Section HUMAN_2.9_Comparative_Immune_Responses_NDV_Vaccines

1 2.9 Comparative Immune Responses Induced by Major Newcastle Disease Vaccine Strains Newcastle disease vaccines do not all behave alike. Virulence, thermal stability, route of delivery, and the kind of immunity each strain induces all differ. Age at vaccination and maternal antibodies change the outcome as well. This section compares the main strains on four points: antibody titres, mucosal immunity, protection against challenge, and virus shedding. 2.9.1 Humoral Immune Responses Haemagglutination inhibition (HI) titres are the usual yardstick for immunogenicity, so they make a natural starting point. The most directly comparable data come from Sarker et al. (2021), who measured titres in layer chickens six weeks after vaccination: 512 for LaSota, 256 for Mukteswar, and 128 for B1. LaSota came out on top, with Mukteswar in the middle. Other studies point the same way (Geletu & Robi, 2024; Manzoor et al., 2022). B1 can still build protective humoral immunity, particularly as an early priming dose (Hu et al., 2022; Sarker et al., 2021). Its titres run lower, though, which suggests that its gentler profile costs some immunogenicity (Hu et al., 2022). VG/GA tells a more mixed story. Tabbu (2015) found significantly higher HI titres than B1/LaSota programmes in Indonesian broilers. Other comparisons are less favourable. A recent pullet study recorded much weaker antibody responses to VG/GA than to a LaSota clone (Audu et al., 2024), and a broiler study found that both VG/GA and LaSota raised serum IgG significantly, with neither clearly pulling ahead (Albarrak et al., 2025). When antibody induction is the measure, I-2 looks broadly comparable to B1 or to standard B1/LaSota schedules (Nili & Rohollahzadeh, 2017; Geletu & Robi, 2024; Lulie et al., 2026). Eye-drop delivery gives the strongest serology in most studies (Trần et al., 1998; Habibi et al., 2014). V4 responds strongly to route. In Cameroonian village chickens, eye-drop vaccination pushed mean titres above log2 5 within three weeks (Bell et al., 1995). Against genotype VII.1.1 challenge, two successive V4 doses protected better and caused less mortality than LaSota (Elbestawy et al., 2023).2 Clone 30 is immunogenic, but it is hard to rank above other classical live strains. In broilers, its seroresponse did not differ significantly from several comparators (Van Eck & Goren, 1991). A bivalent Clone 30 formulation protected about as well as a LaSota-based live vaccine (Ahmed, 2020). Mukteswar is the strongest of these as a booster. It acts quickly and tends to give durable antibody in older or previously primed birds (Hu et al., 2022; Chellappa et al., 2012). Against lentogenic alternatives, however, it has not consistently come out ahead (Bakhtiar et al., 2022). 2.9.2 Mucosal Immune Responses Mucosal immunity matters here because the virus replicates in both the respiratory and intestinal tracts. VG/GA stands out. As an enterotropic strain, it induces NDV-specific IgA, with higher intestinal and bile IgA than LaSota, and it still produces IgA in the upper respiratory tract (Perozo et al., 2008; Brujeni et al., 2019; Al-Karagoly et al., 2019). LaSota is also reported to provide humoral and mucosal protection in flocks (Yan et al., 2025; Lee et al., 2023). Mucosal responses were rarely measured the same way for the other strains, so a direct comparison with B1, I-2, V4, Clone 30, or Mukteswar is not possible from this literature. 2.9.3 Protection Against Challenge and Virus Shedding Protection against death and clinical disease is well documented. Protection against infection and shedding is less so. In an SPF chicken study, B1 protected 60% of birds after genotype VII challenge, against 80% for Clone.12IR and 90% for LaSota (Hassanzadeh et al., 2024). In another challenge study, conventional LaSota programmes protected 93.3% of broilers, yet birds still shed virus for up to 10 days after challenge (Dewidar et al., 2022; Rohaim et al., 2022). The same pattern shows up across strains. Classical genotype I and II vaccines, including B1, LaSota, VG/GA, Clone 30, I-2, and V4, tend to reduce disease and deaths more reliably than they stop infection or replication when the challenge virus is antigenically distant (Hu et al., 2022; Dimitrov et al., 2016). Genotype matching does better on shedding. In one comparison, a genotype-matched vaccine cut oral shedding significantly more than the mismatched Mukteswar preparation, though both protected well against virulent challenge (Wajid et al., 2018). V4 is one of the stronger classical performers against contemporary viruses. Adding it to a genotype VII programme in Egyptian broilers gave 96% protection and reduced tracheal and3 cloacal shedding (Shahin et al., 2019). 2.9.4 Effects of Maternal Antibodies, Route, and Age Maternal antibodies get in the way of live vaccines in young chicks. For B1 this is well documented: maternal antibody can neutralise the vaccine virus, suppress seroconversion, and leave an early gap in protection (Liu et al., 2023; Dimitrov et al., 2021; Rabo et al., 2026). Enterotropic vaccination such as VG/GA runs into the same problem (Rauw et al., 2009). Route matters about as much as strain. Ocular delivery gave the best titres for LaSota (Manzoor et al., 2022), and eye-drop delivery gave the strongest serological responses for I-2 (Trần et al., 1998). Live Mukteswar did best by injection in the same LaSota-versus-Mukteswar study (Manzoor et al., 2022). For V4, a Pakistani route comparison found that ocular dosing gave the best geometric mean titres, followed by drinking water (Tabassum, 2020). Cold-chain failures and uneven administration in the field also reduce seroconversion across strains (Geletu & Robi, 2024; Dimitrov et al., 2016). 2.9.5 Synthesis Table 2.9 summarises the comparative immune responses of the main strains. Table 2.9. Comparative immune responses induced by major Newcastle disease vaccine strains Strain Pathotype / genotype Humoral response Mucosal response Protection and shedding B1 Lentogenic, II Lower HI than LaSota (128 vs 512) Not characterised in the reviewed comparisons 60% protection vs genotype VII; limited control of shedding LaSota Lentogenic, II Highest HI in the comparisons reviewed Protective humoral and mucosal immunity reported Strong mortality protection; does not reliably prevent shedding VG/GA Lentogenic, II (enterotropic) Higher HI than B1/LaSota in Indonesian broilers; lower than LaSota in one pullet study Higher intestinal and bile IgA than LaSota Good clinical protection; limited control of infection and shedding Clone 30 Lentogenic, II (LaSota lineage) Not significantly different from several comparators Not characterised Protection similar to a LaSota-based vaccine I-2 Avirulent, thermostable, I Similar to B1 or B1/LaSota Not characterised Up to 95–100% protection in some trials V4 Avirulent, thermostable Good titres by eye drop; route dependent Not characterised Higher protection than LaSota vs genotype VII.1.1; reduced shedding in a combined programme4 Strain Pathotype / genotype Humoral response Mucosal response Protection and shedding Mukteswar Mesogenic, III Intermediate (HI 256); strong as a booster Not characterised High protection with inactivated booster; weaker shedding control when mismatched Taken together, the studies support a few conclusions. LaSota has generally produced the strongest humoral responses among the classical live vaccines (Sarker et al., 2021; Hassanzadeh et al., 2024), but its genetic distance from contemporary genotype VII viruses remains a problem (Dewidar et al., 2022; Nedeljković et al., 2022). B1 is gentler than LaSota and suits young, susceptible chicks (Hu et al., 2022; Sarker et al., 2021), but its antibody responses are lower. VG/GA is recognised for its intestinal and bile IgA (Perozo et al., 2008; Brujeni et al., 2019). V4 is thermostable and, in some genotype VII challenge models, has matched or beaten LaSota (Wen et al., 2016; Elbestawy et al., 2023). Mukteswar works well as a booster, although its residual virulence limits its use (Hu et al., 2022; Lu et al., 2022). Classical vaccines usually control disease and mortality better than infection or shedding (Dimitrov et al., 2016; Hu et al., 2022). The clearest gains in shedding control come from genotype-matched vaccines (Wajid et al., 2018; Miller et al., 2007) or from programmes that combine vaccine types (Hu et al., 2022; Gomaa et al., 2025). The evidence has real limits, and they should be stated plainly. Most findings come from single studies that differ in bird type, route, dose, and sampling time, and few strains have mucosal data across the board. HI titre is useful, but it is not a full measure of protection. Strains with similar titres can still differ in shedding and transmission, as the sections above show. Any vaccination recommendation drawn from this section should be read with those gaps in mind.