Biology subjects

Baldwin, J.

Publications and source records attributed to Baldwin, J..

4 recordsLinked to original sources

bioRxiv2025

Tropical montane and temperate hummingbirds incubate in small installments over long periods

Life-history strategies and development are shaped by climate and predation. We examined how temperature and nest survival drive incubation behavior in 104 nests of 34 hummingbird species across 2,939m of elevation in the Peruvian and Colombian Andes. At high elevations, cold temperatures led to more frequent, brief incubation bouts and extended incubation periods; survival modulated incubation behavior with no effect on development. Hummingbirds had the highest egg surface-area to volume ratios among all birds; in 147 species, incubation periods increased with decreasing ambient temperatures. We propose a new hypothesis to explain how in cold conditions, heat transfer to the embryo is fragmented into smaller increments and therefore extended over longer periods, underscoring the role of adult behavior in mediating embryonic temperature mismatches and life-history tradeoffs.

ecology↗

bioRxiv2022

Ecological drivers and evolutionary consequences of torpor in Andean hummingbirds

Daily torpor allows endotherms to save energy during energetically stressful (e.g., cold) conditions. Although studies on avian torpor have mostly been conducted under laboratory conditions, information on the usage of torpor in the wild is limited to few, predominantly temperate-zone species. We studied torpor under seminatural conditions from 249 individuals from 29 hummingbird species across a 1,920 m elevational gradient in the western Andes of Colombia using cloacal thermistors. Small birds used torpor more often than large birds, but only at low ambient temperatures, where torpor was prolonged. We also found effects of proxy variables for body condition and energy expenditure on the use of torpor, its characteristics, and impacts. Our results suggest that judicious deployment and subtle modifications of torpor, as well as phylogenetic variation in propensity for torpor, have allowed only certain clades of hummingbirds to colonize and persist in the harsh climate of the high Andes.

ecology↗

bioRxiv2021

Immunisation of ferrets and mice with recombinant SARS-CoV-2 spike protein formulated with Advax-SM adjuvant protects against COVID-19 infection

The development of a safe and effective vaccine is a key requirement to overcoming the COVID-19 pandemic. Recombinant proteins represent the most reliable and safe vaccine approach but generally require a suitable adjuvant for robust and durable immunity. We used the SARS-CoV-2 genomic sequence and in silico structural modelling to design a recombinant spike protein vaccine (Covax-19). A synthetic gene encoding the spike extracellular domain (ECD) was inserted into a baculovirus backbone to express the protein in insect cell cultures. The spike ECD was formulated with Advax-SM adjuvant and first tested for immunogenicity in C57BL/6 and BALB/c mice. The Advax-SM adjuvanted vaccine induced high titers of binding antibody against spike protein that were able to neutralise the original wildtype virus on which the vaccine was based as well as the variant B.1.1.7 lineage virus. The Covax-19 vaccine also induced potent spike-specific CD4+ and CD8+ memory T-cells with a dominant Th1 phenotype, and this was shown to be associated with cytotoxic T lymphocyte killing of spike labelled target cells in vivo. Ferrets immunised with Covax-19 vaccine intramuscularly twice 2 weeks apart made spike receptor binding domain (RBD) IgG and were protected against an intranasal challenge with SARS-CoV-2 virus 2 weeks after the second immunisation. Notably, ferrets that received two 25 or 50g doses of Covax-19 vaccine had no detectable virus in their lungs or in nasal washes at day 3 post-challenge, suggesting the possibility that Covax-19 vaccine may in addition to protection against lung infection also have the potential to block virus transmission. This data supports advancement of Covax-19 vaccine into human clinical trials.

immunology↗

bioRxiv2021

Accelerated vaccine induction of IgM neutralising antibody enables same day vaccine protection against a lethal influenza virus challenge

Novel influenza strains to which humans have no pre-existing immunity can trigger global pandemics without warning. Current pandemic vaccines typically require two doses and up to 6 weeks to induce protective immunity. In addition, to their role in increasing vaccine-induced immune response, adjuvants may also play a part in reducing the time between immunization and vaccine protection, although this role has seldom been previously explored in literature. This study assessed the speed of protection achievable with a standard inactivated influenza vaccine when formulated with or without a novel delta-inulin adjuvant (Advax). When formulated with Advax adjuvant mice were protected even when the vaccine was administered intramuscularly contemporaneously with a lethal intranasal virus challenge. The protection was found to be B-cell dependent and transfer of day 6 immune serum from mice immunised with Advax-adjuvanted influenza vaccine conferred protection to naive animals. This protection was shown to be mediated by vaccine induced IgM rather than IgG neutralising antibodies. The results show that influenza vaccine can be formulated to provide immediate protection following immunization with this novel concept warranting testing in human trials. IMPORTANCEIn the past 100 years there have been several major influenza pandemics that resulted in significant loss of life. The time taken for individuals to develop vaccine protection is an important factor in curbing the spread of infection and reducing pandemic mortality rates. Current influenza vaccines can take up to 5-6 weeks to generate full protection leaving front-line heath care workers and others, at risk for an extended period of time. Our novel accelerated vaccine protection approach provides effectively immediate vaccine protection against lethal virus challenge. This would assist front-line workers to continue to provide essential services and maintain critical infrastructure during pandemic. The study also highlights the often-overlooked role that antigen-specific IgM plays in virus protection and provides a novel adjuvanted strategy for enlisting IgM to provide accelerated vaccine protection.

microbiology↗