Introduction:
Respiratory syncytial virus (RSV) is a common cause of respiratory illness. It mainly affects people with weakened immune systems, chronic heart or lung diseases, and newborns. It is a worldwide causative viral agent that causes severe lower respiratory infections in all age groups. This topic describes the RSV vaccines.
What Is RSV?
RSV, or respiratory syncytial virus, is a leading cause of lower respiratory infection in newborns and children. It also acts on immunocompromised patients and elderly patients. It is a highly contagious virus that affects the lungs and airways. It can even cause death. It is one of the leading causes of bronchiolitis and pneumonia in infants. Nearly 25 to 40 percent of patients develop bronchiolitis or pneumonia in RSV infection. Nearly two percent of newborns have been reported dead due to RSV.
What Is the Structure of RSV?
RSV is a member of the Pneumovirus of the family Paramyxoviridae. It is a single-stranded RNA virus with proteins enclosed in the genome with 15222 nucleotides and three transmembrane proteins, F, G, and SH. The G-proteins present work for viral host cell attachments. The surface fusion (F) and attachment (G) glycoproteins are the viral components that are RSV-neutralizing antibodies; all these are target sites of the vaccine developments.
How Does RSV Spread?
RSV virus spreads from one infected person to another by coughing, sneezing, or droplets getting into the eyes, nose, or mouth, touching the surface infected with the virus, or by direct virus contact like kissing.
What Are the Symptoms of the Patient Infected With RSV?
Symptoms are:
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Fever (low grade).
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Cough.
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Tachypnea (fast breathing).
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Cyanosis (bluish color in the skin, nails, lips, or eyes).
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Audible wheezing.
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Vomiting.
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Irritability.
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Poor sleep.
What Are the Vaccines for RSV?
RSV vaccines are required to protect the patients from re-infections, as the natural immunity to RSV is incomplete, and chances of re-infections are throughout life. Recently, many RSV vaccines have been developed, including the generation of peptides, subunits, and live virus vaccines. Clinical trials of live attenuated RSV vaccine, subunits vaccine, and inactivated vaccines are performing. Vaccines against RSV are:
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Formalin-inactivated RSV vaccine.
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Live virus vaccines.
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Genetically engineered (cDNA-derived) vaccines.
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Recombinant vaccine.
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Subunits vaccine.
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Other - synthetic peptide vaccine.
Are Vaccines Effective Against RSV?
RSV vaccines with their effects are given below:
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Formalin-Inactivated Vaccine (FI-RSV): The FI-RSV vaccine was formed in the 1960s and initiated in infants and children. It is also named lot 100. It was given in two to three injections (intramuscular) doses delivered in gaps of one to three months to infants and two months to seven years of age in children. But the results were possibly unsatisfactory, as it failed to act against the wild type of RSV, and reports of infant death were reported. The formalin-inactivated vaccine induces humoral and cellular responses, which differ from the wild-type RSV infection. In addition, FI-RSV provides high titers of serum antibodies but low levels of RSV neutralization. So, the FI-RSV vaccines are ineffective for RSV as the vaccination remains susceptible to wild-type RSV, has inadequate levels of antibodies that neutralize the RSV in serum, and has no local immunity.
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Live Virus Vaccines: It is a live attenuated RSV vaccine with intranasal immunization that provides systemic and local immunity and protection against upper and lower respiratory tract infections. These live vaccines have a response like natural infection and thus do not produce enhanced disease after witnessing the wild-type RSV. But the live intranasal vaccines infect the newborns even in the presence of maternal antibodies acquired through breastfeeding. Then it was administered in multiple dosages. So, there were different strategies for giving the live attenuated RSV vaccine into the host range mutants as cold-passaged mutants (cp) and temperature-sensitive mutants (ts). Studies are performed to develop the administration of the live attenuated RSV vaccine. The bovine vaccine is also considered to act against RSV. However, there are changes in the amino acids of F and G glycoproteins of bovine and RSV; these are under clinical trial.
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Genetically Engineered (cDNA-Derived) Vaccine: The vaccine formed from the recovered infectious virus from cDNA clones of RSV. Initially, the attenuating vaccine is derived from a single mutation into RSV cDNA and mapped to amino acid 521. Further, the live attenuated RSV vaccine is combined to produce novel cDNA-derived vaccines. As a result, these vaccines are infectious, attenuated, and genetically stable at last, a single foreign gene in the recombinant RSV genome is required to form a c-DNA-derived vaccine, but the IL-6 gene is an effort to enhance immunity in infants.
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Vector Delivery Systems: Recombinant Vaccinia virus with nine RSV proteins was initiated but provided short-term protection. Further, Vaccinia virus F and Vaccinia virus G were introduced to neutralize the antibodies and provide long-term protection. But intradermal immunization with these vaccinations has produced low levels of neutralizing antibodies, insufficient protection of the lower respiratory system, and no protection of the upper respiratory system; thus, the lack of immunity has shown insufficient results. However, other recombinants like adenovirus-RSV recombinants have shown results in dogs but not in chimpanzees.
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Subunit Vaccines: RSV F and G are the viral glycoproteins used to neutralize the antibodies and protect them. These vaccines have a chimeric FG glycoprotein. It has two RSV F subunit vaccines (purified F protein), PFP-1 and PFP-2. RSV-F subunit vaccine was evaluated in infants with chronic pulmonary diseases and in the elderly; it was well tolerated by the people. And even the post-vaccination reaction was less, and there was a rise in RSV-neutralizing antibodies in one-half to three-quarters. The studies evaluated that RSV-PFP vaccines are safe and moderately leading to immunity, hence are useful. But clinical trials of RSV-PFP 2 are in progress.
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Synthetic Peptide Vaccines: It is derived from the bacteria prokaryotes, and it is still under trial.
Conclusion:
Two RSV vaccines are effective; one is the PFP-subunits vaccine used in the immunization of older people and RSV-positive children and the elderly. And another was that cold-pressed live attenuated vaccines are useful for immunizations of newborns. Using DNA-attenuated vaccines requires refining for satisfactory attenuated immunization results for stability. And the use of chimeric vaccines for RSV is appropriate, but the attenuated RSV B vaccines are not identified. However, the RSV vaccination is not to prevent the RSV infection but to prevent the RSV- associated lower respiratory infections.
