The evolution of resistance through costly acquired immunity

We examine the evolutionary dynamics of resistance to parasites through acquired immunity. Resistance can be achieved through the innate mechanisms of avoidance of infection and reduced pathogenicity once infected, through recovery from infection and through remaining immune to infection: acquired immunity. We assume that each of these mechanisms is costly to the host and find that the evolutionary dynamics of innate immunity in hosts that also have acquired immunity are quantitatively the same as in hosts that possess only innate immunity. However, compared with resistance through avoidance or recovery, there is less likely to be polymorphism in the length of acquired immunity within populations. Long-lived organisms that can recover at intermediate rates faced with fast-transmitting pathogens that cause intermediate pathogenicity (mortality of infected individuals) are most likely to evolve long-lived acquired immunity. Our work emphasizes that because whether or not acquired immunity is beneficial depends on the characteristics of the disease, organisms may be selected to only develop acquired immunity to some of the diseases that they encounter

Modeling the long term dynamics of pre-vaccination pertussis

The dynamics of strongly immunizing childhood infections is still not well understood. Although reports of successful modeling of several incidence data records can be found in the literature, the key determinants of the observed temporal patterns have not been clearly identified. In particular, different models of immunity waning and degree of protection applied to disease and vaccine induced immunity have been debated in the literature on pertussis. Here we study the effect of disease acquired immunity on the long term patterns of pertussis prevalence. We compare five minimal models, all of which are stochastic, seasonally forced, well-mixed models of infection based on susceptible-infective-recovered dynamics in a closed population. These models reflect different assumptions about the immune response of naive hosts, namely total permanent immunity, immunity waning, immunity waning together with immunity boosting, reinfection of recovered, and repeat infection after partial immunity waning. The power spectra of the output prevalence time series characterize the long term dynamics of the models. For epidemiological parameters consistent with published data for pertussis, the power spectra show quantitative and even qualitative differences that can be used to test their assumptions by comparison with ensembles of several decades long pre-vaccination data records. We illustrate this strategy on two publicly available historical data sets.Comment: paper (31 pages, 11 figures, 1 table) and supplementary material (19 pages, 5 figures, 2 tables

Plain Reading, Subtle Meaning: Rethinking the IOIA and the Immunity of International Organizations

Immunity is freedom from liability, and as such, it can quite literally provide a “get out of jail free” card. In the United States, international organizations face uncertainty about the scope of their immunity, which is provided by the International Organizations Immunities Act (IOIA). The D.C. Circuit has found that international organizations enjoy absolute immunity under the IOIA. Conversely, the Third Circuit recently held that international organizations are only entitled to restrictive immunity, which limits immunity to claims involving an organization’s public acts and does not exempt them from suits based on their commercial or private conduct. This Note contends that a plain reading of the IOIA, combined with a full understanding of the history and legislative purpose behind the immunity of international organizations, presents a third interpretation. It concludes that the IOIA requires judicial deference to immunity determinations by the executive branch, which provides the flexibility necessary to allow international organizations to operate without undue interference

'Towards a Conceptual Framework for Innate Immunity'

Innate immunity now occupies a central role in immunology. However, artificial immune system models have largely been inspired by adaptive not innate immunity. This paper reviews the biological principles and properties of innate immunity and, adopting a conceptual framework, asks how these can be incorporated into artificial models. The aim is to outline a meta-framework for models of innate immunity

Infection-acquired versus vaccine-acquired immunity in an SIRWS model

Despite high vaccine coverage, pertussis has re-emerged as a public health concern in many countries. One hypothesis posed for re-emergence is the waning of immunity. In some disease systems, the process of waning immunity can be non-linear, involving a complex relationship between the duration of immunity and subsequent boosting of immunity through asymptomatic re-exposure. We present and analyse a model of infectious disease transmission to examine the interplay between infection and immunity. By allowing the duration of infection-acquired immunity to differ from that of vaccine-acquired immunity, we explore the impact of the difference in durations on long-term disease patterns and prevalence of infection. Our model demonstrates that vaccination may induce cyclic behaviour, and its ability to reduce the infection prevalence increases with both the duration of infection-acquired immunity and duration of vaccine-acquired immunity. We find that increasing vaccine coverage, while capable of leading to an increase in overall transmission, always results in a reduction in prevalence of primary infections, with epidemic cycles characterised by a longer interepidemic period and taller peaks. Our results show that the epidemiological patterns of an infectious disease may change considerably when the duration of vaccine-acquired immunity differs from that of infection-acquired immunity. Our study highlights that for any particular disease and associated vaccine, a detailed understanding of the duration of protection and how that duration is influenced by infection prevalence is important as we seek to optimise vaccination strategies.Comment: 21 pages, 5 figure

Foreign Sovereign Immunity and Domestic Officer Suits

Under international law, official-capacity suits brought against a foreign state’s officers are treated as suits against the state itself and thus as subject to the state’s immunity, even in suits alleging human rights abuses. This immunity regime differs from the immunity regime that applies in the United States in suits brought against state and federal officials for violations of federal law. Despite the federal government’s sovereign immunity and the immunity of state governments under Eleventh Amendment jurisprudence, courts often allow suits against federal and state officers for their official actions. This essay attempts to explain why the immunity rules differ between the two regimes. We begin by showing that the differential treatment of foreign and domestic officer suits has deep roots in British and American common law. We then show that Congress has not acted to alter this common law backdrop, and we explain the significance of this fact. Finally, we discuss functional reasons for the long-time differential treatment of suits against domestic and foreign officials

Section 1983: Absolute Immunity for Pretrial Police Testimony

This Note discusses the development of the Supreme Court\u27s approach to section 1983 immunity for trial witnesses. Central to this discussion is an overview of the history of common-law immunities for government officials, the history and purpose of section 1983, and the history of the Supreme Court\u27s section 1983 immunity decisions. The author discusses the current disagreement in the circuits over extending section 1983 immunity to pretrial police testimony. The author also analyzes various possible answers to the question of whether to extend witness immunity under section 1983 to specific pretrial proceedings by applying the current Supreme Court functional categories immunity analysis and the policies for and against extension of absolute immunity to pretrial police testimony. The Note concludes that police officers should enjoy absolute immunity from section 1983 suits that are based solely on their perjured pretrial testimony. However, the author also suggests that a section 1983 plaintiff should be allowed to introduce such testimony as evidence that a police officer initiated a baseless or malicious prosecution against the plaintiff

The Prosecutor\u27s Obligation to Grant Defense Witness Immunity

The author enumerates the three most common situations in which the courts have required the prosecutor to offer immunity to defense witnesses: (1) to safeguard the defendant\u27s right to essential exculpatory testimony; (2) where the use of the prosecutor\u27s powers to grant immunity causes such distortion in the fact-finding process as to require granting immunity to defense witnesses; and (3) where immunity is required to remedy prosecutory misconduct such as the intimidation of witnesses. The use of the missing witness instruction to avoid reaching the constitutional issue is also discussed