Peptide directorySkin, immune & repair

HNP-4

The rare fourth neutrophil defensin, with a sequence of its own.

Where it comes from

Made in
Neutrophil granules, at a hundredth of the level of HNP-1 to 3
Sent out by
With the other neutrophil peptides
Acts on
  • Gram-negative bacteria above all
  • HIV in the laboratory

What it does

  • Kills E. coli more effectively than HNP-1 to 3
  • Blocks HIV entry in cell culture
  • Its sequence resembles the others only in the cysteine frame

In medicine

  • Nothing of its own. It sits at about a hundredth of the level of HNP-1 to 3, too little to measure in ordinary samples, and the usual assay does not see it 1
  • No medicine, and no trial has tested it in people

Beyond the body’s own use

  • It protected blood cells from HIV in culture better than HNP-1 to 3 did, and by a different route: it binds CD4 and gp120 far more weakly, so the effect is not simple sequestration 2
  • Its sequence shares only the six-cysteine frame with the other three, which makes it the test case for how much of a defensin’s killing comes from the fold rather than the sequence 1

Sources

  1. Wilde et al., Purification and characterization of human neutrophil peptide 4, Journal of Biological Chemistry 1989
  2. Wu et al., Human neutrophil alpha-defensin 4 inhibits HIV-1 infection in vitro, FEBS Letters 2005

This card describes what a medicine is for and what the evidence says; it recommends nothing. Talk to your clinician about anything you read here.