So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

Combination of seven surveys of blood parasites in North American passerines reveals weak, highly significant association over species between incidence of chronic blood infections (five genera of protozoa and one nematode) and striking display (three characters: male "brightness," female "brightness," and male song). This result conforms to a model of sexual selection in which (i) coadaptational cycles of host and parasites generate consistently positive offspring-on-parent regression of fitness, and (ii) animals choose mates for genetic disease resistance by scrutiny of characters whose full expression is dependent on health and vigor.

http://max2.ese.u-psud.fr/epc/conservation/PDFs/HIPE/Hamilton1982.pdf

Heritable true fitness and bright birds: a role for parasites?

Sex differences in parasite infections: Patterns and processes

Studies with rodents infected with Trichinella spiralis, Heligmosomoides polygyrus, Nippostronglyus brasiliensis, and Trichuris muris have provided considerable information about immune mechanisms that protect against parasitic gastrointestinal nematodes. Four generalizations can be made: 1. CD4+ T cells are critical for host protection; 2. IL-12 and IFN-gamma inhibit protective immunity; 3. IL-4 can: (a) be required for host protection, (b) limit severity of infection, or (c) induce redundant protective mechanisms; and 4. Some cytokines that are stereotypically produced in response to gastrointestinal nematode infections fail to enhance host protection against some of the parasites that elicit their production. Host protection is redundant at two levels: 1. IL-4 has multiple effects on the immune system and on gut physiology (discussed in this review), more than one of which may protect against a particular parasite; and 2. IL-4 is often only one of multiple stimuli that can induce protection. Hosts may have evolved the ability to recognize features that characterize parasitic gastrointestinal nematodes as a class as triggers for a stereotypic cytokine response, but not the ability to distinguish features of individual parasites as stimuli for more specific protective cytokine responses. As a result, hosts deploy a set of defense mechanisms against these parasites that together control infection by most members of that class, even though a specific defense mechanism may not be required to defend against a particular parasite and may even damage a host infected with that parasite.

CYTOKINE REGULATION OF HOST DEFENSE AGAINST PARASITIC GASTROINTESTINAL NEMATODES: Lessons from Studies with Rodent Models

Aluminum compounds as vaccine adjuvants

Hereford cattle were immunized with membranes and soluble components extracted from the midgut of Boophilus microplus Membrane vaccines protected cattle (91%) against challenge with 3 x 20,000 larval ticks administered at intervals of 7 days Vaccines made from soluble antigens did not protect cattle Antibody levels measured by enzyme-linked immunosorbent assay (ELISA) related to the levels of protection induced by vaccination

Hereford cattle immunized and protected against Boophilus microplus with soluble and membrane-associated antigens from the midgut of ticks.

Vaccines made from gut and gut and synganglion tissue dissected from Boophilus microplus gave 87% and 80% protection, respectively, compared with adjuvant-injected controls in cattle against three infestations with 20,000 larval ticks administered over 14 days. A vaccine prepared from synganglion alone did not protect cattle. Ticks collected from vaccinated cattle produced 95% and 91% fewer eggs, respectively, than ticks from control animals. Vaccinated cattle were protected (36%) 7 months after they had been immunized with tick antigens. Antibody responses to the vaccines were detected by enzyme-linked immunosorbent assay (ELISA).

Vaccines to protect Hereford cattle against the cattle tick, Boophilus microplus.

1. It has been shown that there is a difference between the resistance of male and female mice to infection with Nematospiroides dubius . 2. More parasites were harboured, during both the larval and adult parasitic phases, by male mice. 3. These worms were found to occupy a similar relative length of the intestine between the stomach and the caecum in male and female mice infected for either 5 or 10 days. 4. The relative length of the intestine infected on the fifth day was significantly greater than that infected on the tenth day. This investigation was carried out during the tenure of a Research Studentship from the Department of Scientific and Industrial Research. I should like to thank Professor I. Chester Jones, in whose department the work was done, for the facilities provided and Dr E. T. B. Francis for his helpful and critical supervision.

Certain aspects of the host-parasite relationship of Nematospiroides dubius (Baylis). I. Resistance of male and female mice to experimental infections.

Colin Dobson

Papers

Hereford cattle immunized and protected against Boophilus microplus with soluble and membrane-associated antigens from the midgut of ticks.

Vaccines to protect Hereford cattle against the cattle tick, Boophilus microplus.

Certain aspects of the host-parasite relationship of Nematospiroides dubius (Baylis). I. Resistance of male and female mice to experimental infections.

Predicting resistance of sheep to Haemonchus contortus infections

Passive transfer of immunity with serum in mice infected with Nematospiroides dubius: influence of quality and quantity of immune serum.