A deterministic model for influenza infection with multiple strains and antigenic drift

We describe a multiple strain Susceptible Infected Recovered deterministic model for the spread of an influenza subtype within a population. The model incorporates appearance of new strains due to antigenic drift, and partial immunity to reinfection with related circulating strains. It also includes optional seasonal forcing of the transmission rate of the virus, which allows for comparison between temperate zones and the tropics. Our model is capable of reproducing observed qualitative patterns such as the overall annual outbreaks in the temperate region, a reduced magnitude and an increased frequency of outbreaks in the tropics, and the herald wave phenomenon. Our approach to modelling antigenic drift is novel and further modifications of this model may help improve the understanding of complex influenza dynamics.     

Genetic and antigenic characterization of swine H1N2 influenza viruses isolated from Korean pigs

H1N2 influenza viruses are circulating in pigs worldwide and cause considerable economic losses to the pig industry. We genetically analyzed the genes of our isolates from Korean pigs, and compared the antigenicity of our isolates with swine H1N2 viruses isolated from pigs in the U.S.A. In addition, we serologically surveyed the infection rate of swine H1N2 viruses in pigs. We found that H1N2 isolates from Korean pigs are genetically more related to swine H1N2 viruses isolated from pigs in the U.S.A. than those in European countries. When antigenicity was compared, our isolates were weakly reacted to antibodies against swine H1N2 viruses isolated from pigs in the U.S.A. The serological surveillance using sera from pigs in Korea showed that about 46% was positive for H1N2 viruses. Our results suggest that swine H1N2 viruses are widespread in Korean pigs, and the development of a vaccine against H1N2 viruses may help to control their infection in pigs.     

Bioinformatics technologies for the analysis of antigenic evolution of influenza viruses

Human influenza viruses mutate from time to time, causing annual epidemics worldwide. The strong immune pressure in the human population selects a new variant every year, and the antigenic change is one of the primary reasons why vaccination is not a perfect measure to control seasonal influenza. Thus prediction of antigenic change of influenza A virus has been one of the major public health goals. In this review bioinformatics technologies that have been developed to achieve this goal were summarized.     

The antigenic property of the H5N1 avian influenza viruses isolated in central China

ABSTRACT: BACKGROUND: Three influenza pandemics outbroke in the last century accompanied the viral antigen shift and drift, resulting in the change of antigenic property and the low cross protective ability of the existed antibody to the newly emerged pandemic virus, and eventually the death of millions of people. The antigenic characterizations of the viruses isolated in central China in 2004 and 2006-2007 were investigated in the present study. RESULTS: Hemagglutinin inhibition assay and neutralization assay displayed differential antigenic characteristics of the viruses isolated in central China in two periods (2004 and 2006-2007). HA genes of the viruses mainly located in two branches in phylogeny analysis. 53 mutations of the deduced amino acids of the HA genes were divided into 4 patterns. Mutations in pattern 2 and 3 showed the main difference between viruses isolated in 2004 and 2006-2007. Meanwhile, most amino acids in pattern 2 and 3 located in the globular head of the HA protein, and some of the mutations evenly distributed at the epitope sites. CONCLUSIONS: The study demonstrated that a major antigenic drift had occurred in the viruses isolated in central China. And monitoring the antigenic property should be the priority in preventing the potential pandemic of H5N1 avian influenza virus.     

Properties of hog cholera viruses recently isolated in Japan

Hog cholera (HC) viruses newly isolated in Japan in 1980 and 1981 were examined for pathogenicity and serological properties by the neutralization test with antisera against bovine viral diarrhea-mucosal disease (BVD . MD) and HC viruses. Five of 23 isolates examined were neutralized poorly by BVD . MD antibody, but well by HC antibody. On the contrary, 15 isolates were neutralized readily and two isolates moderately by BVD . MD antibody. The other one reacted poorly with either HC or BVD . MD antibodies. The isolate neutralized poorly by BVD . MD antibody was more highly pathogenic than those neutralized readily. It was concluded that the antigenic properties and pathogenicity of the HC viruses were not monotype , and that HC viruses varying in antigenicity and pathogenicity were present in the field.     

Target-size embracing dimension for sensitive detection of viruses with various sizes and influenza virus strains

The focused ion beam (FIB) technique was employed to precisely fabricate hexagon-like Au nano-rods (fibAu_h) arrays as a surface enhanced Raman scattering - active substrate. A "ring diameter" (D(R)) was created by the convergence of three fibAu_h with respect to the dimension of the target viruses (D(T)), such as adenovirus (Adeno), encephalomyocarditis virus (EMCV), influenza virus (H1N1) with different sizes. Three influenza A virus strains were also compared. The results indicate that as that with a D(R)/D(T) ratio of around 1, the discrimination ability for detecting the target viruses and SERS mechanism become obvious. The enhanced lightning rod effect surrounding the seized target virus is anticipated if its size and dimension is suitably embraced within three fibAu_h. Hence the as-designed fibAu_h sample with a target-size embracing dimension provides good discrimination ability for distinguishing virus of various sizes or virus strains.     

Heterogeneity in antibody range and the antigenic drift of influenza A viruses

In this paper we explore the consequences of a heterogeneous immune response in individuals on the evolution of a rapidly mutating virus. We show that several features of the incidence and phylogenetic patterns typical of influenza A may be understood in this framework. In our model, limited diversity and rapid drift of the circulating viral strains result from the interplay of two interacting subpopulations with different types of immune response, narrow or broad, upon infection. The subpopulation with the narrow immune response acts as a reservoir where consecutive mutations escape immunity and can persist. Strains with a number of accumulated mutations escape immunity in the other subpopulation as well, causing larger epidemic peaks in the whole population, and reducing strain diversity. Overall, our model produces a modulation of epidemic peak heights and patterns of antigenic drift consistent with reported observations, suggesting an underlying mechanism for the evolutionary epidemiology of influenza, in particular, and other infectious diseases, more generally.