Translation of HLA-HIV associations to the cellular level: HIV adapts to inflate CD8 T cell responses against Nef and HLA-adapted variant epitopes

Strong statistical associations between polymorphisms in HIV-1 population sequences and carriage of HLA class I alleles have been widely used to identify possible sites of CD8 T cell immune selection in vivo. However, there have been few attempts to prospectively and systematically test these genetic hypotheses arising from population-based studies at a cellular, functional level. We assayed CD8 T cell epitope-specific IFN-γ responses in 290 individuals from the same cohort, which gave rise to 874 HLA-HIV associations in genetic analyses, taking into account autologous viral sequences and individual HLA genotypes. We found immunological evidence for 58% of 374 associations tested as sites of primary immune selection and identified up to 50 novel HIV-1 epitopes using this reverse-genomics approach. Many HLA-adapted epitopes elicited equivalent or higher-magnitude IFN-γ responses than did the nonadapted epitopes, particularly in Nef. At a population level, inclusion of all of the immunoreactive variant CD8 T cell epitopes in Gag, Pol, Nef, and Env suggested that HIV adaptation leads to an inflation of Nef-directed immune responses relative to other proteins. We concluded that HLA-HIV associations mark viral epitopes subject to CD8 T cell selection. These results can be used to guide functional studies of specific epitopes and escape mutations, as well as to test, train, and evaluate analytical models of viral escape and fitness. The inflation of Nef and HLA-adapted variant responses may have negative effects on natural and vaccine immunity against HIV and, therefore, has implications for diversity coverage approaches in HIV vaccine design.     

Sex differences in yolk hormones depend on maternal social status in Leghorn chickens (Gallus gallus domesticus)

Maternal hormones are known to be present in avian eggs and can have beneficial effects on chick development. Recently, differences in avian yolk steroid concentrations between the sexes have been demonstrated, and in this context steroids have been proposed to be part of the avian sex-determining mechanism. In our study, we show that it is very unlikely that androgen concentrations alone are the decisive part of the sex-determining mechanism. We found that sex-specific differences in the yolk hormones strongly depend on the social rank of the mother. First, dominant females, but not subdominant females, allocated significantly more testosterone to male eggs than to female eggs. Second, subordinate females increased the testosterone concentrations of female eggs. This pattern of yolk hormone deposition can be functionally explained. In polygynous species such as the chicken, reproductive success is more variable in males than in females. Parental investment in sons or daughters is therefore expected to occur in direct relation to parental rearing capacities. We found that the social status of a hen was indeed negatively correlated with her maternal capacities (for example, body mass, egg mass). Differential androgen deposition might thus provide a mechanism for adaptive maternal investment depending on both the sex of the egg and the social status of the mother.     

Testosterone, cuckoldry risk and extra-pair opportunities in the Seychelles warbler

In male birds, testosterone (T) plays an important role in aggressive and mate-attraction behaviour. In the cooperatively breeding Seychelles warbler, Acrocephalus sechellensis, extra-group copulations (EGCs) occur frequently, but are not accompanied by sexual courtship displays as in within-pair copulations. Paternity is nearly always gained by primary males. We investigated whether T levels and sperm storage capability (cloacal protuberance (CP)) in adult primary and subordinate males were related to timing of egg laying, levels of cuckoldry and extra-group paternity (EGP) opportunities. During the sexually active period before egg laying, T levels and CP were only elevated or enlarged (respectively) in primary males, and some suggestion was found that subordinate males do not invest in elevated T levels. The peak in T occurred during the fertile period of the female partner and corresponded to the peak period of male sexual displays and mate guarding, but was independent of cuckoldry risk (density of neighbouring primary males). CP was also enhanced during this period; however, CP but not T remained elevated after egg laying by their mates, and CP but not T was positively related to EGP opportunities (density of neighbouring fertile females). We conclude that T is involved in sexual courtship displays and mate guarding, but not in gaining EGCs. These findings contrast with those in other species where EGP involves elaborate sexual displays.     

Combining Organophosphate Treated Wall Linings and Long-lasting Insecticidal Nets for Improved Control of Pyrethroid Resistant Anopheles gambiae

Background

New approaches to delivering insecticides need to be developed to improve malaria vector control. Insecticidal durable wall lining (DL) and net wall hangings (NWH) are novel alternatives to indoor residual spraying which can be produced in a long-lasting format. Non-pyrethroid versions could be used in combination with long-lasting insecticidal nets for improved control and management of insecticide resistant vector populations.

Methods

Experimental hut trials were carried out in Valley du Kou, Burkina Faso to evaluate the efficacy of pirimiphos methyl treated DL and NWH either alone or in combination with LLINs against pyrethroid resistant Anopheles gambiae ss. Comparison was made with pyrethroid DL. Mosquitoes were genotyped for kdr and ace-1R resistant genes to investigate the insecticide resistance management potential of the combination.

Results

The overall kdr and ace-1^R allele frequencies were 0.95 and 0.01 respectively. Mortality with p-methyl DL and NWH alone was higher than with pyrethroid DL alone (>95% vs 40%; P<0.001). Combining pyrethroid DL with LLINs did not show improvement in mortality (48%) compared to the LLIN alone (44%) (P>0.1). Combining p-methyl DL or NWH with LLINs reduced biting rates significantly (8–9%) compared to p-methyl DL and NWH alone (>40%) and killed all An gambiae that entered the huts. Mosquitoes bearing the ace-1^R gene were more likely to survive in huts with p-methyl DL alone (p<0.03) whereas all resistant and susceptible genotypes were killed by the combination.

Conclusion

P-methyl DL and NWH outperformed pyrethroid DL. Combining p-methyl DL and NWH with LLINs could provide significant epidemiological benefits against a vector population which is resistant to pyrethroids but susceptible to organophosphates. There was evidence that the single intervention would select kdr and ace-1^R resistance genes and the combination intervention might select less strongly. Technology to bind organophosphates to plastic wall lining would be worth developing.     

Prevention of Mother-To-Child Transmission of HIV: Cost-Effectiveness of Antiretroviral Regimens and Feeding Options in Rwanda

Background

Rwanda''s National PMTCT program aims to achieve elimination of new HIV infections in children by 2015. In November 2010, Rwanda adopted the WHO 2010 ARV guidelines for PMTCT recommending Option B (HAART) for all HIV-positive pregnant women extended throughout breastfeeding and discontinued (short course-HAART) only for those not eligible for life treatment. The current study aims to assess the cost-effectiveness of this policy choice.

Methods

Based on a cohort of HIV-infected pregnant women in Rwanda, we modelled the cost-effectiveness of six regimens: dual ARV prophylaxis with either 12 months breastfeeding or replacement feeding; short course HAART (Sc-HAART) prophylaxis with either 6 months breastfeeding, 12 months breastfeeding, or 18 months breastfeeding; and Sc-HAART prophylaxis with replacement feeding. Direct costs were modelled based on all inputs in each scenario and related unit costs. Effectiveness was evaluated by measuring HIV-free survival at 18 months. Savings correspond to the lifetime costs of HIV treatment and care avoided as a result of all vertical HIV infections averted.

Results

All PMTCT scenarios considered are cost saving compared to “no intervention.” Sc-HAART with 12 months breastfeeding or 6 months breastfeeding dominate all other scenarios. Sc-HAART with 12 months breastfeeding allows for more children to be alive and HIV-uninfected by 18 months than Sc-HAART with 6 months breastfeeding for an incremental cost per child alive and uninfected of 11,882 USD. This conclusion is sensitive to changes in the relative risk of mortality by 18 months for exposed HIV-uninfected children on replacement feeding from birth and those who were breastfed for only 6 months compared to those breastfeeding for 12 months or more.

Conclusion

Our findings support the earlier decision by Rwanda to adopt WHO Option B and could inform alternatives for breastfeeding duration. Local contexts and existing care delivery models should be part of national policy decisions.     

Evolution of oil-producing trichomes in Sisyrinchium (Iridaceae): insights from the first comprehensive phylogenetic analysis of the genus

Background and Aims

Sisyrinchium (Iridaceae: Iridoideae: Sisyrinchieae) is one of the largest, most widespread and most taxonomically complex genera in Iridaceae, with all species except one native to the American continent. Phylogenetic relationships within the genus were investigated and the evolution of oil-producing structures related to specialized oil-bee pollination examined.

Methods

Phylogenetic analyses based on eight molecular markers obtained from 101 Sisyrinchium accessions representing 85 species were conducted in the first extensive phylogenetic analysis of the genus. Total evidence analyses confirmed the monophyly of the genus and retrieved nine major clades weakly connected to the subdivisions previously recognized. The resulting phylogenetic hypothesis was used to reconstruct biogeographical patterns, and to trace the evolutionary origin of glandular trichomes present in the flowers of several species.

Key Results and Conclusions

Glandular trichomes evolved three times independently in the genus. In two cases, these glandular trichomes are oil-secreting, suggesting that the corresponding flowers might be pollinated by oil-bees. Biogeographical patterns indicate expansions from Central America and the northern Andes to the subandean ranges between Chile and Argentina and to the extended area of the Paraná river basin. The distribution of oil-flower species across the phylogenetic trees suggests that oil-producing trichomes may have played a key role in the diversification of the genus, a hypothesis that requires future testing.     

Within-clutch patterns of yolk testosterone vary with the onset of incubation in black-headed gulls

Hatching asynchrony in birds produces an age and size hierarchyamong siblings. Later-hatching chicks have a competitive disadvantage,and brood reduction may occur when food availability is insufficientto raise all chicks. When early-hatched chicks fail to surviveor if the circumstances allow raising all chicks, mothers shouldreverse the disadvantage to later-hatched chicks. Increasingdeposition of maternal androgens with the laying sequence hasbeen suggested to compensate for detrimental effects of hatchingasynchrony, allowing a more precise adjustment of the survivalprobabilities of each chick. Here, we show for black-headedgulls that the increase in yolk testosterone with each successiveegg is greater when the mother incubates longer before clutchcompletion, which is the major determinant of the degree ofhatching asynchrony. This finding supports the idea that yolktestosterone has a compensatory function in the context of hatchingasynchrony. Our data further show that if the time needed tocomplete a clutch is lengthened, the developmental differencesdue to incubation between the first- and the last-laid eggsincrease. In addition, the onset of incubation before clutchcompletion occurs sooner as the breeding season progresses.Both long inter-egg intervals and the seasonal shift in incubationbehavior enhance the necessity of compensation for later-hatchingchicks. Indeed, yolk levels of testosterone increased more steeplyover the laying order, if the duration of the egg-laying periodwas extended and in later-laid clutches. We suggest that prolactinplays a key role in the adjustment of testosterone allocationto the incubation pattern.     

Variation in endogenous oxidative stress in Escherichia coli natural isolates during growth in urine

ABSTRACT: BACKGROUND: Uropathogenic strains of Escherichia coli cause symptomatic infections whereas asymptomatic bacteriuria (ABU) strains are well adapted for growth in the human urinary tract, where they establish long-term bacteriuria. Human urine is a very complex growth medium that could be perceived by certain bacteria as a stressful environment. To investigate a possible imbalance between endogenous oxidative response and antioxidant mechanisms, lipid oxidative damage estimated as thiobarbituric acid reactive substances (TBARS) content was evaluated in twenty-one E. coli belonging to various pathovars and phylogenetic groups. Antioxidant defense mechanisms were also analysed. RESULTS: During exponential growth in urine, TBARS level differs between strains, without correlation with the ability to grow in urine which was similarly limited for commensal, ABU and uropathogenic strains. In addition, no correlation between TBARS level and the phylogroup or pathogenic group is apparent. The growth of ABU strain 83972 was associated with a high level of TBARS and more active antioxidant defenses that reduce the imbalance. CONCLUSIONS: Our results indicate that growth capacity in urine is not a property of ABU strains. However, E. coli isolates respond very differently to this stressful environment. In strain ABU 83972, on one hand, the increased level of endogenous reactive oxygen species may be responsible for adaptive mutations. On the other hand, a more active antioxidant defense system could increase the capacity to colonize the bladder.