Table 2.
Examples of recombination or reassortment of live attenuated vaccines and wild-type viruses.
| Live, attenuated vaccine | Target species | Genome type | Vaccine and Recombination event | Estimated frequency | Recombination mechanism | Phenotypic change | Clinical relevance | Epidemiological relevance |
|---|---|---|---|---|---|---|---|---|
| Segmented genome viruses | ||||||||
| African horsesickness | Horses | Reoviridae, orbivirus, 9 serotypes, double-strand RNA, 10 segments | Reassortants with individual genome segments derived from multiple different virus types present in the trivalent vaccine | 3 reported outbreaks caused by distinct reassortant viruses | Reassortment | Increased virulence | Hemorrhagic disease, possibly lower case-fatality | Three outbreaks in Cape Province, South Africa |
| Bluetongue | Sheep, cattle | Reoviridae, orbivirus, 26+ serotypes, double-strand RNA, 10 segments | Three pentavalent vaccines in three sequential inocula: (1) serotypes 1, 4, 6, 12, and 14; (2) serotypes 3, 8, 9, 10, and 11; and (3) serotypes 2, 5, 7, 13, and 19. Reversion or reassortment of LAV vaccine strains and between LAV and wild-type virus | Several reports | Reassortment of LAV vaccine strains and between LAV and wild-type virus | Not reported | No clear cut evidence of increased virulence of reassortant strains reported | None recognized |
| Non-segmented genome viruses | ||||||||
| Newcastle disease virus (NDV) | Chickens | Paramyxovirus negative sense nonsegmented single-strand (ss) RNA | Recombination with wild-type NDV | Probably common | Both intra- and intergenic recombination events between LAVs and wild-type viruses | Unknown | Unknown | Vaccine sequences circulate in recombinant strains play a role in evolution |
| Oral polio vaccine (OPV) | Humans | Picornavirus positive sense non-segmented ssRNA | Recombination with wild-type poliovirus | Relatively common | Homologous intertypic recombination with wild-type polio, Coxsackie, and other enteroviruses | Increased virulence for transgenic mice | Vaccine associated paralytic disease in human | Over 30 described epidemics of vaccine-associated paralytic polio caused by circulating recombinant strains |
| Bovine viral diarrhea | Cows | Pestivirus positive sense non-segmented ssRNA | Recombination of LAV with persistently infecting non-cytopathic viruses | 5 cases, but may be frequent | homologous and nonhomologous recombination | Increased cytopathology in cell culture | Converts non-cytopathic persistently infecting virus to virulent strain causing mucosal disease | Sporadic mucosal disease |
| Infectious laryngotracheitis virus | Chickens | Herpesvirus double stranded linear DNA | Recombination of LAV and wild-type | Common | Homologous recombination | Increased virulence for poultry | Virulent recombinant strains | Outbreaks of disease in poultry flocks |
| Porcine reproductive and respiratory syndrome virus (PRRSV) | Swine | Arterivirus positive sense non-segmented ssRNA | Recombination of LAV and wild type | Single report | Intergenic recombination | Not studied | Isolate made during an outbreak of PRRS but pathogenicity of recombinant not known | Unknown |