Validation of Opsonophagocytic killing assay for “Streptococcus Pneumoniae’’ Internal Guide: Dr ASIT RANJAN GHOSH Professor, SBST External guide: Dr ASHA MALLYA DY DIRECTOR SERUM INSTITUTE OF INDIA LTD. PUNE 411028 Email.Id:[email protected]Kishor kulkarni- 14MBT0022 Email Id: [email protected]om (9422914177
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Validation of Opsonophagocytic assay for pnemococcal vaccine
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Validation of Opsonophagocytic killing assay for “Streptococcus Pneumoniae’’
Internal Guide: Dr ASIT RANJAN GHOSH Professor, SBST
External guide: Dr ASHA MALLYA
DY DIRECTOR SERUM INSTITUTE OF INDIA LTD.PUNE 411028
It is a species of genus streptococcus which belongs to the family of Streptococcaceae. It is a gram –positive diplococcal bacterium. First isolated by Pasteur in 1881. Currently 92 Pneumococcal serotypes are recognized. It is a fastidious bacterium, growing best in 5% carbon dioxide. at 37°C and has a doubling
Time of 20-30 min.
Clinical features : The major clinical syndromes of pneumococcal disease are pneumonia which is to be a major
cause of morbidity and mortality among both the elderly and the very young. Global Estimates suggest that approximately 10 million childhood deaths per year result from
pneumonia, Adults over 65 years old and people with chronic health problems bear the greater burden of
pneumonia
Fig1 Chains of Streptococcus pneumoniae bacteria.
INTRODUCTION
The symptoms of infectious pneumonia are which include the high fever (up to 105 degrees), Drowsiness, Rapid breathing, Chest pain, Cough with mucus.
Vaccination: The antibiotic resistant for Pneumococcal bacteria is also one of the main reason.
The development of an effective vaccine for the prevention of pneumococcal infection plays a crucial role in reducing the disease burden worldwide.
Pneumococcal vaccines are classified into two major categories those are : Pneumococcal Polysaccharide Vaccine (PPV) Pneumococcal Conjugate Polysaccharide Vaccine (PCV).
During this infection pus and fluid fill the in one or both lungs, and this interferes with oxygen absorption, making breathing difficult.
Fig2 Pneumonia Infection
4
Incubation in RT 20 min
Streptococcus pneumoniae
Serum
C1q
+
Baby rabbit sera
HL-60 cells
Plated
Incubation at 37oC for 45 min
INTRODUCTIONOpsonophagocytic Assay (OPA):
The present work relates to the field of Opsonophagocytic Activity (OPA) assays for Gram Positive bacteria, in particular S. pneumoniae
The principle of the Opsonophagocytic assay is based on the detection of the functional antibodies against Streptococcus pneumoniae after complement mediated opsonization through the classical pathway by antibodies in serum samples.
The OPA used in the analysis of pneumococcal vaccines is designed to mimic the in vivo opsonophagocytosis which involves bacteria, antibodies, complement, and phagocytic cells.
INTRODUCTION
Significance of OPA :
Functional antibodies are measured by Opsonophagocytic Assay (OPA) rather than by ELISA Which is helpful to increase the efficacy of the vaccine that's why OPA is considered as de facto gold standard in this field.
This assay provides an exact in vivo condition in in-vitro which involves bacteria, antibodies, complement, and phagocytic cells, that's why this method is widely accepted for measuring the protective capacity of pneumococcal antibodies.
Study shows that there is a substantial of evidence that the rapid clearance of pneumococcal from the blood is due to opsonophagocytosis mediated by type-specific antibody and complement.
This assay has been used extensively over the last 12 years and has effectively become the standard assay .
2.AIM AND OBJECTIVEAIM : The aim of this research project is the “Validation of Opsonophagocytic
killing Assay for Streptococcus Pneumoniae.”
Objectives-The main objectives of the present study include: Validating the performance of the assay in accordance with International Conference for
Harmonization guidelines, including its -
Precision - The degree of agreement of OPA results when serum specimens are tested multiple times.
Linearity - The ability of the OPA to yield titers that are directly proportional to the concentration of antibody.
Accuracy -
The closeness of agreement of a value obtained from the assay to the reference or known value.
Robustness- The susceptibility of these results to deliberate changes in assay conditions.
Specificity- The degree of PnPs-specific opsonophagocytic activity or nonspecific killing.
10 µl of serum diluted in OPB20 µl of bacterial suspension
10 µl complement source40 µl of HL-60 cells
1:32 C
1:64D
1:128 E
1:256 F
1:512 G
1:1024 H
Fig 4 Plate Format For OPA:
Fig 4 Plate Format For OPA
Results and Discussion
1 PRECISION
GRAPH 1.1 PRECISION
64
128
256
1. PRECISION
Result: The serum sample (007 sp) are tested multiple times, the results obtained showed
median titre 64 (n=20) and other titre we got is also + two fold of median titer i.e 128 (n=11 )and 256 (n=2) so 100% of the data was in accordance of qualification criteria.
.
Calculation:The results for precision are plotted with the No of repetitions on the X-axis and the OPA titre obtained on the Y-axis the median titre is calculated according to the statistical method. This median titre is highlighted with Red line.
2.AccuracyTable 2.1 Table 2.2
NS-Negative sera
Table 2.3 Table 2.4
2.Accuracy
Result:The final complied table shows the results for accuracy where in the obtained or observed titers for the serotype ‘A’ were compared with the median titer and a percentage agreement was calculated The results obtained showed 100% agreement (agreement is + two fold titer =64) accuracy for serotype ‘A’ .
Calculation:Table 2.5
3 LINEARITYTable 3.1
Table 3.2
Graph 3.1
Graph 3.2
3 LINEARITYTable 3.3
Serotype A Linearity Run-4
3
56.0
5
y = -0.9415x + 6.0585R2 = 0.9487
0.0
2.0
4.0
6.0
8.0
10.0
0 0.5 1 1.5 2 2.5 3 3.5
Serum Dilution
Titre
Table 3.4
Graph 3.3
Graph 3.4
3 LINEARITY
Calculation: The results for Linearity are plotted by first converting the values for the serum
dilution (007 sp) and the titers obtained in to LOG 2 and then are plotted on the X- axis and the Y-axis respectively. The regression coefficient and the resulting linear equation are obtained through Microsoft EXEL.
Result: The correlation coefficient of the serotype ‘A’-specific OPAs ranged from 0.948 to
1.000 and All slopes were within the acceptable range ,Thus the data support good linearity.
4 ROBUSTNESSTable 4.1
E-Effector, T-Target
Table 4.2
Graph 4.1
Graph 4.2
4 ROBUSTNESS
Serotype A Robustness Run-4
96
64 64
40
20
40
60
80
100
120
400:1 200:1 100:1 50:1
E:T Ratio
Titre
E-Effector, T-Target
Graph 4.3
Graph 4.4
Table 4.3
Table 4.4
4 ROBUSTNESS
Calculation: The results for robustness are plotted with the Dilution for HL-60 cells (i.e.
400:1, 200:1,100:1 and 50:1) on the (EFFECTOR TO TARGET) X-axis and the OPA titre obtained for the same on the Y-axis.
Result: It was observed that the HL-60 ratio till 400:1 , 200:1 and 100:1 showed
no reduction in the titre whereas the ratio of 50:1 shows a dip in the titer values.
5 SPECIFICITYGraph 5.1
Graph 5.2
Table 5.1
Table 5.2
5 SPECIFICITY
Calculation: The result for specificity plotted as on Y axis the no of colonies formed and on X axis different serum dilution, trendlines indicate results for the FOUR different treatments. Result :Specificity (competitive inhibition) –The result shows homologous PnPs inhibited ≥80% of Opsonophagocytic activity and heterologous PnPs or no polysaccharide inhibited ≤20% of opsonophagocytic activity. The data obtained indicate the assays for A Serotype specific.
6 Conclusion
To Establish a more reliable and robust assay certain parameters need to be studied according to the ICH guidelines and After validating the serotype “A” of S. pneumoniae on various parameters like Precision, linearity, Accuracy, Robustness and Specificity. we can concluded that the validation of Opsonophgocytic killing assay for S. pneumoniae is successfully done and the outcomes from the assessment of these parameters is going to help us for understand and to develop new and improved vaccines for various dreadful diseases caused by serotype “A” of S. pneumoniae.
7 References
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