Sexual conflict drives micro- and macroevolution of sexual dimorphism in immunity

BACKGROUND

Sexual dimorphism in immunity is believed to reflect sex differences in reproductive strategies and trade-offs between competing life history demands. Sexual selection can have major effects on mating rates and sex-specific costs of mating and may thereby influence sex differences in immunity as well as associated host-pathogen dynamics. Yet, experimental evidence linking the mating system to evolved sexual dimorphism in immunity are scarce and the direct effects of mating rate on immunity are not well established. Here, we use transcriptomic analyses, experimental evolution and phylogenetic comparative methods to study the association between the mating system and sexual dimorphism in immunity in seed beetles, where mating causes internal injuries in females.

RESULTS

We demonstrate that female phenoloxidase (PO) activity, involved in wound healing and defence against parasitic infections, is elevated relative to males. This difference is accompanied by concomitant sex differences in the expression of genes in the prophenoloxidase activating cascade. We document substantial phenotypic plasticity in female PO activity in response to mating and show that experimental evolution under enforced monogamy (resulting in low remating rates and reduced sexual conflict relative to natural polygamy) rapidly decreases female (but not male) PO activity. Moreover, monogamous females had evolved increased tolerance to bacterial infection unrelated to mating, implying that female responses to costly mating may trade off with other aspects of immune defence, an hypothesis which broadly accords with the documented sex differences in gene expression. Finally, female (but not male) PO activity shows correlated evolution with the perceived harmfulness of male genitalia across 12 species of seed beetles, suggesting that sexual conflict has a significant influence on sexual dimorphisms in immunity in this group of insects.

CONCLUSIONS

Our study provides insights into the links between sexual conflict and sexual dimorphism in immunity and suggests that selection pressures moulded by mating interactions can lead to a sex-specific mosaic of immune responses with important implications for host-pathogen dynamics in sexually reproducing organisms.

Cutting-Edge Single-Molecule Technologies Unveil New Mechanics in Cellular Biochemistry

Single-molecule technologies have expanded our ability to detect biological events individually, in contrast to ensemble biophysical technologies, where the result provides averaged information. Recent developments in atomic force microscopy have not only enabled us to distinguish the heterogeneous phenomena of individual molecules, but also allowed us to view up to the resolution of a single covalent bond. Similarly, optical tweezers, due to their versatility and precision, have emerged as a potent technique to dissect a diverse range of complex biological processes, from the nanomechanics of ClpXP protease-dependent degradation to force-dependent processivity of motor proteins. Despite the advantages of optical tweezers, the time scales used in this technology were inconsistent with physiological scenarios, which led to the development of magnetic tweezers, where proteins are covalently linked with the glass surface, which in turn increases the observation window of a single biomolecule from minutes to weeks. Unlike optical tweezers, magnetic tweezers use magnetic fields to impose torque, which makes them convenient for studying DNA topology and topoisomerase functioning. Using modified magnetic tweezers, researchers were able to discover the mechanical role of chaperones, which support their substrate proteinsby pulling them during translocation and assist their native folding as a mechanical foldase. In this article, we provide a focused review of many of these new roles of single-molecule technologies, ranging from single bond breaking to complex chaperone machinery, along with the potential to design mechanomedicine, which would be a breakthrough in pharmacological interventions against many diseases.

5196Coronary artery calcification predicts MACE and all-cause mortality in individuals undergoing non-cardiac computed tomography for non-cardiovascular indications

Introduction

Coronary artery calcification (CAC) measured on ECG-gated cardiac CT is a strong predictor of cardiovascular (CV) risk in asymptomatic individuals in a primary prevention setting. However, the prognostic value of CAC in an unselected population referred for non-gated non-cardiac chest CT (NCCT) is unknown.

Purpose

To determine whether CAC predicts major adverse cardiovascular events (MACE) and all-cause mortality in patients referred for NCCT for non-CV indications.

Methods

A random sample of 741 individuals, without prior known history of coronary artery disease (CAD) who underwent NCCT for non-CV indications at a tertiary care hospital in 2008 were included in this study. NCCT was assessed qualitatively for the presence and extent of CAC by two experienced physicians. Data abstraction was performed by electronic medical record (EMR) review. Our primary endpoint of MACE, defined as CV mortality, MI, PCI, CABG, heart failure and stroke as well as secondary endpoint of all-cause mortality, over a median follow up of 8 (IQR 4–10) years, was adjudicated per independent review.

Results

Among 741 individuals (mean age 61.1±15.5 years, 60% female, 91% Caucasian), 57% were hypertensive, 30% had hyperlipidemia, 14% were diabetic and the mean ASCVD score was 12.2±11.6. CAC was present in 425/741 (57.4%) individuals. Among those with CAC, it was mild in 172/425 (40%), moderate in 143/425 (34%) and severe in 110/425 (26%) individuals. Overall, MACE occurred in 115/741 (15.5%) patients. Compared to those without MACE, CAC was more prevalent (83% vs. 53%, p<0.001) and extensive (at least moderate: 67% vs. 28%, p<0.001) in those with MACE. Over a median follow up of 8 (IQR 3–10) years, the presence of any CAC was associated with a 4-fold higher risk of MACE (HR 4.22, 95% CI (1.4–8.9), p<0.001), after adjustment for age and gender. On stratification, severe CAC had a near 9-fold increased risk of MACE (HR 8.8, 95% CI (5.1–15.2), p<0.001), followed by moderate CAC with a near 6-fold increased risk of MACE (HR 5.7, 95% CI (2.8–9.8), p<0.001), and a near doubling of MACE risk with mild CAC (HR 1.99, 95% CI (1.1–4.3), p=0.034). Similar results were observed with all-cause mortality (Figure 1).

Conclusions

CAC is an independent predictor of MACE and all-cause mortality in an unselected patient population referred for NCCT for non-CV indications, which may provide an opportunity to improve population health without the need for additional imaging.

Acknowledgement/Funding

Dr. Banerji and Dr. Alvi were supported by NIH/NHLBI 5T32HL076136.

Evidence-based National Vaccine Policy

India has over a century old tradition of development and production of vaccines. The Government rightly adopted self-sufficiency in vaccine production and self-reliance in vaccine technology as its policy objectives in 1986. However, in the absence of a full-fledged vaccine policy, there have been concerns related to demand and supply, manufacture vs. import, role of public and private sectors, choice of vaccines, new and combination vaccines, universal vs. selective vaccination, routine immunization vs. special drives, cost-benefit aspects, regulatory issues, logistics etc. The need for a comprehensive and evidence based vaccine policy that enables informed decisions on all these aspects from the public health point of view brought together doctors, scientists, policy analysts, lawyers and civil society representatives to formulate this policy paper for the consideration of the Government. This paper evolved out of the first ever ICMR-NISTADS national brainstorming workshop on vaccine policy held during 4-5 June, 2009 in New Delhi, and subsequent discussions over email for several weeks, before being adopted unanimously in the present form.