Coexistence Of Multiple Strains Research Articles

HIV-positive deceased donor-to-HIV-positive recipient kidney transplantation: The HOPE must go on.

Nowadays, HIV infection is a chronic disease, this is due to the efficacy of antiretroviral therapy (ART) in the control of viral replication. The prevalence of chronic kidney disease (CKD) among those well-controlled HIV positive (HIV+) patients is higher than in the general population and kidney transplantation has been established as the best therapeutic option for HIV+ patients with end-stage renal disease. However, this population has lower access to transplantation.

Contrasting Patterns of Virus Protection and Functional Incompatibility Genes in Two Conspecific Wolbachia Strains from Drosophila pandora.

Wolbachia infections can present different phenotypes in hosts, including different forms of reproductive manipulation and antiviral protection, which may influence infection dynamics within host populations. In populations of Drosophila pandora two distinct Wolbachia strains coexist, each manipulating host reproduction: strain wPanCI causes cytoplasmic incompatibility (CI), whereas strain wPanMK causes male killing (MK). CI occurs when a Wolbachia-infected male mates with a female not infected with a compatible type of Wolbachia, leading to nonviable offspring. wPanMK can rescue wPanCI-induced CI but is unable to induce CI. The antiviral protection phenotypes provided by the wPanCI and wPanMK infections were characterized; the strains showed differential protection phenotypes, whereby cricket paralysis virus (CrPV)-induced mortality was delayed in flies infected with wPanMK but enhanced in flies infected with wPanCI compared to their respective Wolbachia-cured counterparts. Homologs of the cifA and cifB genes involved in CI identified in wPanMK and wPanCI showed a high degree of conservation; however, the CifB protein in wPanMK is truncated and is likely nonfunctional. The presence of a likely functional CifA in wPanMK and wPanMK's ability to rescue wPanCI-induced CI are consistent with the recent confirmation of CifA's involvement in CI rescue, and the absence of a functional CifB protein further supports its involvement as a CI modification factor. Taken together, these findings indicate that wPanCI and wPanMK have different relationships with their hosts in terms of their protective and CI phenotypes. It is therefore likely that different factors influence the prevalence and dynamics of these coinfections in natural Drosophila pandora hosts.IMPORTANCEWolbachia strains are common endosymbionts in insects, with multiple strains often coexisting in the same species. The coexistence of multiple strains is poorly understood but may rely on Wolbachia organisms having diverse phenotypic effects on their hosts. As Wolbachia is increasingly being developed as a tool to control disease transmission and suppress pest populations, it is important to understand the ways in which multiple Wolbachia strains persist in natural populations and how these might then be manipulated. We have therefore investigated viral protection and the molecular basis of cytoplasmic incompatibility in two coexisting Wolbachia strains with contrasting effects on host reproduction.

Dynamical properties and thresholds of an HIV model with super-infection.

Super-infection by multiple HIV-1 subtypes, previously thought restricted to high risk groups, has now been reported in the general heterosexual populations at relatively the same incidence rate as in high risk groups. We present a simple deterministic HIV model with super-infection by two HIV-1 subtypes. Mathematical characteristics including the basic reproductive number $(\mathcal{R}_0)$, invasion threshold $(\mathcal{R}_{21},\mathcal{R}_{12})$ and conditions for asymptotic stability are derived. In the absence of super-infection the model exhibits competitive exclusion, and all equilibria are globally attracting if they exist except for the disease free which is a saddle for $\mathcal{R}_0>1.$ The results show that the subtype with the dominant reproductive number exceeding unity dominates the weaker subtype forcing it to extinction regardless of the size of the reproductive number. On the other end, super-infection may promote subtype co-existence whenever the minimum of the subtype specific reproductive numbers $(\mathcal{R}_1,\mathcal{R}_2)$ and the invasion reproductive numbers $(\mathcal{R}_{12},\mathcal{R}_{21})$ exceed unity. Our results demonstrate that if the partial reproductive numbers $(\mathcal{R}_1~\mbox{and}~\mathcal{R}_2 )$ and the invasion reproductive number for the weaker subtype $(\mathcal{R}_{21})$ satisfy $\mathcal{R}_2<1,~\mathcal{R}_1>1~\mbox{and}~\mathcal{R}_{21}>1,$ then primary infection by subtype $1$ may stay the extinction of subtype $2$ despite its relatively low reproductive fitness. For certain parameter ranges, hysteresis (including backward bifurcation) occurs with possible differences in the asymptotic level of disease prevalence. Super-infection may thus facilitate the continued re-generation of reproductively noncompetent subtypes whose subtype specific reproductive numbers will be less than unity while at the same time allowing for the mutual coexistence and persistence of multiple strains. Persistence and co-existence of multiple strains has detrimental effect on vaccine design and development and administration of ART where one or more of the strains are drug resistant.

A Novel HIV-1 Second-Generation Recombinant Form (CRF01_AE/07_BC) Among Heterosexuals in Nei Monggoi Autonomous Region in China.

Increasing second-generation recombinant forms (CRF01_AE/07_BC) have been detected in China recently. Here, we isolated a novel CRF01_AE/07_BC second-generation recombinant form in HIV-1-positive Nei Monggoi's heterosexuals with one CRF07_BC inserted into the CRF01_AE backbone. Polygenetic analyses showed that the CRF01_AE region was grouped with the previously reported cluster 5 lineage, which spreads among the sexual population in north of China, inferring that this recombinant event occurred through heterosexual contact in the north of China possibly. The growing emergence of recombinant forms means coexistence of multiple strains and complexity of the HIV-1 epidemic, which reminds us of the urgent necessity to focus the HIV surveillance among the high-risk populations nationwide in China, particularly to enhance preventive measures in HIV-1 low-prevalence areas.

The complete classification for dynamics of an SIS STD model in terms of four parameters

In this paper, a nine-dimensional sexually transmitted disease model proposed by Castillo-Chavez et al. [C. Castillo-Chavez, Wenzhang Huang and Jia Li, The effects of female’s susceptibility on coexistence of multiple pathogen strains of sexually transmitted diseases, J. Math. Biol. 35 (1996) 503–522] is studied. The model involves two competing strains 1 and 2 in a two-sex heterosexually active population that includes a single group of males and two different groups of females. The first and second reproduction numbers R i , ℛ i are defined for strain i , i = 1 , 2 respectively. By applying the theory of type- K monotone dynamical systems, a complete classification for the dynamics of this model is presented in terms of the first and second reproduction numbers R i , ℛ i , i = 1 , 2 . The classification not only is different to the complete classification given by Castillo-Chavez et al. [C. Castillo-Chavez, Wenzhang Huang and Jia Li, Competitive exclusion and coexistence of multiple strains in an SIS STD model, SIAM J. Appl. Math. 59 (1999) 1790–1811], but also can be easily explained in biology. Our results also show that the dynamics of the model is completely determined by the ubiety of two functions.

Probing the Conformation of the Prion Protein within a Single Amyloid Fibril Using a Novel Immunoconformational Assay

The coexistence of multiple strains or subtypes of the disease-related isoform of prion protein (PrP) in natural isolates, together with the observed conformational heterogeneity of PrP amyloid fibrils generated in vitro, indicates the importance of probing the conformation of single particles within heterogeneous samples. Using an array of PrP-specific antibodies, we report the development of a novel immunoconformational assay. Uniquely, application of this new technology allows the conformation of multimeric PrP within a single fibril or particle to be probed without pretreatment of the sample with proteinase K. Using amyloid fibrils prepared from full-length recombinant PrP, we demonstrated the utility of this assay to define (i) PrP regions that are surface-exposed or buried, (ii) the susceptibility of defined PrP regions to GdnHCl-induced denaturation, and (iii) the conformational heterogeneity of PrP fibrils as measured for either the entire fibrillar population or for individual fibrils. Specifically, PrP regions 159-174 and 224-230 were shown to be buried and were the most resistant to denaturation. The 132-156 segment of PrP was found to be cryptic under native conditions and solvent-exposed under partially denaturing conditions, whereas the region 95-105 was solvent-accessible regardless of the solvent conditions. Remarkably, a subfraction of fibrils showed immunoreactivity to PrPSc-specific antibodies designated as IgGs 89-112 and 136-158. The immunoreactivity of the conformational epitopes was reduced upon exposure to partially denaturing conditions. Unexpectedly, PrPSc -specific antibodies revealed conformational polymorphisms even within individual fibrils. Our studies provide valuable new insight into fibrillar substructure and offer a new tool for probing the conformation of single PrP fibrils.

Competitive Exclusion and Coexistence of Multiple Strains in an SIS STD Model

In this paper we give a rather complete analysis for a two-sex, susceptible-infective-susceptible (SIS) sexually transmitted disease (STD) model with two competing strains, where the females are divided into two different groups based on their susceptibility to two distinct pathogenic strains. We investigate the existence and stability of the boundary equilibria that characterize the competitive exclusion of the two competing strains; we also investigate the existence and stability of the positive coexistence equilibrium, which characterizes the possibility of coexistence of the two strains. We obtain sufficient and necessary conditions for the existence and global stability of these equilibria. We verify that there is a strong connection between the stability of the boundary equilibria and the existence of the coexistence equilibrium---that is, there exists a unique coexistence equilibrium if and only if the boundary equilibria both exist and have the same stability. This coexistence is globally stable o...