Immunology -based Vaccine 2

Electron micrograph of respiratory syncytial virus (RSV)

Roberto Garofalo, M.D., Presented by Arunkumar RengarajNanobio Analysis LabInha university

Respiratory syncytial virus (RSV)

Mild,cold-like symptoms in adults and older healthy children.

It can be more serious in young babies, especially those in certain high-risk groups.

Seroprevalent

Seroprevalence is the number of persons in a population who test positive for a specific disease based on

serology (blood serum)

Adenoviruses

Largest nonenveloped viruses

Double-stranded (ds) DNA that is between 26 and 48 Kbp

This can infect the membranes (tissue linings) of the respiratory tract, eyes, intestines, and urinary tract.

Viral vector

Viruses have evolved specialized molecular mechanisms to efficiently transport their genomes inside the cells they infect.

Delivery of genes by a virus is termed transduction and the infected cells are described as transduced

Safety

Low toxicity

Stability

Cell type specificity

Identification

Cotton rats are an important animal model to study infectious diseases because of their unique susceptibility towards human pathogens.

RSV F-protein

Fusion (F) glycoprotein is anchored in the virion membrane in a metastable, pretriggered form

Once triggered, the F protein undergoes a dramatic conformational extension

inserts its hydrophobic fusion peptide into the target cell membrane,

then folds back on itself to bring the membranes together and initiate fusion.

Genbank ACO83301.1

Abstract

Low-seroprevalent human adenovirus serotypes 26 and 35 (ad26 and ad35) encoding the RSV fusion (F) gene.

Single immunization of mice - one of these vectors induced high titers of RSV - neutralizing antibodies and high levels of F specific interferon-gamma-

producing T cells.

A Th1-type immune response was indicated by a high IgG2a/IgG1 ratio of RSV-specific antibodies, strong induction of RSV-specific interferon-gamma and

tumor necrosis factor-alpha cytokine producing CD8 Tcells, and low RSV-specific CD4 T-cell induction.

Both humoral and cellular responses were increased upon a boost with RSV-F expressing heterologous adenovirus vector.

Both single immunization and prime-boost immunization of cotton rats induced high and long-lasting RSV neutralizing antibody titers and protective

immunity against lung and nasal RSV A2 virus load up to at least 30 weeks after immunization.

Cotton rats were also completely protected against challenge with a RSV B strain (B15/97) after heterologous prime-boost immunization.

Lungs from vaccinated animals showed minimal damage or inflammatory infiltrates post-challenge, in contrast to animals vaccinated with formalin-

inactivated virus.

Ad26 and Ad35 have shown acceptable safety and tolerability profiles in multiple Phase 1 and 2a clinical trials as vaccine vectors for different target

diseases.[1,2]

Ad35 vaccine vectors showed good safety and tolerability profiles when tested in infants up to doses of 1 × 1011 vp [3]

Why this Vector?

T lymphocytes are a major source of cytokines.

These cells bear antigen specific receptors on their cell surface to allow recognition of foreign pathogens.

They can also recognise normal tissue during episodes of autoimmune diseases.

There are two main subsets of T lymphocytes, distinguished by the presence of cell surface molecules known as CD4 and CD8. T lymphocytes

expressing CD4 are also known as helper T cells, and these are regarded as being the most prolific cytokine producers.

This subset can be further subdivided into Th1 and Th2, and the cytokines they produce are known as Th1-type cytokines and Th2-type cytokines.

Christie Brough. Biology 307: Immunology. Dr. S. Sarafova. Davidson College. May 4, 2007

Characterization of RSV-specific cellular immune responses

substantial CD8T cell immune responses, and a moderate CD4T cell response.

These data collectively indicate that adenovirus vectors Ad26.RSV.F and

Ad35.RSV.F induce a Th1 type response.

Humoral immune responses induced by prime-boost immunization with Ad26.RSV.F and Ad35.RSV.F

Single immunization induced protective immunity

Virus neutralizing capacity against a wide panel of RSV strains

Fig. 4. Virus neutralizing capacity against a wide panel of RSV strains. Day 49 sera from cotton rats

immunized with Ad26.RSV.F or Ad35.RSV.F (107 vp, n = 5) were used in a virus neutralization assay

with the RSV strains A2, Long, B Wash and clinical isolates RSV 07 -041911, RSV 05-036549, RSV

CL57, RSV CL25, RSV 423, and RSV CL19, RSV B15/97. Sera from animals infected at day 0 i.n.

with 104 pfu of RSV A2 served as control. Palivizumab (Synagis® (MedImmune LCC)) at

concentration of 1.1 g/mL was used in the assay as control reagent. Results are expressed as mean titer

per group with standard deviation. The lower limit of quantification (LLoQ) is set on 4.5 (log2), and

indicated with a dotted line.

Discussion

In BALB/c mice, both Ad26.RSV.F and Ad35.RSV.F immunization induced high levels of RSV neutralizing activity in serum, a pronounced IgG2a antibody

subclass response, substantial CD8T cell immune responses, and a moderate CD4T cell response. These data collectively indicate that adenovirus vectors

Ad26.RSV.F and Ad35.RSV.F induce a Th1 type response.

Single dose administration, either i.n. or i.m., of Ad26.RSV.F or Ad35.RSV.F (109 vp) provided complete protection against RSV challenge load in cotton rats.

In BALB/c mice and cotton rats that were immunized with the Ad5 vector, reduction of viral load in the lungs to levels below detection levels

Heterologous prime-boost (Ad26.RSV.F prime-Ad35.RSV.F boost) immunization was the most potent.

Furthermore, there was no evidence of enhanced pulmonary pathology when vaccination was followed by RSV challenge in cotton rats even at sub-optimal

immunization regimens that allowed breakthrough infection

Reference

[1] Barouch DH, Kik SV, Weverling GJ, Dilan R, King SL, Maxfield LF, et al. International seroepidemiology of adenovirus serotypes 5, 26, 35, and 48 in pediatric and adult populations. Vaccine 2011;29(32):5203–9.

[2] Creech CB, Dekker CL, Ho D, Phillips S, Mackey S, Murray-Krezan C, et al. Randomized: placebo-controlled trial to assess the safety and immunogenicity of an adenovirus type 35-based circumsporozoite malaria vaccine in healthy adults. Hum Vaccin Immunother 2013;9(12):2548–57.

[3] Ouedraogo A, Tiono AB, Kargougou D, Yaro JB, Ouedraogo E, Kabore Y. A phase 1b randomized, controlled, double-blinded dosage-escalation trial to evaluate the safety, reactogenicity and immunogenicity of an adenovirus type 35 based circumsporozoite malaria vaccine in Burkinabe healthy adults 18 to 45 years of age. PLoS One 2013;8(11):e78679