Enveloped, single-stranded RNA negative sense virus with a different gene on each of its 8 segments.Ultimately, the upcoming clinical evaluation of these universal vaccine approaches will be fundamental to determine their effectiveness against preventing influenza virus infection and/or reducing transmission and disease severity. In particular, their strengths and potential shortcomings are discussed. In this review, the most promising under-development universal vaccine approaches are discussed with an emphasis on those targeting the HA glycoprotein. Alternatively, other approaches aim toward eliciting a broader immune response capable of conferring protection against the diversity of currently circulating seasonal influenza strains. conserved viral proteins or protein regions shared amongst seasonal and pre-pandemic strains. One approach is the elicitation of an immune response against the " Achille's heel " of the virus, i.e. A number of novel influenza vaccine approaches are currently under evaluation. There is currently an unmet need to develop an effective " broadly-reactive " or " universal " influenza vaccine capable of conferring protection against both seasonal and newly emerging pre-pandemic strains. For this reason, if an antigenic mismatch exists between the current vaccine and circulating influenza isolates, vaccinated people may not be afforded complete protection. Hypervariability of the amino acid sequences encoding HA and NA is largely responsible for epidemic and pandemic influenza outbreaks, and are the consequence of antigenic drift or shift, respectively. The major targets of the antibody response against influenza virus are the surface glycoprotein antigens hemagglutinin (HA) and neuraminidase (NA). However, the effectiveness of current influenza vaccines are limited because they only confer protective immunity when there is antigenic similarity between the selected vaccine strains and circulating influenza isolates. Annual influenza vaccination is the primary prophylactic countermeasure aimed at limiting influenza burden. ![]() ![]() Influenza virus infection is an ongoing health and economic burden causing epidemics with pandemic potential, affecting 5–30% of the global population annually, and is responsible for millions of hospitalizations and thousands of deaths each year. The role of antigenic shift and drift is very important in recombination and mutation of influenza virus and not to be underestimate. As population is not immune to that particular strain of virus thus it dominate on immune cells and transmissible from person to person. ![]() During antigenic shift all the three viruses' genome intermix and form a new mutant which have most of the genes from human influenza virus while hemagglutinin (HA) and neuraminindase (NA) surface proteins from avian influenza. Beside antigenic drift & shift the one possible reason for mutations in all RNA viruses is because of the virus' RNA polymerase enzyme has no proofreading mechanism during viral replication, thus mutations in influenza occurs frequently and resulting in an error rate between 1×10−3 and 8×10−3 substitutions In pigs the phenomena is more prominent as it is susceptible to three different influenza viruses including human, swine and avian. But due to selection pressure, antigenic shift and antigenic drift the new copies of the influenza virus are formed which have the ability to escape from the immune system and cause pandemic. Normally the surface antigens hemagglutinin and neuraminidase are recognize by the host cell and produce immunity against influenza virus. The structure of the virus is spherical and consist of segmented single stranded ssRNA. Influenza is an infectious disease caused by influenza virus and commonly known as flu.
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