MHC variation, multiple simultaneous infections and physiological condition in the subterranean rodent Ctenomys talarum

Interpopulation differences in parasite load and variable selective pressures on MHC genes inCtenomys talarum

“…Two populations of this species from Buenos Aires Province, Argentina, were included in this study. Cutrera et al (2011Cutrera et al ( , 2012 sampled the population at MdC (37846 0 S, 57826 0 W) in 2006, 2007, and 2008; we subsequently sampled the population at NC (38833 0 S, 58845 0 W) in 2009 and 2010. The 2 populations are located approximately 150 km apart and are not demographically connected (Mora et al 2013).…”

“…The methods used to capture and sample C. talarum at NC were the same as those used at MdC (Cutrera et al 2011), and in both populations animal capture was performed over an area of approximately 2 ha. In brief, animals were captured using plastic tube traps inserted into active burrow entrances (Cutrera et al 2005).…”

“…In particular, comparative studies of these 2 demographically distinct populations have demonstrated that number of alleles, heterozygosity, and estimated intensity of selection at 2 class II loci (DRB and DQA) are greater in the population characterized by higher density (Mar de Cobo [MdC]: mean number of individuals/ha 6 SD: 57 6 6; Necochea [NC]: 15 6 4 individuals/ha-see Busch et al 1989;Malizia et al 1991;) and greater parasite exposure (greater parasite prevalence [the percentage of infected individuals in the population], richness, and intensity of infection- Rossin and Malizia 2002;Rossin et al 2010), as expected if parasite-driven selection maintains MHC polymorphism in this species . Detailed analyses of 1 of these populations (MdC) have revealed that specific DRB alleles are associated with parasite load and intensity of humoral immune response (Cutrera et al 2011), suggesting that individual MHC sequences influence resistance to pathogens. At the same time, field and laboratory studies of animals from this population indicate that females may engage in MHC-associated mate choice (Cutrera et al 2012), providing another potential source of spatial variation in the selective pressures acting on MHC genes.…”

“…Specifically, by contrasting new information from a 2nd population (NC) of C. talarum with data obtained previously for animals at MdC (Cutrera et al 2011(Cutrera et al , 2012, we use the pronounced differences in parasite load between these populations to assess how spatial variation in this attribute influences immunogenetic variation and selection on MHC genes in this species. Gastrointestinal parasite load in C. talarum at NC is markedly lower than at MdC (Rossin and Malizia 2002;Rossin et al 2010).…”

Major Histocompatibility Complex, demographic, and environmental predictors of antibody presence in a free-ranging mammal

“…A potential explanation for this finding is that the mortality of raccoon cubs carrying this allele is higher such that only the non-exposed individuals with Prlo-DRB ⁄ 201 survive. There are multiple examples in the literature that support the relevance of negative-frequency dependent selection on the MHC (Deter et al, 2008;Tollenaere et al, 2008;Cutrera et al, 2011). Interestingly, negative-frequency dependent selection seems to also play an important role in the association between raccoon MHC II DRB variation and rabies virus susceptibility (Srithayakumar et al, 2011).…”