.

By,

MAGESH.R

Under eminent

Guidance of

Mr.C.MUTHURAJ

REVERSE VACCINOLOGY

• A protein with the desired characteristics can be found using computational methods.

• A select set of proteins within that organism may prove useful as a vaccine candidate.

• This is a major improvement is known as REVERSE VACCINOLOGY.

In reverse vaccinology, there are four steps to the overall procedure

:

prediction of vaccine candidates

cloning and expression of the proteins

challenge animal and validate the immune response

and finally clinical trial

Bacterial Genome Statistics•First complete genome sequence available in 1995;

•Now, more than 190 completely sequenced genomes publicly available;

•Provides extensive data for comparative analysis;

•All available statistics of completely sequenced bacterial genomes to date, have been compiled into a single table (present study);

•Allowing for an initial comparative genomics analysis;

Bacterial Genome Sequencing

Global genomic approach to identify new vaccine candidates

Genome SequenceGenome Sequence

Proteomics TechnologiesProteomics

TechnologiesIn silico analysisIn silico analysis

IVET, STM, DNAmicroarrays

High throughputCloning and expression

High throughputCloning and expression

In vitro and in vivo assays forVaccine candidate identification

In vitro and in vivo assays forVaccine candidate identification

In Silico Analysis

Gene/Protein Sequence Database

Disease related protein DB

Candidate Epitope DB

VACCINOME

PeptideMultitope vaccines

Epitope prediction

What Are Epitopes? 

• Antigenic determinants or Epitopes are the portions of the antigen molecules which are responsible for specificity of the antigens in antigen-antibody (Ag-Ab) reactions and that combine with the antigen binding site of Ab, to which they are complementary.

EPITOPES

B-cell epitopes Th-cell epitopes

MERITS & DEMERITS

• Advantages– Fast access to virtually

every antigen– Non-cultivable can be

approached– Non abundant antigens

can be identified– Antigens not expressed

in vitro can be identified.– Non-structural proteins

can be used

• Disadvantages– Non proteinous antigens

like polysaccharides, glycolipids cannot be used.

Genome sequencing & Identification of vaccine Candidates of

Neisseria meningitidis

Complete Genome Sequence of Neisseriameningitidis Serogroup B Strain MC58

Identification of Vaccine Candidates Against Serogroup B Meningococcus by Whole-Genome Sequencing.

Neisseria meningitidis is a human pathogen that, despite available antibiotic therapy, is still a major cause of mortality as a result of sepsis and meningitis.

The availability of an increasing number of bacterialgenome sequences, together with the MenB example, has prompted the application of the reverse vaccinology approachto other pathogens.

.The use of bioinformatics tools in combination with molecular biology techniques, enables the systematic investigation of the utility of potentialgenomic sequences to act as antigens for vaccine production.

It is now possible to conceive of the development of new vaccines against a wide variety of pathogens for which classical vaccinology has failed so far and, in theory, this approach could be extended to parasites and viruses.

Streptococcus pneumoniae

Porphyromonas gingivalis

Staphylococcus aureus

EXAMPLES

In the case of HIV, the scientist have spent two decades expressing every single form of HIV envelope protein as gp120, gp140 or gp160; they have expressed domains of it and synthesized every single peptide of this antigen.

The second antigen that has been the focus of the efforts to develop a vaccine against HIV is also a structural protein (gp55 GAG).

The use of Tat, Nef, Rev, Pol, antigens which is showing very promising results (3-5) is telling us that if we had used reverse vaccinology approach to HIV, HCV and from the very beginning the scientist had considered all possible antigens as targets for vaccine development, perhaps we already had a vaccine available for these viruses.