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Metacyclogenesis is a major determinant of Leishmania promastigote virulence and attenuation

R da Silva1, D L Sacks

  • 1Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892.

Infection and Immunity
|November 1, 1987
PubMed

Insights

Leishmania major virulence in mice depends on the proportion of nonagglutinable (PNA-) promastigotes, which represent infective metacyclic stages. Metacyclogenesis, the development of these stages, varies and is unstable, impacting virulence.

Area of Science:

  • Parasitology
  • Molecular Biology
  • Immunology

Background:

  • Leishmania major virulence is complex and influenced by parasite stage.
  • Peanut agglutinin (PNA) binding distinguishes promastigote populations.
  • Metacyclogenesis is crucial for Leishmania infectivity.

Purpose of the Study:

  • To investigate the in vivo virulence of Leishmania major promastigote populations based on PNA agglutination.
  • To correlate PNA binding with the infective metacyclic stage of Leishmania major.
  • To assess the stability of metacyclogenesis in cloned Leishmania major lines.

Main Methods:

  • Studying virulence patterns of cloned Leishmania major lines in BALB/c mice.
  • Using peanut agglutinin (PNA) agglutination to differentiate promastigote populations.
  • Analyzing the proportion of PNA- (nonagglutinable) promastigotes in cultures.

Main Results:

  • Logarithmic-phase promastigotes (PNA+) were avirulent, while stationary-phase promastigotes (containing PNA- organisms) were virulent.
  • Purified PNA- promastigotes from stationary cultures represented the most virulent inoculum.
  • Metacyclogenesis varied significantly among strains and clones and was unstable during prolonged subculturing, leading to attenuation.

Conclusions:

  • PNA binding is a reliable marker for infective metacyclic stage promastigotes of Leishmania major.
  • Metacyclogenesis is not stable in cloned Leishmania promastigote lines.
  • Virulence comparisons require determination of metacyclic populations in inocula.

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