Month: September 2022

SUICIDE AVERSION. "It has been shown that experimental evolution of phages under conditions of local dispersion leads to ‘prudent’ (less virulent) variants of the virus, in contrast to the virulent forms evolved in a well-mixed environment." https://lnkd.in/d9zsv9R View in LinkedIn

"REDUCED VIRULENCE is the most likely evolutionary outcome under conditions of low pathogen dispersal, whereas intermediate dispersal rates can lead to high virulence. It is therefore plausible that, in structured populations, the host-pathogen arms race has a major effect on the genes involved in cell death and its inhibition." https://lnkd.in/d9zsv9R View in LinkedIn

INHIBITORS OF HOST DEATH. "Numerous viruses indeed have evolved mechanisms preventing host cell death, often by recruiting genes involved in host suicide and turning them into competitive inhibitors of cell death or else via repair of the damage involved in cell death." Cunning strategy. https://lnkd.in/d9zsv9R View in LinkedIn

"ADAPTIVE IMMUNITY provides a direct benefit to the host organism that possesses the immune mechanism and thus does not require population structure to evolve. There are, however, instances when population structure favors fixation of adaptive immunity through a mechanism analogous to the one observed for altruistic suicide." https://lnkd.in/d9zsv9R View in LinkedIn

STRUCTURED POPULATIONS. "Due to limited pathogen dispersion, hosts can benefit from the local decrease in pathogen abundance produced by their neighbors’ adaptive immunity. In a structured population, neighboring hosts are phenotypically correlated, reinforcing the advantage of adaptive immunity and contributing to its fixation. This effect could allow fixation of adaptive immunity even under conditions where the cost-benefit balance is not in its favor." https://lnkd.in/d9zsv9R View in LinkedIn

COEXISTING GROUPS. "On the other hand, if the immune efficacy is too high, hosts with and without adaptive immunity tend to coexist as the former generate environments with low pathogen pressure. This result resembles those obtained by previous theoretical studies on well-mixed populations, which predict lack of fixation for highly effective immunity systems and possible polymorphisms on the degree of immunity evolved by hosts." https://lnkd.in/d9zsv9R View in LinkedIn

TRAIT FIXATION. "High suicide efficacies prevent fixation of adaptive immunity not only in those regions where the cost-benefit balance for adaptive immunity is slightly unfavorable (even if fixation would occur in the absence of suicide by virtue of population structure), but also in some regions where this balance is favorable to adaptive immunity." https://lnkd.in/d9zsv9R View in LinkedIn

COMPETING STRATEGIES. "Similarly, hosts with large suicide efficacy overtake those with adaptive immunity provided that the suicide propensity is greater than a threshold that grows with the efficacy of adaptive immunity. Notwithstanding this general trend, innate and adaptive immunity systems appear to coexist in other regions of the phase space." https://lnkd.in/d9zsv9R View in LinkedIn

LAST RESORT. "Host suicide can potentially evolve either as an immediate response to infection or as a means of last resort after immunity mechanisms fail to stop pathogen reproduction. Intuitively, the second strategy would appear advantageous, and indeed in our model, when the two strategies evolve independently and then are allowed to compete, “suicide after immunity failure wins”." https://lnkd.in/d9zsv9R View in LinkedIn

LOW COST. "Recent experiments with suicide-prone E. coli have shown that at least when defense against highly virulent phages is involved, the cost of suicide could be quite low because the infected bacteria are moribund in any case and have virtually no chance to propagate. Conceivably, these experiments reflect the regime with failing immunity and subsequent low-cost suicide." https://lnkd.in/d9zsv9R View in LinkedIn