Parasite Burden and Constitution of Major Histocompatibility Complex in the Malagasy Mouse Lemur, Microcebus Murinus

Abstract

We investigated the importance of the major histocompatibility complex (MHC) constitution on the parasite burden of free-ranging mouse lemurs (Microcebus murinus) in four littoral forest fragments in southeastern Madagascar. Fourteen different MHC class II DRB-exon 2 alleles were found in 228 individuals with high levels of sequence divergence between alleles. More nonsynonymous than synonymous substitutions in the functional important antigen recognition and binding sites indicated selection processes maintaining MHC polymorphism. Animals from the four forest fragments differed in their infection status (being infected or not), in the number of different nematode morphotypes per individual (NNI) as well as in the fecal egg counts (FEC) values. Heterozygosity in general was uncorrelated with any of these measures of infection. However, a positive relationship was found between specific alleles and parasite load. Whereas the common allele Mimu-DRB*1 was more frequently found in infected individuals and in individuals with high NNI and FEC values (high parasite load), the rare alleles Mimu-DRB*6 and 10 were more prevalent in uninfected individuals and in individuals with low NNI and FEC values (low parasite load). These three alleles associated with parasite load had unique amino acid motifs in the antigen binding sites. This distinguished them from the remaining 11 Mimu-DRB alleles. Our results support the hypothesis that MHC polymorphism in M. murinus is maintained through pathogen-driven selection acting by frequency-dependent selection. This is the first study of the association of MHC variation and parasite burden in a free-ranging primate.

Parasite mediated homogenizing selection at the MHC in guppies

“…In guppies, Scott (1985) found that fish previously infected with gyrodactylus were better able to combat infection, even if the previous infection had been 6 weeks prior (also see Cable and van Oosterhout 2007a). Similarly other studies have found resistance conferred by the MHC to other monogenean parasites (Ottová et al 2007), parasites in the phylum platyhelminths (Wegner et al 2003), and other parasitic worms known as helminths (Schad et al 2005). Therefore it is likely that the MHC can recognize antigens from gyrodactylus and mount a reaction using the adaptive immune system.…”

MHC-associated mating strategies and the importance of overall genetic diversity in an obligate pair-living primate

“…Adaptive variability was studied in the highly polymorphic MHC-DRB exon 2 (171 bp, without primer) which includes the functionally important antigen-binding sites (ABS) (Brown et al 1988(Brown et al , 1993. The PCR amplification was carried out using the primers JS1 and JS2 as described in Schad et al (2004Schad et al ( , 2005 which were originally designed for the closely related lemur species Microcebus murinus but were also successfully applied in different rodent species (Froeschke and Sommer 2005;Harf and Sommer 2005;Meyer-Lucht and Sommer 2005). To genotype the individuals, we used single-strand conformation polymorphism analysis (SSCP) (Orita et al 1989a, b;Meyers and Bull 2002).…”

Parental relatedness and major histocompatibility effects on early embryo survivorship in Atlantic salmon

“…However, overdominance cannot explain all the data, and frequencydependent selection is increasingly gaining support. MHC zygosity does not appear to affect endoparasite load in certain mammals, yet specific alleles are correlated with infection status (Harf and Sommer 2005;Schad et al 2005). In Atlantic salmon, specific MHC alleles confer resistance to Aeromonas salmonicida and infectious salmon anemia virus (Grimholt et al 2003;Langefors et al 2001a).…”