChAdOx1 derived from chimpanzee adenovirus isolate Y25 taken from chimp stool 1960s, selected because human population seroprevalence low compared to human adenovirus 5 where 40-60 percent adults have neutralizing antibodies compromising vector. Vector engineered by deleting E1 genes essential for replication making it replication deficient incapable of causing disease, requiring E1 complementing cells HEK293 for manufacturing

Ref: Voysey Lancet 2021 397:881 AZD1222 ChAdOx1; Oxford ChAdOx1 history; WHO Covishield.

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Vaccine

Viral vector vaccines deliver antigen genes using:

Viral vector vaccines deliver genes encoding pathogen antigens using harmless viruses engineered to be replication deficient as transportation vehicles. Concept employs vector virus lacking pathogenic genes but retaining ability to infect mammalian cells, deliver DNA into nucleus, transcribe transgene using host polymerase, translate antigen intracellularly mimicking natural infection. Vector backbone commonly human adenovirus serotypes 5 and 26, chimpanzee adenovirus ChAdOx1, canarypox ALVAC, modified vaccinia Ankara MVA, vesicular stomatitis virus VSV, adeno associated virus. Deletion of E1

Ref: Tatsis Ertl Mol Ther 2004 Viral vectors; Draper Heeney Nat Rev Microbiol Vector vaccines.

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Vaccine

DPT vaccine provides protection against:

DPT vaccine, also known as triple antigen, provides simultaneous protection against diphtheria, pertussis, tetanus three bacterial diseases responsible for high childhood morbidity mortality before immunization era. Diphtheria caused by Corynebacterium diphtheriae toxigenic strains producing diphtheria toxin transported to heart causing myocarditis, nerves neuritis and kidney necrosis plus pseudomembrane airway obstruction. Pertussis caused by Bordetella pertussis Gram-negative coccobacillus attaching ciliated epithelium via filamentous hemagglutinin, producing pertussis toxin ADP-ribosylating

Ref: CDC Pink Book Diphtheria Pertussis Tetanus DPT; WHO DPT definition combined; Plotkin.

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