Antiviral Immunity

Abstract

Viruses are obligate intracellular parasites that cause infection by invading cells of the body. Their life cycle comprises a relatively short extracellular period, and a longer intracellular period during which they undergo replication.The immune system has non-specific and specific mechanisms that attack the virus in both phases of its life cycle. Nonspecific immune response is mainly mediated by interferons and natural killer cells (NK). Type I interferons are produced by many cell types and lead to both inhibition of viral replication and cell proliferation; they also enhance the ability of NK to lyse infected cells. NK represent a different lineage of lymphocytes that recognize and lyse virally infected cells. They are mainly effective during an early stage of viral infection, since there is no lag phase of clonal expansion for NK as occurs with T and B lymphocytes. Specific immune antiviral mechanisms are both humoral and cellular. Specific antibodies protect against viral infections and play an important role in antiviral immunity, mainly during the early stage of the infection. The most effective antiviral antibodies are neutralizing antibodies which bind to the viral envelope or capsid proteins, and block the virus from entering into host cell. The main effectors involved in specific antiviral immunity are CD8+ cytotoxic T lymphocytes (CTL). These cells recognize viral antigens presented at the cell surface associated with class I MHC molecules. CTL response is not always beneficial, since the tissue destruction caused by CTL is sometimes greater than the damage done by the virus.

Virucidal Activities of Zinc-Finger Antiviral Proteins and Zinc-Binding Domains for Virus Entry, DNA/RNA Replication and Spread

“…The immune system has non-specific and specific mechanism that attack the virus in both phases of its life cycle which specific antibodies protect against viral infections and play an important role in antiviral immunity, mainly during the early stage of the infection [9]. Human coronaviruses (HCoVs) are known as respiratory pathogens that HCoVs play only a minor role in causing gastrointestinal illness in children<6 year old which interest in coronaviruses in relation to enteric diseases in humans increased with the emergence of Severe Acute Respiratory Syndrome (SARS) and identification of SARS Coronavirus in 2003 [10].…”