Antibodies to Highly Pathogenic A/H5Nx (Clade 2.3.4.4) Influenza Viruses in the Sera of Vietnamese Residents

Abstract

To cause a pandemic, an influenza virus has to overcome two main barriers. First, the virus has to be antigenically new to humans. Second, the virus has to be directly transmitted from humans to humans. Thus, if the avian influenza virus is able to pass the second barrier, it could cause a pandemic, since there is no immunity to avian influenza in the human population. To determine whether the adaptation process is ongoing, analyses of human sera could be conducted in populations inhabiting regions where pandemic virus variant emergence is highly possible. This study aimed to analyze the sera of Vietnamese residents using hemagglutinin inhibition reaction (HI) and microneutralization (MN) with A/H5Nx (clade 2.3.4.4) influenza viruses isolated in Vietnam and the Russian Federation in 2017–2018. In this study, we used sera from 295 residents of the Socialist Republic of Vietnam collected from three groups: 52 samples were collected from households in Nam Dinh province, where poultry deaths have been reported (2017); 96 (2017) and 147 (2018) samples were collected from patients with somatic but not infectious diseases in Hanoi. In all, 65 serum samples were positive for HI, at least to one H5 virus used in the study. In MN, 47 serum samples neutralizing one or two viruses at dilutions of 1/40 or higher were identified. We postulate that the rapidly evolving A/H5Nx (clade 2.3.4.4) influenza virus is possibly gradually adapting to the human host, insofar as healthy individuals have antibodies to a wide spectrum of variants of that subtype.

Assessing potential pathogenicity of novel highly pathogenic avian influenza (H5N6) viruses isolated from Mongolian wild duck feces using a mouse model

“…The antigenic characterization assay described by the Centres for Disease Control and Prevention (CDC) suggest that influenza viruses are likely to be antigenically dissimilar if their HI titres vary by five or more fold ( https://www.cdc.gov/flu/about/professionals/antigenic.htm ). Our HI results were highly consistent with previous studies, indicating that H5 HPAIVs from the clade 2.3.4.4 exhibit considerable antigenic variation [ 57–59 ]. Both A/wildDuck/MN/H5N6/2018-19 HPAIVs from subclade 2.3.4.4h were antigenically distinct from H5 HPAIVs from clades 0 and 2.3.4.4e and c, suggesting the development of candidate vaccines for H5 HPAIVs subclade 2.3.4.4h are needed.…”

Humoral Immunity to Influenza Infection among the Russian Population

“…In the case of the influenza virus, the countries of Southeast Asia are recognized as the hot spots for the emergence of viruses with epidemic and pandemic potentials [18]. Indeed, we have demonstrated that among 295 serum samples from healthy donors, collected in Vietnam in 2017-2018, 22% were positive in HI-tests and 16% were positive in MN for A/H5Nx viruses [19]. Since the East Asian-Australasian Flyway connects Vietnam and other Southeast Asian countries with Russia, the variants of the influenza virus with pandemic potential can be assumed to enter the Siberian and Far Eastern regions of Russia by migratory birds and further evolve independently.…”

Development of a Rapid Fluorescent Diagnostic System for Early Detection of the Highly Pathogenic Avian Influenza H5 Clade 2.3.4.4 Viruses in Chicken Stool

“…To date, 42 cases of human infection with influenza A(H5N6) 2.3.4.4 viruses have been reported, 22 of which resulting in death [ 7 , 9 , 10 ]. Moreover, antibodies against 2.3.4.4 viruses were found in the sera of many residents during the 2017−2018 H5 HPAI outbreak in Vietnam [ 11 ]. Taken together, these results strongly suggest that viruses causing poultry outbreaks can also cause human H5 HPAI cases.…”