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Outer membrane proteins P1 and P2 of Haemophilus influenzae type b: structure and identification of surface-exposed
1Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.
Abstract:
The outer membrane proteins (OMPs) P1 and P2 of Haemophilus influenzae type b exhibit molecular size and antigenic variation. Their structural genes have been cloned from prototype isolates of the most common disease-producing clonal groups. The derived amino acid sequences of P1 from strains of OMP subtypes 1H, 3L, and 6U have three variable regions between highly conserved regions. An immunodominant surface-exposed epitope was identified near the carboxyl terminus of P1 proteins from subtype 1H and 3L strains. The P2 genes from subtype 1H, 1L, and 3L isolates were identical. The P2 gene sequence from a subtype 6U isolate differs from the subtype 1H P2 gene by 13 nucleotides, resulting in 10 amino acid changes. The P2 gene from a subtype 2L isolate differs by 1 nucleotide from the subtype 1H P2 gene, resulting in 1 amino acid change at position 166. Two surface-exposed epitopes of OMP P2 were identified, one each between residues 158 and 174 and residues 319 and 341.
Insights
Outer membrane proteins P1 and P2 from Haemophilus influenzae type b show variation. Researchers identified specific epitopes on P1 and P2, crucial for understanding bacterial immune evasion.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Haemophilus influenzae type b (Hib) outer membrane proteins (OMPs) P1 and P2 are key targets for immune responses.
- These OMPs exhibit significant molecular size and antigenic variation, complicating vaccine development and diagnostics.
- Understanding the genetic basis of this variation is crucial for developing effective Hib control strategies.
Purpose of the Study:
- To clone and analyze the structural genes of OMPs P1 and P2 from prevalent Hib clonal groups.
- To identify variable and conserved regions within the P1 and P2 proteins.
- To map surface-exposed epitopes on P1 and P2 that may elicit protective immune responses.
Main Methods:
- Cloning of OMP P1 and P2 structural genes from prototype Hib isolates.
- Derivation and analysis of amino acid sequences for P1 and P2.
- Identification of conserved and variable regions within protein sequences.
- Epitope mapping using sequence analysis and predicted surface exposure.
Main Results:
- P1 proteins from different subtypes (1H, 3L, 6U) showed three variable regions interspersed with conserved regions.
- An immunodominant epitope on P1 was located near the carboxyl terminus in subtypes 1H and 3L.
- P2 genes were identical in subtypes 1H, 1L, and 3L, but showed variations in subtypes 6U and 2L.
- Two distinct surface-exposed epitopes on P2 were identified between residues 158-174 and 319-341.
Conclusions:
- Genetic analysis reveals conserved and variable domains in Hib OMPs P1 and P2.
- Specific epitopes on P1 and P2 have been identified, offering potential targets for vaccine and diagnostic development.
- The observed variations in OMPs P1 and P2 likely contribute to Hib's antigenic diversity and immune evasion capabilities.