A fine functional homology between chitinases from host and parasite is relevant for malaria transmissibility

High levels of plasma chitotriosidase are a marker of macrophage activation in several pathologies and, in particular, in human malaria. Plasmodium falciparum, during its maturative cycle in the midgut of the Anopheles mosquito, secretes a chitinase to disrupt the peritrophic membrane, a necessary step in the migration of the parasite from the midgut to the salivary glands of malaria's vector. The cooperation between human chitotriosidase (Chit) and the chitinase from P. falciparum in attacking the peritrophic membranes in the Anopheles midgut has been recently demonstrated by in vivo experiments. The present study confirms, by computational methods, this functional homology. A simple sequence analysis method, potentially useful to assess fine textual closeness in families of homologous proteins, is reported here and applied to a set of chitinases from mammals and plasmodia. This analysis confirms the clustering and the phylogenetic relationships obtained with well-known alignment methods, but also shows that the sequences of chitinases from malaria hosts and malaria parasites are correlated. This correlation, a sign of functional homology, is discussed as a condition for the spreading of different forms of malaria. From this perspective, one can get insight into the origins of malaria and its genetic or pharmacological control.

Maternally transmitted target antigen for unrestricted killing by NZB T lymphocytes

A new target antigen for unrestricted killing was defined by NZB T lymphocytes which were immunized and restimulated with H-2-identical BALB/c spleen cells. These effector cells killed nearly all target cells tested, irrespective of their H-2 type, but did not kill NZB target cells. The response was shown to have three major components: unrestricted killing specific for Qed-1b, H-2d-restricted killing specific for minor histocompatibility antigens, and unrestricted killing specific for a new antigen, Mta. Mta is present on normal and mitogen-stimulated T and B lymphocytes and on several tumor lines. It was found on cells from 26 mouse strains tested, including two substrains of NZB, representing 9 different H-2 types and 14 different non-H-2 backgrounds. Analysis of the NX8 recombinant inbred lines (derived from Mta-NZB/Icr and Mta+C58/J parents) suggested that Mta is maternally transmitted. This was confirmed by typing of reciprocal F1 hybrids and backcrosses between positive and negative strains: Mta+ females bear Mta+ offspring and Mta- females Mta- offspring, irrespective of the phenotype of the males.